App icon: just the fringe cube, no streamlines

The owner's final choice: the hex-meshed cube with its banded fringe,
drawn a little larger, with no streamlines at any size. The Icon Composer
document is back to the floor and cube groups.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.cargo/config.toml

@@ -1,2 +1,8 @@
 [alias]
 xtask = "run --package xtask --"
+
+# Windows release binaries link the C runtime statically, so they run without the VC++
+# redistributable (packaging/windows/package.ps1 builds with --target, which keeps the flag
+# off build scripts and proc-macros).
+[target.x86_64-pc-windows-msvc]
+rustflags = ["-C", "target-feature=+crt-static"]

.github/CODEOWNERS

@@ -0,0 +1,2 @@
+# Every change to FieldCraft needs the maintainer's review before it merges.
+* @jyviko

.github/ISSUE_TEMPLATE/bug.yml

@@ -0,0 +1,46 @@
+name: Bug report
+description: Something FieldCraft does wrong, a wrong result, or a crash
+labels: [bug]
+body:
+  - type: textarea
+    id: observed
+    attributes:
+      label: Observed failure
+      description: Exactly what happened. Quote error messages and wrong numbers as they appear.
+    validations:
+      required: true
+  - type: textarea
+    id: reproduction
+    attributes:
+      label: Reproduction
+      description: Numbered steps, or a script (`fieldcraft-cli run script.json`, control-channel JSON lines), with the sample, corpus part or attached `.fieldcraft` / `.solidcraft` file that shows it.
+      placeholder: |
+        1. fieldcraft --sample cantilever
+        2. Mesh ▸ Tet ▸ OK
+        3. ...
+    validations:
+      required: true
+  - type: textarea
+    id: evidence
+    attributes:
+      label: Evidence
+      description: Screenshots, log output, numbers. For a crash, attach the crash report (`fieldcraft-cli crashes`, then `crashes show <id>`).
+  - type: textarea
+    id: expected
+    attributes:
+      label: Expected behaviour
+      description: What should happen instead, and why — a closed form, a published benchmark, the documentation, or how the rest of the app behaves. Never output from a commercial CAE product.
+    validations:
+      required: true
+  - type: textarea
+    id: investigation
+    attributes:
+      label: Investigation
+      description: Anything you found about the cause — code you suspect, what you ruled out. Leave empty if you have not looked.
+  - type: input
+    id: version
+    attributes:
+      label: Version and platform
+      placeholder: "v0.5.5 (or commit), macOS 15 arm64"
+    validations:
+      required: true

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1 @@
+blank_issues_enabled: false

.github/ISSUE_TEMPLATE/feature.yml

@@ -0,0 +1,28 @@
+name: Feature request
+description: A capability FieldCraft should have
+labels: [enhancement]
+body:
+  - type: textarea
+    id: current
+    attributes:
+      label: Current behaviour
+      description: What you can and cannot do today, and what happens when you try.
+    validations:
+      required: true
+  - type: textarea
+    id: need
+    attributes:
+      label: What you need and why
+      description: The analysis or workflow you are trying to do.
+    validations:
+      required: true
+  - type: textarea
+    id: expected
+    attributes:
+      label: Expected behaviour
+      description: What FieldCraft should do, as precisely as you can.
+  - type: textarea
+    id: reference
+    attributes:
+      label: References
+      description: Papers, textbooks, public specifications or published benchmarks that define the behaviour. Do not paste text, files or results from commercial CAE products.

.github/dependabot.yml

@@ -0,0 +1,59 @@
+# Weekly dependency updates against develop, the trunk, grouped so each ecosystem opens one pull
+# request a week. Security updates are switched on in the repository settings and open their own
+# pull requests as advisories appear. CI runs the full gate on Dependabot's pull requests
+# (.github/workflows/ci.yml).
+version: 2
+updates:
+  - package-ecosystem: cargo
+    directory: /
+    target-branch: develop
+    schedule:
+      interval: weekly
+      day: monday
+      time: "05:00"
+      timezone: Etc/UTC
+    open-pull-requests-limit: 5
+    commit-message:
+      prefix: deps
+    groups:
+      # Compatible updates (Cargo.lock only) in one pull request; a breaking release of a
+      # dependency comes on its own, since it usually needs code changes.
+      cargo-compatible:
+        update-types: [minor, patch]
+    ignore:
+      # Pinned to the SolidCraft commit FieldCraft builds against, together with the truck and
+      # egui-wgpu patches from that commit ([patch.crates-io] in Cargo.toml); moved by hand.
+      - dependency-name: "solidcraft-*"
+      - dependency-name: "truck-*"
+      - dependency-name: matext4cgmath
+      - dependency-name: egui-wgpu
+      # The egui line follows SolidCraft's (its egui-wgpu fixes are patched in): patch releases
+      # come with the group, a new line (0.36 -> 0.37) moves by hand with SolidCraft.
+      - dependency-name: egui
+        update-types: ["version-update:semver-major", "version-update:semver-minor"]
+      - dependency-name: eframe
+        update-types: ["version-update:semver-major", "version-update:semver-minor"]
+      # The shared Craft components follow VectorCraft's rev.
+      - dependency-name: craft-ui
+      # The exact predicates' BigInt must be num-rational's (0.4 uses num-bigint 0.4): both move
+      # together, by hand.
+      - dependency-name: num-bigint
+        update-types: ["version-update:semver-major", "version-update:semver-minor"]
+      - dependency-name: num-rational
+        update-types: ["version-update:semver-major", "version-update:semver-minor"]
+
+  - package-ecosystem: github-actions
+    directory: /
+    target-branch: develop
+    schedule:
+      interval: weekly
+      day: monday
+      time: "05:00"
+      timezone: Etc/UTC
+    open-pull-requests-limit: 3
+    commit-message:
+      prefix: ci
+    groups:
+      # Actions are pinned by commit SHA with a version comment; Dependabot updates both.
+      actions:
+        patterns: ["*"]

.github/pull_request_template.md

@@ -0,0 +1,11 @@
+Closes #
+
+## What and why
+
+## How it was verified
+<!-- Tests added or changed; oracle cases (tests/oracle) for solver and meshing results, with their cited references. -->
+
+## Checklist
+- [ ] The issue was assigned to me before I started (see CONTRIBUTING.md)
+- [ ] `cargo fmt --all`, `cargo clippy -p <crates I touched> --all-targets -- -D warnings` and their tests pass
+- [ ] No code, text or data from GPL-family projects or commercial CAE products

.github/release-notes.md

@@ -0,0 +1,27 @@
+FieldCraft is open-source CAE pre-processing in Rust: it turns geometry into analysis-ready
+finite element models, writes Abaqus, Nastran and LS-DYNA decks, and solves linear static and
+modal problems with its own solver. AI agents can drive it over MCP (`fieldcraft-cli mcp`).
+[README](https://github.com/jyviko/fieldcraft#readme) ·
+[roadmap](https://github.com/jyviko/fieldcraft/blob/main/ROADMAP.md) ·
+[issues](https://github.com/jyviko/fieldcraft/issues)
+
+**Which file?**
+- **macOS 11+** (Apple silicon and Intel): open `fieldcraft-{version}-macos-universal.dmg` and
+  drag `FieldCraft.app` onto Applications. The command-line tool is in
+  `fieldcraft-cli-{version}-macos-universal.zip`.
+- **Linux** (x86_64, glibc 2.35+: Ubuntu 22.04, Debian 12, Fedora 36 or newer):
+  `fieldcraft-{version}-linux-x86_64.AppImage` (`chmod +x`, then run it), or unpack
+  `fieldcraft-{version}-linux-x86_64.tar.gz` and run `bin/fieldcraft` (`bin/fieldcraft-cli` is the
+  command-line tool).
+- **Windows 10+** (x64): unzip `fieldcraft-{version}-windows-x64.zip` and run `fieldcraft.exe`
+  (`fieldcraft-cli.exe` is the command-line tool).
+- `SHA256SUMS.txt`: `sha256sum -c SHA256SUMS.txt --ignore-missing` (macOS:
+  `shasum -a 256 -c SHA256SUMS.txt --ignore-missing`).
+
+To start with a sample model, run the app with `--sample cantilever` (macOS:
+`/Applications/FieldCraft.app/Contents/MacOS/FieldCraft --sample cantilever`).
+
+**Signing.** {macos_signing} The Linux and Windows builds are not signed; on Windows, SmartScreen
+may say "Windows protected your PC": choose **More info**, then **Run anyway**.
+
+Every package carries `LICENSE-MIT`, `LICENSE-APACHE`, `NOTICE` and `THIRD-PARTY-LICENSES.txt`.

.github/workflows/arch-check.yml

@@ -0,0 +1,83 @@
+# Linux on other architectures, weekly and on demand: CI and the release build x86_64 Linux,
+# macOS and Windows only.
+# - arm64: a native runner builds the shipped binaries (release profile) and runs the CLI and
+#   engine tests.
+# - riscv64: cross-built with Ubuntu's GNU toolchain and linked; the CLI then runs under QEMU.
+#   The GUI needs no target system libraries at link time (Wayland, X11 and GL are opened at run
+#   time), so only the cross C toolchain and libc are installed.
+# The RISC-V job is adapted from SolidCraft's CI (see ATTRIBUTION.md).
+name: Linux arm64 and riscv64
+
+on:
+  schedule:
+    - cron: '17 5 * * 1'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: arch-check-${{ github.ref }}
+  cancel-in-progress: false
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  arm64:
+    name: Linux arm64 (native)
+    runs-on: ubuntu-24.04-arm
+    timeout-minutes: 90
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
+        with:
+          key: arm64
+          save-if: ${{ github.ref == 'refs/heads/develop' }}
+      - name: Build fieldcraft and fieldcraft-cli (release)
+        run: cargo build --locked --release -p fieldcraft -p fieldcraft-cli
+      - name: Run the binaries
+        run: |
+          file target/release/fieldcraft target/release/fieldcraft-cli
+          target/release/fieldcraft --version
+          target/release/fieldcraft-cli --version
+          target/release/fieldcraft-cli commands >/dev/null
+      - name: CLI and engine tests
+        run: cargo test --locked --profile ci -p fieldcraft-cli -p fieldcraft-engine
+
+  riscv64:
+    name: Linux riscv64 (cross)
+    runs-on: ubuntu-24.04
+    timeout-minutes: 90
+    env:
+      TARGET: riscv64gc-unknown-linux-gnu
+      CARGO_TARGET_RISCV64GC_UNKNOWN_LINUX_GNU_LINKER: riscv64-linux-gnu-gcc
+      CARGO_TARGET_RISCV64GC_UNKNOWN_LINUX_GNU_RUNNER: qemu-riscv64 -L /usr/riscv64-linux-gnu
+      CC_riscv64gc_unknown_linux_gnu: riscv64-linux-gnu-gcc
+      CXX_riscv64gc_unknown_linux_gnu: riscv64-linux-gnu-g++
+      AR_riscv64gc_unknown_linux_gnu: riscv64-linux-gnu-ar
+      PKG_CONFIG_ALLOW_CROSS: 1
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          targets: riscv64gc-unknown-linux-gnu
+      - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
+        with:
+          key: riscv64
+          save-if: ${{ github.ref == 'refs/heads/develop' }}
+      - name: Install the cross toolchain and QEMU
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends gcc-riscv64-linux-gnu g++-riscv64-linux-gnu \
+            libc6-dev-riscv64-cross qemu-user
+      - name: Build fieldcraft and fieldcraft-cli
+        run: cargo build --locked --profile ci --target "$TARGET" -p fieldcraft -p fieldcraft-cli
+      - name: Run the CLI under QEMU
+        run: |
+          bin="target/$TARGET/ci"
+          file "$bin/fieldcraft" "$bin/fieldcraft-cli"
+          qemu-riscv64 -L /usr/riscv64-linux-gnu "$bin/fieldcraft-cli" --version
+          qemu-riscv64 -L /usr/riscv64-linux-gnu "$bin/fieldcraft-cli" commands >/dev/null
+          qemu-riscv64 -L /usr/riscv64-linux-gnu "$bin/fieldcraft" --version

.github/workflows/ci.yml

@@ -1,10 +1,21 @@
 name: CI
 
-# CI runs once per merge, on main (AGENTS.md, "Workflow for every change"): pull requests are
-# checked locally on the crates they touch and merged; a red main is fixed forward.
+# CI runs once per merge on `develop`, the trunk (AGENTS.md, "Workflow for every change"): the core
+# team's pull requests are checked locally on the crates they touch and merged; a red trunk is
+# fixed forward. `main` holds released code only (docs/releasing.md).
+# Pull requests from forks (outside contributors) run the full gate, once the maintainer approves
+# the run, so the review sees it; so do Dependabot's (.github/dependabot.yml), which nobody tests
+# locally. The heavy job stays off pull requests.
 on:
+  pull_request:
+    paths:
+      - '**'
+      - '!**/*.md'
+      - '!docs/**'
+      - 'docs/features.md'
+      - 'docs/oracle.md'
   push:
-    branches: [main]
+    branches: [develop]
     # A merge that only touches prose starts no run. The generated pages are checked by the jobs
     # (features.md by `cargo xtask ci`, oracle.md by the oracle job), so they still count.
     # (Later patterns override earlier ones.)
@@ -15,8 +26,11 @@ on:
       - 'docs/features.md'
       - 'docs/oracle.md'
   schedule:
-    # Nightly: the heavy tests on main.
+    # Nightly, on the default branch (develop): the heavy tests.
     - cron: '23 3 * * *'
+    # Weekly: the oracle on macOS too, so results that differ by platform show up in CI (the
+    # fixtures are often blessed on a Mac; #115).
+    - cron: '41 4 * * 0'
   workflow_dispatch:
 
 permissions:
@@ -26,7 +40,7 @@ permissions:
 # once, at the tip. Nightly and manual runs are grouped apart and never cancelled by a merge.
 concurrency:
   group: ci-${{ github.ref }}-${{ github.event_name }}
-  cancel-in-progress: ${{ github.event_name == 'push' }}
+  cancel-in-progress: ${{ github.event_name == 'push' || github.event_name == 'pull_request' }}
 
 env:
   CARGO_TERM_COLOR: always
@@ -34,6 +48,7 @@ env:
 jobs:
   ci:
     name: cargo xtask ci
+    if: github.event.schedule != '41 4 * * 0' && (github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name != github.repository || github.event.pull_request.user.login == 'dependabot[bot]')
     runs-on: ubuntu-24.04
     timeout-minutes: 60
     steps:
@@ -44,12 +59,19 @@ jobs:
           targets: wasm32-unknown-unknown
       - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
         with:
-          save-if: ${{ github.ref == 'refs/heads/main' }}
+          save-if: ${{ github.ref == 'refs/heads/develop' }}
+      # A dependency update changes THIRD-PARTY-LICENSES.txt, which Dependabot cannot regenerate:
+      # regenerate it here so the gate checks everything else, and dependabot-licences.yml commits
+      # it to the pull request.
+      - name: Regenerate THIRD-PARTY-LICENSES.txt (Dependabot)
+        if: github.event.pull_request.user.login == 'dependabot[bot]'
+        run: cargo xtask licences
       - run: cargo xtask ci
 
   heavy:
     # The heavy verification and corpus tests (#[ignore]d) and the doc tests.
     name: cargo xtask test --heavy
+    if: github.event.schedule != '41 4 * * 0' && github.event_name != 'pull_request'
     runs-on: ubuntu-24.04
     timeout-minutes: 60
     steps:
@@ -57,7 +79,7 @@ jobs:
       - uses: dtolnay/rust-toolchain@stable
       - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
         with:
-          save-if: ${{ github.ref == 'refs/heads/main' }}
+          save-if: ${{ github.ref == 'refs/heads/develop' }}
       - run: cargo xtask test --heavy
 
   oracle:
@@ -65,6 +87,7 @@ jobs:
     # its fixture, and docs/oracle.md must be the table the cases produce. Cases marked `slow`
     # run here too while the whole set stays within a few minutes; `--quick` skips them.
     name: cargo xtask oracle
+    if: github.event.schedule != '41 4 * * 0' && (github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name != github.repository || github.event.pull_request.user.login == 'dependabot[bot]')
     runs-on: ubuntu-24.04
     timeout-minutes: 45
     steps:
@@ -73,13 +96,32 @@ jobs:
       - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
         with:
           key: oracle
-          save-if: ${{ github.ref == 'refs/heads/main' }}
+          save-if: ${{ github.ref == 'refs/heads/develop' }}
+      - run: cargo xtask oracle
+      - name: docs/oracle.md is current
+        run: git diff --exit-code docs/oracle.md
+
+  oracle-macos:
+    # The same oracle on macOS, weekly and on demand: the solvers must agree across platforms
+    # to the fixture bands, and docs/oracle.md must read the same.
+    name: cargo xtask oracle (macOS)
+    if: github.event.schedule == '41 4 * * 0' || github.event_name == 'workflow_dispatch'
+    runs-on: macos-14
+    timeout-minutes: 60
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
+        with:
+          key: oracle-macos
+          save-if: ${{ github.ref == 'refs/heads/develop' }}
       - run: cargo xtask oracle
       - name: docs/oracle.md is current
         run: git diff --exit-code docs/oracle.md
 
   advisories:
     name: Dependency advisories and sources
+    if: github.event.schedule != '41 4 * * 0' && (github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name != github.repository || github.event.pull_request.user.login == 'dependabot[bot]')
     runs-on: ubuntu-24.04
     timeout-minutes: 20
     steps:

.github/workflows/dependabot-licences.yml

@@ -0,0 +1,40 @@
+# Dependabot's Cargo updates change THIRD-PARTY-LICENSES.txt (`cargo xtask licences`), which
+# Dependabot cannot regenerate: this commits the regenerated file to its pull request. CI's own
+# run on the pull request regenerates it too, so its result covers everything else.
+name: Dependabot licences
+
+on:
+  pull_request:
+    branches: [develop]
+    paths: [Cargo.lock]
+
+permissions:
+  contents: write
+
+concurrency:
+  group: dependabot-licences-${{ github.head_ref }}
+  cancel-in-progress: true
+
+jobs:
+  licences:
+    if: github.event.pull_request.user.login == 'dependabot[bot]'
+    runs-on: ubuntu-24.04
+    timeout-minutes: 20
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          ref: ${{ github.head_ref }}
+      - uses: dtolnay/rust-toolchain@stable
+      - run: cargo xtask licences
+      - name: Commit the regenerated file
+        run: |
+          if git diff --quiet -- THIRD-PARTY-LICENSES.txt; then
+            echo "THIRD-PARTY-LICENSES.txt is up to date"
+            exit 0
+          fi
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          # [skip ci]: the pull request's CI run already regenerated this file and tested the
+          # tree with it; a bot-authored commit would otherwise wait for a maintainer's approval.
+          git commit -m "deps: regenerate THIRD-PARTY-LICENSES.txt [skip ci]" -- THIRD-PARTY-LICENSES.txt
+          git push origin "HEAD:${GITHUB_HEAD_REF}"

.github/workflows/packaging-lint.yml

@@ -0,0 +1,79 @@
+# Quick static checks for the release pipeline (seconds, no Rust build): workflow syntax, the
+# packaging shell and PowerShell scripts, the macOS property lists and the Linux desktop entry.
+# These files are otherwise exercised only by a full release run (release.yml).
+# Adapted from SolidCraft's packaging-lint.yml, itself adapted from PhotoCraft's (see ATTRIBUTION.md).
+name: Packaging lint
+
+on:
+  push:
+    branches: [develop]
+    paths: [".github/workflows/**", "packaging/**"]
+  pull_request:
+    paths: [".github/workflows/**", "packaging/**"]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: packaging-lint-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  lint:
+    name: Packaging lint
+    runs-on: ubuntu-24.04
+    timeout-minutes: 10
+    env:
+      ACTIONLINT_VERSION: 1.7.12
+      ACTIONLINT_SHA256: 8aca8db96f1b94770f1b0d72b6dddcb1ebb8123cb3712530b08cc387b349a3d8
+      PSSCRIPTANALYZER_VERSION: 1.24.0
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - name: Install tools
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends shellcheck desktop-file-utils libxml2-utils
+          archive="$RUNNER_TEMP/actionlint.tar.gz"
+          curl -fsSL -o "$archive" \
+            "https://github.com/rhysd/actionlint/releases/download/v${ACTIONLINT_VERSION}/actionlint_${ACTIONLINT_VERSION}_linux_amd64.tar.gz"
+          echo "$ACTIONLINT_SHA256  $archive" | sha256sum -c -
+          tar -xzf "$archive" -C "$RUNNER_TEMP" actionlint
+      - name: actionlint
+        # Also runs shellcheck on every `run:` script.
+        run: '"$RUNNER_TEMP/actionlint" -color'
+      - name: shellcheck
+        # packaging/.shellcheckrc lets the scripts' `source=../env.sh` directives resolve.
+        run: shellcheck packaging/*.sh packaging/*/*.sh packaging/linux/AppRun
+      - name: PowerShell
+        shell: pwsh
+        run: |
+          $failed = $false
+          foreach ($f in Get-ChildItem packaging/windows/*.ps1) {
+            $errors = $null
+            [System.Management.Automation.Language.Parser]::ParseFile($f.FullName, [ref]$null, [ref]$errors) | Out-Null
+            if ($errors) {
+              $errors | ForEach-Object { Write-Output "::error file=$($f.FullName),line=$($_.Extent.StartLineNumber)::$($_.Message)" }
+              $failed = $true
+            } else {
+              Write-Output "parsed $($f.Name)"
+            }
+          }
+          if ($failed) { exit 1 }
+          if (-not (Get-Module -ListAvailable PSScriptAnalyzer | Where-Object Version -eq $env:PSSCRIPTANALYZER_VERSION)) {
+            Install-Module PSScriptAnalyzer -RequiredVersion $env:PSSCRIPTANALYZER_VERSION -Scope CurrentUser -Force
+          }
+          Import-Module PSScriptAnalyzer -RequiredVersion $env:PSSCRIPTANALYZER_VERSION
+          $issues = Invoke-ScriptAnalyzer -Path packaging/windows -Recurse -Severity Error, Warning
+          $issues | ForEach-Object { Write-Output "::error file=$($_.ScriptPath),line=$($_.Line)::$($_.RuleName): $($_.Message)" }
+          if ($issues) { exit 1 }
+      - name: Property lists and desktop entry
+        run: |
+          app_id="$(sed -n 's/^APP_ID=//p' packaging/env.sh)"
+          test -n "$app_id"
+          xmllint --noout packaging/macos/*.plist*
+          desktop="packaging/linux/$app_id.desktop"
+          desktop-file-validate "$desktop"
+          # The window's X11 class / Wayland app_id is packaging's APP_ID (apps/fieldcraft/src/main.rs).
+          grep -qx "StartupWMClass=$app_id" "$desktop"
+          grep -qF "const APP_ID: &str = \"$app_id\";" apps/fieldcraft/src/main.rs

.github/workflows/pages.yml

@@ -0,0 +1,84 @@
+# The web app (apps/fieldcraft-web, docs/web.md) on GitHub Pages: https://jyviko.github.io/fieldcraft/
+# After SolidCraft's pages.yml (MIT OR Apache-2.0; see ATTRIBUTION.md).
+#
+# A push to `main` (a release; main holds released code only) builds the app with Trunk (release,
+# wasm-opt) and deploys it. A merge to `develop` that touches code builds it without deploying, so a
+# broken web build shows up before the release. A manual run builds the branch it runs on and
+# deploys only from `main`. Needs Settings › Pages › Source = GitHub Actions, and `main` allowed
+# by the github-pages environment's deployment branches.
+name: Pages
+
+on:
+  push:
+    branches: [main, develop]
+    # As ci.yml: a merge that only touches prose builds nothing.
+    paths:
+      - '**'
+      - '!**/*.md'
+      - '!docs/**'
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+# One deployment at a time; a newer push waits its turn instead of cancelling a deploy part way.
+concurrency:
+  group: pages-${{ github.ref }}
+  cancel-in-progress: false
+
+env:
+  CARGO_TERM_COLOR: always
+  TRUNK_VERSION: v0.21.14
+  TRUNK_SHA256: f2b4680cd239693a646a2795e4633c625328d7b2a044fbe749fa3a2fe9e7036b
+
+jobs:
+  build:
+    runs-on: ubuntu-24.04
+    timeout-minutes: 60
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          targets: wasm32-unknown-unknown
+      - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
+        with:
+          key: web
+          save-if: ${{ github.ref == 'refs/heads/develop' }}
+      - name: Install Trunk
+        run: |
+          mkdir -p "$HOME/.local/bin"
+          curl -sSfL -o trunk.tar.gz "https://github.com/trunk-rs/trunk/releases/download/${TRUNK_VERSION}/trunk-x86_64-unknown-linux-gnu.tar.gz"
+          echo "${TRUNK_SHA256}  trunk.tar.gz" | sha256sum -c -
+          tar -xzf trunk.tar.gz -C "$HOME/.local/bin"
+          echo "$HOME/.local/bin" >> "$GITHUB_PATH"
+      - name: Build the web app
+        working-directory: apps/fieldcraft-web
+        run: trunk build --release --public-url /fieldcraft/
+      - name: Bundle size
+        run: |
+          {
+            echo "### Web app bundle"
+            echo '| file | bytes | gzip |'
+            echo '|---|---:|---:|'
+            for f in dist/web/*.wasm dist/web/*.js; do
+              echo "| $(basename "$f") | $(stat -c %s "$f") | $(gzip -9 -c "$f" | wc -c) |"
+            done
+          } >> "$GITHUB_STEP_SUMMARY"
+      - if: github.ref == 'refs/heads/main'
+        uses: actions/upload-pages-artifact@fc324d3547104276b827a68afc52ff2a11cc49c9 # v5.0.0
+        with:
+          path: dist/web
+
+  deploy:
+    if: github.ref == 'refs/heads/main'
+    needs: build
+    runs-on: ubuntu-24.04
+    permissions:
+      pages: write
+      id-token: write
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - id: deployment
+        uses: actions/deploy-pages@368f82528645a54fb793d4d04e342629a3f51346 # v5.0.1

.github/workflows/release.yml

@@ -0,0 +1,253 @@
+# Release builds (docs/releasing.md), after SolidCraft's and VectorCraft's release.yml
+# (MIT OR Apache-2.0; see ATTRIBUTION.md).
+#
+# A push to `main` (fast-forwarded from a verified `develop` commit; main holds released code only)
+# builds every package and creates or updates the
+# DRAFT GitHub Release "FieldCraft v<version>", with SHA256SUMS.txt and generated notes. The
+# version is [workspace.package] version in Cargo.toml; a suffix (0.2.0-rc.1) makes a
+# pre-release. A person verifies the draft and publishes it; this workflow never publishes,
+# and pushes to develop or tags never start it.
+#
+#   macOS universal (arm64 + x86_64)   .dmg with FieldCraft.app, the CLI as a .zip   packaging/macos
+#   Linux x86_64 (glibc 2.35+)         .tar.gz and .AppImage                          packaging/linux
+#   Windows x64                        .zip with fieldcraft.exe and fieldcraft-cli.exe packaging/windows
+#
+# macOS: signed with a Developer ID and notarized when the APPLE_* secrets exist, ad-hoc
+# otherwise (the release notes say which). Linux and Windows builds are not signed.
+#
+# Dry run: `gh workflow run release.yml --ref <branch>` builds everything and uploads the
+# `release-assets` artifact without creating a release. `-f draft=true` on `main` retries
+# the draft.
+name: Release
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+    inputs:
+      draft:
+        description: "Create/update the draft release (main only; off: build artifacts only)"
+        type: boolean
+        default: false
+
+permissions:
+  contents: read
+
+concurrency:
+  group: release-${{ github.ref }}
+  # Never cancel a run mid-notarization or mid-upload; a newer push waits its turn.
+  cancel-in-progress: false
+
+env:
+  CARGO_TERM_COLOR: always
+  CARGO_INCREMENTAL: 0
+
+jobs:
+  version:
+    runs-on: ubuntu-24.04
+    outputs:
+      version: ${{ steps.v.outputs.version }}
+      prerelease: ${{ steps.v.outputs.prerelease }}
+      draft: ${{ steps.v.outputs.draft }}
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - id: v
+        name: Resolve the version
+        env:
+          REQUEST_DRAFT: ${{ github.event_name == 'push' || inputs.draft }}
+        run: |
+          . packaging/env.sh
+          if ! printf '%s' "$VERSION" | grep -Eq '^(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)(-[0-9A-Za-z-]+(\.[0-9A-Za-z-]+)*)?$'; then
+            echo "::error::Cargo.toml must contain a version like 1.2.3 or 1.2.3-rc.1, not '$VERSION'"
+            exit 1
+          fi
+          if [ "$REQUEST_DRAFT" = true ] && [ "$GITHUB_REF" != refs/heads/main ]; then
+            echo "::error::Draft releases are built from main only"
+            exit 1
+          fi
+          case "$VERSION" in *-*) pre=true ;; *) pre=false ;; esac
+          { echo "version=$VERSION"; echo "prerelease=$pre"; echo "draft=$REQUEST_DRAFT"; } >>"$GITHUB_OUTPUT"
+          echo "### FieldCraft v$VERSION (\`${GITHUB_SHA::9}\`)" >>"$GITHUB_STEP_SUMMARY"
+
+  macos:
+    name: macOS universal
+    needs: version
+    runs-on: macos-14
+    timeout-minutes: 120
+    outputs:
+      signing: ${{ steps.package.outputs.signing }}
+    env:
+      FIELDCRAFT_VERSION: ${{ needs.version.outputs.version }}
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          targets: aarch64-apple-darwin, x86_64-apple-darwin
+      - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
+        with:
+          key: release-macos-universal
+          # Release runs are rare: only release-branch runs keep a cache, so dry runs don't evict CI's.
+          save-if: ${{ github.ref == 'refs/heads/main' }}
+      - name: Import the signing certificate (skipped without APPLE_CERTIFICATE)
+        env:
+          APPLE_CERTIFICATE: ${{ secrets.APPLE_CERTIFICATE }}
+          APPLE_CERTIFICATE_PASSWORD: ${{ secrets.APPLE_CERTIFICATE_PASSWORD }}
+          KEYCHAIN_PASSWORD: ${{ secrets.KEYCHAIN_PASSWORD }}
+        run: packaging/macos/import-cert.sh
+      - name: Build, sign, notarize and package (the dmg is mounted and checked)
+        id: package
+        env:
+          APPLE_ID: ${{ secrets.APPLE_ID }}
+          APPLE_PASSWORD: ${{ secrets.APPLE_PASSWORD }}
+          APPLE_TEAM_ID: ${{ secrets.APPLE_TEAM_ID }}
+        run: packaging/macos/package.sh --arch universal
+      - uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
+        with:
+          name: release-macos
+          path: dist/release/*
+          if-no-files-found: error
+      - name: Remove the temporary keychain
+        if: always()
+        run: |
+          if [ -n "${MACOS_KEYCHAIN:-}" ]; then security delete-keychain "$MACOS_KEYCHAIN" || true; fi
+
+  linux:
+    name: Linux x86_64
+    needs: version
+    # The oldest GitHub-hosted image, so the binaries need only glibc >= 2.35.
+    runs-on: ubuntu-22.04
+    timeout-minutes: 90
+    env:
+      FIELDCRAFT_VERSION: ${{ needs.version.outputs.version }}
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - name: Install packaging tools
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends desktop-file-utils
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
+        with:
+          key: release-linux-x86_64
+          # Release runs are rare: only release-branch runs keep a cache, so dry runs don't evict CI's.
+          save-if: ${{ github.ref == 'refs/heads/main' }}
+      - name: Build and package (tar.gz, AppImage)
+        run: packaging/linux/package.sh
+      - name: Check the packages
+        run: |
+          . packaging/env.sh
+          list="$(tar -tzf dist/release/*.tar.gz)"
+          for f in bin/fieldcraft bin/fieldcraft-cli "share/applications/$APP_ID.desktop" \
+            share/doc/fieldcraft/THIRD-PARTY-LICENSES.txt; do
+            grep -Fx -- "fieldcraft-$VERSION-linux-x86_64/$f" <<<"$list"
+          done
+          ldd target/release/fieldcraft
+          for appimage in dist/release/*.AppImage; do
+            chmod +x "$appimage"
+            APPIMAGE_EXTRACT_AND_RUN=1 "$appimage" --version
+          done
+      - uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
+        with:
+          name: release-linux-x86_64
+          path: dist/release/*
+          if-no-files-found: error
+
+  windows:
+    name: Windows x64
+    needs: version
+    runs-on: windows-latest
+    timeout-minutes: 90
+    env:
+      FIELDCRAFT_VERSION: ${{ needs.version.outputs.version }}
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          targets: x86_64-pc-windows-msvc
+      - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
+        with:
+          key: release-windows-x64
+          # Release runs are rare: only release-branch runs keep a cache, so dry runs don't evict CI's.
+          save-if: ${{ github.ref == 'refs/heads/main' }}
+      - name: Build and package (zip)
+        shell: pwsh
+        run: ./packaging/windows/package.ps1
+      - uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
+        with:
+          name: release-windows-x64
+          path: dist/release/*
+          if-no-files-found: error
+
+  release:
+    name: Draft release (or dry-run artifacts)
+    needs: [version, macos, linux, windows]
+    runs-on: ubuntu-24.04
+    permissions:
+      contents: write
+    env:
+      VERSION: ${{ needs.version.outputs.version }}
+      PRERELEASE: ${{ needs.version.outputs.prerelease }}
+      MACOS_SIGNING: ${{ needs.macos.outputs.signing }}
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      GH_REPO: ${{ github.repository }}
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - uses: actions/download-artifact@9000827ccba6bdab643e8b6fd33ac0654aef8333 # v8.0.2
+        with:
+          pattern: release-*
+          path: artifacts
+          merge-multiple: true
+      - name: Check the set, checksums and notes
+        run: |
+          for f in "fieldcraft-$VERSION-macos-universal.dmg" "fieldcraft-cli-$VERSION-macos-universal.zip" \
+            "fieldcraft-$VERSION-linux-x86_64.tar.gz" "fieldcraft-$VERSION-linux-x86_64.AppImage" \
+            "fieldcraft-$VERSION-windows-x64.zip"; do
+            test -s "artifacts/$f" || { echo "::error::missing $f"; exit 1; }
+          done
+          (cd artifacts && sha256sum -- * | tee SHA256SUMS.txt)
+          # The macOS paragraph says how the app was signed (packaging/macos/package.sh).
+          case "$MACOS_SIGNING" in
+            notarized) macos="The macOS app is signed with a Developer ID and notarized by Apple." ;;
+            signed) macos="The macOS app is signed with a Developer ID but **not notarized**: the first time, right-click \`FieldCraft.app\` in Applications and choose **Open**." ;;
+            *) macos="The macOS app is **ad-hoc signed and not notarized**: macOS blocks the first launch. Right-click \`FieldCraft.app\` in Applications and choose **Open** (then **Open** again), or run \`xattr -dr com.apple.quarantine /Applications/FieldCraft.app\`." ;;
+          esac
+          awk -v v="$VERSION" -v m="$macos" '{ gsub(/\{version\}/, v); gsub(/\{macos_signing\}/, m); print }' \
+            .github/release-notes.md >notes.md
+          cat notes.md >>"$GITHUB_STEP_SUMMARY"
+      - name: Upload the dry-run artifacts
+        if: needs.version.outputs.draft != 'true'
+        uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
+        with:
+          name: release-assets
+          path: |
+            artifacts/*
+            notes.md
+          if-no-files-found: error
+      - name: Create or update the draft release
+        if: needs.version.outputs.draft == 'true'
+        working-directory: artifacts
+        run: |
+          tag="v$VERSION"
+          title="FieldCraft v$VERSION"
+          if gh api "repos/$GH_REPO/git/matching-refs/tags/$tag" --jq '.[].ref' | grep -Fxq "refs/tags/$tag"; then
+            echo "::error::Tag $tag already exists. Choose a new version; never move a release tag."
+            exit 1
+          fi
+          if draft="$(gh release view "$tag" --json isDraft --jq .isDraft 2>/dev/null)"; then
+            if [ "$draft" != true ]; then
+              echo "::error::Release $tag is already published. Bump the version before releasing."
+              exit 1
+            fi
+            # A rebuild of the same version replaces the draft's assets (removing names it no longer
+            # makes); its notes are kept.
+            assets="$(gh release view "$tag" --json assets --jq '.assets[].name')"
+            while IFS= read -r asset; do
+              if [ -n "$asset" ]; then gh release delete-asset "$tag" "$asset" --yes; fi
+            done <<<"$assets"
+            gh release edit "$tag" --draft --title "$title" --target "$GITHUB_SHA" --prerelease="$PRERELEASE"
+            gh release upload "$tag" -- *
+          else
+            gh release create "$tag" --draft --title "$title" --target "$GITHUB_SHA" \
+              --notes-file ../notes.md --generate-notes --prerelease="$PRERELEASE" -- *
+          fi
+          echo "Draft release **$title** at \`${GITHUB_SHA::9}\`: $(gh release view "$tag" --json url --jq .url)" >>"$GITHUB_STEP_SUMMARY"

AGENTS.md

@@ -99,7 +99,7 @@ People trust FieldCraft with their models; a crash loses their work. **This outr
   1. Work in your own worktree on a branch, with your own `CARGO_TARGET_DIR`. While you work:
      `cargo check` and the tests of the crates you touch (`cargo test -p <crate>`). Commit after
      each working step (a layer that compiles with its tests passing), not one big commit per PR.
-     Every commit lands on `main` as it is, so each one must build and pass its tests and say
+     Every commit lands on `develop` as it is, so each one must build and pass its tests and say
      what it does: `git bisect` walks them one by one.
   2. When the change is done: review it once with `/simplify`, then `cargo fmt --all` and
      `cargo clippy -p <crate> --all-targets -- -D warnings` for each crate you touched, once.
@@ -108,29 +108,34 @@ People trust FieldCraft with their models; a crash loses their work. **This outr
      oracle cases or solver numerics change (`cargo xtask oracle`).
   3. Fold every fix into the commit it fixes, never a separate "fmt", "clippy", "review fixes" or
      "regenerate features.md" commit: `git commit --fixup <sha>`, then
-     `git rebase -i --autosquash origin/main` (`GIT_SEQUENCE_EDITOR=true` keeps it
+     `git rebase -i --autosquash origin/develop` (`GIT_SEQUENCE_EDITOR=true` keeps it
      non-interactive). A regenerated page goes into the commit that changed what it lists.
-  4. Rebase onto the latest `origin/main` (never merge `main` into a branch), rerun the tests of
-     the touched crates, push, open the PR and merge it yourself with a rebase merge, which keeps
-     `main` linear and every commit bisectable: `gh pr merge <N> --rebase --delete-branch`, run as
-     its own command. Never squash. Then remove your worktree and delete your local branch.
+  4. Branch from and rebase onto the latest `origin/develop`, the trunk (never merge `develop` into
+     a branch), rerun the tests of
+     the touched crates, push, open the PR and merge it with a rebase merge, which keeps `develop`
+     linear and every commit bisectable. `develop` and `main` are protected (CODEOWNERS review, linear history,
+     rebase merges only); the core team merges as the maintainer with
+     `gh pr merge <N> --rebase --admin --delete-branch`, run as its own command. Outside
+     contributors' pull requests wait for the maintainer's review (CONTRIBUTING.md). Never squash.
+     Then remove your worktree and delete your local branch.
   5. Never run the full gate locally: no `cargo xtask ci`, no `cargo clippy --workspace`, no
      `cargo xtask wasm` or `oracle` unless step 2 calls for it. Never watch CI. GitHub CI runs
      `cargo xtask ci` (fmt, assets, licences, layers, clippy -D warnings, tests, wasm), the
-     oracle, the heavy tests and the advisories once per merge on `main`; the coordinator
+     oracle, the heavy tests and the advisories once per merge on `develop`; the coordinator
      watches it and sends a failure back to the change that caused it, which is fixed forward
      at once.
-- **Keep the main gate fast** (under ~3 minutes on CI). A test that takes more than a few seconds
+- **Keep the trunk gate fast** (under ~3 minutes on CI). A test that takes more than a few seconds
   (convergence studies, the whole corpus, cross-checks between solvers) is
   `#[ignore = "heavy: cargo xtask test --heavy (CI heavy job)"]`, with a fast representative
-  test left in the main gate. The `heavy` CI job runs `cargo xtask test --heavy` (every ignored
-  test, benchmarks included, and the doc tests) on every merge to `main`, nightly and on
+  test left in the trunk gate. The `heavy` CI job runs `cargo xtask test --heavy` (every ignored
+  test, benchmarks included, and the doc tests) on every merge to `develop`, nightly and on
   demand (`gh workflow run CI --ref <branch>`). Hostile-input tests run commands on sessions with small
   work caps (`Session::limits`) so refusals are instant; never lower the production caps for a
   test.
 - **Publishing**: `origin` is github.com/jyviko/fieldcraft. Changes land through pull requests
   as the workflow above describes; the coordinator reads every merged diff and sends findings
-  back as fix-forward work. Never force-push `main`. Never commit `plan/`, `.agent-files/`,
+  back as fix-forward work. Never force-push `develop` or `main`; `main` holds released code and moves only by
+  fast-forward at a release (docs/releasing.md). Never commit `plan/`, `.agent-files/`,
   `worktrees/` or `target*/`; check `git ls-files` before pushing.
 
 ## Running

ATTRIBUTION.md

@@ -15,6 +15,7 @@ is committed and listed here with its exports.
 | File | Author | Source | Licence |
 |---|---|---|---|
 | docs/media/ibeam-analysis.mp4, docs/media/ibeam-analysis.gif | FieldCraft contributors | Original: the FieldCraft window captured during an MCP session, generated by `tools/demo-video/make.py` | MIT OR Apache-2.0 |
+| docs/media/bracket-partition.png, docs/media/bracket-hex.png, docs/media/bracket-stress.png, docs/media/setup-symbols.png | FieldCraft contributors | Original: FieldCraft renders (headless MCP screenshots and a window capture) of corpus parts and the cantilever sample | MIT OR Apache-2.0 |
 | crates/decks/tests/golden/nastran/*.bdf | FieldCraft contributors | Written by our Nastran writer from our own test models (crates/decks/tests/nastran.rs) | MIT OR Apache-2.0 |
 | assets/icons/assembly.instance.svg, assets/icons/assembly.instance.vectorcraft | FieldCraft contributors | Original toolbar icon drawn with VectorCraft from `assets/icons/src/assembly.instance.json` (`cargo xtask icons`) | MIT OR Apache-2.0 |
 | assets/icons/deck.read.svg, assets/icons/deck.read.vectorcraft | FieldCraft contributors | Original toolbar icon drawn with VectorCraft from `assets/icons/src/deck.read.json` (`cargo xtask icons`) | MIT OR Apache-2.0 |
@@ -48,6 +49,7 @@ is committed and listed here with its exports.
 | assets/icons/mesh.element.add.svg, assets/icons/mesh.element.add.vectorcraft | FieldCraft contributors | Original toolbar icon drawn with VectorCraft from `assets/icons/src/mesh.element.add.json` (`cargo xtask icons`) | MIT OR Apache-2.0 |
 | assets/icons/mesh.hex.decompose.svg, assets/icons/mesh.hex.decompose.vectorcraft | FieldCraft contributors | Original toolbar icon drawn with VectorCraft from `assets/icons/src/mesh.hex.decompose.json` (`cargo xtask icons`) | MIT OR Apache-2.0 |
 | assets/icons/mesh.hex.dominant.svg, assets/icons/mesh.hex.dominant.vectorcraft | FieldCraft contributors | Original toolbar icon drawn with VectorCraft from `assets/icons/src/mesh.hex.dominant.json` (`cargo xtask icons`) | MIT OR Apache-2.0 |
+| assets/icons/mesh.hex.blocks.svg, assets/icons/mesh.hex.blocks.vectorcraft | FieldCraft contributors | Original toolbar icon drawn with VectorCraft from `assets/icons/src/mesh.hex.blocks.json` (`cargo xtask icons`) | MIT OR Apache-2.0 |
 | assets/icons/mesh.hex.mapped.svg, assets/icons/mesh.hex.mapped.vectorcraft | FieldCraft contributors | Original toolbar icon drawn with VectorCraft from `assets/icons/src/mesh.hex.mapped.json` (`cargo xtask icons`) | MIT OR Apache-2.0 |
 | assets/icons/mesh.hex.octree.svg, assets/icons/mesh.hex.octree.vectorcraft | FieldCraft contributors | Original toolbar icon drawn with VectorCraft from `assets/icons/src/mesh.hex.octree.json` (`cargo xtask icons`) | MIT OR Apache-2.0 |
 | assets/icons/mesh.hex.polycube.svg, assets/icons/mesh.hex.polycube.vectorcraft | FieldCraft contributors | Original toolbar icon drawn with VectorCraft from `assets/icons/src/mesh.hex.polycube.json` (`cargo xtask icons`) | MIT OR Apache-2.0 |
@@ -132,12 +134,11 @@ is committed and listed here with its exports.
 | assets/icons/ui.sun.svg, assets/icons/ui.sun.vectorcraft | FieldCraft contributors | Original interface icon (navigation bar, title bar, browser) drawn with VectorCraft from `assets/icons/src/ui.sun.json` (`cargo xtask icons`) | MIT OR Apache-2.0 |
 | assets/icons/ui.views.svg, assets/icons/ui.views.vectorcraft | FieldCraft contributors | Original interface icon (navigation bar, title bar, browser) drawn with VectorCraft from `assets/icons/src/ui.views.json` (`cargo xtask icons`) | MIT OR Apache-2.0 |
 | assets/icons/ui.zoom.svg, assets/icons/ui.zoom.vectorcraft | FieldCraft contributors | Original interface icon (navigation bar, title bar, browser) drawn with VectorCraft from `assets/icons/src/ui.zoom.json` (`cargo xtask icons`) | MIT OR Apache-2.0 |
-| assets/app-icon/icon.vectorcraft, assets/app-icon/icon.svg, assets/app-icon/icon.png | FieldCraft contributors | Original application icon (an L bracket with a bolt hole under a structured hexahedral mesh, on a rounded-square backdrop), drawn with VectorCraft by `cargo xtask app-icon` (xtask/src/app_icon.rs); editable source, SVG and 1024 × 1024 PNG export | MIT OR Apache-2.0 |
-| assets/app-icon/icon-small.vectorcraft, assets/app-icon/icon-small.svg, assets/app-icon/icon-small.png | FieldCraft contributors | Original simplified application icon for 16–32 px (no mesh or floor grid), drawn with VectorCraft by `cargo xtask app-icon` (xtask/src/app_icon.rs) | MIT OR Apache-2.0 |
+| assets/app-icon/icon.vectorcraft, assets/app-icon/icon.svg, assets/app-icon/icon.png | FieldCraft contributors | Original application icon (a hexahedral-meshed cube with a banded colour fringe on its faces on a rounded-square backdrop), drawn with VectorCraft by `cargo xtask app-icon` (xtask/src/app_icon.rs); editable source, SVG and 1024 × 1024 PNG export | MIT OR Apache-2.0 |
+| assets/app-icon/icon-small.vectorcraft, assets/app-icon/icon-small.svg, assets/app-icon/icon-small.png | FieldCraft contributors | Original simplified application icon for 16–32 px (the fringe cube alone; no mesh or floor grid), drawn with VectorCraft by `cargo xtask app-icon` (xtask/src/app_icon.rs) | MIT OR Apache-2.0 |
 | assets/app-icon/layers/01-floor.vectorcraft, assets/app-icon/FieldCraft.icon/Assets/01-floor.svg | FieldCraft contributors | Original isometric floor grid with a radial fade (Default appearance), drawn with VectorCraft by `cargo xtask app-icon` (xtask/src/app_icon.rs) | MIT OR Apache-2.0 |
 | assets/app-icon/layers/01-floor-dark.vectorcraft, assets/app-icon/FieldCraft.icon/Assets/01-floor-dark.svg | FieldCraft contributors | Original isometric floor grid with a radial fade (Dark appearance), drawn with VectorCraft by `cargo xtask app-icon` (xtask/src/app_icon.rs) | MIT OR Apache-2.0 |
-| assets/app-icon/layers/02-part.vectorcraft, assets/app-icon/FieldCraft.icon/Assets/02-part.svg | FieldCraft contributors | Original bracket faces with transparent gaps at the shared edges, drawn with VectorCraft by `cargo xtask app-icon` (xtask/src/app_icon.rs) | MIT OR Apache-2.0 |
-| assets/app-icon/layers/03-mesh.vectorcraft, assets/app-icon/FieldCraft.icon/Assets/03-mesh.svg | FieldCraft contributors | Original hexahedral mesh lines (O-grid around the hole) clipped to the bracket's faces, drawn with VectorCraft by `cargo xtask app-icon` (xtask/src/app_icon.rs) | MIT OR Apache-2.0 |
+| assets/app-icon/layers/02-part.vectorcraft, assets/app-icon/FieldCraft.icon/Assets/02-part.svg | FieldCraft contributors | Original cube faces with a banded colour fringe and transparent gaps at the shared edges, and the hexahedral mesh lines clipped to them, drawn with VectorCraft by `cargo xtask app-icon` (xtask/src/app_icon.rs) | MIT OR Apache-2.0 |
 | assets/app-icon/FieldCraft.icon/icon.json | FieldCraft contributors | Icon Composer composition of the layers above (Default and Dark floor grid), written by `cargo xtask app-icon` (xtask/src/app_icon.rs) | MIT OR Apache-2.0 |
 | assets/app-icon/Assets.car | FieldCraft contributors | Apple actool compilation of assets/app-icon/FieldCraft.icon; contains original artwork only | MIT OR Apache-2.0 |
 | assets/app-icon/icon.icns | FieldCraft contributors | iconutil compilation of assets/app-icon/icon.iconset | MIT OR Apache-2.0 |
@@ -152,6 +153,7 @@ is committed and listed here with its exports.
 | assets/app-icon/icon.iconset/icon_256x256@2x.png | FieldCraft contributors | sips export (512 px) of assets/app-icon/icon.png | MIT OR Apache-2.0 |
 | assets/app-icon/icon.iconset/icon_512x512.png | FieldCraft contributors | sips export (512 px) of assets/app-icon/icon.png | MIT OR Apache-2.0 |
 | assets/app-icon/icon.iconset/icon_512x512@2x.png | FieldCraft contributors | sips export (1024 px) of assets/app-icon/icon.png | MIT OR Apache-2.0 |
+| packaging/macos/README.txt, packaging/linux/io.github.jyviko.fieldcraft.desktop, packaging/macos/entitlements.plist | FieldCraft contributors | Original packaging text: the disk image's install note, the Linux desktop entry and the (empty) hardened-runtime entitlements | MIT OR Apache-2.0 |
 | crates/ui-egui/fonts/Inter-SemiBold.ttf | The Inter Project Authors | https://github.com/rsms/inter release v4.1 (Inter-4.1.zip, extras/ttf/Inter-SemiBold.ttf), unmodified; licence text in crates/ui-egui/fonts/OFL.txt; the interface's caps labels (theme::LABEL_FAMILY) | SIL OFL 1.1 |
 
 ## Adapted code
@@ -169,6 +171,15 @@ is committed and listed here with its exports.
 | apps/fieldcraft/src/control_server.rs | SolidCraft `apps/solidcraft/src/control_server.rs` | MIT OR Apache-2.0 |
 | crates/mcp/src/ (JSON-RPC framing, MCP lifecycle, tool schema checks, the control-channel backend, base64) | SolidCraft `crates/mcp/src/` | MIT OR Apache-2.0 |
 | crates/io/src/roots.rs (the rules of read and write roots) | VectorCraft's automation roots (docs/mcp.md there) | MIT OR Apache-2.0 |
+| packaging/env.sh, packaging/.shellcheckrc, packaging/macos/package.sh, packaging/macos/Info.plist.in, packaging/linux/package.sh, packaging/linux/AppRun, packaging/windows/package.ps1 | SolidCraft `packaging/` and VectorCraft `packaging/` (signing and notarization in macos/package.sh) | MIT OR Apache-2.0 |
+| packaging/macos/import-cert.sh | VectorCraft `packaging/macos/import-cert.sh` | MIT OR Apache-2.0 |
+| packaging/windows/check-exe.ps1 | SolidCraft `packaging/windows/check-icon.ps1` | MIT OR Apache-2.0 |
+| apps/fieldcraft-web/ (the web runner, browser file services and downloads, Trunk configuration, index.html) | VectorCraft `apps/vectorcraft-web/` and SolidCraft `apps/solidcraft-web/` | MIT OR Apache-2.0 |
+| crates/io/src/memory.rs (files kept in memory for the browser build) | SolidCraft `crates/io/src/vfs.rs` | MIT OR Apache-2.0 |
+| .github/workflows/pages.yml | SolidCraft `.github/workflows/pages.yml` | MIT OR Apache-2.0 |
+| .github/workflows/release.yml, .github/release-notes.md, docs/releasing.md | SolidCraft `.github/workflows/release.yml`, `.github/release-notes.md`, `docs/releasing.md`; VectorCraft `.github/workflows/release.yml` | MIT OR Apache-2.0 |
+| .github/workflows/packaging-lint.yml | SolidCraft `.github/workflows/packaging-lint.yml` (itself adapted from PhotoCraft, https://github.com/storytold/photocraft, Apache-2.0) | MIT OR Apache-2.0 |
+| .github/workflows/arch-check.yml (the riscv64 cross build) | SolidCraft `.github/workflows/ci.yml` (`riscv64-gates`) | MIT OR Apache-2.0 |
 
 ## Test oracles
 

CODE_OF_CONDUCT.md

@@ -0,0 +1,16 @@
+# Code of conduct
+
+FieldCraft is built in the open by people with different backgrounds and levels of experience.
+Everyone taking part — in issues, pull requests, reviews and discussions — is expected to:
+
+- be respectful and assume good intent; criticise work, never people;
+- keep discussion technical, specific and on topic;
+- not harass, insult, demean or discriminate against anyone, publicly or privately;
+- respect the project's decisions on scope, licences and clean-room rules.
+
+The maintainer may edit or remove comments, close threads, and block anyone who does not follow
+this code. Report problems privately to the maintainer through the contact on the GitHub
+profile of [@jyviko](https://github.com/jyviko).
+
+This code is our own, written in the spirit of the
+[Contributor Covenant](https://www.contributor-covenant.org/).

CONTRIBUTING.md

@@ -1,10 +1,80 @@
-# Contributing
+# Contributing to FieldCraft
 
-Thanks for helping. Read [AGENTS.md](AGENTS.md) first: it holds the rules every change follows,
-whether a person or an agent writes it.
+FieldCraft is one open-source modeler for structures, heat and fluids, written in pure Rust: open a
+parametric SolidCraft part, mesh it (tet or all-hex), define the analysis, solve it with our own
+implicit, explicit, thermal or lattice Boltzmann solvers, and look at verified results — from the
+desktop app, the command line, or an AI agent over MCP.
 
-1. Branch from `main`, keep a pull request to one topic.
-2. Run `cargo xtask ci` before pushing; CI runs the same gates.
+Help is welcome, whether that's a one-line fix, a verification benchmark, a file format or owning a
+whole solver. This page covers how to build it, the few rules that aren't negotiable, where help is
+needed most, and how to claim work. The rules every change follows, by a person or an agent, are in
+[AGENTS.md](AGENTS.md).
+
+## Get it running (about 10 minutes on a fast machine)
+
+You need stable Rust 1.95 or newer.
+
+```sh
+git clone https://github.com/jyviko/fieldcraft && cd fieldcraft
+cargo run --release -p fieldcraft -- --sample cantilever   # the desktop app on a sample model
+cargo run -p fieldcraft-cli -- commands                    # every command and its parameters
+cargo test -p fieldcraft-solver                            # the tests of one crate
+cargo xtask oracle --quick                                 # the verification cases (docs/oracle.md)
+```
+
+`develop` is the trunk and `main` holds released code. The layers and crates are in
+[docs/architecture.md](docs/architecture.md); every user-visible capability is a command in
+`crates/engine/src/cmd/` ([docs/features.md](docs/features.md) lists them).
+
+## Where help is wanted most
+
+See the [`help wanted`](https://github.com/jyviko/fieldcraft/labels/help%20wanted) and
+[`good first issue`](https://github.com/jyviko/fieldcraft/labels/good%20first%20issue) labels, and
+the `area:` labels for your field. In order of how much they would help users:
+
+1. **Reproducible meshes** ([#115](https://github.com/jyviko/fieldcraft/issues/115)). The same part
+   must give the same tet mesh on every platform and every run, as the solvers already do.
+2. **All-hex meshing of thin and curved parts** ([#85](https://github.com/jyviko/fieldcraft/issues/85)).
+   The octree mesher over-refines thin walls; concave transition templates and an up-front depth
+   are next. Hex meshing is the centre of gravity of the project.
+3. **Getting results in and out**: ParaView export ([#90](https://github.com/jyviko/fieldcraft/issues/90)),
+   Gmsh import ([#91](https://github.com/jyviko/fieldcraft/issues/91)), Abaqus deck reading
+   ([#98](https://github.com/jyviko/fieldcraft/issues/98)), CSV and STL
+   ([#92](https://github.com/jyviko/fieldcraft/issues/92), [#93](https://github.com/jyviko/fieldcraft/issues/93)).
+4. **Verification benchmarks** ([#97](https://github.com/jyviko/fieldcraft/issues/97),
+   [#106](https://github.com/jyviko/fieldcraft/issues/106)). An engineer with a published benchmark
+   can add it as an oracle case without touching solver code.
+5. **Nonlinear elements and materials**: incompatible modes at finite strain
+   ([#82](https://github.com/jyviko/fieldcraft/issues/82)), kinematic hardening
+   ([#81](https://github.com/jyviko/fieldcraft/issues/81)), and the material library
+   ([#99](https://github.com/jyviko/fieldcraft/issues/99)).
+6. **The app**: typed command forms ([#112](https://github.com/jyviko/fieldcraft/issues/112)), XY and
+   path plots ([#94](https://github.com/jyviko/fieldcraft/issues/94), [#95](https://github.com/jyviko/fieldcraft/issues/95)).
+
+Bigger areas on the [roadmap](ROADMAP.md) — contact, dynamics, composites, coupled fields, wave
+propagation, turbulence — are open to anyone who wants to own one: start a thread in
+[Discussions](https://github.com/jyviko/fieldcraft/discussions).
+
+## Before you start: claim an issue
+
+Every change starts from an issue, and only the maintainer merges.
+
+1. Pick an open issue labelled **help wanted** or **good first issue** that is not labelled
+   **claimed**. If what you want to do has no issue, open one first and wait for a reply.
+2. Comment that you would like to take it. The maintainer assigns it to you and labels it
+   **claimed**; then it is yours. Work on unassigned issues may not be accepted.
+3. Open a draft pull request early, linked with `Closes #N`. An issue with no visible progress
+   for 14 days goes back to the pool.
+
+Issues labelled **in progress** are being worked on by the core team; please don't start on them.
+
+## Making the change
+
+1. Branch from `develop` (the trunk; `main` holds released code only) and open the pull request
+   against `develop`. Keep it to one topic.
+2. Before pushing: `cargo fmt --all`, and `cargo clippy -p <crate> --all-targets -- -D warnings`
+   and `cargo test -p <crate>` for the crates you touched. CI runs the full gate on your pull
+   request once the maintainer approves the run.
 3. User-visible behaviour is a command (`crates/engine/src/cmd/`) with tests, including hostile
    parameters.
 4. Meshing and solver algorithms cite the paper they come from in the module docs.
@@ -12,3 +82,8 @@ whether a person or an agent writes it.
    (see [docs/adr/0001-libraries.md](docs/adr/0001-libraries.md)).
 
 By contributing you agree your work is licensed under MIT OR Apache-2.0.
+
+`develop` and `main` are protected: changes land on `develop` only through pull requests that the
+maintainer has reviewed,
+as rebase merges (keep each commit building and passing its tests). Be kind: see the
+[code of conduct](CODE_OF_CONDUCT.md).

Cargo.lock

@@ -425,6 +425,12 @@ version = "1.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f2032f911046de80f0a198e0901378627c33f59ea0ac00e363d481118bd70a53"
 
+[[package]]
+name = "base64"
+version = "0.22.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72b3254f16251a8381aa12e40e3c4d2f0199f8c6508fbecb9d91f575e0fbb8c6"
+
 [[package]]
 name = "bit-set"
 version = "0.10.0"
@@ -461,6 +467,15 @@ dependencies = [
  "generic-array",
 ]
 
+[[package]]
+name = "block-buffer"
+version = "0.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d2f6c7dbe95a6ed67ad9f18e57daf93a2f034c524b99fd2b76d18fdfeb6660aa"
+dependencies = [
+ "hybrid-array",
+]
+
 [[package]]
 name = "block2"
 version = "0.5.1"
@@ -694,6 +709,12 @@ dependencies = [
  "crossbeam-utils",
 ]
 
+[[package]]
+name = "const-oid"
+version = "0.10.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a6ef517f0926dd24a1582492c791b6a4818a4d94e789a334894aa15b0d12f55c"
+
 [[package]]
 name = "convert_case"
 version = "0.4.0"
@@ -749,6 +770,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "cpufeatures"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5ca28b0ae3115b884660db4118d803791fd6756b6e88f39c0f3f7859060d7566"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "craft-ui"
 version = "0.1.0"
@@ -807,6 +837,15 @@ dependencies = [
  "typenum",
 ]
 
+[[package]]
+name = "crypto-common"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ce6e4c961d6cd6c9a86db418387425e8bdeaf05b3c8bc1411e6dca4c252f1453"
+dependencies = [
+ "hybrid-array",
+]
+
 [[package]]
 name = "cursor-icon"
 version = "1.2.0"
@@ -849,8 +888,19 @@ version = "0.10.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9ed9a281f7bc9b7576e61468ba615a66a5c8cfdff42420a70aa82701a3b1e292"
 dependencies = [
- "block-buffer",
- "crypto-common",
+ "block-buffer 0.10.4",
+ "crypto-common 0.1.7",
+]
+
+[[package]]
+name = "digest"
+version = "0.11.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f1dd6dbb5841937940781866fa1281a1ff7bd3bf827091440879f9994983d5c2"
+dependencies = [
+ "block-buffer 0.12.1",
+ "const-oid",
+ "crypto-common 0.2.2",
 ]
 
 [[package]]
@@ -1035,6 +1085,20 @@ dependencies = [
  "bytemuck",
 ]
 
+[[package]]
+name = "embed-resource"
+version = "3.0.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6168487b5e7eb2673e6efe1200b1848016e436a6ca0b8031bf04bd9d493a249f"
+dependencies = [
+ "cc",
+ "memchr",
+ "rustc_version",
+ "toml",
+ "vswhom",
+ "winreg",
+]
+
 [[package]]
 name = "endi"
 version = "1.1.1"
@@ -1173,10 +1237,11 @@ checksum = "b97b65636e5b9ef369943878ac74335ba1c55c1cb6adbf1e2c293c624248d693"
 
 [[package]]
 name = "fieldcraft"
-version = "0.1.0"
+version = "0.5.5"
 dependencies = [
  "eframe",
  "egui",
+ "embed-resource",
  "fieldcraft-engine",
  "fieldcraft-io",
  "fieldcraft-ui-egui",
@@ -1187,7 +1252,7 @@ dependencies = [
 
 [[package]]
 name = "fieldcraft-cli"
-version = "0.1.0"
+version = "0.5.5"
 dependencies = [
  "fieldcraft-engine",
  "fieldcraft-io",
@@ -1197,7 +1262,7 @@ dependencies = [
 
 [[package]]
 name = "fieldcraft-decks"
-version = "0.1.0"
+version = "0.5.5"
 dependencies = [
  "fieldcraft-model",
  "serde_json",
@@ -1206,7 +1271,7 @@ dependencies = [
 
 [[package]]
 name = "fieldcraft-engine"
-version = "0.1.0"
+version = "0.5.5"
 dependencies = [
  "fieldcraft-decks",
  "fieldcraft-explicit",
@@ -1228,7 +1293,7 @@ dependencies = [
 
 [[package]]
 name = "fieldcraft-explicit"
-version = "0.1.0"
+version = "0.5.5"
 dependencies = [
  "fieldcraft-fem",
  "fieldcraft-model",
@@ -1239,7 +1304,7 @@ dependencies = [
 
 [[package]]
 name = "fieldcraft-fem"
-version = "0.1.0"
+version = "0.5.5"
 dependencies = [
  "fieldcraft-model",
  "thiserror 2.0.21",
@@ -1247,7 +1312,7 @@ dependencies = [
 
 [[package]]
 name = "fieldcraft-geometry"
-version = "0.1.0"
+version = "0.5.5"
 dependencies = [
  "fieldcraft-model",
  "quick-xml",
@@ -1263,20 +1328,20 @@ dependencies = [
 
 [[package]]
 name = "fieldcraft-io"
-version = "0.1.0"
+version = "0.5.5"
 dependencies = [
  "fieldcraft-model",
  "log",
  "serde",
  "serde_json",
- "sha2",
+ "sha2 0.11.1",
  "thiserror 2.0.21",
  "zip",
 ]
 
 [[package]]
 name = "fieldcraft-lbm"
-version = "0.1.0"
+version = "0.5.5"
 dependencies = [
  "fieldcraft-mesh",
  "fieldcraft-model",
@@ -1286,7 +1351,7 @@ dependencies = [
 
 [[package]]
 name = "fieldcraft-mcp"
-version = "0.1.0"
+version = "0.5.5"
 dependencies = [
  "fieldcraft-engine",
  "fieldcraft-io",
@@ -1297,7 +1362,7 @@ dependencies = [
 
 [[package]]
 name = "fieldcraft-mesh"
-version = "0.1.0"
+version = "0.5.5"
 dependencies = [
  "fieldcraft-model",
  "num-bigint",
@@ -1309,7 +1374,7 @@ dependencies = [
 
 [[package]]
 name = "fieldcraft-model"
-version = "0.1.0"
+version = "0.5.5"
 dependencies = [
  "serde",
  "serde_json",
@@ -1318,14 +1383,14 @@ dependencies = [
 
 [[package]]
 name = "fieldcraft-parallel"
-version = "0.1.0"
+version = "0.5.5"
 dependencies = [
  "rayon",
 ]
 
 [[package]]
 name = "fieldcraft-render"
-version = "0.1.0"
+version = "0.5.5"
 dependencies = [
  "fieldcraft-model",
  "png",
@@ -1335,9 +1400,10 @@ dependencies = [
 
 [[package]]
 name = "fieldcraft-solver"
-version = "0.1.0"
+version = "0.5.5"
 dependencies = [
  "fieldcraft-fem",
+ "fieldcraft-mesh",
  "fieldcraft-model",
  "fieldcraft-parallel",
  "serde",
@@ -1346,7 +1412,7 @@ dependencies = [
 
 [[package]]
 name = "fieldcraft-testkit"
-version = "0.1.0"
+version = "0.5.5"
 dependencies = [
  "fieldcraft-engine",
  "fieldcraft-geometry",
@@ -1357,7 +1423,7 @@ dependencies = [
 
 [[package]]
 name = "fieldcraft-ui-egui"
-version = "0.1.0"
+version = "0.5.5"
 dependencies = [
  "craft-ui",
  "egui",
@@ -1374,6 +1440,25 @@ dependencies = [
  "serde_json",
 ]
 
+[[package]]
+name = "fieldcraft-web"
+version = "0.5.5"
+dependencies = [
+ "base64",
+ "eframe",
+ "egui",
+ "fieldcraft-engine",
+ "fieldcraft-io",
+ "fieldcraft-ui-egui",
+ "js-sys",
+ "log",
+ "rfd",
+ "serde_json",
+ "wasm-bindgen",
+ "wasm-bindgen-futures",
+ "web-sys",
+]
+
 [[package]]
 name = "find-msvc-tools"
 version = "0.1.14"
@@ -1734,6 +1819,15 @@ version = "0.4.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7f24254aa9a54b5c858eaee2f5bccdb46aaf0e486a595ed5fd8f86ba55232a70"
 
+[[package]]
+name = "hybrid-array"
+version = "0.4.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "27f864f10dfb56725ce5ce5472bc52252c8f93a4ab86327122cebf62c5f59a17"
+dependencies = [
+ "typenum",
+]
+
 [[package]]
 name = "iana-time-zone"
 version = "0.1.65"
@@ -3206,6 +3300,15 @@ dependencies = [
  "syn 3.0.9",
 ]
 
+[[package]]
+name = "serde_spanned"
+version = "1.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4e7523beb55eece201a2356bee0bbca0d1ab466c14c07703b2e0ee6d42cb0c2c"
+dependencies = [
+ "serde_core",
+]
+
 [[package]]
 name = "sha2"
 version = "0.10.9"
@@ -3213,8 +3316,19 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a7507d819769d01a365ab707794a4084392c824f54a7a6a7862f8c3d0892b283"
 dependencies = [
  "cfg-if",
- "cpufeatures",
- "digest",
+ "cpufeatures 0.2.17",
+ "digest 0.10.7",
+]
+
+[[package]]
+name = "sha2"
+version = "0.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "47d7069beb7d6ac7b9acd1039986e73443f24234f41074da099d6f994ac9ad19"
+dependencies = [
+ "cfg-if",
+ "cpufeatures 0.3.1",
+ "digest 0.11.3",
 ]
 
 [[package]]
@@ -3381,7 +3495,7 @@ dependencies = [
  "log",
  "serde",
  "serde_json",
- "sha2",
+ "sha2 0.10.9",
  "solidcraft-geom",
  "solidcraft-kernel",
  "solidcraft-sketch",
@@ -3423,7 +3537,7 @@ dependencies = [
  "quick-xml",
  "serde",
  "serde_json",
- "sha2",
+ "sha2 0.10.9",
  "solidcraft-doc",
  "solidcraft-geom",
  "solidcraft-kernel",
@@ -3658,6 +3772,21 @@ dependencies = [
  "pin-project-lite",
 ]
 
+[[package]]
+name = "toml"
+version = "1.1.8+spec-1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "20489e00e4d8741d6be680764cc12e270655e375a20d1011e844a9c3379e678d"
+dependencies = [
+ "indexmap",
+ "serde_core",
+ "serde_spanned",
+ "toml_datetime",
+ "toml_parser",
+ "toml_writer",
+ "winnow",
+]
+
 [[package]]
 name = "toml_datetime"
 version = "1.1.2+spec-1.1.0"
@@ -3688,6 +3817,12 @@ dependencies = [
  "winnow",
 ]
 
+[[package]]
+name = "toml_writer"
+version = "1.1.3+spec-1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "06bdbd8cfc056b8d2e2e85f29b56a3bdbecb527cef81eb39e3e7b98af4652770"
+
 [[package]]
 name = "tracing"
 version = "0.1.44"
@@ -3981,6 +4116,26 @@ version = "0.9.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0b928f33d975fc6ad9f86c8f283853ad26bdd5b10b7f1542aa2fa15e2289105a"
 
+[[package]]
+name = "vswhom"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "be979b7f07507105799e854203b470ff7c78a1639e330a58f183b5fea574608b"
+dependencies = [
+ "libc",
+ "vswhom-sys",
+]
+
+[[package]]
+name = "vswhom-sys"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fb067e4cbd1ff067d1df46c9194b5de0e98efd2810bbc95c5d5e5f25a3231150"
+dependencies = [
+ "cc",
+ "libc",
+]
+
 [[package]]
 name = "walkdir"
 version = "2.5.0"
@@ -4750,6 +4905,16 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "winreg"
+version = "0.56.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7d6f32a0ff4a9f6f01231eb2059cc85479330739333e0e58cadf03b6af2cca10"
+dependencies = [
+ "cfg-if",
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "wit-bindgen"
 version = "0.57.1"
@@ -4821,7 +4986,7 @@ checksum = "e450f9b2ed1dff33c94c12589a87338689467b9c4f5d8a5710bd09a847d2c8a7"
 
 [[package]]
 name = "xtask"
-version = "0.1.0"
+version = "0.5.5"
 dependencies = [
  "serde_json",
 ]

Cargo.toml

@@ -3,7 +3,7 @@ resolver = "3"
 members = ["crates/*", "apps/*", "xtask"]
 
 [workspace.package]
-version = "0.1.0"
+version = "0.5.5"
 edition = "2024"
 license = "MIT OR Apache-2.0"
 rust-version = "1.95"
@@ -39,7 +39,7 @@ zip = { version = "3", default-features = false, features = ["deflate"] }
 quick-xml = "0.41"
 
 # content hashes and part checksums of .fieldcraft files (the version SolidCraft uses)
-sha2 = "0.10"
+sha2 = "0.11"
 
 # images (PNG snapshots and screenshots)
 png = "0.18"
@@ -88,6 +88,14 @@ opt-level = 1
 [profile.dev.package.fieldcraft-lbm]
 opt-level = 3
 
+# Meshing and the sparse solver are compute loops too: the tet quality stage and the
+# mesh-convergence oracle cases (tests/oracle) run in tests.
+[profile.dev.package.fieldcraft-mesh]
+opt-level = 3
+
+[profile.dev.package.fieldcraft-solver]
+opt-level = 3
+
 # Tests and lints (`cargo xtask ci`, GitHub CI). Debug assertions are off because truck's
 # debug-only checks reject valid geometry (SolidCraft builds its tests the same way).
 [profile.ci]
@@ -104,6 +112,12 @@ opt-level = 2
 [profile.ci.package.fieldcraft-lbm]
 opt-level = 3
 
+[profile.ci.package.fieldcraft-mesh]
+opt-level = 3
+
+[profile.ci.package.fieldcraft-solver]
+opt-level = 3
+
 [profile.release]
 opt-level = 3
 lto = "thin"

README.md

@@ -6,8 +6,13 @@ explicit, thermal and lattice Boltzmann solvers, and decks for Abaqus, Nastran a
 desktop app, the command line and AI agents (over MCP) drive the same commands.
 
 **Status:** early but working end to end — open a part, mesh it, define the analysis, solve,
-see the results. Hex meshing is the centre of gravity; the next large step is the nonlinear
-implicit solver that contact, elastomers and composites need. See [ROADMAP.md](ROADMAP.md).
+see the results — with a nonlinear implicit solver (large deformation, plasticity, rubber) now
+in place. Hex meshing is the centre of gravity. Next: buckling and arc-length, contact, then
+the wider material and multiphysics library. See [ROADMAP.md](ROADMAP.md).
+**Want to help?** Pick an issue labelled
+[good first issue](https://github.com/jyviko/fieldcraft/labels/good%20first%20issue) or
+[help wanted](https://github.com/jyviko/fieldcraft/labels/help%20wanted) and read
+[CONTRIBUTING.md](CONTRIBUTING.md).
 
 ![An AI agent analyses an I-beam cantilever in FieldCraft over MCP: open, hex mesh, steel, clamp and tip load, solve, von Mises contours, the deformed shape and an orbit round it](docs/media/ibeam-analysis.gif)
 
@@ -17,34 +22,70 @@ solves, and shows the von Mises stress and the deformed shape (tip deflection 0.
 theory with shear 0.177 mm).
 [MP4](docs/media/ibeam-analysis.mp4) · regenerated by [tools/demo-video](tools/demo-video/README.md).
 
+## Download
+
+[![Download for macOS](https://img.shields.io/badge/macOS-Download-000000?style=for-the-badge&logo=apple&logoColor=white)](https://github.com/jyviko/fieldcraft/releases/latest)
+[![Download for Windows](https://img.shields.io/badge/Windows-Download-0078D6?style=for-the-badge)](https://github.com/jyviko/fieldcraft/releases/latest)
+[![Download for Linux](https://img.shields.io/badge/Linux-Download-FCC624?style=for-the-badge&logo=linux&logoColor=black)](https://github.com/jyviko/fieldcraft/releases/latest)
+
+- **macOS:** open the `.dmg` and drag FieldCraft into Applications (Apple silicon and Intel).
+- **Windows:** unzip and run `fieldcraft.exe`.
+- **Linux:** the `.AppImage` (allow it to run as a program), or the `.tar.gz`.
+- **Command line:** `fieldcraft-cli` ships in every package; AI agents connect to it over MCP
+  ([docs/mcp.md](docs/mcp.md)).
+
+Every release lists its checksums in `SHA256SUMS.txt`. Building from source is in
+[CONTRIBUTING.md](CONTRIBUTING.md#get-it-running-about-10-minutes-on-a-fast-machine).
+
+## Hex meshing a part that does not sweep
+
+A filleted L-bracket with a hole through each leg cannot be swept in one piece. Split into 30
+cells in SolidCraft, FieldCraft meshes it all-hex as one conforming mesh — O-grids round the holes,
+graded through the fillet — and its hex20 tip deflection matches a fine tet10 solution to 0.1 %.
+The same part also meshes all-hex automatically with the octree mesher (`mesh.hex.octree`).
+
+| Cells | Conforming hex mesh | Von Mises (clamp and load drawn) |
+|---|---|---|
+| ![The bracket split into 30 coloured cells](docs/media/bracket-partition.png) | ![The all-hex mesh with O-grids round the holes](docs/media/bracket-hex.png) | ![Von Mises stress peaking at the hole, with the clamp cones and load arrows](docs/media/bracket-stress.png) |
+
 ## What it does today
 
 - **Geometry in:** SolidCraft designs (`.solidcraft`) with persistent face, edge and body names,
   and face-tagged 3MF meshes; surface checks (weld, manifold, orientation, self-intersection).
 - **Meshing:** constrained Delaunay tetrahedra (tet4, tet10) with exact predicates and a
-  certified validity gate; structured hex by sweeping, revolving and mapping (hex8, hex20; 16 of
-  the 21 corpus parts mesh all-hex); 2D quad and tri meshes; quality metrics per element and set.
+  certified validity gate; Delaunay refinement, smoothing and sliver removal; structured hex by
+  sweeping, revolving and mapping (hex8, hex20), and conforming multi-block hex across a part
+  split into cells (`mesh.hex.blocks`); unstructured octree all-hex for any part
+  (`mesh.hex.octree`); 2D quad and tri meshes; quality metrics per element and set.
 - **Elements:** solids (tet4, tet10, wedge6, hex8 with incompatible modes, hex20 full and
   reduced, hybrid u–p for near-incompressible materials), plane stress, plane strain and
   axisymmetric, trusses, Timoshenko beams, MITC3/MITC4 shells, springs, dashpots and point masses.
 - **Model:** sets bound to geometry names, so they survive remeshing; isotropic and orthotropic
-  elasticity, J2 plasticity, Johnson–Cook damage, thermal properties; fixed, displacement,
+  elasticity, J2 plasticity (isotropic and kinematic hardening, Johnson–Cook), Johnson–Cook
+  damage, neo-Hookean, Mooney–Rivlin and Yeoh hyperelasticity, thermal properties; fixed, displacement,
   symmetry and temperature conditions; forces, moments, pressure, gravity, centrifugal and heat
   loads; reference points with kinematic and distributing couplings; undo, redo and a
   text-diffable `.fieldcraft` file.
-- **Solvers:** linear static and frequency (supernodal Cholesky, block Lanczos); steady and
+- **Solvers:** linear static and frequency (supernodal Cholesky, block Lanczos); nonlinear static
+  by Newton–Raphson with automatic increments — large deformation (total Lagrangian) on every
+  solid element, follower pressure, finite- and small-strain plasticity sharing one return map
+  with the explicit solver, rubber and thermal strain, with measured quadratic convergence; steady and
   transient heat transfer and coupled thermal stress; explicit dynamics with plasticity, damage,
   erosion and rigid walls; D3Q19 lattice Boltzmann flow with forces on the part's faces. Results
   never depend on the thread count.
 - **Decks:** Abaqus, Nastran and LS-DYNA writers, each refusing by name what it cannot express.
 - **Results:** contours of stress, strain and displacement with a legend, deformed shapes, mode
-  shapes, explicit frames, probes and reaction sums; the analysis setup drawn in the viewport.
+  shapes, explicit and nonlinear frames, probes and reaction sums; supports, loads, reference
+  points and couplings drawn in the viewport.
 - **Verification:** every capability is checked against closed forms and published benchmarks
-  (NAFEMS, MacNeal–Harder, Scordelis–Lo) in [`tests/oracle`](tests/oracle), with results frozen
-  so they cannot drift: [docs/oracle.md](docs/oracle.md).
+  (NAFEMS, MacNeal–Harder, Scordelis–Lo, the elastica, Hill's plastic cylinder, Rivlin's tube) in [`tests/oracle`](tests/oracle), with results frozen
+  so they cannot drift: 170 of 176 quantities pass in 50 cases, the 6 others documented known
+  failures ([docs/oracle.md](docs/oracle.md)).
 - **Driving it:** a desktop app in the Craft family's layout, a CLI, a JSON control channel and an
   MCP server; every capability is a command ([docs/features.md](docs/features.md)).
 
+![The FieldCraft window: a clamped cantilever with its supports, pressure, gravity and a coupled reference point drawn in the viewport](docs/media/setup-symbols.png)
+
 ## Build
 
 ```sh
@@ -65,6 +106,7 @@ Rust 1.95 or later, with the `wasm32-unknown-unknown` target for `cargo xtask ci
 - [Libraries and licences](docs/adr/0001-libraries.md)
 - [AI agents (MCP)](docs/mcp.md): `claude mcp add fieldcraft -- /path/to/fieldcraft-cli mcp`
 - [Control protocol](docs/control-protocol.md): driving the desktop app
+- [Releasing](docs/releasing.md): how a release is built, verified and published
 - [Contributing](CONTRIBUTING.md) and [agent instructions](AGENTS.md)
 
 ## License

ROADMAP.md

@@ -28,11 +28,11 @@ pressure) is a degree of freedom of the existing DOF framework, not a separate s
 |---|---|---|
 | M0 Foundation | Workspace, quality gates, FE model, command engine with rollback and panic guard, CLI, geometry boundary on SolidCraft | done |
 | M1 Geometry in and surface preparation | Open `.solidcraft` designs with persistent face names, assemblies placed (done); face-tagged 3MF (done); test corpus, `cargo xtask corpus` (done); exact predicates (done); quality metrics and certified validity gate (done); weld, closed/manifold/orientation and self-intersection checks, feature edges (`fieldcraft-mesh::surface`, `mesh.surface.check`, done) | in progress |
-| M2 Tet meshing and size field | Size field (global, per face and edge seeds, curvature and proximity; the `fieldcraft_mesh::size::SizeField` trait and edge-division helpers are in); Bowyer–Watson Delaunay (exact, symbolic perturbation, verified; `fieldcraft-mesh::delaunay`, done); robust CDT boundary recovery (Diazzi et al. 2023: implicit LNC Steiner points on segments, gift-wrapping facet recovery, inside/outside labelling, B-rep face tags on boundary tet faces, few-ulp rounding repair checked by the validity gate; `fieldcraft-mesh::cdt` and `mesh.tet.generate`, done: all 20 valid corpus parts); Delaunay refinement, ODT smoothing, sliver removal; tet4 and tet10 with mid-side nodes on the B-rep; mesh verify per set | in progress |
+| M2 Tet meshing and size field | Size field (global, per face and edge seeds, curvature and proximity; the `fieldcraft_mesh::size::SizeField` trait and edge-division helpers are in); Bowyer–Watson Delaunay (exact, symbolic perturbation, verified; `fieldcraft-mesh::delaunay`, done); robust CDT boundary recovery (Diazzi et al. 2023: implicit LNC Steiner points on segments, gift-wrapping facet recovery, inside/outside labelling, B-rep face tags on boundary tet faces, flip repair of rounding (§5.1) checked by the validity gate; `fieldcraft-mesh::cdt` and `mesh.tet.generate`, done: all 20 valid corpus parts); quality stage (done: `fieldcraft-mesh::tet` — curvature-graded size field, edge-collapse coarsening, constrained Delaunay refinement with boundary points on the B-rep faces and curves, ODT smoothing, Klingner–Shewchuk improvement, tet4 and tet10 with mid-side nodes on the B-rep, quality report; one validity criterion shared by the gate and both solvers; the filleted-bracket fillet stress converges, tests/oracle); mesh verify per set | in progress |
 | M3 First deck | Sets and surfaces bound to SolidCraft face, edge, vertex and body names, resolved after meshing; materials (isotropic and orthotropic elastic, density) with a unit-system label and consistency check; sections (solid, shell, beam profiles) assigned by set; element formulation per region mapped to each solver; BCs (fixed, displacement, symmetry); loads (force and moment on reference points, pressure, gravity); reference points with kinematic and distributing coupling; steps (linear static, frequency) with explicit per-step load and BC tables and output presets; `model.check` naming every missing or bad item; `model.*` and `mesh.tag` commands (model definition: done); writers for Abaqus input (done: `deck.write`), Nastran SOL 101/103 (done: `deck.write`) and LS-DYNA implicit (done); the `.fieldcraft` file (text definition, binary mesh, geometry references reopened on load, journal; atomic saves, autosave and recovery; undo/redo on the journal: done) | in progress |
 | M4 Own solver and first results | Element library per docs/elements.md (1D and 2D first); Linear static and modal solver (tet4/10, wedge6, hex8, hex20; sparse direct, Lanczos), verified against analytic solutions (solver: done — `fieldcraft-fem` kernels, `fieldcraft-solver` with nested dissection, sparse Cholesky and block Lanczos, `solve.static`/`solve.frequency`/`solve.probe`, patch, cantilever, Lamé, Kirsch and beam-frequency tests; reference points with kinematic and distributing couplings and moments by master–slave constraint elimination, verified by rigid motion, clamping, Saint-Venant tension, bending and tube torsion; 1D elements I: rod2/rod3 trusses, point masses, rotary inertia, springs and dashpots in both solvers and all three decks, verified by the method of joints, the three-bar truss, spring–mass, two-mass chain and torsional pendulum frequencies, and damped decay; 2D elements: plane stress, plane strain and axisymmetric tri3, tri6, quad4 (incompatible modes QM6), quad8 with two degrees of freedom per node, centrifugal loads, `mesh.planar` 2D meshes of polygons and planar faces, verified by patch tests, Kirsch, Lamé (plane strain and axisymmetric), rotating discs and cylinders, and a plane stress cantilever; deck mapping to Abaqus CPS/CPE/CAX, Nastran membranes, LS-DYNA ELFORM 12/13); shells and beams (done: quad4 MITC4 and tri3 MITC3 flat shells with a Hughes–Brezzi drilling rotation, two-node Timoshenko beams with profile properties and orientations, six degrees of freedom at shell and beam nodes shared with solids and trusses, section forces and surface stresses, verified by shell patch tests, Navier's plate, cantilever and portal-frame beams, and the Scordelis–Lo and pinched-cylinder benchmarks); results display (done: `results.*` commands, deformed shape to scale, banded contours of displacement, von Mises, principal and component stresses with a legend, mode shapes with their frequencies and animation, probing a node by clicking it, reaction force and moment sums per set, stale results marked after an edit; explicit steps: field frames by slider or animation with contours per frame, energy histories plotted) | started |
-| M5 Structured hex | 2D quad meshing of faces (`fieldcraft-mesh::quad`: transfinite mapped meshes, free all-quad meshes of polygons with holes on prescribed boundary nodes, exact planar quad validity, shared `SizeField` and even edge divisions; done for planar faces); mapped hex of six-sided regions (trivariate TFI, curved faces) and sweep meshing (multi-level extrusions with imprinted cross-sections, revolutions, one-to-one sweeps through linking faces; interval assignment, hex8/hex20 on the geometry, B-rep face tags, `mesh.hex.generate`/`sweep`/`mapped`: done, 16 of 21 corpus parts all-hex); conforming interfaces and tet–hex transition; automatic decomposition into sweepable and mappable regions, proposed as SolidCraft splits | started |
-| M6 Automatic hex | Octree/grid-dual all-hex for any part; hex-dominant by tet recombination; polycube for blocky parts; smoothing, untangling, boundary padding, layers through thin walls; mesh editing and orphan-mesh import | planned |
+| M5 Structured hex | 2D quad meshing of faces (`fieldcraft-mesh::quad`: transfinite mapped meshes, free all-quad meshes of polygons with holes on prescribed boundary nodes, exact planar quad validity, shared `SizeField` and even edge divisions; done for planar faces); mapped hex of six-sided regions (trivariate TFI, curved faces) and sweep meshing (multi-level extrusions with imprinted cross-sections, revolutions, one-to-one sweeps through linking faces; interval assignment, hex8/hex20 on the geometry, B-rep face tags, `mesh.hex.generate`/`sweep`/`mapped`: done, 16 of 21 corpus parts all-hex); conforming interfaces between cells (done: `mesh.hex.blocks` meshes a part split with SolidCraft's Split Body into mapped blocks as one conforming mesh — composite faces for seams and tangent faces, interval assignment over all cells, shared faces meshed once, grading off holes and fillets, free-internal-face check; the filleted bracket in 30 cells, hex20 within 0.1 % of a fine tet10 tip deflection); sweepable cells in a conforming mesh and tet–hex transition; automatic decomposition into sweepable and mappable regions, proposed as SolidCraft splits | started |
+| M6 Automatic hex | Octree/grid all-hex for any part (first version: done — `fieldcraft-mesh::octree`, `mesh.hex.octree`: 3-refinement grid with conforming templates refined by curvature, thickness and narrow faces, a core cleared to a manifold boundary, feature map onto it, padding and a pillow per patch capturing every sharp curve, foldover-free fitting, certified validity, B-rep face tags; the corpus hex column and the filleted-bracket oracle case; next: transitions for concave refined regions so thin and curved parts stop over-refining); hex-dominant by tet recombination; polycube for blocky parts; layers through thin walls; mesh editing and orphan-mesh import | started |
 | M7 Assemblies, contact and friction | Needs M15. Part instances from SolidCraft occurrences; tie between non-matching meshes (mortar); implicit contact: surface-to-surface mortar and node-to-surface, penalty and augmented Lagrange, self-contact, automatic pair detection with a bounding-volume search shared with explicit contact; friction: Coulomb with stick–slip, static/kinetic, anisotropic, pressure-, rate- and temperature-dependent coefficients; contact output (pressure, slip, status); thermal contact conductance and frictional heating; wear (Archard); bolt pretension, connectors with behaviour (elastic, damped, stops, locks); amplitudes, multiple steps, restart; nonlinear steps in all three decks. Verified by Hertz (sphere and cylinder), the Cattaneo–Mindlin partial-slip problem, the sliding block, NAFEMS contact benchmarks | planned |
 | M8 Materials, explicit, shells, composites | Plasticity, hyperelasticity, damage data per solver; explicit dynamics decks (Abaqus/Explicit, LS-DYNA); midsurface shells; composite layups and material orientations, continuum shells on swept hex; hybrid (mixed u–p) hex8/hex20/tet10 for nearly incompressible materials (done); heat transfer (solids done: steady and θ-method transient conduction with flux, convection and sources, thermal strain in static steps (solids and 2D) and explicit dynamics (with plasticity), coupled temperature–displacement, `solve.heat`; deck output, 2D/shell/beam conduction planned) | started |
 | M9 Post-processing and deck readers | Results readers for public formats (Nastran OP2, LS-DYNA d3plot, Abaqus `.fil`); XY and path plots, cuts, display groups, free-body forces; deck readers that keep unknown keywords; mesh convergence studies | planned |
@@ -41,9 +41,9 @@ pressure) is a degree of freedom of the existing DOF framework, not a separate s
 | M12 CFD: lattice Boltzmann | D3Q19/D3Q27 on grids voxelised from the face-tagged surface; TRT, regularised and cumulant collision; interpolated walls, inlets and outlets; LES (Smagorinsky, WALE) with wall models; thermal LBM and conjugate heat transfer with the structure's thermal solver; non-Newtonian viscosity (power-law, Carreau–Yasuda, Cross, Herschel–Bulkley, Bingham) and temperature-dependent viscosity; porous media (Brinkman, Darcy–Forchheimer); multiphase and free surface (M13); validation by the lid-driven cavity, backward-facing step, cylinder wake (Strouhal) and turbulent channel; octree refinement shared with the hex mesher; wgpu backend (deterministic per device, checked against the CPU) (CPU core: done — `fieldcraft-lbm` with D3Q19 TRT and Guo forcing, halfway bounce-back and moving walls, slip and periodic faces, Zou–He velocity and pressure faces, exact voxelisation of obstacle bodies, momentum-exchange forces per face; fluid materials, fluid domains and fluid steps in the model; `model.fluid_domain.*`, `solve.fluid`; verified by Poiseuille channel and pipe, Couette, Taylor–Green decay, sphere-array Stokes drag and mass conservation; Schäfer–Turek 2D-1 as a benchmark) | started |
 | M13 Fluid–structure interaction | Immersed-boundary coupling of the lattice Boltzmann fluid with the explicit or implicit structure; interface force transfer; sub-cycling; Aitken then interface quasi-Newton coupling; free-surface flow | planned |
 | M14 Blast and impact fluids | EOS-driven fluids in the explicit solver: ALE multi-material or SPH, with fluid–structure contact | planned |
-| M15 Nonlinear implicit core | Newton–Raphson with line search, automatic increments and cutbacks, convergence on force, displacement and energy; geometric nonlinearity (total and updated Lagrangian, large rotations for shells and beams, follower pressure); every `fem` material behind one interface with its consistent tangent (plasticity, damage and thermal strain from the explicit solver reused implicitly); arc-length (Riks) for snap-through; linear buckling (eigen) with preload stress stiffening, and imperfections from buckling modes; nonlinear stabilisation; restart. Verified by the elastica, Lee's frame, the snap-through arch, the hinged cylindrical shell and plastic collapse loads | planned |
+| M15 Nonlinear implicit core | Newton–Raphson with line search, automatic increments and cutbacks, convergence on force, displacement and energy; geometric nonlinearity (total and updated Lagrangian, large rotations for shells and beams, follower pressure); every `fem` material behind one interface with its consistent tangent (plasticity, damage and thermal strain from the explicit solver reused implicitly); arc-length (Riks) for snap-through; linear buckling (eigen) with preload stress stiffening, and imperfections from buckling modes; nonlinear stabilisation; restart. Verified by the elastica, Lee's frame, the snap-through arch, the hinged cylindrical shell and plastic collapse loads (solids core: done — `nonlinear_static` steps with automatic increments and cutbacks, Newton–Raphson with the consistent tangent, force, displacement and energy convergence and an optional line search; a material point interface (Kirchhoff stress and spatial tangent from F, with history) with St Venant–Kirchhoff and compressible neo-Hookean; total Lagrangian tet4, tet10, wedge6, hex8, hex20 (full and reduced), hybrid hex8/hex20/tet10 by the three-field mixed form, plane strain and axisymmetric elements; follower pressure with its symmetrised load stiffness; Cauchy stress and logarithmic strain, increment history and frames, `solve.nonlinear`; Abaqus and LS-DYNA decks; verified by the patch and objectivity tests, uniaxial stretch, the elastica and tube inflation by a follower pressure (finite-strain Cook's membrane pending its transcribed reference; J2 plasticity on the interface: Simo's exponential return map at finite strain and the radial return at small strain, both with consistent tangents and the return shared with explicit dynamics, bilinear isotropic and kinematic (small strain), tabulated and Johnson–Cook (rate-independent) hardening, hybrid elements included, load paths for cyclic loading, a tangent predictor for path-dependent materials, verified by uniaxial tension to large strain, Hill's thick cylinder (plastic zone and collapse pressure), a cantilever's collapse and the Bauschinger effect, with quadratic Newton convergence; Mooney–Rivlin and Yeoh options (decoupled, hybrid elements), verified in Treloar's three modes and by a stretched tube's inflation; thermal strain by the multiplicative split at finite strain and the additive one at small strain, with temperatures from temperature loads or the step's own conduction, verified by free and constrained expansion and a heated bar held past yield. Next: incompatible modes (EAS), kinematic hardening at finite strain, shells and beams, linear buckling, arc-length with an indefinite factorization) | started |
 | M16 Structural dynamics | Implicit transient (Newmark, HHT-α, generalised-α); modal superposition transient; steady-state harmonic (direct and modal), with Rayleigh, modal, structural and material damping; random vibration from PSDs and response spectrum (SRSS, CQC); complex eigenvalues with damping; rotating machinery (Campbell diagrams, gyroscopic terms); substructures (Craig–Bampton) | planned |
-| M17 Constitutive library and material library | Elastic: transversely isotropic, fully anisotropic (21 constants), temperature-dependent. Elastomers: hyperelastic neo-Hookean, Mooney–Rivlin, Yeoh, Ogden, Arruda–Boyce, Gent, Marlow, with Mullins softening and finite-strain viscoelasticity (Prony series; parallel networks after Bergström–Boyce), foams. Viscoelasticity: small- and finite-strain Prony series, time–temperature superposition (WLF, Arrhenius), storage and loss moduli for harmonic steps. Viscoplasticity and creep: Norton power law, time and strain hardening, Perzyna, Anand, Chaboche combined hardening. Plasticity: Hill anisotropic, Drucker–Prager, Mohr–Coulomb, Cam-clay, crushable foam, concrete damaged plasticity, Gurson. Fluids: Newtonian and non-Newtonian viscosity shared with M12. Material library: curated, cited data sets (steels, aluminium and titanium alloys, polymers, elastomers, composites, tissues) with units and temperature dependence; calibration from test data (uniaxial, biaxial, shear, relaxation, DMA) by least squares with Drucker stability checks; user materials as a safe Rust trait | planned |
+| M17 Constitutive library and material library | Elastic: transversely isotropic, fully anisotropic (21 constants), temperature-dependent. Elastomers: hyperelastic neo-Hookean, Mooney–Rivlin, Yeoh (these three done, in nonlinear steps), Ogden, Arruda–Boyce, Gent, Marlow, with Mullins softening and finite-strain viscoelasticity (Prony series; parallel networks after Bergström–Boyce), foams. Viscoelasticity: small- and finite-strain Prony series, time–temperature superposition (WLF, Arrhenius), storage and loss moduli for harmonic steps. Viscoplasticity and creep: Norton power law, time and strain hardening, Perzyna, Anand, Chaboche combined hardening. Plasticity: Hill anisotropic, Drucker–Prager, Mohr–Coulomb, Cam-clay, crushable foam, concrete damaged plasticity, Gurson. Fluids: Newtonian and non-Newtonian viscosity shared with M12. Material library: curated, cited data sets (steels, aluminium and titanium alloys, polymers, elastomers, composites, tissues) with units and temperature dependence; calibration from test data (uniaxial, biaxial, shear, relaxation, DMA) by least squares with Drucker stability checks; user materials as a safe Rust trait | planned |
 | M18 Composites and anisotropy | Material orientations (rectangular, cylindrical, spherical, from geometry edges and faces, per-element fields, draping of fibres over curved parts); layups on shells and continuum shells, ply stacks on swept hex; classical lamination theory checks; ply stresses and strains through the thickness; failure indices (Tsai–Wu, Tsai–Hill, Hashin, Puck, LaRC) and progressive damage; homogenisation (rule of mixtures, Mori–Tanaka, RVEs with periodic boundary conditions); delamination through M20's cohesive zones. Verified by laminate closed forms and the NAFEMS composite benchmarks | planned |
 | M19 Coupled fields | On the DOF framework, each a degree of freedom beside the displacements: piezoelectricity (electric potential, d/e coupling and permittivity matrices, voltage and charge conditions, resonance and impedance through M16 harmonic steps); poroelasticity (Biot, u–p, Darcy flow, consolidation; Terzaghi and Mandel verification; soils and biphasic tissue); electro-thermal (Joule heating) and thermo-electro-mechanical coupling; acoustics (Helmholtz elements, structure–acoustic coupling, absorbing boundaries); low-frequency electromagnetics later | planned |
 | M20 Damage, fracture, fatigue and adhesion | Continuum damage beyond Johnson–Cook (Lemaitre, ductile and shear criteria) for implicit and explicit; fracture mechanics (J-integral and stress intensity factors, crack-front meshes from the hex mesher; XFEM later); fatigue (S–N and ε–N with mean-stress corrections, rainflow counting, Paris crack growth); adhesion and debonding by cohesive zones (bilinear and exponential traction–separation, mixed mode with Benzeggagh–Kenane) as cohesive elements and cohesive contact; adhesive joints. Verified by DCB, ENF and MMB delamination tests and published fatigue data | planned |
@@ -52,7 +52,7 @@ pressure) is a degree of freedom of the existing DOF framework, not a separate s
 | M23 Wave propagation and ultrasound | Elastic, acoustic and coupled waves from the explicit solver's 1D bar today to guided and ultrasonic waves, by two methods. Finite differences first, for fast 2D (then 3D) ultrasound on regular grids: staggered-grid velocity–stress FDTD (Virieux) and the elastodynamic finite integration technique for solids, the rotated staggered grid for anisotropic media, a k-space pseudospectral scheme for weakly heterogeneous tissue and water, all on grids voxelised from the face-tagged geometry by the LBM's exact voxeliser, with heterogeneous, layered and fluid–solid media, CPML boundaries, threads and the GPU backend; staircased curved boundaries scatter spuriously, so the FD grid is checked against the finite elements on curved parts. Finite elements for curved geometry and coupling with structures: spectral elements (high-order Gauss–Lobatto–Legendre hexes with diagonal mass) on the hex meshes, and a mesh check in elements per wavelength with the dispersion error it implies; absorbing boundaries (convolutional PML, absorbing layers with increasing damping) and infinite media; tone-burst sources (Hann-windowed cycles), point, line and surface excitation, and piezoelectric transducers (M19); anisotropic media (composites, crystals) and viscoelastic, power-law-in-frequency attenuation; fluid–solid interfaces and fluid-loaded plates; ultrasound in water and tissue, nonlinear acoustics (Westervelt, KZK) for focused ultrasound. Guided waves: dispersion curves by semi-analytical finite elements (SAFE) for plates, pipes, rails and layered and anisotropic laminates — Lamb, Rayleigh, Love and SH modes — with phase and group velocities and mode shapes; mode-selective excitation. Output: A-scans and B-scans at sensors, wavefield snapshots, 2D FFT (frequency–wavenumber) for mode identification, and time–frequency diagrams of any signal — short-time Fourier spectrograms, continuous wavelet transforms (Morlet), reassigned spectrograms and smoothed pseudo Wigner–Ville — with the SAFE or Rayleigh–Lamb group-velocity curves overlaid as arrival times, and group velocities extracted from the ridges. GPU paths (M12's backend) for long runs. Verified by Lamb's problem (point load on a half-space), Rayleigh-wave speed, Rayleigh–Lamb dispersion, Love waves in a layer over a half-space, reflection and transmission at interfaces, and published guided-wave measurements | planned |
 | Continuous: verification and validation | Every capability checked against theory (closed forms), experiments (published measurements) and published benchmarks (NAFEMS, vendor benchmark and verification manuals such as Abaqus's), each case our own model in `tests/oracle/` with its cited reference and tolerance; `cargo xtask oracle` runs them and writes docs/oracle.md; once a case matches, our result is frozen as a fixture so fidelity cannot regress (docs/verification.md). Runner, fixtures and CI job: done; 26 theory cases (patch tests of every solid element, cantilevers, Lamé in 3D, plane strain and axisymmetric, Kirsch in 3D and plane stress, rotating disc and cylinder, beam frequencies, couplings, explicit waves, impact and J2 plasticity, CDT invariants), 9 published benchmarks (MacNeal–Harder solid tests, Scordelis–Lo with solids, NAFEMS LE1 in 3D and 2D, LE10, FV32) and 9 pending cases with citations (shells, thermal, static plasticity, Taylor bar, CFD); `mesh.block` mapped blocks and 2D patches build their meshes | started |
 | Continuous: performance | CPU first, deterministic: results never depend on the thread count (fixed partitions, sums in a fixed order; checked by hashing results on 1, 2 and 7 threads). Supernodal left-looking Cholesky (11–15× faster than the column solver on one thread), parallel element matrices, stresses and Lanczos products, explicit element updates and LBM cell blocks on rayon threads (done — `fieldcraft-parallel`, `threads` on the solve commands, `FIELDCRAFT_THREADS`); parallel forward/back substitution and explicit tet4 assembly; GPU paths later, within a stated tolerance of the CPU | started |
-| Continuous: desktop and agents | Desktop app (viewport, model tree, commands, control channel, the open design drawn, `ui.capture` of the whole window offscreen: done; toolbar of every capability from the catalogue, ready or coming soon with its milestone, icons drawn with VectorCraft, docs/features.md: done; the Craft-family shell — title bar, workspaces and ribbon drop-downs, browser, context panel, command search, journal timeline, light and dark themes — native file pickers with background opening, drag and drop and recent files, samples and one-click Solve: done; MCP server over stdio, headless or bridged to the app, with read and write roots, docs/mcp.md: done; caps labels in Inter SemiBold; the README's analysis video recorded through MCP by `tools/demo-video`: done; support, load, reference-point and coupling symbols in the viewport and headless renders, with their browser toggles: done; a camera parameter for screenshots, a ribbon that follows the command being run: in progress), browser build, command schema as the public API | started |
+| Continuous: desktop and agents | Desktop app (viewport, model tree, commands, control channel, the open design drawn, `ui.capture` of the whole window offscreen: done; toolbar of every capability from the catalogue, ready or coming soon with its milestone, icons drawn with VectorCraft, docs/features.md: done; the Craft-family shell — title bar, workspaces and ribbon drop-downs, browser, context panel, command search, journal timeline, light and dark themes — native file pickers with background opening, drag and drop and recent files, samples and one-click Solve: done; MCP server over stdio, headless or bridged to the app, with read and write roots, docs/mcp.md: done; caps labels in Inter SemiBold; the README's analysis video recorded through MCP by `tools/demo-video`: done; support, load, reference-point and coupling symbols in the viewport and headless renders, with their browser toggles: done; selection by picking in the viewport — geometry faces, edges, vertices and bodies, mesh nodes, element faces and elements, box selection, hover, a Target row in command forms, `ui.select`/`ui.selection` and MCP `select`: done; a camera parameter for screenshots, a ribbon that follows the command being run: in progress; the browser build — the same app in a web page with browser file pickers, downloads, drops and autosave to browser storage, deployed to GitHub Pages from each release, docs/web.md: done), command schema as the public API | started |
 
 ## Next
 
@@ -60,14 +60,15 @@ In progress, in this order of landing:
 
 1. Tet quality: sliver repair and Delaunay refinement to a size field, so curved and filleted parts
    (the filleted bracket) solve on tets (M2).
-2. Octree all-hex for any part (M6), the project's main meshing goal.
+2. Octree all-hex (M6): concave transitions (Schneiders' modified templates or Livesu's dual schemes) so curved and thin-walled parts mesh without filling their hull with fine cells.
 3. The analysis video regenerated with the setup's symbols (done: support, load, reference-point
    and coupling symbols in the viewport and headless renders), captions and an orbit (screenshot
    camera and the ribbon following the command: done).
 4. A Scordelis–Lo refinement study (32×32×2, 64×64×4, hex20 full and reduced) separating
    discretisation error from the solid-versus-shell model difference (−0.33 % today).
 5. The nonlinear implicit core (M15), the gate for contact (M7), elastomers and viscoelasticity
-   (M17), composite failure (M18), adhesion (M20) and tissues (M21).
+   (M17), composite failure (M18), adhesion (M20) and tissues (M21): solids, hyperelasticity and
+   follower pressure done; J2 plasticity and Mooney–Rivlin on the material point interface next.
 
 ## Gap review (2026-10-14)
 
@@ -75,9 +76,9 @@ What exists and what is missing, by area; each gap is in a milestone above.
 
 | Area | Today | Missing |
 |---|---|---|
-| Solution procedures | Linear static, frequency (Lanczos), steady and transient heat, coupled temperature–displacement, explicit dynamics, LBM flow | Nonlinear static and geometric nonlinearity, arc-length, buckling (M15); implicit, harmonic, random and spectrum dynamics (M16) |
+| Solution procedures | Linear static, nonlinear static (solids with geometric and material nonlinearity: hyperelasticity, J2 plasticity), frequency (Lanczos), steady and transient heat, coupled temperature–displacement, explicit dynamics, LBM flow | Nonlinear shells and beams, arc-length, buckling (M15); implicit, harmonic, random and spectrum dynamics (M16) |
 | Contact, friction, adhesion | Explicit planar rigid walls (frictionless); couplings, springs, dashpots | Implicit and explicit deformable contact, tie, friction laws, thermal contact, wear (M7); cohesive adhesion and debonding (M20) |
-| Materials | Isotropic and orthotropic elasticity, density, thermal, J2 plasticity (bilinear, table, Johnson–Cook), Johnson–Cook damage and erosion, Newtonian fluids | Hyperelastic and elastomers, viscoelasticity, viscoplasticity and creep, anisotropic and pressure-dependent plasticity, non-Newtonian viscosity, a cited material library and calibration (M17) |
+| Materials | Isotropic and orthotropic elasticity, density, thermal, J2 plasticity (bilinear, table, Johnson–Cook), Johnson–Cook damage and erosion, compressible neo-Hookean, Mooney–Rivlin and Yeoh hyperelasticity, Newtonian fluids | Elastomers beyond Yeoh (Ogden, Arruda–Boyce and the rest), viscoelasticity, viscoplasticity and creep, anisotropic and pressure-dependent plasticity, non-Newtonian viscosity, a cited material library and calibration (M17) |
 | Composites and anisotropy | Orthotropic constants | Orientations, layups, ply results, failure criteria, homogenisation (M18) |
 | Coupled fields | Thermal–structural (one way and coupled) | Piezoelectric, poroelastic, electro-thermal, acoustics (M19) |
 | Failure | Johnson–Cook damage and element erosion (explicit) | Fracture mechanics, fatigue, cohesive zones, composite progressive damage (M18, M20) |

THIRD-PARTY-LICENSES.txt

@@ -1,6 +1,6 @@
 Third-party software in FieldCraft
 
-FieldCraft (the desktop app, fieldcraft-cli and the web app) is built from the 444 crates below.
+FieldCraft (the desktop app, fieldcraft-cli and the web app) is built from the 452 crates below.
 Generated by `cargo xtask licences` from Cargo.lock and the crates' own licence files.
 FieldCraft's own licence is in LICENSE-MIT and LICENSE-APACHE, and NOTICE.
 
@@ -41,11 +41,13 @@ atomic-waker 1.1.2  (Apache-2.0 OR MIT)
 atspi 0.29.0  (Apache-2.0 OR MIT)
 atspi-common 0.13.0  (Apache-2.0 OR MIT)
 atspi-proxies 0.13.0  (Apache-2.0 OR MIT)
+base64 0.22.1  (MIT OR Apache-2.0)
 bit-set 0.10.0  (Apache-2.0 OR MIT)
 bit-vec 0.9.1  (Apache-2.0 OR MIT)
 bitflags 1.3.2  (MIT/Apache-2.0)
 bitflags 2.13.2  (MIT OR Apache-2.0)
 block-buffer 0.10.4  (MIT OR Apache-2.0)
+block-buffer 0.12.1  (MIT OR Apache-2.0)
 block2 0.5.1  (MIT)
 block2 0.6.2  (MIT)
 blocking 1.7.0  (Apache-2.0 OR MIT)
@@ -68,12 +70,14 @@ codespan-reporting 0.13.1  (Apache-2.0)
 color 0.3.3  (Apache-2.0 OR MIT)
 combine 4.6.8  (MIT)
 concurrent-queue 2.5.0  (Apache-2.0 OR MIT)
+const-oid 0.10.2  (Apache-2.0 OR MIT)
 convert_case 0.4.0  (MIT)
 core-foundation 0.9.4  (MIT OR Apache-2.0)
 core-foundation-sys 0.8.7  (MIT OR Apache-2.0)
 core-graphics 0.23.2  (MIT OR Apache-2.0)
 core-graphics-types 0.1.3  (MIT OR Apache-2.0)
 cpufeatures 0.2.17  (MIT OR Apache-2.0)
+cpufeatures 0.3.1  (MIT OR Apache-2.0)
 craft-ui 0.1.0  (MIT OR Apache-2.0)
 crc32fast 1.5.2  (MIT OR Apache-2.0)
 crossbeam-deque 0.8.8  (MIT OR Apache-2.0)
@@ -81,11 +85,13 @@ crossbeam-epoch 0.9.21  (MIT OR Apache-2.0)
 crossbeam-utils 0.8.23  (MIT OR Apache-2.0)
 crunchy 0.2.4  (MIT)
 crypto-common 0.1.7  (MIT OR Apache-2.0)
+crypto-common 0.2.2  (MIT OR Apache-2.0)
 cursor-icon 1.2.0  (MIT OR Apache-2.0 OR Zlib)
 data-url 0.3.2  (MIT OR Apache-2.0)
 derive_arbitrary 1.5.0  (MIT OR Apache-2.0)
 derive_more 0.99.20  (MIT)
 digest 0.10.7  (MIT OR Apache-2.0)
+digest 0.11.3  (MIT OR Apache-2.0)
 dispatch 0.2.0  (MIT)
 dispatch2 0.3.1  (Zlib OR Apache-2.0 OR MIT)
 dlib 0.5.3  (MIT)
@@ -148,6 +154,7 @@ hashbrown 0.16.1  (MIT OR Apache-2.0)
 hashbrown 0.17.1  (MIT OR Apache-2.0)
 hermit-abi 0.5.3  (MIT OR Apache-2.0)
 hex 0.4.3  (MIT OR Apache-2.0)
+hybrid-array 0.4.15  (MIT OR Apache-2.0)
 iana-time-zone 0.1.65  (MIT OR Apache-2.0)
 iana-time-zone-haiku 0.1.2  (MIT OR Apache-2.0)
 image 0.25.10  (MIT OR Apache-2.0)
@@ -290,6 +297,7 @@ serde_derive 1.0.229  (MIT OR Apache-2.0)
 serde_json 1.0.154  (MIT OR Apache-2.0)
 serde_repr 0.1.21  (MIT OR Apache-2.0)
 sha2 0.10.9  (MIT OR Apache-2.0)
+sha2 0.11.1  (MIT OR Apache-2.0)
 signal-hook-registry 1.4.8  (MIT OR Apache-2.0)
 simd-adler32 0.3.10  (MIT)
 simd_cesu8 1.2.0  (Apache-2.0 OR MIT)
@@ -746,14 +754,14 @@ DEALINGS IN THE SOFTWARE.
 ================================================================================
 ahash 0.8.12, arbitrary 1.5.0, arrayvec 0.7.8, async-channel 2.5.0, async-executor 1.14.0, async-io
 2.6.0, async-lock 3.4.2, async-process 2.5.0, async-recursion 1.2.0, async-signal 0.2.14, async-task
-4.7.1, atomic-waker 1.1.2, bitflags 1.3.2, bitflags 2.13.2, blocking 1.7.0, bumpalo 3.20.3, cfg-if
-1.0.5, cgl 0.3.2, concurrent-queue 2.5.0, core-foundation 0.9.4, core-foundation-sys 0.8.7,
-core-graphics 0.23.2, core-graphics-types 0.1.3, crossbeam-deque 0.8.8, crossbeam-epoch 0.9.21,
-crossbeam-utils 0.8.23, data-url 0.3.2, derive_arbitrary 1.5.0, either 1.19.0, equivalent 1.0.2,
-errno 0.3.14, euclid 0.22.14, event-listener 5.4.2, event-listener-strategy 0.5.4, fastrand 2.5.0,
-flate2 1.1.10, futures-lite 2.6.1, gethostname 1.1.0, glow 0.17.0, hashbrown 0.16.1, hashbrown
-0.17.1, hermit-abi 0.5.3, indexmap 2.14.2, itertools 0.13.0, itertools 0.15.0, js-sys 0.3.106,
-khronos-egl 6.0.0, linux-raw-sys 0.12.1, linux-raw-sys 0.4.15, lock_api 0.4.14, log 0.4.34,
+4.7.1, atomic-waker 1.1.2, base64 0.22.1, bitflags 1.3.2, bitflags 2.13.2, blocking 1.7.0, bumpalo
+3.20.3, cfg-if 1.0.5, cgl 0.3.2, concurrent-queue 2.5.0, core-foundation 0.9.4, core-foundation-sys
+0.8.7, core-graphics 0.23.2, core-graphics-types 0.1.3, crossbeam-deque 0.8.8, crossbeam-epoch
+0.9.21, crossbeam-utils 0.8.23, data-url 0.3.2, derive_arbitrary 1.5.0, either 1.19.0, equivalent
+1.0.2, errno 0.3.14, euclid 0.22.14, event-listener 5.4.2, event-listener-strategy 0.5.4, fastrand
+2.5.0, flate2 1.1.10, futures-lite 2.6.1, gethostname 1.1.0, glow 0.17.0, hashbrown 0.16.1,
+hashbrown 0.17.1, hermit-abi 0.5.3, indexmap 2.14.2, itertools 0.13.0, itertools 0.15.0, js-sys
+0.3.106, khronos-egl 6.0.0, linux-raw-sys 0.12.1, linux-raw-sys 0.4.15, lock_api 0.4.14, log 0.4.34,
 num-complex 0.4.6, num-traits 0.2.19, once_cell 1.21.4, ordered-stream 0.2.0, parking 2.2.1,
 parking_lot 0.12.5, parking_lot_core 0.9.12, percent-encoding 2.3.2, piper 0.2.5, plain 0.2.3, png
 0.18.1, polling 3.11.0, pollster 0.4.0, pollster 1.0.1, rayon 1.12.0, rayon-core 1.13.0,
@@ -2219,6 +2227,32 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 
+================================================================================
+base64 0.22.1
+================================================================================
+
+The MIT License (MIT)
+
+Copyright (c) 2015 Alice Maz
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+
 ================================================================================
 bit-set 0.10.0
 ================================================================================
@@ -2546,7 +2580,9 @@ IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 DEALINGS IN THE SOFTWARE.
 
 ================================================================================
-block-buffer 0.10.4, cpufeatures 0.2.17, crypto-common 0.1.7, digest 0.10.7, sha2 0.10.9
+block-buffer 0.10.4, block-buffer 0.12.1, const-oid 0.10.2, cpufeatures 0.2.17, cpufeatures 0.3.1,
+crypto-common 0.1.7, crypto-common 0.2.2, digest 0.10.7, digest 0.11.3, hybrid-array 0.4.15, sha2
+0.10.9, sha2 0.11.1
 ================================================================================
 
 Apache License
@@ -2751,6 +2787,36 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 
+================================================================================
+block-buffer 0.12.1
+================================================================================
+
+Copyright (c) 2018-2025 The RustCrypto Project Developers
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+
 ================================================================================
 branches 0.3.0, rclite 0.2.8
 ================================================================================
@@ -3379,6 +3445,36 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 
+================================================================================
+const-oid 0.10.2, cpufeatures 0.3.1
+================================================================================
+
+Copyright (c) 2020-2026 The RustCrypto Project Developers
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+
 ================================================================================
 cpufeatures 0.2.17
 ================================================================================
@@ -3731,6 +3827,36 @@ OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
 IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 DEALINGS IN THE SOFTWARE.
 
+================================================================================
+crypto-common 0.2.2
+================================================================================
+
+Copyright (c) 2021-2026 RustCrypto Developers
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+
 ================================================================================
 cursor-icon 1.2.0
 ================================================================================
@@ -4063,6 +4189,37 @@ OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
 IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 DEALINGS IN THE SOFTWARE.
 
+================================================================================
+digest 0.11.3
+================================================================================
+
+Copyright (c) 2017-2025 RustCrypto Developers
+Copyright (c) 2017 Artyom Pavlov
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+
 ================================================================================
 dlib 0.5.3
 ================================================================================
@@ -6093,6 +6250,36 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
 
+================================================================================
+hybrid-array 0.4.15
+================================================================================
+
+Copyright (c) 2022-2026 The RustCrypto Project Developers
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+
 ================================================================================
 iana-time-zone 0.1.65, iana-time-zone-haiku 0.1.2
 ================================================================================
@@ -9890,6 +10077,39 @@ OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
 IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 DEALINGS IN THE SOFTWARE.
 
+================================================================================
+sha2 0.11.1
+================================================================================
+
+Copyright (c) 2016-2026 The RustCrypto Project Developers
+Copyright (c) 2016 Artyom Pavlov
+Copyright (c) 2009-2013 Mozilla Foundation
+Copyright (c) 2006-2009 Graydon Hoare
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+
 ================================================================================
 signal-hook-registry 1.4.8
 ================================================================================

apps/fieldcraft-cli/src/main.rs

@@ -2,6 +2,7 @@
 //! fieldcraft-cli run <script.json>
 //! fieldcraft-cli features
 //! fieldcraft-cli mcp [--connect ADDR | --headless] [--automation-read-root DIR] [--automation-write-root DIR]
+//! fieldcraft-cli --version
 #![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
 #![forbid(unsafe_code)]
 
@@ -26,6 +27,7 @@ usage:
       --automation-read-root DIR       files may be read only inside DIR
       --automation-write-root DIR      files may be written only inside DIR (with either root,
                                        the access a root left out is not granted)
+  fieldcraft-cli --version             print the version
 ";
 
 /// Largest script accepted (bytes).
@@ -46,6 +48,10 @@ fn main() -> ExitCode {
         }
         Some("mcp") => mcp(args.get(1..).unwrap_or(&[])),
         Some("run") => args.get(1).ok_or_else(|| format!("run needs a script\n\n{USAGE}")).and_then(|p| run(p)),
+        Some("-V" | "--version") => {
+            println!("fieldcraft-cli {}", env!("CARGO_PKG_VERSION"));
+            Ok(())
+        }
         Some("-h" | "--help" | "help") | None => {
             print!("{USAGE}");
             Ok(())

apps/fieldcraft-cli/tests/version.rs

@@ -0,0 +1,12 @@
+//! `fieldcraft-cli --version`, which the release packaging runs to check each build.
+
+use std::process::Command;
+
+#[test]
+fn version_prints_the_workspace_version() {
+    for flag in ["--version", "-V"] {
+        let out = Command::new(env!("CARGO_BIN_EXE_fieldcraft-cli")).arg(flag).output().unwrap();
+        assert!(out.status.success(), "{flag}: {out:?}");
+        assert_eq!(String::from_utf8_lossy(&out.stdout).trim(), format!("fieldcraft-cli {}", env!("CARGO_PKG_VERSION")));
+    }
+}

apps/fieldcraft-web/Cargo.toml

@@ -0,0 +1,34 @@
+[package]
+name = "fieldcraft-web"
+description = "FieldCraft in the browser (eframe web runner, WebGPU with WebGL2 fallback)"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+publish = false
+
+[lints]
+workspace = true
+
+[[bin]]
+name = "fieldcraft-web"
+path = "src/main.rs"
+
+[dependencies]
+fieldcraft-engine = { workspace = true }
+fieldcraft-ui-egui = { workspace = true }
+fieldcraft-io = { workspace = true }
+egui = { workspace = true }
+serde_json = { workspace = true }
+log = { workspace = true }
+
+[target.'cfg(target_arch = "wasm32")'.dependencies]
+# `wgpu` pulls egui-wgpu's defaults: WebGPU plus the WebGL2 fallback.
+eframe = { workspace = true, features = ["default_fonts", "wgpu", "accesskit"] }
+# `file-handle-inner`: a picked file's size, checked before it is read.
+rfd = { workspace = true, features = ["file-handle-inner"] }
+wasm-bindgen = "0.2"
+wasm-bindgen-futures = "0.4"
+js-sys = "0.3"
+web-sys = { version = "0.3", features = ["Window", "Document", "Element", "HtmlElement", "HtmlCanvasElement", "HtmlAnchorElement", "Blob", "BlobPropertyBag", "Url", "Location", "DomTokenList", "CssStyleDeclaration", "Event", "EventTarget", "BeforeUnloadEvent", "Storage"] }
+# Autosaves kept in the browser's local storage, which holds text.
+base64 = "0.22"

apps/fieldcraft-web/Trunk.toml

@@ -0,0 +1,10 @@
+# Build with: trunk build --release   (from apps/fieldcraft-web; docs/web.md)
+[build]
+target = "index.html"
+dist = "../../dist/web"
+public_url = "./"
+filehash = true
+
+[serve]
+addresses = ["127.0.0.1"]
+port = 8790

apps/fieldcraft-web/index.html

@@ -0,0 +1,54 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=no">
+  <title>FieldCraft</title>
+  <meta name="description" content="Open-source CAE modeling in Rust: mesh a part, set up the analysis and solve it, in your browser.">
+  <link data-trunk rel="rust" data-bin="fieldcraft-web" data-wasm-opt="z" data-weak-refs />
+  <link data-trunk rel="icon" type="image/svg+xml" href="../../assets/app-icon/icon-small.svg" />
+  <link data-trunk rel="copy-file" href="../../assets/app-icon/icon.iconset/icon_128x128@2x.png" data-target-path="icons" />
+  <link rel="apple-touch-icon" href="icons/icon_128x128@2x.png">
+  <style>
+    html, body { margin: 0; padding: 0; width: 100%; height: 100%; overflow: hidden; background: #262c37; }
+    #fieldcraft_canvas { position: absolute; inset: 0; width: 100%; height: 100%; display: block; }
+    #fieldcraft_loading { position: absolute; inset: 0; display: flex; flex-direction: column; align-items: center; justify-content: center;
+      gap: 16px; padding: 0 16px; text-align: center; color: #c3cad6; font: 14px system-ui, sans-serif; pointer-events: none; }
+    #fieldcraft_loading img { width: 96px; height: 96px; }
+    #fieldcraft_loading p { margin: 0; max-width: 32em; }
+    #fieldcraft_loading.failed { pointer-events: auto; }
+    #fieldcraft_loading.failed img, #fieldcraft_loading.failed .spinner { display: none; }
+    .spinner { width: 24px; height: 24px; border-radius: 50%; border: 3px solid #4a5468; border-top-color: #c3cad6; animation: spin 0.9s linear infinite; }
+    @keyframes spin { to { transform: rotate(360deg); } }
+    @media (prefers-reduced-motion: reduce) { .spinner { animation: none; } }
+  </style>
+</head>
+<body>
+  <canvas id="fieldcraft_canvas"></canvas>
+  <div id="fieldcraft_loading">
+    <img src="icons/icon_128x128@2x.png" alt="">
+    <div class="spinner"></div>
+    <p>Loading FieldCraft&hellip;</p>
+    <noscript><p>FieldCraft needs JavaScript and WebAssembly.</p></noscript>
+  </div>
+  <script>
+    // The page could not load or start the app (no WebAssembly, a failed download): say so
+    // instead of loading forever. Once the app runs it removes the loading screen.
+    (function () {
+      function fail(why) {
+        var el = document.getElementById("fieldcraft_loading");
+        if (!el || el.classList.contains("failed")) return;
+        el.classList.add("failed");
+        el.textContent = "";
+        ["FieldCraft could not start: " + why, "It needs a current browser with WebAssembly and WebGPU or WebGL2."].forEach(function (t) {
+          var p = document.createElement("p");
+          p.textContent = t;
+          el.appendChild(p);
+        });
+      }
+      if (typeof WebAssembly !== "object") fail("this browser has no WebAssembly.");
+      addEventListener("unhandledrejection", function (e) { fail(String(e.reason && e.reason.message || e.reason)); });
+    })();
+  </script>
+</body>
+</html>

apps/fieldcraft-web/src/main.rs

@@ -0,0 +1,76 @@
+//! FieldCraft in the browser.
+//!
+//! Runs the same [`fieldcraft_ui_egui::ModelApp`] as the desktop app through eframe's web runner
+//! (wgpu: WebGPU where available, WebGL2 otherwise). Build with `trunk build --release` from this
+//! directory (output in `dist/web`); docs/web.md says what works in the browser.
+//!
+//! Differences from the desktop app, all behind the UI's host services:
+//! - files live in the page ([`fieldcraft_io::fs`] keeps them in memory): File › Open and drops
+//!   read the computer's files into it; Save, Save As and Write Deck hand the written file out as
+//!   a download;
+//! - autosaves for recovery are kept in the browser's local storage ([`storage`]);
+//! - no control channel (a page can't listen on a socket);
+//! - background jobs (meshing, solving) run on the page's one thread once the window has shown
+//!   that they run.
+//!
+//! Address flags: `?sample` or `?sample=cantilever` opens a sample, `?webgl` forces WebGL2.
+#![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
+#![forbid(unsafe_code)]
+
+#[cfg(target_arch = "wasm32")]
+mod storage;
+#[cfg(target_arch = "wasm32")]
+mod web;
+
+#[cfg(target_arch = "wasm32")]
+fn main() {
+    web::start();
+}
+
+#[cfg(not(target_arch = "wasm32"))]
+fn main() {
+    eprintln!("fieldcraft-web only runs in the browser: build it with `trunk build --release` in apps/fieldcraft-web (docs/web.md)");
+}
+
+/// The sample an address asks for (`?sample` opens the first sample, `?sample=NAME` that one).
+#[cfg_attr(not(target_arch = "wasm32"), allow(dead_code))]
+fn sample_in_query(query: &str) -> Option<String> {
+    let first = fieldcraft_engine::sample::SAMPLES.first().map_or("", |s| s.name);
+    query.trim_start_matches('?').split('&').find_map(|kv| {
+        let (key, value) = kv.split_once('=').unwrap_or((kv, ""));
+        (key == "sample").then(|| if value.is_empty() { first } else { value }.to_string())
+    })
+}
+
+/// The name a file from the computer is kept under in the page: its last path part, without
+/// characters a path would read as folders.
+#[cfg_attr(not(target_arch = "wasm32"), allow(dead_code))]
+fn safe_name(name: &str) -> String {
+    let last = name.rsplit(['/', '\\']).next().unwrap_or_default();
+    let clean: String = last.chars().filter(|c| !c.is_control()).take(200).collect();
+    if clean.is_empty() || clean == "." || clean == ".." { "file".to_string() } else { clean }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn samples_from_the_address() {
+        assert_eq!(sample_in_query(""), None);
+        assert_eq!(sample_in_query("?sample").as_deref(), Some("parts"));
+        assert_eq!(sample_in_query("?webgl&sample=cantilever").as_deref(), Some("cantilever"));
+        assert_eq!(sample_in_query("?sample=").as_deref(), Some("parts"));
+        assert_eq!(sample_in_query("?samples=x"), None);
+    }
+
+    #[test]
+    fn file_names_stay_in_their_folder() {
+        assert_eq!(safe_name("beam.fieldcraft"), "beam.fieldcraft");
+        assert_eq!(safe_name("../../etc/passwd"), "passwd");
+        assert_eq!(safe_name("C:\\work\\plate.solidcraft"), "plate.solidcraft");
+        assert_eq!(safe_name(".."), "file");
+        assert_eq!(safe_name(""), "file");
+        assert_eq!(safe_name("a\u{0}b.3mf"), "ab.3mf");
+    }
+}

apps/fieldcraft-web/src/storage.rs

@@ -0,0 +1,101 @@
+//! Autosaves kept in the browser.
+//!
+//! The engine's recovery folder is [`fieldcraft_io::recovery::BROWSER_DIR`] among the page's
+//! files, which last only as long as the page. This mirrors it to the browser's local storage
+//! (kept across visits, shared by the site's tabs): each file as base64 under
+//! [`PREFIX`]`<file name>`. At start the stored files go back into the folder, so the desktop's
+//! recovery flow (File › Recover…, `file.recovery.*`) offers what a closed or crashed page left.
+//!
+//! Local storage holds a few megabytes per site: an autosave larger than [`MAX_AUTOSAVE_BYTES`]
+//! (or one the browser refuses) is not kept, and the status bar says so.
+
+use std::collections::BTreeSet;
+use std::path::Path;
+
+use base64::Engine as _;
+use base64::engine::general_purpose::STANDARD;
+use fieldcraft_io::recovery::BROWSER_DIR;
+
+const PREFIX: &str = "fieldcraft-recovery/";
+
+/// Largest stored file taken back (local storage itself holds less).
+const MAX_STORED_CHARS: usize = 64 << 20;
+
+/// Largest autosave kept: base64 makes it a third larger, and browsers give a site about 5 MB.
+pub const MAX_AUTOSAVE_BYTES: usize = 3 << 20;
+
+fn local_storage() -> Result<web_sys::Storage, String> {
+    web_sys::window().ok_or("no window")?.local_storage().map_err(crate::web::js_err)?.ok_or_else(|| "browser storage is turned off".into())
+}
+
+/// The mirror: the stored files this page knows of (took back or wrote), by file name.
+#[derive(Default)]
+pub struct Store {
+    known: BTreeSet<String>,
+}
+
+pub fn dir() -> &'static Path {
+    Path::new(BROWSER_DIR)
+}
+
+/// A file name of the recovery folder that is safe as a key (the engine's ids and extensions).
+fn valid(name: &str) -> bool {
+    !name.is_empty() && name.len() <= 100 && name.chars().all(|c| c.is_ascii_alphanumeric() || c == '-' || c == '.') && !name.starts_with('.')
+}
+
+impl Store {
+    /// Put the stored files back into the recovery folder.
+    pub fn load() -> Store {
+        let mut store = Store::default();
+        let s = match local_storage() {
+            Ok(s) => s,
+            Err(e) => {
+                log::warn!("autosaves: {e}");
+                return store;
+            }
+        };
+        let keys: Vec<String> = (0..s.length().unwrap_or(0)).filter_map(|i| s.key(i).ok().flatten()).collect();
+        for key in keys {
+            let Some(name) = key.strip_prefix(PREFIX).filter(|n| valid(n)) else { continue };
+            let Some(text) = s.get_item(&key).ok().flatten().filter(|t| t.len() <= MAX_STORED_CHARS) else { continue };
+            let Ok(bytes) = STANDARD.decode(text.as_bytes()).map_err(|e| log::warn!("autosave {name} is damaged: {e}")) else { continue };
+            match fieldcraft_io::fs::insert(&dir().join(name), bytes) {
+                Ok(()) => {
+                    store.known.insert(name.to_string());
+                }
+                Err(e) => log::warn!("autosave {name}: {e}"),
+            }
+        }
+        store
+    }
+
+    /// Keep a file the engine wrote in the recovery folder.
+    pub fn put(&mut self, path: &Path, bytes: &[u8]) -> Result<(), String> {
+        let name =
+            path.file_name().and_then(|n| n.to_str()).filter(|n| valid(n)).ok_or_else(|| format!("{}: not a recovery file", path.display()))?;
+        if bytes.len() > MAX_AUTOSAVE_BYTES {
+            return Err(format!("the model ({} MB) is too large for the browser's storage", bytes.len() >> 20));
+        }
+        self.known.insert(name.to_string());
+        local_storage()?
+            .set_item(&format!("{PREFIX}{name}"), &STANDARD.encode(bytes))
+            .map_err(|e| format!("browser storage is full or turned off ({})", crate::web::js_err(e)))
+    }
+
+    /// Drop the stored files whose entries left the recovery folder (cleared once saved,
+    /// recovered and discarded). Only files this page knows of: another tab's stay.
+    pub fn sync_removals(&mut self) {
+        let present: BTreeSet<String> =
+            fieldcraft_io::fs::list(dir()).iter().filter_map(|p| p.file_name().and_then(|n| n.to_str()).map(str::to_string)).collect();
+        let gone: Vec<String> = self.known.difference(&present).cloned().collect();
+        if gone.is_empty() {
+            return;
+        }
+        let Ok(s) = local_storage() else { return };
+        for name in gone {
+            if s.remove_item(&format!("{PREFIX}{name}")).is_ok() {
+                self.known.remove(&name);
+            }
+        }
+    }
+}

apps/fieldcraft-web/src/web.rs

@@ -0,0 +1,326 @@
+//! The browser shell: the web services of the UI (file pickers, downloads), dropped files, the
+//! autosave, and eframe's web runner.
+//!
+//! Structure follows VectorCraft's `apps/vectorcraft-web/src/web.rs` and SolidCraft's
+//! `apps/solidcraft-web/src/main.rs` (MIT OR Apache-2.0), see ATTRIBUTION.md.
+
+use std::cell::{Cell, RefCell};
+use std::path::Path;
+use std::rc::Rc;
+
+use fieldcraft_engine::Session;
+use fieldcraft_engine::autosave::Autosaver;
+use fieldcraft_ui_egui::files::Kind;
+use fieldcraft_ui_egui::{Filter, ModelApp, Services};
+use wasm_bindgen::JsCast as _;
+
+use crate::storage::{self, Store};
+
+const CANVAS_ID: &str = "fieldcraft_canvas";
+const LOADING_ID: &str = "fieldcraft_loading";
+const DEPTH_BITS: u8 = 24;
+
+/// The page's folder for files from the computer and the files commands write.
+const FILES_DIR: &str = "/files";
+
+/// How often unsaved changes are autosaved for recovery (seconds), as on the desktop.
+const AUTOSAVE_SECONDS: f64 = 30.0;
+
+/// Files read from the computer (picked together or dropped together), waiting for the next
+/// frame: (name, bytes or why they could not be read) each.
+type Batch = Vec<(String, Result<Vec<u8>, String>)>;
+type Inbox = Rc<RefCell<Vec<Batch>>>;
+
+/// Largest file read from the computer: what the page can hold.
+const MAX_READ_BYTES: f64 = fieldcraft_io::memory::MAX_TOTAL_BYTES as f64;
+
+/// Why a file of `size` bytes is not read, if it is too large.
+fn too_large(size: f64) -> Option<String> {
+    (size > MAX_READ_BYTES)
+        .then(|| format!("{} MB is more than this page holds ({} MB)", (size / 1048576.0).round(), fieldcraft_io::memory::MAX_TOTAL_BYTES >> 20))
+}
+
+/// Hand files read from the computer to the next frame.
+fn deliver(inbox: &Inbox, ctx: &egui::Context, batch: Batch) {
+    inbox.borrow_mut().push(batch);
+    ctx.request_repaint();
+}
+
+/// Where a file named `name` is kept in the page.
+fn page_path(name: &str) -> String {
+    format!("{FILES_DIR}/{}", crate::safe_name(name))
+}
+
+thread_local! {
+    /// The model has unsaved changes: leaving the page asks first.
+    static UNSAVED: Cell<bool> = const { Cell::new(false) };
+}
+
+pub fn js_err(e: wasm_bindgen::JsValue) -> String {
+    e.as_string().unwrap_or_else(|| format!("{e:?}"))
+}
+
+fn query() -> String {
+    web_sys::window().and_then(|w| w.location().search().ok()).unwrap_or_default()
+}
+
+fn element(id: &str) -> Option<web_sys::Element> {
+    web_sys::window()?.document()?.get_element_by_id(id)
+}
+
+pub fn start() {
+    eframe::WebLogger::init(log::LevelFilter::Info).ok();
+    // The browser's clock for the recovery entries (the plain wasm target has none).
+    fieldcraft_io::recovery::set_clock(|| js_sys::Date::now().max(0.0) as u64);
+    let Some(window) = web_sys::window() else { return };
+    ask_before_unload(&window);
+    let Some(canvas) = element(CANVAS_ID).and_then(|e| e.dyn_into::<web_sys::HtmlCanvasElement>().ok()) else {
+        log::error!("missing <canvas id=\"{CANVAS_ID}\">");
+        return;
+    };
+    wasm_bindgen_futures::spawn_local(async move {
+        let result = eframe::WebRunner::new()
+            .start(
+                canvas,
+                web_options(),
+                Box::new(|cc| {
+                    let inbox = Inbox::default();
+                    let mut app = ModelApp::new(Session::default()).with_services(services(inbox.clone(), cc.egui_ctx.clone()));
+                    if let Some(rs) = &cc.wgpu_render_state {
+                        let info = rs.adapter.get_info();
+                        log::info!("fieldcraft-web: graphics {:?} {}, MSAA {}x", info.backend, info.name, rs.msaa_samples);
+                        app.set_wgpu(rs, DEPTH_BITS, rs.msaa_samples, &cc.egui_ctx);
+                    }
+                    // The autosaves a closed or crashed page left, back in the recovery folder.
+                    let store = Store::load();
+                    let listed = app.session.execute("file.recovery.list", &serde_json::json!({}));
+                    let recoverable = listed.ok().and_then(|v| v.as_array().map(Vec::len)).unwrap_or(0);
+                    let autosaver = Autosaver::new(storage::dir()).map_err(|e| log::warn!("autosave unavailable: {e}")).ok();
+                    if let Some(name) = crate::sample_in_query(&query()) {
+                        app.open_sample(&name);
+                    }
+                    if recoverable > 0 {
+                        app.set_status(format!("{recoverable} autosaved model(s) can be recovered: File › Recover…"), false);
+                    }
+                    Ok(Box::new(Shell { app, inbox, store, autosaver, autosaved_at: 0.0, storage_error: false }))
+                }),
+            )
+            .await;
+        match result {
+            Ok(()) => {
+                if let Some(el) = element(LOADING_ID) {
+                    el.remove();
+                }
+            }
+            Err(e) => failed(&format!("FieldCraft could not start: {}", js_err(e))),
+        }
+    });
+}
+
+/// The runner's options: wgpu (WebGPU where available, else WebGL2; `?webgl` forces WebGL2).
+fn web_options() -> eframe::WebOptions {
+    let mut options = eframe::WebOptions { depth_buffer: DEPTH_BITS, ..Default::default() };
+    if query().split(['?', '&']).any(|kv| kv == "webgl")
+        && let eframe::egui_wgpu::WgpuSetup::CreateNew(create) = &mut options.wgpu_options.wgpu_setup
+    {
+        create.instance_descriptor.backends = eframe::wgpu::Backends::GL;
+    }
+    options
+}
+
+/// Replace the loading screen with why the app could not start.
+fn failed(why: &str) {
+    log::error!("{why}");
+    let Some(el) = element(LOADING_ID) else { return };
+    let Some(document) = web_sys::window().and_then(|w| w.document()) else { return };
+    el.set_text_content(None);
+    // Best effort: the console has the message too.
+    let _ = el.class_list().add_1("failed");
+    for line in
+        [why, "FieldCraft needs a browser with WebGPU or WebGL2 (a current Chrome, Edge, Firefox or Safari) and graphics acceleration turned on."]
+    {
+        if let Ok(p) = document.create_element("p") {
+            p.set_text_content(Some(line));
+            let _ = el.append_child(&p);
+        }
+    }
+}
+
+/// The browser's "leave site? changes you made may not be saved" prompt while the model has
+/// unsaved changes (a page that is closing can't show its own dialog).
+fn ask_before_unload(window: &web_sys::Window) {
+    let on_unload = wasm_bindgen::closure::Closure::<dyn FnMut(web_sys::BeforeUnloadEvent)>::new(|e: web_sys::BeforeUnloadEvent| {
+        if UNSAVED.with(Cell::get) {
+            e.prevent_default();
+            e.set_return_value("unsaved");
+        }
+    });
+    if let Err(e) = window.add_event_listener_with_callback("beforeunload", on_unload.as_ref().unchecked_ref()) {
+        log::warn!("couldn't ask before leaving: {}", js_err(e));
+    }
+    // The listener lives as long as the page.
+    on_unload.forget();
+}
+
+/// The UI's host services in the browser.
+fn services(inbox: Inbox, ctx: egui::Context) -> Services {
+    Services {
+        // The browser's file picker: the files arrive in a later frame (the picker and the reads
+        // are asynchronous), so the call itself picks nothing.
+        pick_open: Some(Box::new(move |filters: &[Filter]| {
+            let (inbox, ctx) = (inbox.clone(), ctx.clone());
+            let dialog = filters.iter().fold(rfd::AsyncFileDialog::new(), |d, f| d.add_filter(f.name, f.extensions));
+            wasm_bindgen_futures::spawn_local(async move {
+                let Some(files) = dialog.pick_files().await else { return };
+                let mut batch = Vec::with_capacity(files.len());
+                for f in files {
+                    let read = match too_large(f.inner().size()) {
+                        Some(why) => Err(why),
+                        None => Ok(f.read().await),
+                    };
+                    batch.push((f.file_name(), read));
+                }
+                deliver(&inbox, &ctx, batch);
+            });
+            None
+        })),
+        // Saving writes into the page; the shell hands each written file out as a download.
+        pick_save: Some(Box::new(|name: &str, _: &[Filter]| Some(page_path(name)))),
+        // The recent list holds the page's files, which go with the page.
+        recent_path: None,
+    }
+}
+
+/// The app with the browser's files around it.
+struct Shell {
+    app: ModelApp,
+    inbox: Inbox,
+    store: Store,
+    /// `None` when autosave could not start.
+    autosaver: Option<Autosaver>,
+    /// App time of the last autosave check.
+    autosaved_at: f64,
+    /// The last autosave did not fit in the browser's storage (said once until one fits).
+    storage_error: bool,
+}
+
+impl Shell {
+    /// Files read from the computer go into the page's folder, then open: a model with the
+    /// design and meshes it refers to picked or dropped with it, else each file in turn.
+    fn open_arrived(&mut self) {
+        let batches: Vec<_> = self.inbox.borrow_mut().drain(..).collect();
+        for batch in batches {
+            let mut paths = Vec::with_capacity(batch.len());
+            for (name, read) in batch {
+                let path = page_path(&name);
+                match read.and_then(|bytes| fieldcraft_io::fs::insert(Path::new(&path), bytes).map_err(|e| e.to_string())) {
+                    Ok(()) => paths.push(path),
+                    Err(e) => self.app.set_status(format!("{name}: {e}"), true),
+                }
+            }
+            let model = paths.iter().find(|p| Kind::of(p) == Some(Kind::Model)).cloned();
+            match model {
+                // Its geometry files open with it, from the same folder.
+                Some(model) => self.app.open_path(&model),
+                None => {
+                    for p in &paths {
+                        self.app.open_path(p);
+                    }
+                }
+            }
+        }
+    }
+
+    /// What commands wrote: autosaves to the browser's storage, everything else downloaded.
+    fn hand_out_writes(&mut self) {
+        for (path, bytes) in fieldcraft_io::fs::take_writes() {
+            if path.parent() == Some(storage::dir()) {
+                match self.store.put(&path, &bytes) {
+                    Ok(()) => self.storage_error = false,
+                    Err(e) if !self.storage_error => {
+                        self.storage_error = true;
+                        self.app.set_status(format!("Autosave: {e}. Save the model to keep it (File › Save downloads it)"), true);
+                    }
+                    Err(e) => log::warn!("autosave: {e}"),
+                }
+            } else if let Err(e) = download(&path, &bytes) {
+                self.app.set_status(format!("{}: the download did not start ({e})", path.display()), true);
+            }
+        }
+        self.store.sync_removals();
+    }
+
+    fn autosave(&mut self, ctx: &egui::Context) {
+        let Some(a) = &mut self.autosaver else { return };
+        if self.app.now - self.autosaved_at >= AUTOSAVE_SECONDS {
+            self.autosaved_at = self.app.now;
+            if let Err(e) = a.save(&self.app.session) {
+                log::warn!("autosave: {e}");
+            }
+        }
+        ctx.request_repaint_after(std::time::Duration::from_secs_f64(AUTOSAVE_SECONDS));
+    }
+}
+
+impl eframe::App for Shell {
+    fn logic(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
+        self.open_arrived();
+        self.app.logic(ctx);
+        self.autosave(ctx);
+        UNSAVED.with(|u| u.set(self.app.session.is_dirty() && !self.app.session.journal.is_empty()));
+    }
+
+    /// Dropped files are read here (browsers read them asynchronously) and arrive through the
+    /// inbox; the app never sees their names as paths.
+    fn raw_input_hook(&mut self, ctx: &egui::Context, raw: &mut egui::RawInput) {
+        let dropped = std::mem::take(&mut raw.dropped_files);
+        if !dropped.is_empty() {
+            let (inbox, ctx) = (self.inbox.clone(), ctx.clone());
+            wasm_bindgen_futures::spawn_local(async move {
+                let mut batch = Vec::with_capacity(dropped.len());
+                for f in dropped {
+                    let name = f.path().to_string_lossy().to_string();
+                    let read = match f.web_file().and_then(|w| too_large(w.size())) {
+                        Some(why) => Err(why),
+                        None => f.bytes_async().await,
+                    };
+                    batch.push((name, read));
+                }
+                deliver(&inbox, &ctx, batch);
+            });
+        }
+        self.app.raw_input_hook(raw);
+    }
+
+    fn ui(&mut self, ui: &mut egui::Ui, _frame: &mut eframe::Frame) {
+        self.app.ui(ui);
+        // Once a frame, after everything that writes: autosaves, saves and decks.
+        self.hand_out_writes();
+    }
+}
+
+/// Hand `bytes` out as a download named after the last part of `path`.
+fn download(path: &Path, bytes: &[u8]) -> Result<(), String> {
+    let name = path.file_name().and_then(|n| n.to_str()).unwrap_or("fieldcraft").to_string();
+    let window = web_sys::window().ok_or("no window")?;
+    let document = window.document().ok_or("no document")?;
+    let parts = js_sys::Array::of1(&js_sys::Uint8Array::from(bytes));
+    let options = web_sys::BlobPropertyBag::new();
+    options.set_type("application/octet-stream");
+    let blob = web_sys::Blob::new_with_u8_array_sequence_and_options(&parts, &options).map_err(js_err)?;
+    let url = web_sys::Url::create_object_url_with_blob(&blob).map_err(js_err)?;
+    let a: web_sys::HtmlAnchorElement = document.create_element("a").map_err(js_err)?.dyn_into().map_err(|_| "not a link")?;
+    a.set_href(&url);
+    a.set_download(&name);
+    a.style().set_property("display", "none").map_err(js_err)?;
+    document.body().ok_or("no body")?.append_child(&a).map_err(js_err)?;
+    a.click();
+    a.remove();
+    // Revoked once the click has been dispatched; the download keeps its own reference.
+    let revoke = wasm_bindgen::closure::Closure::once_into_js(move || {
+        let _ = web_sys::Url::revoke_object_url(&url);
+    });
+    // The download has started: a timer that can't be set leaves the URL allocated, no more.
+    let _ = window.set_timeout_with_callback_and_timeout_and_arguments_0(revoke.unchecked_ref(), 10_000);
+    Ok(())
+}

apps/fieldcraft/Cargo.toml

@@ -18,3 +18,7 @@ eframe = { workspace = true, features = ["default_fonts", "wgpu", "accesskit", "
 egui = { workspace = true }
 serde_json = { workspace = true }
 log = { workspace = true }
+
+[build-dependencies]
+# The Windows executable's icon resource (build.rs).
+embed-resource = "3.0.12"

apps/fieldcraft/build.rs

@@ -0,0 +1,20 @@
+//! Windows builds embed the application icon (assets/app-icon/icon.ico) in `fieldcraft.exe`, so
+//! Explorer, the taskbar and shortcuts show it. Other targets need nothing here.
+#![forbid(unsafe_code)]
+
+use std::path::PathBuf;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let icon = PathBuf::from(std::env::var("CARGO_MANIFEST_DIR")?).join("../../assets/app-icon/icon.ico");
+    println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo:rerun-if-changed={}", icon.display());
+    if std::env::var("CARGO_CFG_TARGET_OS")? != "windows" {
+        return Ok(());
+    }
+    let out = PathBuf::from(std::env::var("OUT_DIR")?);
+    let rc = out.join("fieldcraft.rc");
+    std::fs::write(&rc, format!("1 ICON \"{}\"\n", icon.display().to_string().replace('\\', "/")))?;
+    // Missing resource tools are a build error, rather than silently shipping a generic icon.
+    embed_resource::compile_for(&rc, ["fieldcraft"], embed_resource::NONE).manifest_required()?;
+    Ok(())
+}

apps/fieldcraft/src/main.rs

@@ -22,6 +22,9 @@ const DEPTH_BITS: u8 = 24;
 /// The window draws its own caption buttons where the OS ones would sit apart from the app bar.
 const CUSTOM_TITLEBAR: bool = !cfg!(target_os = "macos");
 const MSAA: u16 = 4;
+/// The reverse-DNS application id: the Wayland app_id / X11 class, matched to the packaged
+/// `.desktop` entry (packaging/linux), and the macOS bundle id (packaging/macos/Info.plist.in).
+const APP_ID: &str = "io.github.jyviko.fieldcraft";
 
 /// The window and Dock icon: the 256 px export of the application icon (assets/app-icon).
 const ICON_PNG: &[u8] = include_bytes!("../../../assets/app-icon/icon.iconset/icon_128x128@2x.png");
@@ -148,6 +151,7 @@ fn main() -> eframe::Result {
     let options = eframe::NativeOptions {
         viewport: egui::ViewportBuilder::default()
             .with_title("FieldCraft")
+            .with_app_id(APP_ID)
             .with_icon(app_icon())
             .with_inner_size([1400.0, 900.0])
             .with_min_inner_size([960.0, 600.0])

assets/app-icon/FieldCraft.icon/Assets/01-floor-dark.svg

@@ -4,15 +4,15 @@
     <clipPath id="clip-path-1">
       <path d="M320 100 L704 100 C854 100 924 170 924 320 L924 704 C924 854 854 924 704 924 L320 924 C170 924 100 854 100 704 L100 320 C100 170 170 100 320 100 Z"/>
     </clipPath>
-    <radialGradient id="radial-gradient-1" cx="0" cy="0" r="578" gradientTransform="matrix(1 0 0 0.5 512 720)" gradientUnits="userSpaceOnUse">
-      <stop offset="0" stop-color="#4f8a82"/>
-      <stop offset="0.3" stop-color="#4f8a82" stop-opacity="0.9"/>
-      <stop offset="0.65" stop-color="#4f8a82" stop-opacity="0.35"/>
-      <stop offset="1" stop-color="#4f8a82" stop-opacity="0"/>
+    <radialGradient id="radial-gradient-1" cx="0" cy="0" r="560" gradientTransform="matrix(1 0 0 0.5 512 650)" gradientUnits="userSpaceOnUse">
+      <stop offset="0" stop-color="#4f6a86"/>
+      <stop offset="0.3" stop-color="#4f6a86" stop-opacity="0.9"/>
+      <stop offset="0.65" stop-color="#4f6a86" stop-opacity="0.35"/>
+      <stop offset="1" stop-color="#4f6a86" stop-opacity="0"/>
     </radialGradient>
   </defs>
   <title>FieldCraft icon floor grid (Dark)</title>
   <g id="Floor_grid" data-name="Floor grid" clip-path="url(#clip-path-1)">
-    <path id="floor_grid" data-name="floor grid" d="M154.62 100 L100 131.53 M869.38 100 L924 131.53 M368.82 100 L100 255.2 M655.18 100 L924 255.2 M583.01 100 L100 378.87 M440.99 100 L924 378.87 M797.21 100 L100 502.53 M226.79 100 L924 502.53 M924 150.47 L100 626.2 M100 150.47 L924 626.2 M924 274.13 L100 749.87 M100 274.13 L924 749.87 M924 397.8 L100 873.53 M100 397.8 L924 873.53 M924 521.47 L226.79 924 M100 521.47 L797.21 924 M924 645.13 L440.99 924 M100 645.13 L583.01 924 M924 768.8 L655.18 924 M100 768.8 L368.82 924 M924 892.47 L869.38 924 M100 892.47 L154.62 924" fill="none" stroke="url(#radial-gradient-1)" stroke-width="3" stroke-linejoin="round"/>
+    <path id="floor_grid" data-name="floor grid" d="M165.59 100 L100 137.87 M858.41 100 L924 137.87 M295.49 100 L100 212.87 M728.51 100 L924 212.87 M425.4 100 L100 287.87 M598.6 100 L924 287.87 M555.3 100 L100 362.87 M468.7 100 L924 362.87 M685.21 100 L100 437.87 M338.79 100 L924 437.87 M815.11 100 L100 512.87 M208.89 100 L924 512.87 M924 112.13 L100 587.87 M100 112.13 L924 587.87 M924 187.13 L100 662.87 M100 187.13 L924 662.87 M924 262.13 L100 737.87 M100 262.13 L924 737.87 M924 337.13 L100 812.87 M100 337.13 L924 812.87 M924 412.13 L100 887.87 M100 412.13 L924 887.87 M924 487.13 L167.32 924 M100 487.13 L856.68 924 M924 562.13 L297.23 924 M100 562.13 L726.77 924 M924 637.13 L427.13 924 M100 637.13 L596.87 924 M924 712.13 L557.03 924 M100 712.13 L466.97 924 M924 787.13 L686.94 924 M100 787.13 L337.06 924 M924 862.13 L816.84 924 M100 862.13 L207.16 924" fill="none" stroke="url(#radial-gradient-1)" stroke-width="3" stroke-linejoin="round"/>
   </g>
 </svg>

assets/app-icon/FieldCraft.icon/Assets/01-floor.svg

@@ -4,15 +4,15 @@
     <clipPath id="clip-path-1">
       <path d="M320 100 L704 100 C854 100 924 170 924 320 L924 704 C924 854 854 924 704 924 L320 924 C170 924 100 854 100 704 L100 320 C100 170 170 100 320 100 Z"/>
     </clipPath>
-    <radialGradient id="radial-gradient-1" cx="0" cy="0" r="578" gradientTransform="matrix(1 0 0 0.5 512 720)" gradientUnits="userSpaceOnUse">
-      <stop offset="0" stop-color="#7fa8a2"/>
-      <stop offset="0.3" stop-color="#7fa8a2" stop-opacity="0.9"/>
-      <stop offset="0.65" stop-color="#7fa8a2" stop-opacity="0.35"/>
-      <stop offset="1" stop-color="#7fa8a2" stop-opacity="0"/>
+    <radialGradient id="radial-gradient-1" cx="0" cy="0" r="560" gradientTransform="matrix(1 0 0 0.5 512 650)" gradientUnits="userSpaceOnUse">
+      <stop offset="0" stop-color="#8aa0b4"/>
+      <stop offset="0.3" stop-color="#8aa0b4" stop-opacity="0.9"/>
+      <stop offset="0.65" stop-color="#8aa0b4" stop-opacity="0.35"/>
+      <stop offset="1" stop-color="#8aa0b4" stop-opacity="0"/>
     </radialGradient>
   </defs>
   <title>FieldCraft icon floor grid</title>
   <g id="Floor_grid" data-name="Floor grid" clip-path="url(#clip-path-1)">
-    <path id="floor_grid" data-name="floor grid" d="M154.62 100 L100 131.53 M869.38 100 L924 131.53 M368.82 100 L100 255.2 M655.18 100 L924 255.2 M583.01 100 L100 378.87 M440.99 100 L924 378.87 M797.21 100 L100 502.53 M226.79 100 L924 502.53 M924 150.47 L100 626.2 M100 150.47 L924 626.2 M924 274.13 L100 749.87 M100 274.13 L924 749.87 M924 397.8 L100 873.53 M100 397.8 L924 873.53 M924 521.47 L226.79 924 M100 521.47 L797.21 924 M924 645.13 L440.99 924 M100 645.13 L583.01 924 M924 768.8 L655.18 924 M100 768.8 L368.82 924 M924 892.47 L869.38 924 M100 892.47 L154.62 924" fill="none" stroke="url(#radial-gradient-1)" stroke-width="3" stroke-linejoin="round"/>
+    <path id="floor_grid" data-name="floor grid" d="M165.59 100 L100 137.87 M858.41 100 L924 137.87 M295.49 100 L100 212.87 M728.51 100 L924 212.87 M425.4 100 L100 287.87 M598.6 100 L924 287.87 M555.3 100 L100 362.87 M468.7 100 L924 362.87 M685.21 100 L100 437.87 M338.79 100 L924 437.87 M815.11 100 L100 512.87 M208.89 100 L924 512.87 M924 112.13 L100 587.87 M100 112.13 L924 587.87 M924 187.13 L100 662.87 M100 187.13 L924 662.87 M924 262.13 L100 737.87 M100 262.13 L924 737.87 M924 337.13 L100 812.87 M100 337.13 L924 812.87 M924 412.13 L100 887.87 M100 412.13 L924 887.87 M924 487.13 L167.32 924 M100 487.13 L856.68 924 M924 562.13 L297.23 924 M100 562.13 L726.77 924 M924 637.13 L427.13 924 M100 637.13 L596.87 924 M924 712.13 L557.03 924 M100 712.13 L466.97 924 M924 787.13 L686.94 924 M100 787.13 L337.06 924 M924 862.13 L816.84 924 M100 862.13 L207.16 924" fill="none" stroke="url(#radial-gradient-1)" stroke-width="3" stroke-linejoin="round"/>
   </g>
 </svg>

assets/app-icon/FieldCraft.icon/Assets/02-part.svg

@@ -1,38 +1,51 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="1024" height="1024" viewBox="0 0 1024 1024">
   <defs>
-    <linearGradient id="linear-gradient-1" x1="512" y1="141" x2="512" y2="376.622" gradientUnits="userSpaceOnUse">
-      <stop offset="0" stop-color="#86e3d3"/>
-      <stop offset="1" stop-color="#4cc4b1"/>
-    </linearGradient>
-    <linearGradient id="linear-gradient-2" x1="512" y1="457.259" x2="512" y2="755.042" gradientUnits="userSpaceOnUse">
-      <stop offset="0" stop-color="#86e3d3"/>
-      <stop offset="1" stop-color="#4cc4b1"/>
-    </linearGradient>
-    <linearGradient id="linear-gradient-3" x1="512" y1="209.598" x2="512" y2="624.284" gradientUnits="userSpaceOnUse">
-      <stop offset="0" stop-color="#20b39f"/>
-      <stop offset="1" stop-color="#118c7c"/>
-    </linearGradient>
-    <linearGradient id="linear-gradient-4" x1="512" y1="588.018" x2="512" y2="878.381" gradientUnits="userSpaceOnUse">
-      <stop offset="0" stop-color="#20b39f"/>
-      <stop offset="1" stop-color="#118c7c"/>
-    </linearGradient>
-    <linearGradient id="linear-gradient-5" x1="512" y1="335.738" x2="512" y2="878.381" gradientUnits="userSpaceOnUse">
-      <stop offset="0" stop-color="#0f786d"/>
-      <stop offset="1" stop-color="#0a544e"/>
-    </linearGradient>
-    <linearGradient id="linear-gradient-6" x1="512" y1="558.616" x2="512" y2="658.304" gradientUnits="userSpaceOnUse">
-      <stop offset="0" stop-color="#0b665e"/>
-      <stop offset="1" stop-color="#04302c"/>
-    </linearGradient>
+    <clipPath id="clip-path-1">
+      <path d="M512 200 L764.81 345.96 L512 491.92 L259.19 345.96 Z"/>
+    </clipPath>
+    <clipPath id="clip-path-2">
+      <path d="M252.19 358.08 L505 504.04 L505 795.96 L252.19 650 Z"/>
+    </clipPath>
+    <clipPath id="clip-path-3">
+      <path d="M771.81 650 L519 795.96 L519 504.04 L771.81 358.08 Z"/>
+    </clipPath>
+    <clipPath id="clip-path-4">
+      <path d="M512 200 L764.81 345.96 L512 491.92 L259.19 345.96 Z M252.19 358.08 L505 504.04 L505 795.96 L252.19 650 Z M771.81 650 L519 795.96 L519 504.04 L771.81 358.08 Z"/>
+    </clipPath>
   </defs>
-  <title>FieldCraft icon part</title>
-  <g id="Part">
-    <path id="wall_top" data-name="wall top" d="M512 141 L825.3 321.88 L730.48 376.62 L417.19 195.74 Z" fill="url(#linear-gradient-1)"/>
-    <path id="base_top" data-name="base top" d="M401.19 457.26 L714.48 638.14 L512 755.04 L198.7 574.16 Z M521.64 643.71 C555.35 624.24 555.35 592.68 521.64 573.22 C487.92 553.75 433.26 553.75 399.55 573.22 C365.83 592.68 365.83 624.24 399.55 643.71 C433.26 663.17 487.92 663.17 521.64 643.71 Z" fill="url(#linear-gradient-2)"/>
-    <path id="wall_front" data-name="wall front" d="M409.19 209.6 L722.48 390.48 L722.48 624.28 L409.19 443.4 Z" fill="url(#linear-gradient-3)"/>
-    <path id="base_front" data-name="base front" d="M190.7 588.02 L504 768.9 L504 878.38 L190.7 697.5 Z" fill="url(#linear-gradient-4)"/>
-    <path id="end" d="M833.3 697.5 L520 878.38 L520 768.9 L738.48 642.76 L738.48 390.48 L833.3 335.74 Z" fill="url(#linear-gradient-5)"/>
-    <path id="bolt_hole" data-name="bolt hole" d="M521.64 643.71 C487.92 663.17 433.26 663.17 399.55 643.71 C365.83 624.24 365.83 592.68 399.55 573.22 C433.26 553.75 487.92 553.75 521.64 573.22 C555.35 592.68 555.35 624.24 521.64 643.71 Z" fill="url(#linear-gradient-6)"/>
+  <title>FieldCraft icon cube</title>
+  <g id="Top_face" data-name="Top face" clip-path="url(#clip-path-1)">
+    <path id="top" d="M512 200 L764.81 345.96 L512 491.92 L259.19 345.96 Z" fill="#2c4fbf"/>
+    <path id="top_band_1" data-name="top band 1" d="M844.55 692 C660.89 798.04 363.11 798.04 179.45 692 C-4.22 585.96 -4.22 414.04 179.45 308 C363.11 201.96 660.89 201.96 844.55 308 C1028.22 414.04 1028.22 585.96 844.55 692 Z" fill="#2f86e0"/>
+    <path id="top_band_2" data-name="top band 2" d="M789.99 660.5 C636.46 749.14 387.54 749.14 234.01 660.5 C80.47 571.86 80.47 428.14 234.01 339.5 C387.54 250.86 636.46 250.86 789.99 339.5 C943.53 428.14 943.53 571.86 789.99 660.5 Z" fill="#22bcd8"/>
+    <path id="top_band_3" data-name="top band 3" d="M738.03 630.5 C613.2 702.57 410.8 702.57 285.97 630.5 C161.13 558.43 161.13 441.57 285.97 369.5 C410.8 297.43 613.2 297.43 738.03 369.5 C862.87 441.57 862.87 558.43 738.03 630.5 Z" fill="#3fc584"/>
+    <path id="top_band_4" data-name="top band 4" d="M686.07 600.5 C589.93 656 434.07 656 337.93 600.5 C241.79 545 241.79 455 337.93 399.5 C434.07 344 589.93 344 686.07 399.5 C782.21 455 782.21 545 686.07 600.5 Z" fill="#f0d13a"/>
+    <path id="top_band_5" data-name="top band 5" d="M634.11 570.5 C566.67 609.44 457.33 609.44 389.89 570.5 C322.45 531.56 322.45 468.44 389.89 429.5 C457.33 390.56 566.67 390.56 634.11 429.5 C701.55 468.44 701.55 531.56 634.11 570.5 Z" fill="#f28a2b"/>
+    <path id="top_band_6" data-name="top band 6" d="M582.15 540.5 C543.41 562.87 480.59 562.87 441.85 540.5 C403.11 518.13 403.11 481.87 441.85 459.5 C480.59 437.13 543.41 437.13 582.15 459.5 C620.89 481.87 620.89 518.13 582.15 540.5 Z" fill="#de3b2f"/>
+    <path id="top_shade" data-name="top shade" d="M512 200 L764.81 345.96 L512 491.92 L259.19 345.96 Z" fill="#ffffff" opacity="0.1"/>
+  </g>
+  <g id="Left_face" data-name="Left face" clip-path="url(#clip-path-2)">
+    <path id="left" d="M252.19 358.08 L505 504.04 L505 795.96 L252.19 650 Z" fill="#2c4fbf"/>
+    <path id="left_band_1" data-name="left band 1" d="M844.55 692 C844.55 479.92 695.66 222.04 512 116 C328.34 9.96 179.45 95.92 179.45 308 C179.45 520.08 328.34 777.96 512 884 C695.66 990.04 844.55 904.08 844.55 692 Z" fill="#2f86e0"/>
+    <path id="left_band_2" data-name="left band 2" d="M789.99 660.5 C789.99 483.22 665.53 267.64 512 179 C358.47 90.36 234.01 162.22 234.01 339.5 C234.01 516.78 358.47 732.36 512 821 C665.53 909.64 789.99 837.78 789.99 660.5 Z" fill="#22bcd8"/>
+    <path id="left_band_3" data-name="left band 3" d="M738.03 630.5 C738.03 486.35 636.83 311.07 512 239 C387.17 166.93 285.97 225.35 285.97 369.5 C285.97 513.65 387.17 688.93 512 761 C636.83 833.07 738.03 774.65 738.03 630.5 Z" fill="#3fc584"/>
+    <path id="left_band_4" data-name="left band 4" d="M686.07 600.5 C686.07 489.49 608.14 354.5 512 299 C415.86 243.5 337.93 288.49 337.93 399.5 C337.93 510.51 415.86 645.5 512 701 C608.14 756.5 686.07 711.51 686.07 600.5 Z" fill="#f0d13a"/>
+    <path id="left_band_5" data-name="left band 5" d="M634.11 570.5 C634.11 492.63 579.44 397.94 512 359 C444.56 320.06 389.89 351.63 389.89 429.5 C389.89 507.37 444.56 602.06 512 641 C579.44 679.94 634.11 648.37 634.11 570.5 Z" fill="#f28a2b"/>
+    <path id="left_band_6" data-name="left band 6" d="M582.15 540.5 C582.15 495.76 550.74 441.37 512 419 C473.26 396.63 441.85 414.76 441.85 459.5 C441.85 504.24 473.26 558.63 512 581 C550.74 603.37 582.15 585.24 582.15 540.5 Z" fill="#de3b2f"/>
+    <path id="left_shade" data-name="left shade" d="M252.19 358.08 L505 504.04 L505 795.96 L252.19 650 Z" fill="#000000" opacity="0.12"/>
+  </g>
+  <g id="Right_face" data-name="Right face" clip-path="url(#clip-path-3)">
+    <path id="right" d="M771.81 650 L519 795.96 L519 504.04 L771.81 358.08 Z" fill="#2c4fbf"/>
+    <path id="right_band_1" data-name="right band 1" d="M179.45 692 C179.45 479.92 328.34 222.04 512 116 C695.66 9.96 844.55 95.92 844.55 308 C844.55 520.08 695.66 777.96 512 884 C328.34 990.04 179.45 904.08 179.45 692 Z" fill="#2f86e0"/>
+    <path id="right_band_2" data-name="right band 2" d="M234.01 660.5 C234.01 483.22 358.47 267.64 512 179 C665.53 90.36 789.99 162.22 789.99 339.5 C789.99 516.78 665.53 732.36 512 821 C358.47 909.64 234.01 837.78 234.01 660.5 Z" fill="#22bcd8"/>
+    <path id="right_band_3" data-name="right band 3" d="M285.97 630.5 C285.97 486.35 387.17 311.07 512 239 C636.83 166.93 738.03 225.35 738.03 369.5 C738.03 513.65 636.83 688.93 512 761 C387.17 833.07 285.97 774.65 285.97 630.5 Z" fill="#3fc584"/>
+    <path id="right_band_4" data-name="right band 4" d="M337.93 600.5 C337.93 489.49 415.86 354.5 512 299 C608.14 243.5 686.07 288.49 686.07 399.5 C686.07 510.51 608.14 645.5 512 701 C415.86 756.5 337.93 711.51 337.93 600.5 Z" fill="#f0d13a"/>
+    <path id="right_band_5" data-name="right band 5" d="M389.89 570.5 C389.89 492.63 444.56 397.94 512 359 C579.44 320.06 634.11 351.63 634.11 429.5 C634.11 507.37 579.44 602.06 512 641 C444.56 679.94 389.89 648.37 389.89 570.5 Z" fill="#f28a2b"/>
+    <path id="right_band_6" data-name="right band 6" d="M441.85 540.5 C441.85 495.76 473.26 441.37 512 419 C550.74 396.63 582.15 414.76 582.15 459.5 C582.15 504.24 550.74 558.63 512 581 C473.26 603.37 441.85 585.24 441.85 540.5 Z" fill="#de3b2f"/>
+    <path id="right_shade" data-name="right shade" d="M771.81 650 L519 795.96 L519 504.04 L771.81 358.08 Z" fill="#000000" opacity="0.3"/>
+  </g>
+  <g id="Mesh" clip-path="url(#clip-path-4)">
+    <path id="hexahedral_mesh" data-name="hexahedral mesh" d="M576.95 237.5 L317.14 387.5 M447.05 237.5 L706.86 387.5 M317.14 687.5 L317.14 387.5 M252.19 575 L512 725 M706.86 687.5 L706.86 387.5 M771.81 575 L512 725 M641.9 275 L382.1 425 M382.1 275 L641.9 425 M382.1 725 L382.1 425 M252.19 500 L512 650 M641.9 725 L641.9 425 M771.81 500 L512 650 M706.86 312.5 L447.05 462.5 M317.14 312.5 L576.95 462.5 M447.05 762.5 L447.05 462.5 M252.19 425 L512 575 M576.95 762.5 L576.95 462.5 M771.81 425 L512 575" fill="none" stroke="#0b2236" stroke-width="3.5" stroke-linejoin="round" opacity="0.45"/>
   </g>
 </svg>

assets/app-icon/FieldCraft.icon/Assets/03-mesh.svg

@@ -1,12 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="1024" height="1024" viewBox="0 0 1024 1024">
-  <defs>
-    <clipPath id="clip-path-1">
-      <path d="M512 141 L825.3 321.88 L730.48 376.62 L417.19 195.74 Z M401.19 457.26 L714.48 638.14 L512 755.04 L198.7 574.16 Z M521.64 643.71 C555.35 624.24 555.35 592.68 521.64 573.22 C487.92 553.75 433.26 553.75 399.55 573.22 C365.83 592.68 365.83 624.24 399.55 643.71 C433.26 663.17 487.92 663.17 521.64 643.71 Z M409.19 209.6 L722.48 390.48 L722.48 624.28 L409.19 443.4 Z M190.7 588.02 L504 768.9 L504 878.38 L190.7 697.5 Z M833.3 697.5 L520 878.38 L520 768.9 L738.48 642.76 L738.48 390.48 L833.3 335.74 Z"/>
-    </clipPath>
-  </defs>
-  <title>FieldCraft icon mesh</title>
-  <g id="Mesh" clip-path="url(#clip-path-1)">
-    <path id="hexahedral_mesh" data-name="hexahedral mesh" d="M460.59 482.32 L242.11 608.46 M679.07 608.46 L460.59 734.6 M354.57 484.18 L405.97 513.86 M624.45 640 L675.86 669.67 M299.95 515.71 L351.35 545.39 M569.83 671.53 L621.24 701.21 M245.32 547.25 L296.73 576.92 M515.21 703.07 L566.62 732.75 M460.59 482.32 L460.59 230.04 M563.41 170.68 L460.59 230.04 M515.21 513.86 L515.21 261.57 M618.03 202.22 L515.21 261.57 M569.83 545.39 L569.83 293.11 M672.65 233.75 L569.83 293.11 M624.45 576.93 L624.45 324.65 M727.27 265.29 L624.45 324.65 M679.07 608.46 L679.07 356.18 M781.89 296.82 L679.07 356.18 M409.19 389.57 L730.48 575.07 M409.19 326.5 L730.48 512 M409.19 263.43 L730.48 448.93 M460.59 170.68 L781.89 356.18 M242.11 727.18 L242.11 608.46 M296.73 758.72 L296.73 640 M351.35 790.25 L351.35 671.53 M405.97 821.79 L405.97 703.07 M460.59 853.32 L460.59 734.6 M190.7 638.14 L512 823.64 M781.89 727.18 L781.89 356.18 M730.48 756.86 L730.48 638.14 M675.86 788.39 L675.86 669.67 M621.24 819.93 L621.24 701.21 M566.62 851.47 L566.62 732.75 M833.3 638.14 L512 823.64 M833.3 578.78 L730.48 638.14 M833.3 515.71 L730.48 575.07 M833.3 452.64 L730.48 512 M833.3 389.57 L730.48 448.93 M460.59 558.62 L460.59 482.32 M433.29 561.17 L405.97 513.86 M399.55 573.22 L351.35 545.39 M378.69 592.7 L296.73 576.92 M374.26 608.46 L242.11 608.46 M487.89 561.17 L515.21 513.86 M378.69 624.22 L296.73 640 M521.64 573.22 L569.83 545.39 M399.55 643.71 L351.35 671.53 M542.49 592.7 L624.45 576.92 M433.29 655.75 L405.97 703.06 M546.92 608.46 L679.07 608.46 M542.49 624.22 L624.45 640 M521.64 643.71 L569.83 671.53 M487.89 655.75 L515.21 703.07 M460.59 658.3 L460.59 734.6 M545.74 657.62 L540.09 660.8 L534.3 663.92 L528.33 666.99 L522.16 670.03 L515.76 673.05 L509.11 676.08 L502.15 679.15 L494.85 682.27 L487.14 685.51 L478.94 688.9 L470.14 692.52 L460.59 696.45 L451.05 692.52 L442.25 688.9 L434.05 685.51 L426.34 682.27 L419.03 679.15 L412.08 676.08 L405.42 673.05 L399.02 670.03 L392.86 666.99 L386.89 663.92 L381.09 660.8 L375.45 657.62 L369.94 654.36 L364.54 651.01 L359.22 647.57 L353.95 644.01 L348.72 640.31 L343.47 636.47 L338.16 632.45 L332.74 628.24 L327.14 623.79 L321.26 619.05 L315 613.97 L308.19 608.46 L315 602.95 L321.26 597.87 L327.14 593.13 L332.74 588.68 L338.16 584.47 L343.47 580.45 L348.72 576.61 L353.95 572.91 L359.22 569.35 L364.54 565.91 L369.94 562.56 L375.45 559.3 L381.09 556.12 L386.89 553 L392.86 549.93 L399.02 546.89 L405.42 543.87 L412.08 540.84 L419.03 537.77 L426.34 534.65 L434.05 531.41 L442.25 528.02 L451.05 524.4 L460.59 520.47 L470.14 524.4 L478.94 528.02 L487.14 531.41 L494.85 534.65 L502.15 537.77 L509.11 540.84 L515.76 543.87 L522.16 546.89 L528.33 549.93 L534.3 553 L540.09 556.12 L545.74 559.3 L551.25 562.56 L556.65 565.91 L561.97 569.35 L567.23 572.91 L572.47 576.61 L577.72 580.45 L583.02 584.47 L588.44 588.68 L594.05 593.13 L599.92 597.87 L606.19 602.95 L613 608.46 L606.19 613.97 L599.92 619.05 L594.05 623.79 L588.44 628.24 L583.02 632.45 L577.72 636.47 L572.47 640.31 L567.23 644.01 L561.97 647.57 L556.65 651.01 L551.25 654.36 Z" fill="none" stroke="#ffffff" stroke-width="4.5" stroke-linejoin="round" opacity="0.5"/>
-  </g>
-</svg>

assets/app-icon/FieldCraft.icon/icon.json

@@ -1,37 +1,6 @@
 {
   "fill": "system-light",
   "groups": [
-    {
-      "layers": [
-        {
-          "glass-specializations": [
-            {
-              "appearance": "tinted",
-              "value": true
-            }
-          ],
-          "image-name": "03-mesh.svg",
-          "name": "03-mesh",
-          "position": {
-            "scale": 0.9,
-            "translation-in-points": [
-              0,
-              0
-            ]
-          }
-        }
-      ],
-      "name": "03 Mesh",
-      "shadow": {
-        "kind": "none",
-        "opacity": 0
-      },
-      "specular": false,
-      "translucency": {
-        "enabled": false,
-        "value": 0.3
-      }
-    },
     {
       "layers": [
         {

assets/app-icon/README.md

@@ -1,10 +1,11 @@
 # FieldCraft application icon
 
-FieldCraft's mark is an L-shaped bracket with a bolt hole, drawn in isometric view and covered
-by a structured hexahedral mesh with an O-grid around the hole. Its faces are separated by
+FieldCraft's mark is a cube in isometric view, covered by a structured hexahedral mesh, whose
+faces carry a banded colour fringe (blue to red, hottest at the front corner) as a stress or
+temperature result would. Its faces are separated by
 transparent gaps rather than painted edge lines, so the backdrop shows through them in every
 appearance. It is original artwork, attributed in `ATTRIBUTION.md`, and shares the Craft
-family's layout (rounded-square backdrop, isometric floor grid, lit top faces) in its own teal.
+family's layout (rounded-square backdrop, isometric floor grid, lit top faces).
 
 Everything here is generated by `cargo xtask app-icon` (`xtask/src/app_icon.rs`), which computes
 the geometry and draws it with VectorCraft's command-line tool (`VECTORCRAFT_CLI`, else
@@ -14,14 +15,16 @@ hand. It runs on macOS (sips, iconutil, `xcrun actool`) with ImageMagick (`magic
 | File | What it is |
 |---|---|
 | `icon.vectorcraft`, `icon.svg`, `icon.png` | The full icon on its backdrop, 1024 × 1024 |
-| `icon-small.vectorcraft`, `icon-small.svg`, `icon-small.png` | Small-size artwork used at 16–32 px: no mesh or floor grid, faces edge to edge |
+| `icon-small.vectorcraft`, `icon-small.svg`, `icon-small.png` | Small-size artwork used at 16–32 px: the fringe cube alone, no mesh or floor grid, faces edge to edge |
 | `icon.iconset/`, `icon.icns` | macOS iconset (sips) and its iconutil compilation |
 | `icon.ico` | Windows icon, 16–256 px |
-| `FieldCraft.icon/` | Icon Composer document: floor grid (Default and Dark), part and mesh layers, each scaled to 90% |
+| `FieldCraft.icon/` | Icon Composer document: floor grid (Default and Dark), and cube (faces and mesh) layers, each scaled to 90% |
 | `layers/*.vectorcraft` | Editable sources of the Icon Composer layers |
 | `Assets.car` | `actool` compilation of `FieldCraft.icon` for macOS 26 and later (needs Xcode 26 or later; the task skips it with a note otherwise) |
 
 The desktop app embeds `icon.iconset/icon_128x128@2x.png` as its window and Dock icon
-(`apps/fieldcraft/src/main.rs`). There is no macOS bundle yet; packaging will copy
-`Assets.car` and `icon.icns` into `Contents/Resources` and name `FieldCraft` in
-`CFBundleIconName` / `CFBundleIconFile`.
+(`apps/fieldcraft/src/main.rs`). The release packages (docs/releasing.md) use the rest:
+`packaging/macos/package.sh` copies `Assets.car` and `icon.icns` (as `FieldCraft.icns`) into
+`FieldCraft.app/Contents/Resources`, named by `CFBundleIconName` / `CFBundleIconFile`;
+`apps/fieldcraft/build.rs` embeds `icon.ico` in `fieldcraft.exe`; and
+`packaging/linux/package.sh` installs the iconset PNGs as the hicolor icons.

assets/app-icon/icon-small.svg

@@ -1,35 +1,20 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="1024" height="1024" viewBox="0 0 1024 1024">
   <defs>
-    <filter id="filter-1" filterUnits="userSpaceOnUse" x="67" y="67" width="890" height="890" data-vc-blend="multiply" color-interpolation-filters="sRGB"><feGaussianBlur in="SourceAlpha" stdDeviation="7"/><feOffset dx="0" dy="10" result="shadow"/><feFlood flood-color="#1d3b38" flood-opacity="0.22"/><feComposite in2="shadow" operator="in" result="paint"/><feMerge><feMergeNode in="paint"/><feMergeNode in="SourceGraphic"/></feMerge></filter>
+    <filter id="filter-1" filterUnits="userSpaceOnUse" x="67" y="67" width="890" height="890" data-vc-blend="multiply" color-interpolation-filters="sRGB"><feGaussianBlur in="SourceAlpha" stdDeviation="7"/><feOffset dx="0" dy="10" result="shadow"/><feFlood flood-color="#1d2b3b" flood-opacity="0.22"/><feComposite in2="shadow" operator="in" result="paint"/><feMerge><feMergeNode in="paint"/><feMergeNode in="SourceGraphic"/></feMerge></filter>
     <linearGradient id="linear-gradient-1" x1="512" y1="100" x2="512" y2="924" gradientUnits="userSpaceOnUse">
-      <stop offset="0" stop-color="#fbfdfd"/>
-      <stop offset="1" stop-color="#dbe5e4"/>
-    </linearGradient>
-    <linearGradient id="linear-gradient-2" x1="512" y1="141" x2="512" y2="385.86" gradientUnits="userSpaceOnUse">
-      <stop offset="0" stop-color="#86e3d3"/>
-      <stop offset="1" stop-color="#4cc4b1"/>
-    </linearGradient>
-    <linearGradient id="linear-gradient-3" x1="512" y1="452.64" x2="512" y2="764.28" gradientUnits="userSpaceOnUse">
-      <stop offset="0" stop-color="#86e3d3"/>
-      <stop offset="1" stop-color="#4cc4b1"/>
-    </linearGradient>
-    <linearGradient id="linear-gradient-4" x1="512" y1="200.36" x2="512" y2="638.14" gradientUnits="userSpaceOnUse">
-      <stop offset="0" stop-color="#20b39f"/>
-      <stop offset="1" stop-color="#118c7c"/>
-    </linearGradient>
-    <linearGradient id="linear-gradient-5" x1="512" y1="578.78" x2="512" y2="883" gradientUnits="userSpaceOnUse">
-      <stop offset="0" stop-color="#20b39f"/>
-      <stop offset="1" stop-color="#118c7c"/>
-    </linearGradient>
-    <linearGradient id="linear-gradient-6" x1="512" y1="326.5" x2="512" y2="883" gradientUnits="userSpaceOnUse">
-      <stop offset="0" stop-color="#0f786d"/>
-      <stop offset="1" stop-color="#0a544e"/>
-    </linearGradient>
-    <linearGradient id="linear-gradient-7" x1="512" y1="558.616" x2="512" y2="658.304" gradientUnits="userSpaceOnUse">
-      <stop offset="0" stop-color="#0b665e"/>
-      <stop offset="1" stop-color="#04302c"/>
+      <stop offset="0" stop-color="#fbfcfe"/>
+      <stop offset="1" stop-color="#dce3ec"/>
     </linearGradient>
+    <clipPath id="clip-path-1">
+      <path d="M512 200 L771.81 350 L512 500 L252.19 350 Z"/>
+    </clipPath>
+    <clipPath id="clip-path-2">
+      <path d="M252.19 350 L512 500 L512 800 L252.19 650 Z"/>
+    </clipPath>
+    <clipPath id="clip-path-3">
+      <path d="M771.81 650 L512 800 L512 500 L771.81 350 Z"/>
+    </clipPath>
   </defs>
   <title>FieldCraft application icon, small sizes</title>
   <g id="Backdrop">
@@ -37,12 +22,34 @@
       <path id="backdrop" d="M320 100 L704 100 C854 100 924 170 924 320 L924 704 C924 854 854 924 704 924 L320 924 C170 924 100 854 100 704 L100 320 C100 170 170 100 320 100 Z" fill="url(#linear-gradient-1)"/>
     </g>
   </g>
-  <g id="Part">
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assets/app-icon/icon.svg

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+  <g id="Mesh" clip-path="url(#clip-path-5)">
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 </svg>

assets/icons/mesh.hex.blocks.svg

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="24" height="24" viewBox="0 0 24 24">
+  <title>mesh.hex.blocks</title>
+  <g id="Layer_1" data-name="Layer 1">
+    <path d="M12 3 L20 7 L20 16 L12 20 L4 16 L4 7 Z" fill="#2d4e70" stroke="#dde2ea" stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round"/>
+    <path d="M4 7 L12 11 L20 7 M12 11 L12 20" fill="none" stroke="#dde2ea" stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round"/>
+    <path d="M6 8 L6 17 M10 10 L10 19 M4 9.25 L12 13.25 M4 13.75 L12 17.75 M14 10 L14 19 M18 8 L18 17 M12 13.25 L20 9.25 M12 17.75 L20 13.75 M6 6 L14 10 M10 4 L18 8 M14 4 L6 8 M18 6 L10 10" fill="none" stroke="#4f9ce8" stroke-linecap="round" stroke-linejoin="round"/>
+    <path d="M8 5 L16 9 M16 5 L8 9 M8 9 L8 18 M4 11.5 L12 15.5 M16 9 L16 18 M12 15.5 L20 11.5" fill="none" stroke="#dde2ea" stroke-width="1.5" stroke-linecap="round" stroke-linejoin="round"/>
+  </g>
+</svg>

assets/icons/src/mesh.hex.blocks.json

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crates/decks/src/abaqus.rs

@@ -30,7 +30,17 @@
 //! - a frequency step is a perturbation of the last general step: its boundary conditions are
 //!   written against that base state and do not carry on to later steps; loads have no effect on
 //!   natural frequencies and are not written in it;
-//! - every step restates its output request (`*OUTPUT, FIELD, OP=NEW`).
+//! - every step restates its output request (`*OUTPUT, FIELD, OP=NEW`);
+//! - a nonlinear static step is `*STEP, NLGEOM=YES` (or `NO` without nonlinear geometry) with
+//!   `INC=` its increment cap, `*STATIC` with its initial, minimum and maximum increments over a
+//!   step period of 1, and `*CONTROLS, PARAMETERS=LINE SEARCH` when it searches; its iteration cap
+//!   and tolerances are left to Abaqus's controls, whose residual norms are defined differently.
+//!   Abaqus starts each general step from the end of the previous one, while every model step
+//!   starts from the undeformed state; for elastic materials the end state depends on the final
+//!   loads alone, so the two agree. A plastic material's state depends on the path, so a deck
+//!   with nonlinear steps, a plastic material and more than one general step is refused, as is
+//!   a nonlinear step's load path (an amplitude on every load and boundary condition, not
+//!   written yet).
 //!
 //! # Loads
 //!
@@ -96,7 +106,11 @@
 //!
 //! # Materials
 //!
-//! Isotropic elasticity is `*ELASTIC, TYPE=ISOTROPIC`, engineering constants
+//! Isotropic elasticity is `*ELASTIC, TYPE=ISOTROPIC` (or, for a neo-Hookean material in a deck
+//! with nonlinear steps, `*HYPERELASTIC, NEO HOOKE` with C₁₀ = μ/2 and D₁ = 2/κ, the same strain
+//! energy, and likewise `MOONEY-RIVLIN` (C₁₀, C₀₁, D₁) and `YEOH` (C₁₀, C₂₀, C₃₀, D₁, the higher
+//! volumetric terms zero); a linear static step is then refused, since Abaqus's general static step would apply
+//! the hyperelastic law), engineering constants
 //! `TYPE=ENGINEERING CONSTANTS`, density `*DENSITY`. Von Mises plasticity is `*PLASTIC`: a
 //! hardening table as its (yield stress, plastic strain) lines; bilinear isotropic hardening as
 //! two lines, the second at a plastic strain of [`BILINEAR_REACH`] (Abaqus holds the last yield
@@ -116,8 +130,8 @@ use std::collections::{BTreeMap, BTreeSet};
 use std::fmt::Write as _;
 
 use fieldcraft_model::{
-    BeamProfile, BoundaryCondition, CouplingKind, Elastic, Element, ElementKind, Hardening, Integration, Load, Model, OutputVariable, Plastic,
-    Procedure, Resolved, Section, SectionKind, Step, Symmetry, Target,
+    BeamProfile, BoundaryCondition, CouplingKind, Elastic, Element, ElementKind, Hardening, Hyperelastic, Integration, Load, Model, OutputVariable,
+    Plastic, Procedure, Resolved, Section, SectionKind, Step, Symmetry, Target,
 };
 
 use crate::{Error, Result, unsupported};
@@ -219,6 +233,12 @@ pub fn element_type(kind: ElementKind, section: &Section) -> std::result::Result
     Ok(if f.hybrid { format!("{plain}H") } else { plain.to_string() })
 }
 
+/// Whether the model has a nonlinear static step: hyperelastic materials are then written as
+/// `*HYPERELASTIC` (in a deck of linear steps their elastic constants are the whole of it).
+fn has_nonlinear_step(model: &Model) -> bool {
+    model.steps().iter().any(|s| matches!(s.procedure, Procedure::NonlinearStatic(_)))
+}
+
 /// Every element, grouped by element type (from its section) and sorted by label.
 fn elements_by_type<'m>(model: &'m Model, r: &Resolved) -> Result<BTreeMap<String, Vec<(u32, &'m Element)>>> {
     let mut by_type: BTreeMap<String, Vec<(u32, &Element)>> = BTreeMap::new();
@@ -287,6 +307,37 @@ fn check_expressible(model: &Model) -> Result<()> {
     for step in model.steps().iter().filter(|s| matches!(s.procedure, Procedure::ExplicitDynamic(_))) {
         bad.insert(format!("step `{}`: explicit dynamic steps (not written to Abaqus input yet)", step.name));
     }
+    if has_nonlinear_step(model)
+        && let Some(material) = model.hyperelastic_in_use().into_iter().next()
+    {
+        for step in model.steps().iter().filter(|s| matches!(s.procedure, Procedure::Static {})) {
+            bad.insert(format!(
+                "step `{}`: a linear static step beside nonlinear steps of hyperelastic material `{material}` (Abaqus's general static step applies the hyperelastic law; write the linear step to its own deck)",
+                step.name
+            ));
+        }
+    }
+    for step in model.steps() {
+        if let Procedure::NonlinearStatic(n) = &step.procedure
+            && n.load_path.is_some()
+        {
+            bad.insert(format!(
+                "step `{}`: a load path (it would be an amplitude on every load and boundary condition of the step; not written yet)",
+                step.name
+            ));
+        }
+    }
+    let general = model.steps().iter().filter(|s| matches!(s.procedure, Procedure::Static {} | Procedure::NonlinearStatic(_))).count();
+    let plastic_in_use = model.sections().values().find(|s| model.material(&s.material).is_some_and(|m| m.plastic.is_some()));
+    if has_nonlinear_step(model)
+        && general > 1
+        && let Some(section) = plastic_in_use
+    {
+        bad.insert(format!(
+            "plastic material `{}` in a deck of {general} general steps (Abaqus carries the plastic state from one general step to the next, while every model step starts from the undeformed state; write each step to its own deck)",
+            section.material
+        ));
+    }
     for (name, m) in model.materials() {
         if m.damage.is_some() || m.erosion.is_some() {
             bad.insert(format!(
@@ -759,6 +810,21 @@ impl Deck {
         for (name, m) in model.materials() {
             self.line(&format!("*MATERIAL, NAME={name}"));
             match m.elastic {
+                Some(Elastic::Isotropic { young, poisson })
+                    if has_nonlinear_step(model)
+                        && let Some(h) = m.hyperelastic =>
+                {
+                    // The polynomial constants of the option and U = (J − 1)²/D1 with D1 = 2/κ.
+                    let (shear, bulk) = Hyperelastic::moduli(young, poisson);
+                    let [c10, c01, c20, c30] = h.constants(shear);
+                    let (keyword, values) = match h {
+                        Hyperelastic::NeoHookean {} => ("NEO HOOKE", vec![c10, 2.0 / bulk]),
+                        Hyperelastic::MooneyRivlin { .. } => ("MOONEY-RIVLIN", vec![c10, c01, 2.0 / bulk]),
+                        Hyperelastic::Yeoh { .. } => ("YEOH", vec![c10, c20, c30, 2.0 / bulk]),
+                    };
+                    self.line(&format!("*HYPERELASTIC, {keyword}"));
+                    self.numbers_line("", &values)?;
+                }
                 Some(Elastic::Isotropic { young, poisson }) => {
                     self.line("*ELASTIC, TYPE=ISOTROPIC");
                     self.numbers_line("", &[young, poisson])?;
@@ -1038,10 +1104,22 @@ impl Deck {
             self.comment(&format!("Step {}", step.name));
             match step.procedure {
                 Procedure::Fluid { .. } => return Err(crate::fluid_step(FORMAT, &step.name)),
-                Procedure::Static {} => {
-                    self.line(&format!("*STEP, NAME={}, NLGEOM=NO", step.name));
-                    self.line("*STATIC");
-                    self.line("1.0, 1.0");
+                Procedure::Static {} | Procedure::NonlinearStatic(_) => {
+                    if let Procedure::NonlinearStatic(n) = &step.procedure {
+                        let nlgeom = if n.nonlinear_geometry { "YES" } else { "NO" };
+                        self.line(&format!("*STEP, NAME={}, NLGEOM={nlgeom}, INC={}", step.name, n.max_increments));
+                        self.line("*STATIC");
+                        self.numbers_line("", &[n.initial_increment, 1.0, n.min_increment, n.max_increment])?;
+                        if n.line_search {
+                            self.line("*CONTROLS, PARAMETERS=LINE SEARCH");
+                            self.line("5,");
+                        }
+                        self.comment("iterations and convergence: Abaqus's own controls (its residual norms differ from FieldCraft's)");
+                    } else {
+                        self.line(&format!("*STEP, NAME={}, NLGEOM=NO", step.name));
+                        self.line("*STATIC");
+                        self.line("1.0, 1.0");
+                    }
                     self.step_boundaries(model, r, &base_bcs, &step.boundary_conditions)?;
                     if step.loads == base_loads {
                         self.comment("loads: as in the previous general step");

crates/decks/src/lsdyna/mod.rs

@@ -24,7 +24,14 @@
 //!   the set's translations, equal weights);
 //! - per step: `*CONTROL_IMPLICIT_GENERAL`, `*CONTROL_IMPLICIT_SOLUTION` (linear) or
 //!   `*CONTROL_IMPLICIT_EIGENVALUE`, `*CONTROL_TERMINATION` (a static step is one implicit step
-//!   from time 0 to 1 with every load ramped by one curve, `*DEFINE_CURVE`); boundary conditions
+//!   from time 0 to 1 with every load ramped by one curve, `*DEFINE_CURVE`); a nonlinear static
+//!   step runs over the same time with the same ramp (or its load path as the curve), its first
+//!   increment as `dt0`, the nonlinear
+//!   solver with a stiffness reformation every iteration (`ilimit` 1, full Newton) and its
+//!   iteration cap as `maxref`, and `*CONTROL_IMPLICIT_AUTO` with its minimum and maximum
+//!   increments (its increment cap and tolerances have no LS-DYNA counterpart and are left to
+//!   LS-DYNA's defaults; a step without nonlinear geometry and hyperelastic materials in nonlinear
+//!   steps are refused); boundary conditions
 //!   as `*BOUNDARY_SPC_*_ID` (named) and `*BOUNDARY_PRESCRIBED_MOTION_*_ID` for non-zero
 //!   displacements; forces, moments and tractions as `*LOAD_NODE_SET`/`_POINT` from the
 //!   resolved nodal values; pressure as `*LOAD_SEGMENT_SET`; gravity as `*LOAD_BODY_X/Y/Z`
@@ -267,7 +274,21 @@ fn plan<'a>(model: &'a Model, r: &Resolved) -> Result<Plan<'a>> {
         if matches!(step.procedure, Procedure::ExplicitDynamic(_)) {
             refused.insert(format!("step `{}`: explicit dynamic steps (this writer writes implicit analyses so far)", step.name));
         }
-        let is_static = matches!(step.procedure, Procedure::Static {});
+        if let Procedure::NonlinearStatic(n) = &step.procedure {
+            if !n.nonlinear_geometry {
+                refused.insert(format!(
+                    "step `{}`: a nonlinear step without nonlinear geometry (LS-DYNA's nonlinear implicit analysis always follows the deformed shape)",
+                    step.name
+                ));
+            }
+            for material in model.hyperelastic_in_use() {
+                refused.insert(format!(
+                    "step `{}`: hyperelastic material `{material}` in a nonlinear step (LS-DYNA's rubber materials define their volumetric energy differently; not written yet)",
+                    step.name
+                ));
+            }
+        }
+        let is_static = matches!(step.procedure, Procedure::Static {} | Procedure::NonlinearStatic(_));
         for b in &step.boundary_conditions {
             let Some(bc) = model.boundary_conditions().get(b) else { continue };
             match bc.target() {
@@ -793,18 +814,29 @@ fn dof_code(dof: u8) -> i32 {
 fn write_step(d: &mut Deck, model: &Model, r: &Resolved, plan: &Plan, step: &Step, n: u32, constraint_id: &mut u32) -> Result<()> {
     d.line("*TITLE");
     d.line(&step.name);
-    let is_static = matches!(step.procedure, Procedure::Static {});
+    let is_static = matches!(step.procedure, Procedure::Static {} | Procedure::NonlinearStatic(_));
+    let first_increment = if let Procedure::NonlinearStatic(n) = &step.procedure { n.initial_increment } else { 1.0 };
     d.line("*CONTROL_IMPLICIT_GENERAL");
     d.header(&["imflag", "dt0"]);
-    d.card([Field::from(1), Field::from(1.0)]);
-    match step.procedure {
+    d.card([Field::from(1), Field::from(first_increment)]);
+    match &step.procedure {
         Procedure::Fluid { .. } => return Err(crate::fluid_step(FORMAT, &step.name)),
         Procedure::Static {} => {
             d.line("*CONTROL_IMPLICIT_SOLUTION");
             d.header(&["nsolvr"]);
             d.card([Field::from(1)]);
         }
-        Procedure::Frequency { modes, min_hz, max_hz } => {
+        Procedure::NonlinearStatic(n) => {
+            // Nonlinear with a stiffness reformation every iteration (full Newton), at most
+            // `max_iterations` per increment; LS-DYNA's own convergence norms and line search.
+            d.line("*CONTROL_IMPLICIT_SOLUTION");
+            d.header(&["nsolvr", "ilimit", "maxref"]);
+            d.card([Field::from(2), Field::from(1), Field::from(n.max_iterations)]);
+            d.line("*CONTROL_IMPLICIT_AUTO");
+            d.header(&["iauto", "iteopt", "itewin", "dtmin", "dtmax"]);
+            d.card([Field::from(1), Field::Blank, Field::Blank, Field::from(n.min_increment), Field::from(n.max_increment)]);
+        }
+        &Procedure::Frequency { modes, min_hz, max_hz } => {
             d.line("*CONTROL_IMPLICIT_EIGENVALUE");
             d.header(&["neig", "center", "lflag", "lftend", "rflag", "rhtend"]);
             let bound = |b: Option<f64>| match b {
@@ -841,8 +873,13 @@ fn write_step(d: &mut Deck, model: &Model, r: &Resolved, plan: &Plan, step: &Ste
         d.header(&["lcid"]);
         d.card([Field::from(n)]);
         d.header(&["a1", "o1"]);
-        d.card([Field::from(0.0), Field::from(0.0)]);
-        d.card([Field::from(1.0), Field::from(1.0)]);
+        let path = match &step.procedure {
+            Procedure::NonlinearStatic(s) => s.load_path.clone(),
+            _ => None,
+        };
+        for [t, f] in path.unwrap_or_else(|| vec![[0.0, 0.0], [1.0, 1.0]]) {
+            d.card([Field::from(t), Field::from(f)]);
+        }
     }
 
     for b in &step.boundary_conditions {

crates/decks/src/nastran/mod.rs

@@ -280,6 +280,9 @@ fn solution(steps: &[&Step]) -> std::result::Result<u32, String> {
     if let Some(s) = steps.iter().find(|s| matches!(s.procedure, Procedure::ExplicitDynamic(_))) {
         return Err(format!("step `{}`: explicit dynamic steps (Nastran's linear solutions have none)", s.name));
     }
+    if let Some(s) = steps.iter().find(|s| matches!(s.procedure, Procedure::NonlinearStatic(_))) {
+        return Err(format!("step `{}`: nonlinear static steps (Nastran's SOL 400; this writer writes SOL 101 and 103 so far)", s.name));
+    }
     let statics = steps.iter().find(|s| matches!(s.procedure, Procedure::Static {}));
     let modes = steps.iter().find(|s| matches!(s.procedure, Procedure::Frequency { .. }));
     match (statics, modes) {

crates/decks/tests/abaqus.rs

@@ -753,3 +753,78 @@ fn plasticity_is_written_and_failure_reported() {
     let Err(Error::Unsupported { what, .. }) = abaqus::write(&failing) else { panic!("damage is not written") };
     assert!(what.contains("material `Steel`: damage and erosion"), "{what}");
 }
+
+/// A nonlinear static step is a general step with NLGEOM, its increments and its line search; a
+/// neo-Hookean material is then `*HYPERELASTIC` and a linear static step beside it is refused.
+#[test]
+fn nonlinear_steps_and_hyperelastic_materials_are_written() {
+    use fieldcraft_model::{Hyperelastic, NonlinearStatic};
+    let mut m = cantilever();
+    let controls = NonlinearStatic {
+        initial_increment: 0.05,
+        min_increment: 1e-4,
+        max_increment: 0.5,
+        max_increments: 40,
+        line_search: true,
+        ..NonlinearStatic::default()
+    };
+    m.replace_step(step("Bend", Procedure::NonlinearStatic(controls.clone()), &["clamp"], &["end"])).unwrap();
+    let deck = abaqus::write(&m).unwrap();
+    let bend = block(&deck, "Bend");
+    assert_eq!(bend.first(), Some(&"*STEP, NAME=Bend, NLGEOM=YES, INC=40"), "{bend:?}");
+    let at = bend.iter().position(|l| *l == "*STATIC").unwrap();
+    assert_eq!(bend.get(at + 1..at + 4), Some(&["0.05, 1.0, 0.0001, 0.5", "*CONTROLS, PARAMETERS=LINE SEARCH", "5,"][..]), "{bend:?}");
+    assert!(deck.contains("*ELASTIC, TYPE=ISOTROPIC\n210000.0, 0.3\n"), "St Venant–Kirchhoff is the elastic material");
+
+    let small = NonlinearStatic { nonlinear_geometry: false, line_search: false, ..controls };
+    m.replace_step(step("Bend", Procedure::NonlinearStatic(small), &["clamp"], &["end"])).unwrap();
+    m.replace_material("Steel", Material { hyperelastic: Some(Hyperelastic::NeoHookean {}), ..steel() }).unwrap();
+    let deck = abaqus::write(&m).unwrap();
+    let bend = block(&deck, "Bend");
+    assert_eq!(bend.first(), Some(&"*STEP, NAME=Bend, NLGEOM=NO, INC=40"), "{bend:?}");
+    assert!(!bend.iter().any(|l| l.starts_with("*CONTROLS")), "{bend:?}");
+    // μ = E/(2(1 + ν)) = 80769.23…, κ = E/(3(1 − 2ν)) = 175000: C10 = μ/2, D1 = 2/κ.
+    let (c10, d1) = (210_000.0 / 2.6 / 2.0, 2.0 / 175_000.0);
+    let line = deck.split("*HYPERELASTIC, NEO HOOKE\n").nth(1).and_then(|s| s.lines().next()).unwrap();
+    let values: Vec<f64> = line.split(", ").map(|v| v.parse().unwrap()).collect();
+    assert!((values[0] - c10).abs() < 1e-9 * c10 && (values[1] - d1).abs() < 1e-9 * d1, "{line}");
+    assert!(!deck.contains("*ELASTIC"), "{deck}");
+
+    // Mooney–Rivlin and Yeoh: C10 = μ/2 − C01, C01, D1 and C10, C20, C30, D1.
+    m.replace_material("Steel", Material { hyperelastic: Some(Hyperelastic::MooneyRivlin { c01: 10000.0 }), ..steel() }).unwrap();
+    let deck = abaqus::write(&m).unwrap();
+    let line = deck.split("*HYPERELASTIC, MOONEY-RIVLIN\n").nth(1).and_then(|s| s.lines().next()).unwrap();
+    let values: Vec<f64> = line.split(", ").map(|v| v.parse().unwrap()).collect();
+    assert!((values[0] - (c10 - 10000.0)).abs() < 1e-9 * c10 && values[1] == 10000.0 && (values[2] - d1).abs() < 1e-9 * d1, "{line}");
+    m.replace_material("Steel", Material { hyperelastic: Some(Hyperelastic::Yeoh { c20: -50.0, c30: 2.0 }), ..steel() }).unwrap();
+    let deck = abaqus::write(&m).unwrap();
+    let line = deck.split("*HYPERELASTIC, YEOH\n").nth(1).and_then(|s| s.lines().next()).unwrap();
+    let values: Vec<f64> = line.split(", ").map(|v| v.parse().unwrap()).collect();
+    assert!((values[0] - c10).abs() < 1e-9 * c10 && values[1..3] == [-50.0, 2.0] && (values[3] - d1).abs() < 1e-9 * d1, "{line}");
+    m.replace_material("Steel", Material { hyperelastic: Some(Hyperelastic::NeoHookean {}), ..steel() }).unwrap();
+
+    m.add_step(step("Linear", Procedure::Static {}, &["clamp"], &["end"]), None).unwrap();
+    assert!(unsupported(&m).contains("step `Linear`: a linear static step beside nonlinear steps of hyperelastic material `Steel`"));
+    m.remove_step("Bend").unwrap();
+    assert!(abaqus::write(&m).unwrap().contains("*ELASTIC, TYPE=ISOTROPIC\n"), "with linear steps only, the elastic constants are the whole of it");
+}
+
+/// A plastic material in nonlinear steps is `*PLASTIC` in a general step; what Abaqus would
+/// read differently is refused: a load path, and several general steps (Abaqus carries the
+/// plastic state between them).
+#[test]
+fn nonlinear_plastic_steps_and_what_is_refused() {
+    use fieldcraft_model::{Hardening, NonlinearStatic, Plastic};
+    let mut m = cantilever();
+    let plastic = Plastic::Bilinear { yield_stress: 250.0, hardening_modulus: 2000.0, hardening: Hardening::Isotropic };
+    m.replace_material("Steel", Material { plastic: Some(plastic), ..steel() }).unwrap();
+    m.replace_step(step("Bend", Procedure::NonlinearStatic(NonlinearStatic::default()), &["clamp"], &["end"])).unwrap();
+    let deck = abaqus::write(&m).unwrap();
+    assert!(deck.contains("*PLASTIC\n250.0, 0.0\n") && deck.contains("NLGEOM=YES"), "{deck}");
+    let path = NonlinearStatic { load_path: Some(vec![[0.0, 0.0], [0.5, 1.0], [1.0, 0.0]]), ..NonlinearStatic::default() };
+    m.replace_step(step("Bend", Procedure::NonlinearStatic(path), &["clamp"], &["end"])).unwrap();
+    assert!(unsupported(&m).contains("step `Bend`: a load path"));
+    m.replace_step(step("Bend", Procedure::NonlinearStatic(NonlinearStatic::default()), &["clamp"], &["end"])).unwrap();
+    m.add_step(step("Again", Procedure::NonlinearStatic(NonlinearStatic::default()), &["clamp"], &["end"]), None).unwrap();
+    assert!(unsupported(&m).contains("plastic material `Steel` in a deck of 2 general steps"));
+}

crates/decks/tests/lsdyna.rs

@@ -737,3 +737,50 @@ fn plasticity_is_written_as_plastic_materials() {
     let Err(Error::Unsupported { what, .. }) = lsdyna::write(&with(jc, None)) else { panic!() };
     assert!(what.contains("Johnson–Cook"), "{what}");
 }
+
+/// A nonlinear static step: the ramped implicit run with full Newton and automatic increments;
+/// what LS-DYNA cannot take is named.
+#[test]
+fn nonlinear_static_steps() {
+    let mut m = cantilever();
+    let controls =
+        NonlinearStatic { initial_increment: 0.05, min_increment: 1e-4, max_increment: 0.5, max_iterations: 12, ..NonlinearStatic::default() };
+    m.replace_step(step("Bend", Procedure::NonlinearStatic(controls.clone()), &["clamp"], &["tip_load"])).unwrap();
+    let deck = lsdyna::write(&m).unwrap().text;
+    let after = |keyword: &str| -> Vec<String> {
+        let mut lines = deck.lines().skip_while(|l| *l != keyword).skip(1).filter(|l| !l.starts_with('$'));
+        lines.next().unwrap().split_whitespace().map(str::to_string).collect()
+    };
+    let num = |s: &String| s.parse::<f64>().unwrap();
+    let general = after("*CONTROL_IMPLICIT_GENERAL");
+    assert_eq!((num(&general[0]), num(&general[1])), (1.0, 0.05), "{general:?}");
+    let solution = after("*CONTROL_IMPLICIT_SOLUTION");
+    assert_eq!(solution.iter().map(num).collect::<Vec<_>>(), [2.0, 1.0, 12.0], "{solution:?}");
+    let auto = after("*CONTROL_IMPLICIT_AUTO");
+    assert_eq!(auto.iter().map(num).collect::<Vec<_>>(), [1.0, 1e-4, 0.5], "blank fields are skipped: {auto:?}");
+    assert!(deck.contains("*DEFINE_CURVE_TITLE\nBend ramp\n"), "the loads follow the ramp");
+    assert!(deck.contains("*LOAD_NODE"), "{deck}");
+    // A load path is the curve.
+    let path = NonlinearStatic { load_path: Some(vec![[0.0, 0.0], [0.5, 1.0], [1.0, -1.0]]), ..controls.clone() };
+    m.replace_step(step("Bend", Procedure::NonlinearStatic(path), &["clamp"], &["tip_load"])).unwrap();
+    let deck = lsdyna::write(&m).unwrap().text;
+    let curve: Vec<Vec<f64>> = deck
+        .lines()
+        .skip_while(|l| *l != "Bend ramp")
+        .filter(|l| !l.starts_with('$'))
+        .skip(2)
+        .take(3)
+        .map(|l| l.split_whitespace().map(|v| v.parse().unwrap()).collect())
+        .collect();
+    assert_eq!(curve, [vec![0.0, 0.0], vec![0.5, 1.0], vec![1.0, -1.0]], "{deck}");
+
+    m.replace_step(step("Bend", Procedure::NonlinearStatic(NonlinearStatic { nonlinear_geometry: false, ..controls }), &["clamp"], &["tip_load"]))
+        .unwrap();
+    unsupported(&m, "a nonlinear step without nonlinear geometry");
+    m.replace_step(step("Bend", Procedure::NonlinearStatic(NonlinearStatic::default()), &["clamp"], &["tip_load"])).unwrap();
+    m.replace_material("Steel", Material { hyperelastic: Some(Hyperelastic::NeoHookean {}), ..steel() }).unwrap();
+    unsupported(&m, "hyperelastic material `Steel` in a nonlinear step");
+    // In a linear step the elastic constants are the whole of a hyperelastic material.
+    m.replace_step(step("Bend", Procedure::Static {}, &["clamp"], &["tip_load"])).unwrap();
+    assert!(lsdyna::write(&m).unwrap().text.contains("*MAT_ELASTIC_TITLE"));
+}

crates/decks/tests/nastran.rs

@@ -782,3 +782,13 @@ fn plasticity_is_written_as_mats1() {
     let Err(Error::Unsupported { what, .. }) = nastran::write(&m) else { panic!() };
     assert!(what.contains("Johnson–Cook plasticity") && what.contains("damage and erosion"), "{what}");
 }
+
+#[test]
+fn nonlinear_static_steps_are_refused_by_name() {
+    let mut m = cantilever();
+    let name = m.steps()[0].name.clone();
+    let mut s = m.steps()[0].clone();
+    s.set_procedure(Procedure::NonlinearStatic(fieldcraft_model::NonlinearStatic::default()));
+    m.replace_step(s).unwrap();
+    assert!(unsupported(&m).contains(&format!("step `{name}`: nonlinear static steps (Nastran's SOL 400")), "{}", unsupported(&m));
+}

crates/engine/Cargo.toml

@@ -27,3 +27,5 @@ log = { workspace = true }
 
 [dev-dependencies]
 zip = { workspace = true }
+# Multi-body designs from SolidCraft scripts in tests.
+fieldcraft-geometry = { workspace = true, features = ["scripts"] }

crates/engine/src/catalogue.rs

@@ -244,7 +244,7 @@ pub static CATALOGUE: &[Capability] = &[
         "Tet Mesh",
         Mesh,
         "Tet",
-        "Constrained Delaunay tet mesh of a body: every boundary triangle kept, faces tagged (refinement comes next)",
+        "Quality tet4 or tet10 mesh of a body to a size: refined, smoothed and improved, boundary on the B-rep faces, faces tagged",
     ),
     soon("mesh.order.quadratic", "Quadratic", Mesh, "Tet", "M2", "Second-order elements with mid-side nodes on the geometry"),
     ready("mesh.delaunay.points", "Delaunay Points", Mesh, "Tet", "Delaunay tetrahedralization of a point list (debugging aid)"),
@@ -272,9 +272,22 @@ pub static CATALOGUE: &[Capability] = &[
         "Hex mesh swept along extrusions (several levels), around revolutions, or from a source face to a target",
         &["mesh.hex.generate"],
     ),
+    ready(
+        "mesh.hex.blocks",
+        "Block Hex",
+        Mesh,
+        "Structured Hex",
+        "One conforming hex mesh of a part split into six-sided blocks: shared faces meshed once",
+    ),
     soon("mesh.hex.decompose", "Decompose", Mesh, "Structured Hex", "M5", "Find sweepable and mappable regions and propose the splits"),
     soon("mesh.transition", "Transition", Mesh, "Structured Hex", "M5", "Conforming tet–hex interfaces with pyramids"),
-    soon("mesh.hex.octree", "All-Hex", Mesh, "Automatic Hex", "M6", "Octree dual all-hex mesh of any part"),
+    ready(
+        "mesh.hex.octree",
+        "Octree Hex",
+        Mesh,
+        "Automatic Hex",
+        "Unstructured all-hex mesh of any part: adaptive grid, boundary layers on every sharp edge, untangled and proven valid",
+    ),
     soon("mesh.hex.dominant", "Hex-Dominant", Mesh, "Automatic Hex", "M6", "Hex-dominant mesh by recombining tets"),
     soon("mesh.hex.polycube", "Polycube", Mesh, "Automatic Hex", "M6", "Polycube hex mesh of blocky parts"),
     soon("mesh.smooth", "Smooth", Mesh, "Improve", "M6", "Smooth node positions, keeping every element valid"),
@@ -301,7 +314,7 @@ pub static CATALOGUE: &[Capability] = &[
         "Material",
         Properties,
         "Materials",
-        "Elastic (isotropic, orthotropic) material with density",
+        "Elastic (isotropic, orthotropic) material with density; neo-Hookean hyperelasticity for nonlinear steps",
         &["model.material.edit", "model.material.delete"],
     ),
     ready("model.material.plasticity", "Plasticity", Properties, "Materials", "Von Mises plasticity: bilinear, hardening table or Johnson–Cook"),
@@ -343,7 +356,7 @@ pub static CATALOGUE: &[Capability] = &[
         "Step",
         Steps,
         "Steps",
-        "A linear static or frequency step with its output",
+        "A linear or nonlinear static, frequency, heat or explicit step with its output",
         &["model.step.edit", "model.step.delete"],
     ),
     ready("model.step.activate", "Activate", Steps, "Steps", "Choose which loads and boundary conditions act in a step"),
@@ -437,8 +450,8 @@ pub static CATALOGUE: &[Capability] = &[
         "Static",
         Solve,
         "Implicit",
-        "Linear static (or coupled temperature–displacement) solve of a step with FieldCraft's own solver; heat transfer in the drop-down",
-        &["solve.heat"],
+        "Linear static (or coupled temperature–displacement) solve of a step with FieldCraft's own solver; nonlinear static and heat transfer in the drop-down",
+        &["solve.nonlinear", "solve.heat"],
     ),
     ready("solve.frequency", "Frequency", Solve, "Implicit", "Natural frequencies and mode shapes of a frequency step"),
     ready(

crates/engine/src/cmd/define.rs

@@ -81,7 +81,7 @@ definition_commands!(
     Material,
     "material",
     "Material",
-    r#"{"name": "Steel", "elastic": {"type": "isotropic", "young": 210000, "poisson": 0.3} | {"type": "engineering_constants", "young": [E1, E2, E3], "poisson": [ν12, ν13, ν23], "shear": [G12, G13, G23]}, "density": 7.85e-9, "fluid": {"type": "newtonian", "viscosity": 1.0e-9} (dynamic viscosity; a fluid needs a density), "plastic": {…} (see model.material.plasticity), "damage": {…}, "erosion": {…} (see model.material.damage)} — in the model's unit system (model.units), never converted"#,
+    r#"{"name": "Steel", "elastic": {"type": "isotropic", "young": 210000, "poisson": 0.3} | {"type": "engineering_constants", "young": [E1, E2, E3], "poisson": [ν12, ν13, ν23], "shear": [G12, G13, G23]}, "density": 7.85e-9, "fluid": {"type": "newtonian", "viscosity": 1.0e-9} (dynamic viscosity; a fluid needs a density), "plastic": {…} (see model.material.plasticity), "damage": {…}, "erosion": {…} (see model.material.damage), "hyperelastic": {"type": "neo_hookean"} | {"type": "mooney_rivlin", "c01": 0.1} (C10 = μ/2 − C01) | {"type": "yeoh", "c20": -0.01, "c30": 0.001} (C10 = μ/2) (large strain in nonlinear steps, from the isotropic constants: μ = E/(2(1 + ν)), κ = E/(3(1 − 2ν)); without it an elastic material is St Venant–Kirchhoff there)} — in the model's unit system (model.units), never converted"#,
     add_material,
     replace_material,
     remove_material,
@@ -266,7 +266,7 @@ fn fluid_boundary(s: &mut Session, p: &Value) -> Result<Value> {
 pub const STEP_CREATE: CommandSpec = CommandSpec {
     id: "model.step.create",
     label: "New Step",
-    params: r#"{"name": "Bend", "procedure": {"type": "static"} | {"type": "frequency", "modes": 10, "min_hz": 0, "max_hz": 500} | {"type": "fluid", "domain": "Flow", "end_time": 1.0 | "steps": 1000, "time_step": (default: chosen for Mach 0.087 and τ ≤ 1), "frames": 10, "magic": 0.1875 (the two-relaxation-time Λ)} | {"type": "explicit_dynamic", "end_time": 0.001, "dt_scale": 0.9, "max_increments": 10000000, "output_interval", "history_interval", "history_nodes": "set", "initial_velocities": [{"set", "velocity": [vx, vy, vz]}], "rigid_walls": [{"set", "point", "normal"}], "hourglass": {"type": "viscous|stiffness", "coefficient": 0.1}, "bulk_viscosity": {"linear": 0.06, "quadratic": 1.5}}, "output": ["displacement", "reaction_force", "stress", "strain"] (default by procedure), "boundary_conditions": [names], "loads": [names] (active in this step; nothing carries over between steps), "before": "step" (default: last)}"#,
+    params: r#"{"name": "Bend", "procedure": {"type": "static"} | {"type": "nonlinear_static", "nonlinear_geometry": true, "initial_increment": 0.1, "min_increment": 1e-5, "max_increment": 1.0 (fractions of the step), "max_increments": 100, "max_iterations": 16 (per increment), "tolerances": {"force": 1e-6, "displacement": 1e-5, "energy": 1e-10}, "line_search": false, "load_path": [[0, 0], [0.5, 1], [1, 0]] (optional: the load factor against the step fraction, piecewise linear from [0, 0] to fraction 1; increments end at its points)} (loads and prescribed displacements are the load factor times their values; it ramps from 0 to 1 without a load path) | {"type": "frequency", "modes": 10, "min_hz": 0, "max_hz": 500} | {"type": "fluid", "domain": "Flow", "end_time": 1.0 | "steps": 1000, "time_step": (default: chosen for Mach 0.087 and τ ≤ 1), "frames": 10, "magic": 0.1875 (the two-relaxation-time Λ)} | {"type": "explicit_dynamic", "end_time": 0.001, "dt_scale": 0.9, "max_increments": 10000000, "output_interval", "history_interval", "history_nodes": "set", "initial_velocities": [{"set", "velocity": [vx, vy, vz]}], "rigid_walls": [{"set", "point", "normal"}], "hourglass": {"type": "viscous|stiffness", "coefficient": 0.1}, "bulk_viscosity": {"linear": 0.06, "quadratic": 1.5}}, "output": ["displacement", "reaction_force", "stress", "strain"] (default by procedure), "boundary_conditions": [names], "loads": [names] (active in this step; nothing carries over between steps), "before": "step" (default: last)}"#,
     kind: CommandKind::Model,
     run: step_create,
 };

crates/engine/src/cmd/file.rs

@@ -89,6 +89,12 @@ fn open_sample(s: &mut Session, p: &Value) -> Result<Value> {
     Ok(reply)
 }
 
+/// A file of at most `max` bytes, through FieldCraft's file edge ([`fieldcraft_io::fs`]: the disk,
+/// or the page's files in the browser).
+pub(crate) fn read_file(path: &str, max: u64) -> Result<Vec<u8>> {
+    Ok(fieldcraft_io::fs::read_capped(Path::new(path), max)?)
+}
+
 /// `path` made absolute against the working folder (as given where there is none).
 pub(crate) fn absolute(path: &str) -> String {
     std::path::absolute(path).map(|p| p.to_string_lossy().into_owned()).unwrap_or_else(|_| path.to_string())
@@ -119,7 +125,7 @@ fn reopen<T>(
     stored: &SourceFile,
     base: Option<&Path>,
     roots: &Roots,
-    max: usize,
+    max: u64,
     open: impl FnOnce(&[u8]) -> fieldcraft_geometry::Result<T>,
     warnings: &mut Vec<String>,
 ) -> (Option<T>, SourceFile) {
@@ -132,7 +138,7 @@ fn reopen<T>(
             return (None, kept);
         }
     };
-    let bytes = match fieldcraft_geometry::read_file(&checked, max) {
+    let bytes = match read_file(&checked, max) {
         Ok(b) => b,
         Err(e) => {
             warnings.push(format!("{what} `{path}` was not opened ({e}); the model opens without it"));
@@ -173,13 +179,13 @@ impl Session {
         let mut sources = Geometry::default();
         let mut design: Option<Arc<Design>> = None;
         if let Some(stored) = &file.geometry.design {
-            let (opened, source) = reopen("design", stored, base, roots, MAX_DESIGN_BYTES, open_design, &mut warnings);
+            let (opened, source) = reopen("design", stored, base, roots, MAX_DESIGN_BYTES as u64, open_design, &mut warnings);
             design = opened.map(Arc::new);
             sources.design = Some(source);
         }
         let mut surfaces = Vec::new();
         for stored in &file.geometry.meshes {
-            let (opened, source) = reopen("mesh", stored, base, roots, tagged_mesh::MAX_FILE_BYTES, tagged_mesh::read_3mf, &mut warnings);
+            let (opened, source) = reopen("mesh", stored, base, roots, tagged_mesh::MAX_FILE_BYTES as u64, tagged_mesh::read_3mf, &mut warnings);
             surfaces.extend(opened.into_iter().flatten().map(Arc::new));
             sources.meshes.push(source);
         }
@@ -226,8 +232,7 @@ fn load(s: &mut Session, bytes: &[u8], path: Option<String>, saved: bool) -> Res
 
 fn open(s: &mut Session, p: &Value) -> Result<Value> {
     let path = absolute(&file_param(s, p, "path", Access::Read)?);
-    let max = usize::try_from(fieldcraft_io::MAX_FILE_BYTES).unwrap_or(usize::MAX);
-    let bytes = fieldcraft_geometry::read_file(&path, max)?;
+    let bytes = read_file(&path, fieldcraft_io::MAX_FILE_BYTES)?;
     load(s, &bytes, Some(path.clone()), true).map_err(|e| EngineError::Params(format!("{path}: {e}")))
 }
 

crates/engine/src/cmd/geometry.rs

@@ -42,7 +42,7 @@ pub const IMPORT_MESH: CommandSpec = CommandSpec {
 
 fn open(s: &mut Session, p: &Value) -> Result<Value> {
     let path = super::file_param(s, p, "path", Access::Read)?;
-    let bytes = fieldcraft_geometry::read_file(&path, MAX_DESIGN_BYTES)?;
+    let bytes = super::file::read_file(&path, MAX_DESIGN_BYTES as u64)?;
     let source = SourceFile::of(super::file::absolute(&path), &bytes)?;
     let design = open_design(&bytes)?;
     let out = json!({
@@ -101,7 +101,7 @@ fn import_mesh(s: &mut Session, p: &Value) -> Result<Value> {
     if s.sources.meshes.len() >= fieldcraft_io::MAX_MESH_SOURCES {
         return Err(EngineError::Params(format!("a model imports at most {} meshes", fieldcraft_io::MAX_MESH_SOURCES)));
     }
-    let bytes = fieldcraft_geometry::read_file(&path, tagged_mesh::MAX_FILE_BYTES)?;
+    let bytes = super::file::read_file(&path, tagged_mesh::MAX_FILE_BYTES as u64)?;
     let source = SourceFile::of(super::file::absolute(&path), &bytes)?;
     let surfaces = tagged_mesh::read_3mf(&bytes)?;
     let first = s.surfaces.len();

crates/engine/src/cmd/hex.rs

@@ -3,7 +3,7 @@
 use std::borrow::Cow;
 
 use fieldcraft_geometry::{FaceSurface, Shape, SurfaceMesh};
-use fieldcraft_mesh::hex::{HexMesh, HexMethod, HexOptions, Surface, hex_mesh};
+use fieldcraft_mesh::hex::{BoundaryFace, Cell, HexMesh, HexMethod, HexOptions, MAX_CELLS, Surface, hex_mesh, hex_mesh_cells};
 use fieldcraft_mesh::size::UniformSize;
 use fieldcraft_mesh::surface::BoundarySurface;
 use fieldcraft_model::{GeometryRef, Model};
@@ -28,13 +28,13 @@ const MIN_RELATIVE_TOLERANCE: f64 = 1e-5;
 const DEFAULT_RELATIVE_SIZE: f64 = 1.0 / 25.0;
 const DEFAULT_RELATIVE_TOLERANCE: f64 = 1e-3;
 
-/// One body to mesh.
-struct Input<'a> {
-    name: String,
-    mesh: Cow<'a, SurfaceMesh>,
+/// One body to mesh (also the input of `mesh.hex.octree`).
+pub(super) struct Input<'a> {
+    pub(super) name: String,
+    pub(super) mesh: Cow<'a, SurfaceMesh>,
     surfaces: Vec<Option<Surface>>,
-    face_names: Vec<String>,
-    diagonal: f64,
+    pub(super) face_names: Vec<String>,
+    pub(super) diagonal: f64,
 }
 
 fn analytic(s: FaceSurface) -> Surface {
@@ -47,7 +47,7 @@ fn analytic(s: FaceSurface) -> Surface {
     }
 }
 
-fn number(p: &Value, key: &str) -> Result<Option<f64>> {
+pub(super) fn number(p: &Value, key: &str) -> Result<Option<f64>> {
     match p.get(key) {
         None => Ok(None),
         Some(v) => v
@@ -73,7 +73,7 @@ fn shape_input(shape: &Shape, tolerance: Option<f64>) -> Result<Input<'static>>
     Ok(Input { name: shape.name.clone(), mesh: Cow::Owned(shape.tessellate(tol)?), surfaces, face_names, diagonal: diag })
 }
 
-fn inputs<'a>(s: &'a Session, p: &Value) -> Result<Vec<Input<'a>>> {
+pub(super) fn inputs<'a>(s: &'a Session, p: &Value) -> Result<Vec<Input<'a>>> {
     let tolerance = number(p, "tolerance")?;
     match (p.get("body"), p.get("surface")) {
         (Some(b), None) => {
@@ -129,6 +129,134 @@ pub const HEX_MAPPED: CommandSpec = CommandSpec {
     run: hex_mapped,
 };
 
+pub const HEX_BLOCKS: CommandSpec = CommandSpec {
+    id: "mesh.hex.blocks",
+    label: "Block Hex Mesh",
+    params: r#"{"bodies": ["Cell1", "Cell2"] (default: every body of the open design), "size": 2.0 (element size, mm; default 1/25 of the bounding-box diagonal of all of them), "order": 1 (hex8) or 2 (hex20, mid-edge nodes on the geometry), "tolerance": 0.05 (chordal tolerance of the tessellation, mm; default 1e-3 of that diagonal)} — replaces the mesh with one conforming all-hex mesh of a part partitioned into cells (bodies that meet face to face, such as the pieces of solid.split_body in SolidCraft): every cell a mapped block (six four-sided faces; faces that meet smoothly, such as the two halves of a hole, count as one), division counts assigned over all cells together, each shared face meshed once and its nodes merged, radial lines graded off holes and fillets. Elements are tagged with their cell's body and boundary faces with its B-rep faces (`weld`, `weld_distance` and `feature_angle` as in mesh.tet.generate). Reports the cells, the shared faces, counts and quality; a cell that is not a block, or cells that touch without sharing whole faces, is an error that says which"#,
+    kind: CommandKind::Model,
+    run: hex_blocks,
+};
+
+fn hex_blocks(s: &mut Session, p: &Value) -> Result<Value> {
+    let size = number(p, "size")?;
+    let quadratic = order(p)?;
+    let design = s.design.as_deref().ok_or_else(|| EngineError::Params("open a design first".into()))?;
+    let shapes: Vec<&Shape> = match p.get("bodies") {
+        None => design.bodies.iter().collect(),
+        Some(v) => {
+            let names = v.as_array().ok_or_else(|| EngineError::Params("`bodies` must be a list of body names".into()))?;
+            // Bounded before the duplicate check, which is quadratic in the list.
+            if names.len() > MAX_CELLS {
+                return Err(EngineError::Params(format!("`bodies` lists {} bodies; at most {MAX_CELLS} are meshed together", names.len())));
+            }
+            let mut out: Vec<&Shape> = Vec::with_capacity(names.len());
+            for n in names {
+                let name = n.as_str().ok_or_else(|| EngineError::Params("`bodies` must be a list of body names".into()))?;
+                let shape = design.body(name).ok_or_else(|| EngineError::Params(format!("no body `{name}`")))?;
+                if out.iter().any(|b| b.name == shape.name) {
+                    return Err(EngineError::Params(format!("body `{name}` is listed twice")));
+                }
+                out.push(shape);
+            }
+            out
+        }
+    };
+    if shapes.is_empty() || shapes.len() > MAX_CELLS {
+        return Err(EngineError::Params(format!("{} bodies; mesh.hex.blocks meshes 1 to {MAX_CELLS}", shapes.len())));
+    }
+    // One size and one tessellation tolerance for all cells, from their joint extent, so shared
+    // curves are divided alike.
+    let (mut lo, mut hi) = ([f64::INFINITY; 3], [f64::NEG_INFINITY; 3]);
+    for b in &shapes {
+        let m = b.measure()?;
+        for k in 0..3 {
+            lo[k] = lo[k].min(m.bbox_min[k]);
+            hi[k] = hi[k].max(m.bbox_max[k]);
+        }
+    }
+    let diag = diagonal(lo, hi);
+    if !(diag > 0.0 && diag.is_finite()) {
+        return Err(EngineError::Params("the bodies have no extent".into()));
+    }
+    let tolerance = number(p, "tolerance")?.unwrap_or(DEFAULT_RELATIVE_TOLERANCE * diag);
+    if tolerance < MIN_RELATIVE_TOLERANCE * diag {
+        return Err(EngineError::Params(format!("`tolerance` must be at least {} mm", MIN_RELATIVE_TOLERANCE * diag)));
+    }
+    let h = size.unwrap_or(DEFAULT_RELATIVE_SIZE * diag);
+    if h < MIN_RELATIVE_SIZE * diag {
+        return Err(EngineError::Params(format!("`size` must be at least {} mm", MIN_RELATIVE_SIZE * diag)));
+    }
+    let inputs: Vec<Input> = shapes.iter().map(|b| shape_input(b, Some(tolerance))).collect::<Result<_>>()?;
+    let mut surfaces = Vec::with_capacity(inputs.len());
+    for b in &inputs {
+        let options = super::mesh::surface_options(p, &b.mesh)?;
+        surfaces.push(
+            BoundarySurface::new(&b.mesh.positions, &b.mesh.triangles, &b.mesh.tri_face, &options)
+                .map_err(|e| EngineError::Params(format!("body `{}`: {e}", b.name)))?,
+        );
+    }
+    let cells: Vec<Cell> = surfaces.iter().zip(&inputs).map(|(surface, b)| Cell { name: &b.name, surface, faces: &b.surfaces }).collect();
+    let options = HexOptions {
+        method: HexMethod::Mapped,
+        quadratic,
+        chordal_tolerance: tolerance,
+        max_elements: fieldcraft_model::MAX_ELEMENTS / 8,
+        ..HexOptions::default()
+    };
+    let cm = hex_mesh_cells(&cells, &UniformSize(h), &options).map_err(|e| EngineError::Params(e.to_string()))?;
+    let m = &cm.mesh;
+    // Replace the mesh: definitions stay, nodes, elements and geometry tags are new.
+    let mut model = s.model.without_mesh();
+    for (i, xyz) in m.nodes.iter().enumerate() {
+        model.set_node(label(i)?, *xyz)?;
+    }
+    let mut body_tags = Vec::with_capacity(inputs.len());
+    for b in &inputs {
+        body_tags.push(model.geometry_tag(&GeometryRef::body(b.name.as_str())?)?);
+    }
+    for e in 0..m.element_count() {
+        let cell = cm.element_cell.get(e).map_or(0, |&c| c as usize);
+        let nodes: Vec<u32> = m.element(e).unwrap_or(&[]).iter().map(|&i| i + 1).collect();
+        model.set_element(label(e)?, m.kind, nodes)?;
+        model.tag_element(label(e)?, body_tags.get(cell).copied().ok_or_else(|| EngineError::Params("element without a cell".into()))?)?;
+    }
+    tag_faces(&mut model, &inputs, |e| cm.element_cell.get(e as usize).map_or(0, |&c| c as usize), &m.boundary, 1)?;
+    s.model = model;
+    let blocks: Vec<Value> =
+        inputs.iter().zip(&cm.blocks).map(|(b, d)| json!({"body": b.name, "divisions": d, "elements": d.iter().product::<usize>()})).collect();
+    Ok(json!({
+        "cells": inputs.len(),
+        "interfaces": cm.interfaces,
+        "description": m.report.description,
+        "kind": m.kind.name(),
+        "elements": m.element_count(),
+        "nodes": m.nodes.len(),
+        "boundary_faces": m.boundary.len(),
+        "quality": {"min_scaled_jacobian": m.report.min_scaled_jacobian, "mean_scaled_jacobian": m.report.mean_scaled_jacobian},
+        "volume": m.report.volume,
+        "surface_volume": m.report.surface_volume,
+        "size": h,
+        "blocks": blocks,
+    }))
+}
+
+/// A 1-based model label for 0-based index `i`.
+fn label(i: usize) -> Result<u32> {
+    u32::try_from(i).ok().and_then(|x| x.checked_add(1)).ok_or_else(|| EngineError::Params("too many nodes or elements".into()))
+}
+
+/// The `order` parameter: false for hex8, true for hex20.
+fn order(p: &Value) -> Result<bool> {
+    match p.get("order") {
+        None => Ok(false),
+        Some(v) => match v.as_u64() {
+            Some(1) => Ok(false),
+            Some(2) => Ok(true),
+            _ => Err(EngineError::Params("`order` must be 1 (hex8) or 2 (hex20)".into())),
+        },
+    }
+}
+
 fn hex_generate(s: &mut Session, p: &Value) -> Result<Value> {
     let all = [HexMethod::Auto, HexMethod::Swept, HexMethod::Extrude, HexMethod::Sweep, HexMethod::Revolve, HexMethod::Mapped];
     generate(s, p, HexMethod::Auto, &all)
@@ -145,14 +273,7 @@ fn hex_mapped(s: &mut Session, p: &Value) -> Result<Value> {
 /// Mesh with `default` or the `method` parameter, which must be one of `allowed`.
 fn generate(s: &mut Session, p: &Value, default: HexMethod, allowed: &[HexMethod]) -> Result<Value> {
     let size = number(p, "size")?;
-    let quadratic = match p.get("order") {
-        None => false,
-        Some(v) => match v.as_u64() {
-            Some(1) => false,
-            Some(2) => true,
-            _ => return Err(EngineError::Params("`order` must be 1 (hex8) or 2 (hex20)".into())),
-        },
-    };
+    let quadratic = order(p)?;
     let method = match p.get("method") {
         None => default,
         Some(v) => v.as_str().and_then(HexMethod::from_name).filter(|m| allowed.contains(m)).ok_or_else(|| {
@@ -197,7 +318,7 @@ fn generate(s: &mut Session, p: &Value, default: HexMethod, allowed: &[HexMethod
             model.tag_element(element_label, body_tag)?;
             element_label = element_label.checked_add(1).ok_or_else(|| EngineError::Params("too many elements".into()))?;
         }
-        tag_faces(&mut model, b, m, first_element)?;
+        tag_faces(&mut model, std::slice::from_ref(b), |_| 0, &m.boundary, first_element)?;
         report.push(json!({
             "body": b.name,
             "method": m.report.method.name(),
@@ -215,22 +336,26 @@ fn generate(s: &mut Session, p: &Value, default: HexMethod, allowed: &[HexMethod
     Ok(json!({"bodies": report, "nodes": node_label - 1, "elements": element_label - 1}))
 }
 
-/// Tag every boundary element face with its B-rep face.
-fn tag_faces(model: &mut Model, b: &Input<'_>, m: &HexMesh, first_element: u32) -> Result<()> {
-    let mut tags: Vec<Option<u32>> = Vec::new();
-    for f in &m.boundary {
-        let i = f.brep_face as usize;
-        if tags.len() <= i {
-            tags.resize(i + 1, None);
-        }
-        let tag = match tags.get(i).copied().flatten() {
-            Some(t) => t,
+/// Tag every boundary element face with the B-rep face it lies on, of the body
+/// (`bodies[cell(element)]`) its element meshes.
+pub(super) fn tag_faces(
+    model: &mut Model,
+    bodies: &[Input<'_>],
+    cell: impl Fn(u32) -> usize,
+    boundary: &[BoundaryFace],
+    first_element: u32,
+) -> Result<()> {
+    let mut tags: std::collections::BTreeMap<(usize, u32), u32> = std::collections::BTreeMap::new();
+    for f in boundary {
+        let c = cell(f.element);
+        let tag = match tags.get(&(c, f.brep_face)) {
+            Some(&t) => t,
             None => {
+                let b = bodies.get(c).ok_or_else(|| EngineError::Params("a boundary face without its body".into()))?;
+                let i = f.brep_face as usize;
                 let name = b.face_names.get(i).cloned().unwrap_or_else(|| i.to_string());
                 let t = model.geometry_tag(&GeometryRef::face(b.name.as_str(), name)?)?;
-                if let Some(slot) = tags.get_mut(i) {
-                    *slot = Some(t);
-                }
+                tags.insert((c, f.brep_face), t);
                 t
             }
         };
@@ -291,6 +416,89 @@ mod tests {
         assert_eq!(s.model.element_counts(), vec![(fieldcraft_model::ElementKind::Hex8, n)]);
     }
 
+    /// A 20 × 10 × 10 box split by SolidCraft into four cells (x = 10, then y = 5 on each half),
+    /// opened as a design; with `t_junction` the second half is not split, so the first half's
+    /// two cells meet it on one face.
+    fn split_box(t_junction: bool) -> (crate::tests::TempDir, Session) {
+        let mut commands = vec![
+            json!({"command": "solid.box", "params": {"length": 20, "width": 10, "height": 10, "body_name": "Box"}}),
+            json!({"command": "solid.split_body", "params": {"body": "Box", "plane": {"origin": [10, 0, 0], "normal": [1, 0, 0]}}}),
+            json!({"command": "solid.split_body", "params": {"body": "Box (1)", "plane": {"origin": [0, 5, 0], "normal": [0, 1, 0]}}}),
+        ];
+        if !t_junction {
+            commands.push(json!({"command": "solid.split_body", "params": {"body": "Box", "plane": {"origin": [0, 5, 0], "normal": [0, 1, 0]}}}));
+        }
+        let bytes = fieldcraft_geometry::script_design(&json!({"commands": commands}).to_string()).unwrap();
+        let (dir, path) = crate::tests::design_file(&bytes);
+        let mut s = Session::default();
+        s.execute("geometry.open", &json!({"path": path})).unwrap();
+        (dir, s)
+    }
+
+    #[test]
+    fn split_cells_mesh_into_one_conforming_hex_mesh() {
+        let (_dir, mut s) = split_box(false);
+        let r = s.execute("mesh.hex.blocks", &json!({"size": 2.5})).unwrap();
+        assert_eq!(r["cells"], 4, "{r}");
+        assert_eq!(r["interfaces"], 4, "{r}");
+        assert_eq!(r["elements"], 8 * 4 * 4, "{r}");
+        // One 9 × 5 × 5 grid of nodes: the cells' nodes are merged on the interfaces.
+        assert_eq!(r["nodes"], 9 * 5 * 5, "{r}");
+        assert_eq!(s.model.element_counts(), vec![(fieldcraft_model::ElementKind::Hex8, 128)]);
+        assert!((r["volume"].as_f64().unwrap() - 2000.0).abs() < 1e-6, "{r}");
+        // Each cell's elements carry its body, and the outer faces their B-rep faces: a set of
+        // all four bodies skins the box with no internal faces.
+        let bodies = s.execute("geometry.bodies", &json!({})).unwrap();
+        let names: Vec<Value> = bodies.as_array().unwrap().iter().map(|b| json!({"body": b["name"]})).collect();
+        s.execute("model.set.create", &json!({"name": "all", "geometry": names})).unwrap();
+        let all = s.execute("model.set.resolve", &json!({"name": "all"})).unwrap();
+        assert_eq!(all["elements"]["count"], 128, "{all}");
+        assert_eq!(all["faces"]["count"], r["boundary_faces"], "{all}");
+        assert_eq!(r["boundary_faces"], 2 * (8 * 4 + 8 * 4 + 4 * 4), "{r}");
+        let first = bodies[0]["name"].as_str().unwrap();
+        s.execute("model.set.create", &json!({"name": "one", "geometry": [{"body": first}]})).unwrap();
+        assert_eq!(s.execute("model.set.resolve", &json!({"name": "one"})).unwrap()["elements"]["count"], 32);
+        // Hex20 shares mid-edge nodes across the interfaces as well.
+        let q = s.execute("mesh.hex.blocks", &json!({"size": 2.5, "order": 2})).unwrap();
+        assert_eq!(q["kind"], "hex20");
+        assert_eq!(q["nodes"], 9 * 5 * 5 + 8 * 5 * 5 + 9 * 4 * 5 + 9 * 5 * 4, "{q}");
+        // A list of bodies meshes those only.
+        let two = s.execute("mesh.hex.blocks", &json!({"bodies": [bodies[0]["name"], bodies[1]["name"]], "size": 2.5})).unwrap();
+        assert_eq!(two["cells"], 2);
+    }
+
+    #[test]
+    fn cells_that_do_not_conform_and_hostile_params_are_errors() {
+        let (_dir, mut s) = split_box(true);
+        let before = s.model.clone();
+        let e = s.execute("mesh.hex.blocks", &json!({"size": 2.5})).unwrap_err().to_string();
+        assert!(e.contains("do not conform") && e.contains("`Box`"), "{e}");
+        assert_eq!(s.model, before);
+        for p in [
+            json!({"size": 0}),
+            json!({"size": -1}),
+            json!({"size": "big"}),
+            json!({"size": 1e-300}),
+            json!({"order": 3}),
+            json!({"tolerance": -1}),
+            json!({"tolerance": 1e-300}),
+            json!({"bodies": "Box"}),
+            json!({"bodies": []}),
+            json!({"bodies": ["Nope"]}),
+            json!({"bodies": ["Box", "Box"]}),
+            json!({"bodies": [7]}),
+            json!({"size": 1e-3}),
+        ] {
+            assert!(s.execute("mesh.hex.blocks", &p).is_err(), "{p}");
+            assert_eq!(s.model, before, "{p}");
+        }
+        assert!(Session::default().execute("mesh.hex.blocks", &json!({})).is_err());
+        // One cell that is no block says which.
+        let (_dir, mut plate) = opened();
+        let e = plate.execute("mesh.hex.blocks", &json!({})).unwrap_err().to_string();
+        assert!(e.contains("`Body1`") && e.contains("not a logical cube"), "{e}");
+    }
+
     #[test]
     fn hostile_params_are_errors_and_change_nothing() {
         let (_dir, mut s) = opened();

crates/engine/src/cmd/mesh.rs

@@ -6,6 +6,9 @@ use fieldcraft_mesh::cdt::{CdtOptions, tetrahedralize};
 use fieldcraft_mesh::delaunay::Triangulation;
 use fieldcraft_mesh::quality::{self, QualityReport};
 use fieldcraft_mesh::surface::{BoundarySurface, Defect, FeatureKind, SurfaceOptions};
+use fieldcraft_mesh::tet::geometry::AnalyticSurface;
+use fieldcraft_mesh::tet::improve::ImproveOptions;
+use fieldcraft_mesh::tet::{Order, QualityMesh, QualityOptions, TetQuality, quality_mesh, raw_mesh};
 use fieldcraft_model::{ElementKind, GeometryRef, MAX_ELEMENTS};
 use serde_json::{Value, json};
 
@@ -83,7 +86,7 @@ pub const SURFACE_CHECK: CommandSpec = CommandSpec {
 pub const TET_GENERATE: CommandSpec = CommandSpec {
     id: "mesh.tet.generate",
     label: "Generate Tet Mesh",
-    params: r#"{"body": "Body1", "tolerance": 0.05} or {"surface": 0}, the boundary options of mesh.surface.check ("weld", "weld_distance", "feature_angle"), optional "max_steiner": 50000 (0..=10000000), "max_tets": 20000000 (1..=50000000) — the constrained Delaunay tetrahedralization of the welded boundary: every boundary triangle is a union of tet faces, Steiner points only on boundary edges, no quality refinement yet. Adds tet4 elements and their nodes (labels after the largest existing ones), tags the elements with the body and each boundary element face with its geometry face, and fails, changing nothing, if the surface is invalid or the mesh rounded to doubles does not pass the validity gate"#,
+    params: r#"{"body": "Body1" (default: every body of the open design) or "surface": 0 (an imported surface), "tolerance": 0.05 (chordal tolerance of the tessellation, mm; default 1e-3 of the body's bounding-box diagonal), the boundary options of mesh.surface.check ("weld", "weld_distance", "feature_angle"), optional "size": mm (target edge length; default a twentieth of the bounding-box diagonal), "order": "linear" | "quadratic" (tet4 or tet10; quadratic mid-edge nodes lie on the B-rep faces), "quality": true (false: the raw constrained Delaunay tetrahedralization), "quality_target": 40 (degrees: tetrahedra whose smallest dihedral-angle sine is at least sin of this are left alone by improvement, 5..=60), "curvature_angle": 22.5 (degrees per element along curved boundary, 0 for none, at most 90), "grading": 0.3 (largest size change per unit length, 0.05..=2), "max_passes": 20 (improvement passes, 0..=200), "max_points": 1000000 (1..=20000000), "max_steiner": 50000 (0..=10000000), "max_tets": 5000000 (1..=50000000) — the constrained Delaunay tetrahedralization of the welded boundary (every boundary triangle a union of tet faces), refined to the size field with its boundary vertices on the B-rep faces, smoothed and improved (Delaunay refinement, ODT smoothing, Klingner–Shewchuk improvement), with a quality report. Adds the elements and their nodes (labels after the largest existing ones), tags the elements with the body and each boundary element face with its geometry face, and fails, changing nothing, if a surface is invalid or a mesh does not pass the validity gate. Reports the totals and, under `bodies`, each body's counts, size and quality report"#,
     kind: CommandKind::Model,
     run: tet_generate,
 };
@@ -91,9 +94,11 @@ pub const TET_GENERATE: CommandSpec = CommandSpec {
 /// The most Steiner points and tetrahedra `mesh.tet.generate` may be asked for.
 const TET_MAX_STEINER: u64 = 10_000_000;
 const TET_MAX_TETS: u64 = 50_000_000;
+const TET_MAX_POINTS: u64 = 20_000_000;
+const TET_MAX_PASSES: u64 = 200;
 
 /// An optional whole-number parameter in `range`.
-fn optional_count(p: &Value, key: &str, default: u64, range: std::ops::RangeInclusive<u64>) -> Result<usize> {
+pub(super) fn optional_count(p: &Value, key: &str, default: u64, range: std::ops::RangeInclusive<u64>) -> Result<usize> {
     let v = match p.get(key) {
         None => default,
         Some(v) => v
@@ -114,59 +119,216 @@ pub(super) fn surface_options(p: &Value, mesh: &SurfaceMesh) -> Result<SurfaceOp
     })
 }
 
-fn tet_generate(s: &mut Session, p: &Value) -> Result<Value> {
-    let cdt_options = CdtOptions {
-        max_steiner: optional_count(p, "max_steiner", s.limits.max_steiner as u64, 0..=TET_MAX_STEINER)?,
-        max_tets: optional_count(p, "max_tets", s.limits.max_tets as u64, 1..=TET_MAX_TETS)?,
-    };
-    let (surface, body, face_names) = {
-        let Input { mesh, body, faces } = surface_input(s, p)?;
-        let options = surface_options(p, &mesh)?;
-        (BoundarySurface::new(&mesh.positions, &mesh.triangles, &mesh.tri_face, &options)?, body, faces)
-    };
-    let cdt = tetrahedralize(&surface, &cdt_options)?;
-    let gate = cdt.gate(surface.volume())?.into_result()?;
+/// An optional number in `range`.
+fn number_in(p: &Value, key: &str, default: f64, range: std::ops::RangeInclusive<f64>) -> Result<f64> {
+    let v = optional_number(p, key, default)?;
+    if range.contains(&v) { Ok(v) } else { Err(EngineError::Params(format!("`{key}` must be a number in {}..={}", range.start(), range.end()))) }
+}
 
-    let (first_node, first_element) = super::fresh_labels(&s.model, cdt.points.len(), cdt.tets.len())?;
-    for (i, xyz) in cdt.points.iter().enumerate() {
+/// The quality options of `mesh.tet.generate`, and whether the quality stage runs at all.
+fn quality_options(p: &Value, max_tets: u64) -> Result<(QualityOptions, bool)> {
+    let d = QualityOptions::default();
+    let size = match p.get("size") {
+        None => None,
+        Some(v) => Some(
+            v.as_f64()
+                .filter(|h| *h > 0.0 && h.is_finite() && *h <= fieldcraft_model::MAX_COORD)
+                .ok_or_else(|| EngineError::Params("`size` must be a positive number (mm)".into()))?,
+        ),
+    };
+    let order = match p.get("order") {
+        None => Order::Linear,
+        Some(v) => match v.as_str() {
+            Some("linear") => Order::Linear,
+            Some("quadratic") => Order::Quadratic,
+            _ => return Err(EngineError::Params("`order` must be \"linear\" or \"quadratic\"".into())),
+        },
+    };
+    let target = number_in(p, "quality_target", 40.0, 5.0..=60.0)?;
+    let improve_options = ImproveOptions {
+        max_passes: optional_count(p, "max_passes", d.improve_options.max_passes as u64, 0..=TET_MAX_PASSES)?,
+        good: fieldcraft_mesh::tet::geometry::sin_cos(target.to_radians()).0,
+        ..d.improve_options
+    };
+    let quality = super::opt::<bool>(p, "quality")?.unwrap_or(true);
+    if !quality && order == Order::Quadratic {
+        return Err(EngineError::Params("quadratic elements need the quality stage (`quality`: true)".into()));
+    }
+    let options = QualityOptions {
+        size,
+        curvature_angle: number_in(p, "curvature_angle", d.curvature_angle.to_degrees(), 0.0..=90.0)?.to_radians(),
+        grading: number_in(p, "grading", d.grading, 0.05..=2.0)?,
+        improve_options,
+        order,
+        max_tets: optional_count(p, "max_tets", max_tets, 1..=TET_MAX_TETS)?,
+        max_points: optional_count(p, "max_points", d.max_points as u64, 1..=TET_MAX_POINTS)?,
+        ..d
+    };
+    Ok((options, quality))
+}
+
+/// The exact surfaces of a body's faces, for the quality stage's projections (none when the
+/// kernel cannot give them: the stage then keeps to the tessellation).
+pub fn analytic_surfaces(shape: &fieldcraft_geometry::Shape) -> Vec<Option<AnalyticSurface>> {
+    use fieldcraft_geometry::FaceSurface as F;
+    shape
+        .face_surfaces()
+        .unwrap_or_default()
+        .into_iter()
+        .map(|f| {
+            f.map(|f| match f {
+                F::Plane { normal, point } => AnalyticSurface::Plane { normal, point },
+                F::Cylinder { origin, axis, radius } => AnalyticSurface::Cylinder { origin, axis, radius },
+                F::Cone { apex, axis, half_angle } => AnalyticSurface::Cone { apex, axis, half_angle },
+                F::Sphere { center, radius } => AnalyticSurface::Sphere { center, radius },
+                F::Torus { center, axis, major, minor } => AnalyticSurface::Torus { center, axis, major, minor },
+            })
+        })
+        .collect()
+}
+
+fn quality_json(q: &TetQuality) -> Value {
+    json!({
+        "tets": q.tets,
+        "min_dihedral": q.min_dihedral,
+        "max_dihedral": q.max_dihedral,
+        "min_radius_ratio": q.min_radius_ratio,
+        "mean_radius_ratio": q.mean_radius_ratio,
+        "slivers": q.slivers,
+        "inadmissible": q.inadmissible,
+    })
+}
+
+/// One body's tetrahedra, ready to add, with what its report needs of the surface and the CDT.
+struct BodyTets {
+    name: String,
+    face_names: Vec<String>,
+    mesh: QualityMesh,
+    steiner: usize,
+    cavities: usize,
+    surface_volume: f64,
+}
+
+/// Mesh one body or imported surface; the model is not touched. With `several` bodies an error
+/// names the body.
+fn mesh_body(
+    s: &Session,
+    p: &Value,
+    input: super::hex::Input,
+    cdt: &CdtOptions,
+    options: &QualityOptions,
+    quality: bool,
+    several: bool,
+) -> Result<BodyTets> {
+    let mesh = || -> Result<BodyTets> {
+        // The exact faces of a design body; an imported surface keeps to its triangles.
+        let analytic = match p.get("surface") {
+            None => s.design.as_deref().and_then(|d| d.body(&input.name)).map(analytic_surfaces).unwrap_or_default(),
+            Some(_) => Vec::new(),
+        };
+        let surface = BoundarySurface::new(&input.mesh.positions, &input.mesh.triangles, &input.mesh.tri_face, &surface_options(p, &input.mesh)?)?;
+        let tets = tetrahedralize(&surface, cdt)?;
+        let mesh = if quality { quality_mesh(&surface, &tets, analytic, options)? } else { raw_mesh(&surface, &tets)? };
+        Ok(BodyTets {
+            name: input.name.clone(),
+            face_names: input.face_names.clone(),
+            mesh,
+            steiner: tets.steiner.len(),
+            cavities: tets.stats.cavities,
+            surface_volume: surface.volume(),
+        })
+    };
+    mesh().map_err(|e| if several { EngineError::Params(format!("body `{}`: {e}", input.name)) } else { e })
+}
+
+fn tet_generate(s: &mut Session, p: &Value) -> Result<Value> {
+    let (options, quality) = quality_options(p, s.limits.max_tets as u64)?;
+    let cdt_options =
+        CdtOptions { max_steiner: optional_count(p, "max_steiner", s.limits.max_steiner as u64, 0..=TET_MAX_STEINER)?, max_tets: options.max_tets };
+    // Every body is meshed before the model changes; with several, an error names its body.
+    let inputs = super::hex::inputs(s, p)?;
+    let several = inputs.len() > 1;
+    let mut meshed = Vec::with_capacity(inputs.len());
+    for input in inputs {
+        meshed.push(mesh_body(s, p, input, &cdt_options, &options, quality, several)?);
+    }
+
+    let mut bodies = Vec::with_capacity(meshed.len());
+    for b in &meshed {
+        let (first_node, first_element) = add_tets(s, &b.name, &b.face_names, &b.mesh)?;
+        let r = &b.mesh.report;
+        bodies.push(json!({
+            "body": b.name,
+            "nodes": b.mesh.points.len(),
+            "elements": b.mesh.elements.len(),
+            "first_node": first_node,
+            "first_element": first_element,
+            "steiner": b.steiner,
+            "cavities": b.cavities,
+            "boundary_faces": b.mesh.boundary.len(),
+            "volume": r.volume,
+            "boundary_volume": r.boundary_volume,
+            "surface_volume": b.surface_volume,
+            "size": r.size,
+            "quality": {
+                "cdt": quality_json(&r.input),
+                "mesh": quality_json(&r.output),
+                "refined": r.refine.iter().map(|x| x.interior + x.boundary).sum::<usize>(),
+                "odt_moves": r.odt_moves,
+                "improvement": {"passes": r.improve.passes, "smoothed": r.improve.smoothed, "topological": r.improve.topological, "inserted": r.improve.inserted},
+                "straightened": r.straightened,
+                "stopped": r.stopped,
+            },
+        }));
+    }
+    let sum = |f: fn(&BodyTets) -> f64| meshed.iter().map(f).sum::<f64>();
+    let count = |f: fn(&BodyTets) -> usize| meshed.iter().map(f).sum::<usize>();
+    let first = bodies.first();
+    Ok(json!({
+        "kind": meshed.first().map(|b| b.mesh.kind.name()),
+        "nodes": count(|b| b.mesh.points.len()),
+        "elements": count(|b| b.mesh.elements.len()),
+        "first_node": first.map(|b| b["first_node"].clone()),
+        "first_element": first.map(|b| b["first_element"].clone()),
+        "boundary_faces": count(|b| b.mesh.boundary.len()),
+        "volume": sum(|b| b.mesh.report.volume),
+        "boundary_volume": sum(|b| b.mesh.report.boundary_volume),
+        "surface_volume": sum(|b| b.surface_volume),
+        "bodies": bodies,
+    }))
+}
+
+/// Add one body's elements after the model's largest labels, tagging them with the body and each
+/// boundary element face with its geometry face; returns the first node and element labels.
+fn add_tets(s: &mut Session, body: &str, face_names: &[String], mesh: &QualityMesh) -> Result<(u32, u32)> {
+    let (first_node, first_element) = super::fresh_labels(&s.model, mesh.points.len(), mesh.elements.len())?;
+    for (i, xyz) in mesh.points.iter().enumerate() {
         s.model.set_node(first_node + i as u32, *xyz)?;
     }
-    let body_tag = s.model.geometry_tag(&GeometryRef::body(body.clone())?)?;
-    for (i, t) in cdt.tets.iter().enumerate() {
+    let body_tag = s.model.geometry_tag(&GeometryRef::body(body)?)?;
+    for (i, e) in mesh.elements.iter().enumerate() {
         let label = first_element + i as u32;
-        s.model.set_element(label, ElementKind::Tet4, t.iter().map(|&v| first_node + v).collect())?;
+        s.model.set_element(label, mesh.kind, e.iter().map(|&v| first_node + v).collect())?;
         s.model.tag_element(label, body_tag)?;
     }
     let mut face_tags: Vec<Option<u32>> = vec![None; face_names.len()];
-    for b in &cdt.boundary {
-        let face = surface.tri_face().get(b.triangle as usize).copied().unwrap_or(u32::MAX) as usize;
+    for b in &mesh.boundary {
+        let face = b.face as usize;
         let tag = match face_tags.get(face).copied().flatten() {
             Some(t) => t,
             None => {
-                let name =
-                    face_names.get(face).ok_or_else(|| EngineError::Params(format!("boundary triangle {} has no geometry face", b.triangle)))?;
-                let t = s.model.geometry_tag(&GeometryRef::face(body.clone(), name.clone())?)?;
+                let name = face_names.get(face).ok_or_else(|| EngineError::Params(format!("boundary face {} has no geometry face", b.face)))?;
+                let t = s.model.geometry_tag(&GeometryRef::face(body, name.clone())?)?;
                 if let Some(slot) = face_tags.get_mut(face) {
                     *slot = Some(t);
                 }
                 t
             }
         };
-        let number = b.tet4_face().ok_or_else(|| EngineError::Params(format!("boundary face {} has no tet4 face number", b.opposite)))?;
+        let number = b.element_face().ok_or_else(|| EngineError::Params(format!("boundary face {} has no element face number", b.opposite)))?;
         s.model.tag_element_face(first_element + b.tet, number, tag)?;
     }
-    Ok(json!({
-        "body": body,
-        "nodes": cdt.points.len(),
-        "elements": cdt.tets.len(),
-        "first_node": first_node,
-        "first_element": first_element,
-        "steiner": cdt.steiner.len(),
-        "cavities": cdt.stats.cavities,
-        "boundary_faces": cdt.boundary.len(),
-        "volume": gate.volume,
-        "boundary_volume": surface.volume(),
-    }))
+    Ok((first_node, first_element))
 }
 
 pub const PLANAR: CommandSpec = CommandSpec {
@@ -367,6 +529,7 @@ fn quality_report(s: &mut Session, p: &Value) -> Result<Value> {
         })
         .collect();
     Ok(json!({
+        "summary": quality_summary(&r),
         "measured": r.measured,
         "skipped": skipped,
         "valid": r.valid,
@@ -378,21 +541,33 @@ fn quality_report(s: &mut Session, p: &Value) -> Result<Value> {
     }))
 }
 
-/// A boundary to mesh: the surface, with the body name and the geometry name of each face index
-/// for tagging.
-struct Input<'a> {
-    mesh: Cow<'a, SurfaceMesh>,
-    body: String,
-    faces: Vec<String>,
+/// A quality report in a line, for the status bar and the CLI: the elements measured, how many
+/// are invalid or undetermined, and the scaled Jacobian's minimum and mean.
+fn quality_summary(r: &QualityReport) -> String {
+    if r.measured == 0 {
+        return "no elements to measure".into();
+    }
+    let mut text = format!("{} elements", r.measured);
+    if r.invalid.is_empty() && r.undetermined.is_empty() {
+        text.push_str(", all valid");
+    }
+    if !r.invalid.is_empty() {
+        text.push_str(&format!(", {} invalid", r.invalid.len()));
+    }
+    if !r.undetermined.is_empty() {
+        text.push_str(&format!(", {} undetermined", r.undetermined.len()));
+    }
+    let jacobian = r.metrics.iter().find(|m| m.metric == quality::Metric::ScaledJacobian && m.count > 0);
+    if let Some((min, mean)) = jacobian.and_then(|m| m.mean.map(|mean| (m.min, mean))) {
+        text.push_str(&format!("; scaled Jacobian min {min:.3}, mean {mean:.3}"));
+    }
+    text
 }
 
 /// The surface named by `body` (tessellated at `tolerance`) or `surface` (an imported index).
-fn surface_input<'a>(s: &'a Session, p: &Value) -> Result<Input<'a>> {
+fn surface_input<'a>(s: &'a Session, p: &Value) -> Result<Cow<'a, SurfaceMesh>> {
     match (p.get("body"), p.get("surface")) {
-        (Some(_), None) => {
-            let (shape, mesh) = super::geometry::body_mesh(s, p)?;
-            Ok(Input { mesh: Cow::Owned(mesh), body: shape.name.clone(), faces: shape.faces().iter().map(|f| f.name.clone()).collect() })
-        }
+        (Some(_), None) => Ok(Cow::Owned(super::geometry::body_mesh(s, p)?.1)),
         (None, Some(i)) => {
             let n = s.surfaces.len();
             let t = i
@@ -400,7 +575,7 @@ fn surface_input<'a>(s: &'a Session, p: &Value) -> Result<Input<'a>> {
                 .and_then(|i| usize::try_from(i).ok())
                 .and_then(|i| s.surfaces.get(i))
                 .ok_or_else(|| EngineError::Params(format!("`surface` must be the index of an imported surface (there are {n})")))?;
-            Ok(Input { mesh: Cow::Borrowed(&t.mesh), body: t.name.clone(), faces: (0..t.faces).map(|f| f.to_string()).collect() })
+            Ok(Cow::Borrowed(&t.mesh))
         }
         _ => Err(EngineError::Params("give either `body` (with `tolerance`) or `surface`".into())),
     }
@@ -411,7 +586,7 @@ fn defect_json(d: &Defect) -> Value {
 }
 
 fn surface_check(s: &mut Session, p: &Value) -> Result<Value> {
-    let mesh = surface_input(s, p)?.mesh;
+    let mesh = surface_input(s, p)?;
     let options = surface_options(p, &mesh)?;
     let surface = match BoundarySurface::new(&mesh.positions, &mesh.triangles, &mesh.tri_face, &options) {
         Ok(surface) => surface,
@@ -612,6 +787,7 @@ mod tests {
         // The certified quality report agrees.
         let q = s.execute("mesh.quality", &json!({})).unwrap();
         assert_eq!(q["valid"].as_u64().unwrap() as usize, elements);
+        assert!(q["summary"].as_str().unwrap().starts_with(&format!("{elements} elements, all valid; scaled Jacobian min ")), "{q}");
         // A second run appends after the existing labels.
         let again = s.execute("mesh.tet.generate", &json!({"body": "Body1", "tolerance": 0.5})).unwrap();
         assert_eq!(again["first_element"].as_u64().unwrap() as usize, elements + 1);
@@ -626,16 +802,60 @@ mod tests {
             json!({"body": "Body1", "tolerance": 0.5, "max_tets": 0}),
             json!({"body": "Body1", "tolerance": 0.5, "max_tets": 10}),
             json!({"body": "Body1", "tolerance": 0.5, "max_tets": "many"}),
-            json!({"body": "Body1"}),
+            json!({"body": "Body1", "tolerance": -1}),
             json!({"body": "Nope", "tolerance": 0.5}),
+            json!({"body": "Body1", "surface": 0}),
             json!({"surface": 0}),
-            json!({}),
         ] {
             assert!(s.execute("mesh.tet.generate", &bad).is_err(), "{bad}");
         }
         assert_eq!((s.journal.len(), &s.model), (journal, &model), "failures change nothing");
     }
 
+    /// Without parameters every body of the open design is meshed, each at a tolerance from its
+    /// size; an error says which body it is about.
+    #[test]
+    fn tet_generate_defaults_to_every_body() {
+        let commands = json!({"commands": [
+            {"command": "solid.box", "params": {"length": 20, "width": 10, "height": 10, "body_name": "Box"}},
+            {"command": "solid.split_body", "params": {"body": "Box", "plane": {"origin": [10, 0, 0], "normal": [1, 0, 0]}}},
+        ]});
+        let bytes = fieldcraft_geometry::script_design(&commands.to_string()).unwrap();
+        let (_dir, path) = crate::tests::design_file(&bytes);
+        let mut s = Session::default();
+        assert!(s.execute("mesh.tet.generate", &json!({})).unwrap_err().to_string().contains("open a design first"));
+        s.execute("geometry.open", &json!({"path": path})).unwrap();
+        let r = s.execute("mesh.tet.generate", &json!({})).unwrap();
+        let bodies = r["bodies"].as_array().unwrap();
+        assert_eq!(bodies.len(), 2, "{r}");
+        assert_eq!(r["kind"], "tet4");
+        assert!((r["volume"].as_f64().unwrap() - 2000.0).abs() < 1e-6, "{r}");
+        assert_eq!(s.model.elements().len() as u64, r["elements"].as_u64().unwrap());
+        assert_eq!(s.model.classification().elements().len(), s.model.elements().len(), "every element is on its body");
+        // The second body's labels follow the first's.
+        assert_eq!(bodies[1]["first_element"].as_u64(), Some(bodies[0]["elements"].as_u64().unwrap() + 1));
+        assert_eq!(s.journal.len(), 2);
+        // A body named alone takes the same default tolerance.
+        let one = s.execute("mesh.tet.generate", &json!({"body": bodies[0]["body"]})).unwrap();
+        assert_eq!(one["elements"], bodies[0]["elements"]);
+        let e = s.execute("mesh.tet.generate", &json!({"max_tets": 1})).unwrap_err().to_string();
+        assert!(e.starts_with("body `Box"), "{e}");
+    }
+
+    /// The quality report's one-line summary counts the inverted elements.
+    #[test]
+    fn quality_summary_counts_invalid_elements() {
+        let mut s = Session::default();
+        assert_eq!(s.execute("mesh.quality", &json!({})).unwrap()["summary"], "no elements to measure");
+        for (label, xyz) in [(1, [0, 0, 0]), (2, [1, 0, 0]), (3, [0, 1, 0]), (4, [0, 0, 1])] {
+            s.execute("mesh.node.add", &json!({"label": label, "xyz": xyz})).unwrap();
+        }
+        s.execute("mesh.element.add", &json!({"label": 1, "kind": "tet4", "nodes": [1, 2, 3, 4]})).unwrap();
+        s.execute("mesh.element.add", &json!({"label": 2, "kind": "tet4", "nodes": [1, 3, 2, 4]})).unwrap();
+        let q = s.execute("mesh.quality", &json!({})).unwrap();
+        assert!(q["summary"].as_str().unwrap().starts_with("2 elements, 1 invalid; scaled Jacobian min -"), "{q}");
+    }
+
     /// The session's caps are the defaults of `max_steiner` and `max_tets`; a parameter overrides them.
     #[test]
     fn tet_generate_honours_the_session_caps() {
@@ -656,6 +876,53 @@ mod tests {
         assert!(r["elements"].as_u64().unwrap() > 0, "{r}");
     }
 
+    /// The quality stage: a graded, improved tet4 mesh with its report, and tet10 with mid-edge
+    /// nodes on the bore; the raw tetrahedralization on request.
+    #[test]
+    fn tet_generate_quality_report_and_quadratic_elements() {
+        use std::sync::Arc;
+
+        use fieldcraft_geometry::open_design;
+        use fieldcraft_geometry::sample::{Plate, plate_design};
+
+        let plate = Plate::default();
+        let design = Arc::new(open_design(&plate_design(&plate).unwrap()).unwrap());
+        let mut s = Session { design: Some(design.clone()), ..Session::default() };
+        let r = s.execute("mesh.tet.generate", &json!({"body": "Body1", "tolerance": 0.2, "size": 6})).unwrap();
+        let q = &r["bodies"][0]["quality"];
+        assert_eq!(q["mesh"]["inadmissible"], json!(0), "{r}");
+        assert_eq!(q["mesh"]["slivers"], json!(0), "{r}");
+        assert!(q["mesh"]["min_dihedral"].as_f64().unwrap() > 15.0, "{r}");
+        assert!(q["mesh"]["max_dihedral"].as_f64().unwrap() < 165.0, "{r}");
+        assert!(q["cdt"]["slivers"].as_u64().unwrap() > 0, "{r}");
+        // The mesh fills what its boundary encloses, which is the plate within the chordal error.
+        let (volume, boundary) = (r["volume"].as_f64().unwrap(), r["boundary_volume"].as_f64().unwrap());
+        assert!((volume - boundary).abs() <= 1e-9 * boundary, "{r}");
+        let exact = plate.width * plate.depth * plate.thickness - std::f64::consts::PI * 0.25 * plate.hole_diameter.powi(2) * plate.thickness;
+        // The bore's chordal error at 0.2 mm is at most 2/3 · 0.2 · its area (≈ 42 mm³).
+        assert!((volume - exact).abs() < 42.0, "{volume} vs {exact}");
+
+        // Quadratic: mid-edge nodes on the bore's cylinder.
+        let mut s = Session { design: Some(design), ..Session::default() };
+        let r = s.execute("mesh.tet.generate", &json!({"body": "Body1", "tolerance": 0.2, "size": 6, "order": "quadratic"})).unwrap();
+        assert_eq!(r["kind"], json!("tet10"), "{r}");
+        assert!(s.model.elements().values().all(|e| e.kind == fieldcraft_model::ElementKind::Tet10));
+        let report = s.execute("mesh.quality", &json!({})).unwrap();
+        assert_eq!(report["valid"].as_u64().unwrap(), r["elements"].as_u64().unwrap(), "{report}");
+        // Nodes on the bore (within the tessellation's reach of its axis) lie on its radius.
+        let (cx, cy) = (plate.depth / 2.0, plate.depth / 2.0);
+        let radius = plate.hole_diameter / 2.0;
+        let mut on_bore = 0;
+        for n in s.model.nodes().values() {
+            let d = ((n.xyz[0] - cx).powi(2) + (n.xyz[1] - cy).powi(2)).sqrt();
+            if (d - radius).abs() < 0.05 {
+                on_bore += 1;
+                assert!((d - radius).abs() < 1e-9, "a bore node at {:?} is {d} from the axis", n.xyz);
+            }
+        }
+        assert!(on_bore > 20, "{on_bore}");
+    }
+
     #[test]
     fn tet_generate_on_an_imported_surface_and_an_open_one() {
         use std::sync::Arc;
@@ -671,12 +938,17 @@ mod tests {
         for mesh in [tet, open] {
             s.surfaces.push(Arc::new(TaggedSurface { name: "Tet".into(), mesh, faces: 2 }));
         }
-        let r = s.execute("mesh.tet.generate", &json!({"surface": 0})).unwrap();
+        let r = s.execute("mesh.tet.generate", &json!({"surface": 0, "quality": false})).unwrap();
         assert_eq!((r["elements"].clone(), r["nodes"].clone(), r["boundary_faces"].clone()), (json!(1), json!(4), json!(4)));
         let element = s.model.element(1).unwrap();
         assert_eq!(element.nodes.len(), 4);
+        // Refined to a size, the flat-faced tetrahedron keeps its volume exactly.
+        let r = s.execute("mesh.tet.generate", &json!({"surface": 0, "size": 0.3})).unwrap();
+        assert!(r["elements"].as_u64().unwrap() > 1, "{r}");
+        assert!((r["volume"].as_f64().unwrap() - 1.0 / 6.0).abs() < 1e-12, "{r}");
+        let total = s.model.elements().len();
         assert!(s.execute("mesh.tet.generate", &json!({"surface": 1})).is_err(), "an open surface bounds no volume");
-        assert_eq!(s.model.elements().len(), 1);
+        assert_eq!(s.model.elements().len(), total);
     }
 
     #[test]

crates/engine/src/cmd/mod.rs

@@ -8,7 +8,10 @@ pub(crate) mod file;
 mod geometry;
 mod hex;
 pub(crate) mod mesh;
+
+pub use mesh::analytic_surfaces;
 mod model;
+pub(crate) mod octree;
 mod results;
 pub(crate) mod solve;
 mod tags;
@@ -36,10 +39,12 @@ pub static ALL: &[CommandSpec] = &[
     mesh::SURFACE_CHECK,
     mesh::PLANAR,
     mesh::TET_GENERATE,
+    octree::HEX_OCTREE,
     block::BLOCK,
     hex::HEX_GENERATE,
     hex::HEX_SWEEP,
     hex::HEX_MAPPED,
+    hex::HEX_BLOCKS,
     tags::TAG,
     tags::TAG_CLEAR,
     model::UNITS,
@@ -95,6 +100,7 @@ pub static ALL: &[CommandSpec] = &[
     deck::WRITE,
     solve::RUN,
     solve::STATIC,
+    solve::NONLINEAR,
     solve::FREQUENCY,
     solve::HEAT,
     solve::EXPLICIT,

crates/engine/src/cmd/octree.rs

@@ -0,0 +1,177 @@
+//! Unstructured all-hexahedral meshing (`mesh.hex.octree`) of the open design's bodies or of
+//! imported surfaces.
+
+use fieldcraft_mesh::octree::{OctreeHexMesh, OctreeOptions, octree_hex_mesh};
+use fieldcraft_mesh::size::UniformSize;
+use fieldcraft_mesh::surface::BoundarySurface;
+use fieldcraft_model::{ElementKind, GeometryRef, MAX_ELEMENTS};
+use serde_json::{Value, json};
+
+use super::hex::{Input, inputs, number, tag_faces};
+use super::mesh::optional_count;
+use crate::{CommandKind, CommandSpec, EngineError, Result, Session};
+
+pub const HEX_OCTREE: CommandSpec = CommandSpec {
+    id: "mesh.hex.octree",
+    label: "Octree Hex Mesh",
+    params: r#"{"body": "Body1" (default: every body of the open design) or "surface": 0 (an imported surface), "size": 2.0 (element size in the interior, mm; default 1/25 of the bounding-box diagonal), "tolerance": 0.05 (chordal tolerance of the tessellation, mm; default 1e-3 of the diagonal), "max_depth": 3 (refinement levels below the size, each a third, 0..=5), "max_elements": 2000000 (1..=10000000; default the session limit), "attempts": 4 (builds, refining where one failed, 1..=8), "max_sweeps": 300 (optimiser sweeps, 0..=10000), and the boundary options of mesh.tet.generate ("weld", "weld_distance", "feature_angle")} — replaces the mesh with an unstructured all-hex8 mesh of any part: an adaptive 3-refinement grid with conforming transition templates, a core inside the part, two boundary layers that capture every B-rep face boundary and sharp edge, and untangling. Every element is proven valid; boundary element faces are tagged with their B-rep faces (named as in geometry.bodies; by index when a face has no name), so sets by geometry resolve. Reports per body the elements, quality, volume and grid statistics"#,
+    kind: CommandKind::Model,
+    run: hex_octree,
+};
+
+/// Smallest element size, relative to the bounding-box diagonal (the grid's cell count grows
+/// with the cube of its inverse).
+const MIN_RELATIVE_SIZE: f64 = 1e-3;
+/// Default element size, relative to the bounding-box diagonal.
+const DEFAULT_RELATIVE_SIZE: f64 = 1.0 / 25.0;
+/// Caps on the options.
+const MAX_DEPTH: u64 = 5;
+const MAX_ATTEMPTS: u64 = 8;
+const MAX_SWEEPS: u64 = 10_000;
+const MAX_HEX_ELEMENTS: u64 = 10_000_000;
+/// The session default of `max_elements` ([`crate::Limits::max_hex_elements`]).
+pub(crate) const DEFAULT_MAX_ELEMENTS: usize = 2_000_000;
+
+fn hex_octree(s: &mut Session, p: &Value) -> Result<Value> {
+    let size = number(p, "size")?;
+    let defaults = OctreeOptions::default();
+    let options = OctreeOptions {
+        max_depth: u8::try_from(optional_count(p, "max_depth", u64::from(defaults.max_depth), 0..=MAX_DEPTH)?).unwrap_or(defaults.max_depth),
+        max_elements: optional_count(p, "max_elements", s.limits.max_hex_elements as u64, 1..=MAX_HEX_ELEMENTS)?.min(MAX_ELEMENTS),
+        attempts: optional_count(p, "attempts", defaults.attempts as u64, 1..=MAX_ATTEMPTS)?,
+        max_sweeps: optional_count(p, "max_sweeps", defaults.max_sweeps as u64, 0..=MAX_SWEEPS)?,
+        ..defaults
+    };
+    let bodies = inputs(s, p)?;
+    let mut meshes: Vec<(Input, OctreeHexMesh)> = Vec::with_capacity(bodies.len());
+    let mut total = 0usize;
+    for b in bodies {
+        if !(b.diagonal > 0.0 && b.diagonal.is_finite()) {
+            return Err(EngineError::Params(format!("body `{}` has no extent", b.name)));
+        }
+        let h = size.unwrap_or(DEFAULT_RELATIVE_SIZE * b.diagonal);
+        if h < MIN_RELATIVE_SIZE * b.diagonal {
+            return Err(EngineError::Params(format!("`size` must be at least {} mm for body `{}`", MIN_RELATIVE_SIZE * b.diagonal, b.name)));
+        }
+        let surface_options = super::mesh::surface_options(p, &b.mesh)?;
+        let surface = BoundarySurface::new(&b.mesh.positions, &b.mesh.triangles, &b.mesh.tri_face, &surface_options)
+            .map_err(|e| EngineError::Params(format!("body `{}`: {e}", b.name)))?;
+        let left = OctreeOptions { max_elements: options.max_elements.saturating_sub(total).max(1), ..options.clone() };
+        let mesh = octree_hex_mesh(&surface, &UniformSize(h), &left).map_err(|e| EngineError::Params(format!("body `{}`: {e}", b.name)))?;
+        total += mesh.hexes.len();
+        meshes.push((b, mesh));
+    }
+    // Replace the mesh: definitions stay, nodes, elements and geometry tags are new.
+    let mut model = s.model.without_mesh();
+    let mut report = Vec::with_capacity(meshes.len());
+    let (mut node_label, mut element_label) = (1u32, 1u32);
+    for (b, m) in &meshes {
+        let first_node = node_label;
+        for xyz in &m.nodes {
+            model.set_node(node_label, *xyz)?;
+            node_label = node_label.checked_add(1).ok_or_else(|| EngineError::Params("too many nodes".into()))?;
+        }
+        let body_tag = model.geometry_tag(&GeometryRef::body(b.name.as_str())?)?;
+        let first_element = element_label;
+        for hx in &m.hexes {
+            model.set_element(element_label, ElementKind::Hex8, hx.iter().map(|&i| first_node + i).collect())?;
+            model.tag_element(element_label, body_tag)?;
+            element_label = element_label.checked_add(1).ok_or_else(|| EngineError::Params("too many elements".into()))?;
+        }
+        tag_faces(&mut model, std::slice::from_ref(b), |_| 0, &m.boundary, first_element)?;
+        let r = &m.report;
+        report.push(json!({
+            "body": b.name,
+            "kind": "hex8",
+            "elements": m.hexes.len(),
+            "nodes": m.nodes.len(),
+            "boundary_faces": m.boundary.len(),
+            "quality": {"min_scaled_jacobian": r.min_scaled_jacobian, "mean_scaled_jacobian": r.mean_scaled_jacobian},
+            "volume": r.volume,
+            "surface_volume": r.surface_volume,
+            "grid": {"cells": r.grid_cells, "core_elements": r.core_elements, "layer_elements": r.layer_elements, "frame": r.frame},
+            "features": {"corners": r.corners, "curves": r.curves, "patches": r.patches},
+            "attempts": r.attempts,
+            "retries": r.retries,
+            "sweeps": r.sweeps,
+        }));
+    }
+    s.model = model;
+    Ok(json!({"bodies": report, "nodes": node_label - 1, "elements": element_label - 1}))
+}
+
+#[cfg(test)]
+mod tests {
+    use std::sync::Arc;
+
+    use fieldcraft_geometry::open_design;
+    use fieldcraft_geometry::sample::{Plate, plate_design};
+    use serde_json::json;
+
+    use crate::Session;
+
+    fn opened() -> Session {
+        let plate = Plate::default();
+        Session { design: Some(Arc::new(open_design(&plate_design(&plate).unwrap()).unwrap())), ..Session::default() }
+    }
+
+    #[test]
+    fn plate_with_a_hole_meshes_all_hex_and_face_sets_resolve() {
+        let mut s = opened();
+        let r = s.execute("mesh.hex.octree", &json!({"body": "Body1", "size": 5.0, "max_depth": 2})).unwrap();
+        let body = &r["bodies"][0];
+        let n = body["elements"].as_u64().unwrap() as usize;
+        assert!(n > 50, "{r}");
+        assert!(body["quality"]["min_scaled_jacobian"].as_f64().unwrap() > 0.0, "{r}");
+        assert_eq!(s.model.element_counts(), vec![(fieldcraft_model::ElementKind::Hex8, n)]);
+        let (v, sv) = (body["volume"].as_f64().unwrap(), body["surface_volume"].as_f64().unwrap());
+        assert!((v - sv).abs() < 0.02 * sv, "{r}");
+        // The certified quality report agrees.
+        let q = s.execute("mesh.quality", &json!({})).unwrap();
+        assert_eq!(q["valid"].as_u64().unwrap() as usize, n);
+        // Every boundary face is tagged: the skin of the body set; each named face resolves.
+        s.execute("model.set.create", &json!({"name": "skin", "geometry": [{"body": "Body1"}]})).unwrap();
+        let skin = s.execute("model.set.resolve", &json!({"name": "skin"})).unwrap();
+        assert_eq!(skin["faces"]["count"], body["boundary_faces"], "{skin}");
+        let bodies = s.execute("geometry.bodies", &json!({})).unwrap();
+        for f in bodies[0]["faces"].as_array().unwrap() {
+            let name = f["name"].as_str().unwrap();
+            s.execute("model.set.create", &json!({"name": "f", "geometry": [{"body": "Body1", "face": name}]})).unwrap();
+            let set = s.execute("model.set.resolve", &json!({"name": "f"})).unwrap();
+            assert!(set["faces"]["count"].as_u64().unwrap() > 0, "face {name}: {set}");
+            s.execute("model.set.delete", &json!({"name": "f"})).unwrap();
+        }
+    }
+
+    #[test]
+    fn hostile_params_are_errors_and_change_nothing() {
+        let mut s = opened();
+        let before = s.model.clone();
+        for p in [
+            json!({"body": "Body1", "size": 0}),
+            json!({"body": "Body1", "size": -1}),
+            json!({"body": "Body1", "size": 1e-300}),
+            json!({"body": "Body1", "size": "big"}),
+            json!({"body": "Body1", "tolerance": 1e-300}),
+            json!({"body": "Body1", "tolerance": -1}),
+            json!({"body": "Body1", "max_depth": 9}),
+            json!({"body": "Body1", "max_depth": -1}),
+            json!({"body": "Body1", "max_elements": 0}),
+            json!({"body": "Body1", "max_elements": 1e300}),
+            json!({"body": "Body1", "attempts": 0}),
+            json!({"body": "Body1", "attempts": 100}),
+            json!({"body": "Body1", "max_sweeps": "many"}),
+            json!({"body": "Body1", "size": 5.0, "max_depth": 2, "max_elements": 10}),
+            json!({"body": "Nope"}),
+            json!({"body": 7}),
+            json!({"surface": 0}),
+            json!({"surface": -1}),
+            json!({"body": "Body1", "surface": 0}),
+        ] {
+            let r = s.execute("mesh.hex.octree", &p);
+            assert!(r.is_err(), "{p}: {r:?}");
+            assert_eq!(s.model, before, "{p}");
+        }
+        assert!(Session::default().execute("mesh.hex.octree", &json!({})).is_err());
+    }
+}

crates/engine/src/cmd/results.rs

@@ -43,7 +43,7 @@ pub const ANIMATE: CommandSpec = CommandSpec {
 pub const FRAME: CommandSpec = CommandSpec {
     id: "results.frame",
     label: "Field Frame",
-    params: r#"{"step": "Impact", "frame": 3, "time": 0.002} — shows a field frame of a solved explicit step, by index from 0 or the frame nearest a time (neither: the last); the deformed shape and contours follow it"#,
+    params: r#"{"step": "Impact", "frame": 3, "time": 0.002} — shows a field frame of a solved explicit step, by index from 0 or the frame nearest a time (neither: the last), or of a nonlinear static step (one per converged increment, `time` its load factor; the deformed shape follows it, its contours show the final state); the deformed shape and contours follow it"#,
     kind: CommandKind::Session,
     run: frame,
 };
@@ -79,21 +79,23 @@ fn solved_list(s: &Session) -> String {
 enum Want {
     Any,
     Frequency,
-    Explicit,
+    /// Steps with frames: explicit dynamics and nonlinear static (one per converged increment).
+    Frames,
 }
 
 impl Want {
     fn fits(self, s: &Session, step: &str) -> bool {
         s.latest_result(step).is_some_and(|(r, _)| match (self, r.kind()) {
-            (Want::Any, _) | (Want::Frequency, Kind::Frequency(_)) | (Want::Explicit, Kind::Explicit(_)) => true,
-            (Want::Frequency | Want::Explicit, _) => false,
+            (Want::Any, _) | (Want::Frequency, Kind::Frequency(_)) | (Want::Frames, Kind::Explicit(_)) => true,
+            (Want::Frames, Kind::Static(r)) => r.nonlinear.is_some(),
+            (Want::Frequency | Want::Frames, _) => false,
         })
     }
     fn name(self) -> &'static str {
         match self {
             Want::Any => "solved",
             Want::Frequency => "frequency",
-            Want::Explicit => "explicit",
+            Want::Frames => "explicit or nonlinear static",
         }
     }
 }
@@ -222,9 +224,10 @@ fn animate(s: &mut Session, p: &Value) -> Result<Value> {
 }
 
 fn frame(s: &mut Session, p: &Value) -> Result<Value> {
-    let step = step_for(s, p, Want::Explicit)?;
+    let step = step_for(s, p, Want::Frames)?;
     let times: Vec<f64> = match s.latest_result(&step).map(|(r, _)| r.kind()) {
         Some(Kind::Explicit(e)) => e.frames.iter().map(|f| f.time).collect(),
+        Some(Kind::Static(r)) => r.nonlinear.as_ref().map(|h| h.load_factors()).unwrap_or_default(),
         _ => Vec::new(),
     };
     let last = times.len().checked_sub(1).ok_or_else(|| EngineError::Params(format!("step `{step}` has no field frames")))?;

crates/engine/src/cmd/solve.rs

@@ -7,7 +7,8 @@ use fieldcraft_mesh::surface::{BoundarySurface, SurfaceOptions};
 use fieldcraft_model::FluidDomain;
 use fieldcraft_parallel as parallel;
 use fieldcraft_solver::{
-    FrequencyOptions, Limits, Location, MassKind, StaticResult, StepResult as ImplicitResult, solve_frequency, solve_heat, solve_static,
+    FrequencyOptions, Limits, Location, MassKind, StaticResult, StepResult as ImplicitResult, solve_frequency, solve_heat, solve_nonlinear,
+    solve_static,
 };
 use serde_json::{Value, json};
 
@@ -30,6 +31,14 @@ pub const STATIC: CommandSpec = CommandSpec {
     run: run_static,
 };
 
+pub const NONLINEAR: CommandSpec = CommandSpec {
+    id: "solve.nonlinear",
+    label: "Solve Nonlinear Static Step",
+    params: r#"{"step": "Inflate", "max_dofs": 6000000, "max_factor_entries": 400000000, "max_newton_iterations": 100000, "threads": 8} — solves a nonlinear static step (the only one when `step` is left out) in load increments with Newton–Raphson iterations and keeps the result in the session: the final displacements, reactions, Cauchy stresses and logarithmic strains (small strains without nonlinear geometry), the equivalent plastic strain of plastic materials (the largest in the summary), every increment's load factor, iterations and residuals (force, displacement and energy, relative to their tolerances' scales), and a displacement frame per converged increment; the caps may only be lowered (`max_newton_iterations` over the whole step); `threads` as for solve.static"#,
+    kind: CommandKind::Model,
+    run: run_nonlinear,
+};
+
 pub const HEAT: CommandSpec = CommandSpec {
     id: "solve.heat",
     label: "Solve Heat Transfer Step",
@@ -73,7 +82,7 @@ pub const FLUID: CommandSpec = CommandSpec {
 pub const PROBE: CommandSpec = CommandSpec {
     id: "solve.probe",
     label: "Probe Results",
-    params: r#"{"step": "Load", "nodes": [1, 2], "mode": 1, "frame": 0} — the stored result at nodes: displacement, rotation, reaction, reaction moment, stress and von Mises (static, with `elements` each element's results: solid, 2D and truss nodal stresses, shell section forces (N, M, Q per length in the element's axes) and bottom, middle and top stresses, beam end forces (N, V_y, V_z, T, M_y, M_z in its axes)), the shape of mode `mode` with its rotations (frequency, from 1), or displacement and velocity in field frame `frame` (explicit, from 0; the last by default) at `nodes` (or at the nodes nearest to points: "at": [[x, y, z], ...], lowest label on a tie, each entry then giving its `xyz` and `distance`) and, with `elements` (explicit), each element's stress, von Mises stress, strain, equivalent plastic strain, damage, temperature and whether it has eroded; a coupled reference point's label gives its six displacements (translations, rotations) and reactions (forces, moments). Fluid steps: {"step": "Flow", "points": [[x, y, z]], "frame": 10 (default the last)} gives velocity and pressure in the cells at the points; {"step": "Flow", "forces": ["x_min", "F2:top", "Body1/F2:top"]} gives those walls' force histories"#,
+    params: r#"{"step": "Load", "nodes": [1, 2] (or "set": "fillet", a set's nodes), "mode": 1, "frame": 0} — the stored result at nodes (with `max_von_mises`, the largest among them, for static steps): displacement, rotation, reaction, reaction moment, stress and von Mises (static, with `elements` each element's results: solid, 2D and truss nodal stresses (and, in a nonlinear step, the equivalent plastic strain at the integration points of a plastic element), shell section forces (N, M, Q per length in the element's axes) and bottom, middle and top stresses, beam end forces (N, V_y, V_z, T, M_y, M_z in its axes)), the shape of mode `mode` with its rotations (frequency, from 1), or displacement and velocity in field frame `frame` (explicit, from 0; the last by default) at `nodes` (or at the nodes nearest to points: "at": [[x, y, z], ...], lowest label on a tie, each entry then giving its `xyz` and `distance`) and, with `elements` (explicit), each element's stress, von Mises stress, strain, equivalent plastic strain, damage, temperature and whether it has eroded; a coupled reference point's label gives its six displacements (translations, rotations) and reactions (forces, moments). Fluid steps: {"step": "Flow", "points": [[x, y, z]], "frame": 10 (default the last)} gives velocity and pressure in the cells at the points; {"step": "Flow", "forces": ["x_min", "F2:top", "Body1/F2:top"]} gives those walls' force histories"#,
     kind: CommandKind::Model,
     run: probe,
 };
@@ -117,6 +126,7 @@ fn limits(p: &Value) -> Result<Limits> {
         max_dofs: cap(p, "max_dofs", Limits::MAX_DOFS)?,
         max_factor_entries: cap(p, "max_factor_entries", Limits::MAX_FACTOR_ENTRIES)?,
         max_lanczos_vectors: cap(p, "max_iterations", Limits::MAX_LANCZOS_VECTORS)?,
+        max_newton_iterations: cap(p, "max_newton_iterations", Limits::MAX_NEWTON_ITERATIONS)?,
     })
 }
 
@@ -142,6 +152,7 @@ fn run_all(s: &mut Session, _: &Value) -> Result<Value> {
                 Procedure::Frequency { .. } => run_frequency,
                 Procedure::ExplicitDynamic(_) => run_explicit,
                 Procedure::Fluid { .. } => run_fluid,
+                Procedure::NonlinearStatic(_) => run_nonlinear,
             };
             (st.name.clone(), st.procedure.name(), solve)
         })
@@ -193,6 +204,37 @@ fn run_static(s: &mut Session, p: &Value) -> Result<Value> {
     Ok(summary)
 }
 
+fn run_nonlinear(s: &mut Session, p: &Value) -> Result<Value> {
+    let limits = limits(p)?;
+    let step = opt::<String>(p, "step")?;
+    let model = &s.model;
+    let r = parallel::with_threads(threads(s, p)?, || solve_nonlinear(model, step.as_deref(), &limits))?;
+    let history = r.nonlinear.as_ref();
+    let summary = json!({
+        "step": r.step,
+        "dofs": r.stats.dofs,
+        "equations": r.stats.equations,
+        "factor_entries": r.stats.factor_entries,
+        "increments": history.map(|h| &h.increments),
+        "iterations": history.map(|h| h.iterations),
+        "frames": history.map(|h| h.load_factors()),
+        "max_displacement": largest(r.nodes.iter().zip(&r.displacement).map(|(l, u)| (*l, crate::results::magnitude(*u)))),
+        "max_von_mises": largest(r.nodes.iter().zip(&r.von_mises).map(|(l, v)| (*l, *v))),
+        "max_plastic_strain": largest(r.elements.iter().flat_map(|e| e.plastic_strain.iter().map(|v| (e.label, *v)))),
+        "applied_total": r.applied_total,
+        "reaction_total": r.reaction_total,
+        "reference_points": r.reference_points.iter().map(|p| json!({
+            "name": p.name,
+            "label": p.label,
+            "displacement": p.displacement,
+            "reaction": p.reaction,
+        })).collect::<Vec<_>>(),
+        "warnings": r.warnings,
+    });
+    s.store_result(StepResult::Implicit(ImplicitResult::Static(r)));
+    Ok(summary)
+}
+
 fn run_heat(s: &mut Session, p: &Value) -> Result<Value> {
     let limits = limits(p)?;
     let step = opt::<String>(p, "step")?;
@@ -447,13 +489,21 @@ fn probe(s: &mut Session, p: &Value) -> Result<Value> {
     }
     let (nodes, located) = match (p.get("nodes"), p.get("at")) {
         (Some(_), None) => (labels(p, "nodes", MAX_PROBE)?, None),
+        (None, None) if p.get("set").is_some() => {
+            let name = opt::<String>(p, "set")?.unwrap_or_default();
+            let set = s.model.resolve_set(&name)?;
+            if set.nodes.len() > MAX_PROBE {
+                return Err(EngineError::Params(format!("set `{name}` has {} nodes; a probe takes at most {MAX_PROBE}", set.nodes.len())));
+            }
+            (set.nodes, None)
+        }
         (None, Some(_)) => {
             let at = points(p, "at", MAX_PROBE)?;
             let found = nearest_nodes(&s.model, result.nodes(), &at)?;
             (found.iter().map(|(l, _, _)| *l).collect(), Some(found))
         }
         (None, None) if matches!(result.as_ref(), StepResult::Explicit(_)) || p.get("elements").is_some() => (Vec::new(), None),
-        _ => return Err(EngineError::Params("give either `nodes` or `at`".into())),
+        _ => return Err(EngineError::Params("give one of `nodes`, `at` or `set`".into())),
     };
     let mut out = match result.as_ref() {
         StepResult::Explicit(r) => {
@@ -463,6 +513,16 @@ fn probe(s: &mut Session, p: &Value) -> Result<Value> {
         StepResult::Implicit(r) => probe_implicit(r, &step, &nodes, p)?,
         StepResult::Fluid(r) => probe_fluid(r, p)?,
     };
+    // The largest von Mises stress among the probed nodes (static results).
+    let peak = out.get("nodes").and_then(Value::as_array).and_then(|entries| {
+        entries
+            .iter()
+            .filter_map(|e| Some((e.get("node")?.as_u64()?, e.get("von_mises")?.as_f64()?)))
+            .fold(None, |best: Option<(u64, f64)>, (n, v)| if best.is_none_or(|b| v > b.1) { Some((n, v)) } else { best })
+    });
+    if let (Some((node, value)), Some(obj)) = (peak, out.as_object_mut()) {
+        obj.insert("max_von_mises".into(), json!({"node": node, "value": value}));
+    }
     if let (Some(found), Some(entries)) = (located, out.get_mut("nodes").and_then(Value::as_array_mut)) {
         for (entry, (_, xyz, distance)) in entries.iter_mut().zip(found) {
             if let Some(obj) = entry.as_object_mut() {
@@ -572,7 +632,11 @@ fn by_label<T>(list: &[T], label: u32, key: impl Fn(&T) -> u32) -> Option<&T> {
 /// The stored results of one element of a static step.
 fn element_result(r: &StaticResult, label: u32) -> Option<Value> {
     if let Some(e) = by_label(&r.elements, label, |e| e.label) {
-        return Some(json!({"element": label, "kind": e.kind.name(), "stress": e.nodal}));
+        let mut v = json!({"element": label, "kind": e.kind.name(), "stress": e.nodal});
+        if !e.plastic_strain.is_empty() {
+            v["plastic_strain"] = json!(e.plastic_strain);
+        }
+        return Some(v);
     }
     if let Some(e) = by_label(&r.shells, label, |e| e.label) {
         let s = &e.stress;
@@ -1354,4 +1418,51 @@ pub(crate) mod tests {
         assert_eq!(fields, vec![crate::results::Field::Temperature, crate::results::Field::HeatFlux]);
         assert!(crate::results::displacements(heat, crate::results::Pick::default()).is_err());
     }
+
+    /// `solve.nonlinear`: a cantilever bent far by a dead tip load, with its increment history,
+    /// a frame per converged increment shown by `results.frame`, `solve.run` dispatching to it,
+    /// and the same bits on 1, 2 and 7 threads.
+    #[test]
+    fn nonlinear_steps_solve_with_their_history_and_frames() {
+        let solve = |threads: usize| -> (Value, u64, Session) {
+            let mut s = Session::default();
+            cantilever(&mut s);
+            let script = json!([
+                {"command": "model.section.edit", "params": {"name": "bar", "set": "all", "material": "Mat", "kind": {"type": "solid"}, "formulation": {}}},
+                {"command": "model.step.create", "params": {"name": "Large", "procedure": {"type": "nonlinear_static", "initial_increment": 0.25},
+                    "boundary_conditions": ["clamp"], "loads": ["push"]}},
+                {"command": "model.load.edit", "params": {"name": "push", "type": "force", "target": {"set": "tip"}, "vector": [0, 0, -15]}},
+            ]);
+            s.run_script(&script).unwrap();
+            let r = s.execute("solve.nonlinear", &json!({"step": "Large", "threads": threads})).unwrap();
+            let hash = result_hash(&s, "Large");
+            (r, hash, s)
+        };
+        let (r, one, mut s) = solve(1);
+        for threads in [2, 7] {
+            assert_eq!(solve(threads).1, one, "{threads} threads");
+        }
+        let increments = r["increments"].as_array().unwrap();
+        assert!(increments.iter().any(|i| i["converged"] == true) && increments.last().unwrap()["load_factor"] == 1.0, "{r}");
+        assert!(increments[0]["iterations"].as_array().is_some_and(|it| !it.is_empty() && it[0]["force"].is_number()), "{r}");
+        let frames = r["frames"].as_array().unwrap().len();
+        assert_eq!(frames, 1 + increments.iter().filter(|i| i["converged"] == true).count());
+        // Far from linear: P L² / (E I) = 15·100/(1000/12) = 18, the tip swings well down and in.
+        let tip = r["max_displacement"]["value"].as_f64().unwrap();
+        assert!(tip > 8.0 && tip < 12.0, "{r}");
+        let view = s.execute("results.frame", &json!({"step": "Large", "frame": 1})).unwrap();
+        assert_eq!(view["view"]["frame"], 1, "{view}");
+        assert!(view["load_factor"].as_f64().is_some_and(|f| f > 0.0 && f < 1.0), "{view}");
+        assert!(s.execute("results.frame", &json!({"step": "Large", "frame": frames})).is_err());
+        let probe = s.execute("solve.probe", &json!({"step": "Large", "nodes": [11]})).unwrap();
+        assert!(probe["nodes"][0]["displacement"][2].as_f64().is_some_and(|w| w < -5.0), "{probe}");
+        // solve.run solves every step with its own solver; the hostile caps are refused.
+        assert!(s.execute("solve.nonlinear", &json!({"step": "Large", "max_newton_iterations": 0})).is_err());
+        assert!(s.execute("solve.nonlinear", &json!({"step": "Large", "max_newton_iterations": 1e300})).is_err());
+        let e = s.execute("solve.nonlinear", &json!({"step": "Large", "max_newton_iterations": 2})).unwrap_err().to_string();
+        assert!(e.contains("Newton iterations"), "{e}");
+        assert!(s.execute("solve.nonlinear", &json!({"step": "Bend"})).is_err(), "a linear step");
+        let all = s.execute("solve.run", &json!({})).unwrap();
+        assert_eq!(all["steps"].as_array().map(Vec::len), Some(3), "{all}");
+    }
 }

crates/engine/src/lib.rs

@@ -15,6 +15,8 @@
 pub mod autosave;
 pub mod catalogue;
 pub mod cmd;
+
+pub use cmd::analytic_surfaces;
 pub mod history;
 pub mod results;
 pub mod sample;
@@ -135,6 +137,8 @@ pub struct Limits {
     pub max_steiner: usize,
     /// `mesh.tet.generate`'s `max_tets`.
     pub max_tets: usize,
+    /// `mesh.hex.octree`'s `max_elements`.
+    pub max_hex_elements: usize,
     /// Threads the solvers use (the `solve.*` commands' `threads`): by default
     /// `FIELDCRAFT_THREADS` or the available cores, 1 to [`fieldcraft_parallel::MAX_THREADS`].
     /// Results do not depend on it.
@@ -144,7 +148,12 @@ pub struct Limits {
 impl Default for Limits {
     fn default() -> Self {
         let cdt = fieldcraft_mesh::cdt::CdtOptions::default();
-        Limits { max_steiner: cdt.max_steiner, max_tets: cdt.max_tets, threads: fieldcraft_parallel::default_threads() }
+        Limits {
+            max_steiner: cdt.max_steiner,
+            max_tets: cdt.max_tets,
+            max_hex_elements: cmd::octree::DEFAULT_MAX_ELEMENTS,
+            threads: fieldcraft_parallel::default_threads(),
+        }
     }
 }
 
@@ -358,7 +367,8 @@ mod tests {
             json!({"format": "nastran", "path": "/no/such/dir/part.bdf", "steps": vec!["x".repeat(1000); 2000]}),
             json!({"format": "nastran", "path": "/no/such/dir/part.bdf", "steps": {}}),
             json!({"path": 7}),
-            json!({"body": "Body1", "tolerance": 0.05}),
+            // (`max_points` and `max_passes` keep mesh.tet.generate's quality stage small.)
+            json!({"body": "Body1", "tolerance": 0.05, "max_points": 3000, "max_passes": 1}),
             json!({"body": null, "tolerance": "fine"}),
             json!({"elements": [u32::MAX, -1, 1.5]}),
             json!({"elements": {}, "bins": -5}),
@@ -378,7 +388,7 @@ mod tests {
             json!({"polygon": [[0, 0], [1, 0], [0, 1]], "holes": [[[0.1, 0.1], [0.2, 0.1], [0.1, 0.2]], [[0.1, 0.1], [0.2, 0.1], [0.1, 0.2]]], "size": 0.2}),
             json!({"polygon": [["a", 0], [1, null], {}], "size": "big", "kind": 7}),
             json!({"polygon": [[0, 0], [1, 0], [0, 1]], "size": 1e300, "kind": "tri6", "max_elements": 1e300}),
-            json!({"body": "Body1", "face": "", "tolerance": 0.05, "size": 1}),
+            json!({"body": "Body1", "face": "", "tolerance": 0.05, "size": 1, "max_points": 3000, "max_passes": 1}),
             // Structured hex meshing.
             json!({"size": -1, "order": 9, "method": "x"}),
             json!({"size": 1e-300}),
@@ -471,9 +481,11 @@ mod tests {
             json!({"geometry": {"body": "Bar", "vertex": "v"}, "nodes": [1], "edges": [{"element": 1, "edge": 0}]}),
         ];
         // Small work caps, so input that would mesh up to the production caps (needle triangles
-        // need Steiner points all along them) is refused at once. The caps themselves are what
+        // need Steiner points all along them, an octree hex mesh is fitted and untangled) is
+        // refused at once. The caps themselves are what
         // `tet_generate_honours_the_session_caps` checks.
-        let capped = || Session { limits: Limits { max_steiner: 64, max_tets: 100_000, ..Limits::default() }, ..Session::default() };
+        let capped =
+            || Session { limits: Limits { max_steiner: 64, max_tets: 100_000, max_hex_elements: 500, ..Limits::default() }, ..Session::default() };
         for spec in commands() {
             for p in &hostile {
                 let mut s = capped();
@@ -506,15 +518,34 @@ mod tests {
             json!({"body": "Body1", "tolerance": 1e-300}),
             json!({"body": "Body1", "tolerance": 1e300}),
             json!({"body": "Body2", "tolerance": 0.1}),
-            json!({"body": "Body1", "tolerance": 0.5, "surface": 0}),
-            json!({"body": "Body1", "tolerance": 0.5, "weld": 0}),
-            json!({"body": "Body1", "tolerance": 0.5, "weld": 1e-3}),
-            json!({"body": "Body1", "tolerance": 0.5, "weld": f64::MIN_POSITIVE}),
-            json!({"body": "Body1", "tolerance": 0.5, "weld": 0, "weld_distance": 0}),
-            json!({"body": "Body1", "tolerance": 0.5, "weld_distance": 1e300}),
-            json!({"body": "Body1", "tolerance": 0.5, "weld_distance": 0.05}),
-            json!({"body": "Body1", "tolerance": 0.5, "feature_angle": 1e-300}),
-            json!({"body": "Body1", "tolerance": 0.5, "feature_angle": null}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "max_passes": 1, "surface": 0}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "max_passes": 1, "weld": 0}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "max_passes": 1, "weld": 1e-3}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "max_passes": 1, "weld": f64::MIN_POSITIVE}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "max_passes": 1, "weld": 0, "weld_distance": 0}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "max_passes": 1, "weld_distance": 1e300}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "max_passes": 1, "weld_distance": 0.05}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "max_passes": 1, "feature_angle": 1e-300}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "max_passes": 1, "feature_angle": null}),
+            // The quality stage's own parameters, hostile, with small caps so this stays fast.
+            json!({"body": "Body1", "tolerance": 0.5, "size": 0}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": -1}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 1e300}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 1e-300, "max_points": 2000, "max_tets": 5000}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": "fine"}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "order": "cubic"}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "order": "quadratic", "quality": false}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "quality": "yes"}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "quality_target": 0}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "quality_target": 1e300}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "curvature_angle": -1}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "curvature_angle": 1e-300, "max_points": 2000}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "grading": 0}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "grading": f64::MAX}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "max_passes": 1e9}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "max_points": 0}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 20, "max_points": 30, "max_passes": 1}),
+            json!({"body": "Body1", "tolerance": 0.5, "size": 0.5, "max_tets": 3000, "max_passes": 1}),
             json!({"body": "Body1", "size": 1e-300}),
             json!({"body": "Body1", "size": 1e300, "order": 2}),
             json!({"body": "Body1", "size": 4, "method": "sweep", "order": 2}),
@@ -530,9 +561,14 @@ mod tests {
 
     /// A design file in a fresh temporary directory (removed when the guard drops).
     pub(crate) fn sample_design_file(plate: &Plate) -> (TempDir, String) {
+        design_file(&plate_design(plate).unwrap())
+    }
+
+    /// Design file bytes written to a temporary directory.
+    pub(crate) fn design_file(bytes: &[u8]) -> (TempDir, String) {
         let dir = TempDir::new();
-        let path = dir.0.join("plate.solidcraft");
-        std::fs::write(&path, plate_design(plate).unwrap()).unwrap();
+        let path = dir.0.join("design.solidcraft");
+        std::fs::write(&path, bytes).unwrap();
         (dir, path.to_string_lossy().into_owned())
     }
 

crates/engine/src/results.rs

@@ -268,7 +268,12 @@ impl ResultsView {
 /// of the picked mode or the picked frame's displacement, in [`StepResult::nodes`] order.
 pub fn displacements(r: &StepResult, pick: Pick) -> Result<&[[f64; 3]]> {
     match r.kind() {
-        Kind::Static(s) => Ok(&s.displacement),
+        Kind::Static(s) => match (pick.frame, &s.nonlinear) {
+            (Some(k), Some(h)) => h.frames.get(k).map(|f| f.displacement.as_slice()).ok_or_else(|| {
+                EngineError::Params(format!("step `{}` has frames 0 to {}; there is no frame {k}", s.step, h.frames.len().saturating_sub(1)))
+            }),
+            _ => Ok(&s.displacement),
+        },
         Kind::Frequency(f) => pick
             .mode
             .checked_sub(1)
@@ -418,7 +423,13 @@ impl Session {
                     out["time"] = json!(t);
                 }
             }
-            Kind::Static(_) => {}
+            Kind::Static(s) => {
+                if let Some(h) = &s.nonlinear {
+                    out["frames"] = json!(h.load_factors());
+                    let shown = v.frame.and_then(|k| h.frames.get(k)).or(h.frames.last());
+                    out["load_factor"] = json!(shown.map(|f| f.load_factor));
+                }
+            }
         }
         out
     }

crates/engine/src/view.rs

@@ -32,6 +32,8 @@ pub struct Palette {
     pub mesh_edge: Rgb,
     pub geometry: Rgb,
     pub geometry_edge: Rgb,
+    /// The bodies of a design with several, in turn.
+    pub bodies: [Rgb; 8],
     /// Faces of nodes without a value in a contour plot.
     pub no_result: Rgb,
     /// The contour colour scale, low to high.
@@ -52,6 +54,16 @@ impl Palette {
         mesh_edge: Rgb(0x1e, 0x23, 0x2a),
         geometry: Rgb(0xb4, 0xba, 0xc4),
         geometry_edge: Rgb(0x2a, 0x30, 0x3a),
+        bodies: [
+            Rgb(0x8f, 0xb4, 0xd9),
+            Rgb(0xe0, 0xa4, 0x6c),
+            Rgb(0x8c, 0xc4, 0x8a),
+            Rgb(0xd6, 0x8c, 0x96),
+            Rgb(0xb0, 0x9c, 0xd8),
+            Rgb(0xd8, 0xc8, 0x70),
+            Rgb(0x7c, 0xc4, 0xc0),
+            Rgb(0xc0, 0xa0, 0x84),
+        ],
         no_result: Rgb(0x9a, 0xa0, 0xaa),
         contour: [Rgb(0x2b, 0x4f, 0xd8), Rgb(0x2f, 0xb8, 0xe0), Rgb(0x3c, 0xc8, 0x64), Rgb(0xf0, 0xd2, 0x3c), Rgb(0xe0, 0x40, 0x2e)],
         glyphs: GlyphColors {
@@ -125,7 +137,7 @@ fn model_scene(d: &DisplayMesh, p: &Palette) -> Scene {
     s.tris = d.tris.iter().map(|t| SceneTri { p: t.p, normal: t.normal, color: p.element(t.kind) }).collect();
     let faces_drawn = d.tris.is_empty();
     if faces_drawn {
-        s.tris.extend(d.surface_tris.iter().map(|t| SceneTri { p: t.p, normal: t.normal, color: p.geometry }));
+        s.tris.extend(d.surface_tris.iter().map(|t| SceneTri { p: t.p, normal: t.normal, color: d.body_color(t, p.geometry, &p.bodies) }));
     }
     s.lines = d.edges.iter().map(|e| SceneLine { a: e.p[0], b: e.p[1], color: p.mesh_edge, width: EDGE_WIDTH }).collect();
     let edge = if faces_drawn { p.mesh_edge } else { p.geometry_edge };

crates/explicit/src/system.rs

@@ -139,6 +139,9 @@ fn invalid(m: impl Into<String>) -> Error {
 fn material(model: &Model, name: &str) -> Result<Material> {
     let m = model.material(name).ok_or_else(|| invalid(format!("material `{name}` is missing")))?;
     let elastic = m.elastic.as_ref().ok_or_else(|| invalid(format!("material `{name}` has no elastic constants")))?;
+    if let Some(h) = m.hyperelastic {
+        return Err(Error::NotSupported(format!("{} hyperelastic material `{name}` in explicit dynamics", h.name())));
+    }
     let density = m
         .density
         .filter(|d| *d > 0.0 && d.is_finite())

crates/fem/src/constitutive.rs

@@ -0,0 +1,491 @@
+//! The material point of finite-strain analysis: from the deformation gradient F (and the
+//! material's history) to the stress and its consistent tangent.
+//!
+//! **Stress measure.** A material returns the **Kirchhoff stress** τ = J σ (J = det F, σ the
+//! Cauchy stress) and the **spatial tangent** c of the Lie derivative of τ, L_v τ = c : d, with
+//! d the rate of deformation. Both are 6-vectors and 6 × 6 matrices in the order xx, yy, zz,
+//! xy, xz, yz, c taking engineering shears like the small-strain elasticity matrices (so the
+//! linear elasticity D is c at F = I). This is the total Lagrangian formulation written with
+//! spatial quantities: τ = F S Fᵀ and c_ijkl = F_iI F_jJ F_kK F_lL C_IJKL push the second
+//! Piola–Kirchhoff stress S and its material tangent C = ∂S/∂E forward, so the internal forces
+//! ∫ Bₓᵀ τ dV₀ and the stiffness ∫ (Bₓᵀ c Bₓ + ∇ₓN·τ∇ₓN) dV₀, with the shape function gradients
+//! of the current configuration and integrals over the reference volume, are exactly the total
+//! Lagrangian ∫ B₀ᵀ S dV₀ and its linearization (J. Bonet, R. D. Wood, *Nonlinear Continuum
+//! Mechanics for Finite Element Analysis*, 2nd ed., Cambridge 2008, §7.4 and §9.2; G. A.
+//! Holzapfel, *Nonlinear Solid Mechanics*, Wiley 2000, §6.6). Finite-strain plasticity (the
+//! exponential return map of J. C. Simo, CMAME 99:61–112, 1992) gives τ and c directly, which is
+//! why the interface is spatial.
+//!
+//! **History.** A material keeps [`MaterialModel::history_len`] numbers per integration point.
+//! An evaluation reads the history committed at the end of the last converged increment and
+//! writes the updated one to a separate slice; the solver commits it when the increment
+//! converges, so a rejected iteration or a cut-back increment leaves no trace. The elastic
+//! materials here keep none.
+//!
+//! **Materials:**
+//! - **St Venant–Kirchhoff**: S = D E with E = ½(FᵀF − I) the Green–Lagrange strain and D the
+//!   small-strain elasticity (isotropic or orthotropic in the global axes): an elastic material
+//!   in a nonlinear step. Exact for large rotations with small strains; it softens without bound
+//!   in large compression, so large strains want a hyperelastic model.
+//! - **Neo-Hookean** (compressible, with the isochoric–volumetric split of P. J. Flory,
+//!   *Thermodynamic relations for high elastic materials*, Trans. Faraday Soc. 57:829–838, 1961):
+//!   W = μ/2 (Ī₁ − 3) + U(J), Ī₁ = J^(−2/3) tr b, U = κ/2 (J − 1)². Then
+//!   τ = μ dev b̄ + J U′ I with b̄ = J^(−2/3) b, and
+//!   c = ⅔ μ tr b̄ ℙ − ⅔ (τ_iso ⊗ I + I ⊗ τ_iso) + J (p̃ I ⊗ I − 2p 𝕀), with p = U′(J),
+//!   p̃ = p + J U″(J), 𝕀 the symmetric fourth-order identity and ℙ = 𝕀 − ⅓ I ⊗ I (Holzapfel 2000,
+//!   §6.6, eqs. 6.165–6.169 and 6.193, in Kirchhoff form). The split is what the mixed (hybrid)
+//!   elements need: they take the isochoric part from [`MaterialModel::isochoric`] and the
+//!   volumetric one from [`MaterialModel::volumetric`] with the element's own dilatation.
+//! - **Mooney–Rivlin and Yeoh**: decoupled polynomials
+//!   W̄ = C₁₀ (Ī₁ − 3) + C₀₁ (Ī₂ − 3) + C₂₀ (Ī₁ − 3)² + C₃₀ (Ī₁ − 3)³ with the neo-Hookean volume; their fictitious stress and
+//!   elasticity from Holzapfel 2000, eqs. 6.193 and 6.168 ([`MaterialModel::Polynomial`]).
+//! - **J2 plasticity** ([`crate::elastoplastic`]): Simo's multiplicative plasticity with the
+//!   exponential return map in the principal logarithmic strains (finite strain), or the
+//!   additive radial return (small strain, [`MaterialModel::small_strain`]); decoupled too, the
+//!   return deviatoric and the Hencky volume K/2 (ln J)².
+
+use std::sync::Arc;
+
+use fieldcraft_model::{Elastic, Hyperelastic};
+
+use crate::dense::det3;
+use crate::elastoplastic;
+use crate::material::{Elasticity, elasticity, stress};
+use crate::plasticity::J2;
+use crate::rotation::{IDENTITY, Mat3, mul, transpose, voigt};
+use crate::{Error, Result};
+
+/// A 6 × 6 tangent in Voigt order, engineering-shear columns.
+pub type Tangent = [[f64; 6]; 6];
+
+/// The (row, column) of each Voigt component.
+pub const PAIRS: [(usize, usize); 6] = [(0, 0), (1, 1), (2, 2), (0, 1), (0, 2), (1, 2)];
+
+/// The Kirchhoff stress and the spatial tangent of a material point.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct Response {
+    pub stress: [f64; 6],
+    pub tangent: Tangent,
+}
+
+/// The constitutive model of a solid in a nonlinear step.
+#[derive(Debug, Clone, PartialEq)]
+pub enum MaterialModel {
+    StVenantKirchhoff(Box<Elasticity>),
+    NeoHookean {
+        shear: f64,
+        bulk: f64,
+    },
+    /// A decoupled polynomial in the isochoric invariants,
+    /// W̄ = C₁₀ (Ī₁ − 3) + C₀₁ (Ī₂ − 3) + C₂₀ (Ī₁ − 3)² + C₃₀ (Ī₁ − 3)³ with `c` = (C₁₀, C₀₁, C₂₀, C₃₀), and U = κ/2 (J − 1)²:
+    /// Mooney–Rivlin and Yeoh.
+    Polynomial {
+        name: &'static str,
+        c: [f64; 4],
+        bulk: f64,
+    },
+    /// Von Mises plasticity (shared: one per material, whatever the element count).
+    Plastic(Arc<J2>),
+}
+
+/// The 6 × 6 matrix of the symmetric fourth-order identity 𝕀 (engineering-shear columns).
+pub(crate) fn identity4() -> Tangent {
+    let mut i4 = [[0.0; 6]; 6];
+    for k in 0..6 {
+        i4[k][k] = if k < 3 { 1.0 } else { 0.5 };
+    }
+    i4
+}
+
+/// The matrix T with (F A Fᵀ) = T a for a symmetric A of Voigt vector a (tensor components):
+/// T[(ij)][(IJ)] = F_iI F_jJ + F_iJ F_jI for I ≠ J and F_iI F_jI for I = J. A tangent pushes
+/// forward as T C Tᵀ.
+pub fn push_forward(f: &Mat3) -> Tangent {
+    let mut t = [[0.0; 6]; 6];
+    for (a, &(i, j)) in PAIRS.iter().enumerate() {
+        for (b, &(ii, jj)) in PAIRS.iter().enumerate() {
+            t[a][b] = if ii == jj { f[i][ii] * f[j][ii] } else { f[i][ii] * f[j][jj] + f[i][jj] * f[j][ii] };
+        }
+    }
+    t
+}
+
+/// T C Tᵀ.
+fn sandwich(t: &Tangent, c: &Tangent) -> Tangent {
+    let mut tc = [[0.0; 6]; 6];
+    for a in 0..6 {
+        for b in 0..6 {
+            tc[a][b] = (0..6).map(|k| t[a][k] * c[k][b]).sum();
+        }
+    }
+    let mut out = [[0.0; 6]; 6];
+    for a in 0..6 {
+        for b in 0..6 {
+            out[a][b] = (0..6).map(|k| tc[a][k] * t[b][k]).sum();
+        }
+    }
+    out
+}
+
+/// det F, refusing an inverted or collapsed point.
+fn jacobian(f: &Mat3) -> Result<f64> {
+    let j = det3(f);
+    if j > 0.0 && j.is_finite() { Ok(j) } else { Err(Error::Degenerate(format!("the material is inverted (J = det F = {j:.3e} is not positive)"))) }
+}
+
+impl MaterialModel {
+    /// The model of a material's elastic behaviour in a nonlinear step: the hyperelastic option
+    /// when the material has one (its isotropic constants give μ and κ), St Venant–Kirchhoff
+    /// otherwise.
+    pub fn from_model(elastic: &Elastic, hyperelastic: Option<&Hyperelastic>) -> Result<MaterialModel> {
+        match hyperelastic {
+            None => Ok(MaterialModel::StVenantKirchhoff(Box::new(elasticity(elastic)?))),
+            Some(h) => {
+                let (young, poisson) = crate::material::isotropic_constants(elastic, h.name())?;
+                let (shear, bulk) = Hyperelastic::moduli(young, poisson);
+                Ok(Self::hyperelastic(h, shear, bulk))
+            }
+        }
+    }
+
+    /// The hyperelastic model of an option with small-strain moduli μ and κ.
+    fn hyperelastic(h: &Hyperelastic, shear: f64, bulk: f64) -> MaterialModel {
+        match h {
+            Hyperelastic::NeoHookean {} => MaterialModel::NeoHookean { shear, bulk },
+            _ => MaterialModel::Polynomial { name: h.name(), c: h.constants(shear), bulk },
+        }
+    }
+
+    /// The model of an element whose elasticity is `d` (the small-strain one) and whose material
+    /// has the large-strain option `hyperelastic`: the hyperelastic models take μ = D₄₄ and
+    /// κ = D₁₂ + ⅔ μ of an isotropic `d`, St Venant–Kirchhoff `d` itself.
+    pub fn from_elasticity(d: &Elasticity, hyperelastic: Option<&Hyperelastic>) -> MaterialModel {
+        match hyperelastic {
+            None => MaterialModel::StVenantKirchhoff(Box::new(*d)),
+            Some(h) => Self::hyperelastic(h, d[3][3], d[0][1] + 2.0 / 3.0 * d[3][3]),
+        }
+    }
+
+    pub fn name(&self) -> &'static str {
+        match self {
+            MaterialModel::StVenantKirchhoff(_) => "St Venant–Kirchhoff",
+            MaterialModel::NeoHookean { .. } => "neo-Hookean",
+            MaterialModel::Polynomial { name, .. } => name,
+            MaterialModel::Plastic(_) => "J2 plastic",
+        }
+    }
+
+    /// History variables per integration point.
+    pub fn history_len(&self) -> usize {
+        match self {
+            MaterialModel::Plastic(_) => elastoplastic::HISTORY,
+            _ => 0,
+        }
+    }
+
+    /// Whether the response depends on the path (the material keeps history), so the solver
+    /// treats it with the inelastic kinematics and predictors.
+    pub fn is_path_dependent(&self) -> bool {
+        self.history_len() > 0
+    }
+
+    /// The equivalent plastic strain in one point's history; `None` for an elastic material.
+    pub fn plastic_strain(&self, history: &[f64]) -> Option<f64> {
+        match self {
+            MaterialModel::Plastic(_) => Some(elastoplastic::value(history, elastoplastic::PLASTIC_STRAIN)),
+            _ => None,
+        }
+    }
+
+    /// Whether the strain energy splits into isochoric and volumetric parts (what mixed
+    /// elements need).
+    pub fn is_decoupled(&self) -> bool {
+        !matches!(self, MaterialModel::StVenantKirchhoff(_))
+    }
+
+    /// The Kirchhoff stress and spatial tangent at deformation gradient `f` and (for
+    /// temperature-dependent plasticity) temperature `temperature`, from the history
+    /// `committed` (written, updated, to `updated`).
+    pub fn response(&self, f: &Mat3, temperature: Option<f64>, committed: &[f64], updated: &mut [f64]) -> Result<Response> {
+        updated.iter_mut().zip(committed).for_each(|(u, c)| *u = *c);
+        let j = jacobian(f)?;
+        match self {
+            MaterialModel::StVenantKirchhoff(d) => {
+                let c = mul(&transpose(f), f);
+                let e = [0.5 * (c[0][0] - 1.0), 0.5 * (c[1][1] - 1.0), 0.5 * (c[2][2] - 1.0), c[0][1], c[0][2], c[1][2]];
+                let s = stress(d, &e);
+                let t = push_forward(f);
+                Ok(Response { stress: std::array::from_fn(|a| (0..6).map(|b| t[a][b] * s[b]).sum()), tangent: sandwich(&t, d) })
+            }
+            MaterialModel::NeoHookean { .. } | MaterialModel::Polynomial { .. } | MaterialModel::Plastic(_) => {
+                let iso = self.isochoric(f, temperature, committed, updated)?;
+                let (p, dp) = self.volumetric(j, false).ok_or_else(|| Error::Invalid("volumetric response".into()))?;
+                Ok(add_pressure(&iso, j, p, j * dp))
+            }
+        }
+    }
+
+    /// The isochoric part of a decoupled material (τ_iso = dev τ̄ and its tangent), from the
+    /// history `committed`; the history that changes is written to `updated`, which the caller
+    /// starts as a copy of `committed`.
+    pub fn isochoric(&self, f: &Mat3, temperature: Option<f64>, committed: &[f64], updated: &mut [f64]) -> Result<Response> {
+        let mu = match self {
+            MaterialModel::NeoHookean { shear, .. } => *shear,
+            MaterialModel::Plastic(j2) => return elastoplastic::finite_isochoric(j2, f, temperature, committed, updated),
+            MaterialModel::Polynomial { c, .. } => return polynomial_isochoric(c, f),
+            MaterialModel::StVenantKirchhoff(_) => {
+                return Err(Error::NotSupported(format!("the isochoric–volumetric split of a {} material", self.name())));
+            }
+        };
+        let j = jacobian(f)?;
+        let scale = j.powf(-2.0 / 3.0);
+        let b = mul(f, &transpose(f));
+        let bbar = voigt(&b).map(|v| scale * v);
+        let tr = bbar[0] + bbar[1] + bbar[2];
+        let mut tau = bbar.map(|v| mu * v);
+        for v in tau.iter_mut().take(3) {
+            *v -= mu * tr / 3.0;
+        }
+        let i4 = identity4();
+        let mut c = [[0.0; 6]; 6];
+        for a in 0..6 {
+            for b in 0..6 {
+                let (ia, ib) = (if a < 3 { 1.0 } else { 0.0 }, if b < 3 { 1.0 } else { 0.0 });
+                let projector = i4[a][b] - ia * ib / 3.0;
+                c[a][b] = 2.0 / 3.0 * mu * tr * projector - 2.0 / 3.0 * (tau[a] * ib + ia * tau[b]);
+            }
+        }
+        Ok(Response { stress: tau, tangent: c })
+    }
+
+    /// U′(J) and U″(J) of a decoupled material's volumetric energy at dilatation J (with
+    /// `small`, J = 1 + tr ε of small strain, where every material's is K/2 (J − 1)²).
+    pub fn volumetric(&self, j: f64, small: bool) -> Option<(f64, f64)> {
+        match self {
+            MaterialModel::NeoHookean { bulk, .. } | MaterialModel::Polynomial { bulk, .. } => Some((bulk * (j - 1.0), *bulk)),
+            MaterialModel::Plastic(j2) => elastoplastic::volumetric(j2, j, small),
+            MaterialModel::StVenantKirchhoff(_) => None,
+        }
+    }
+
+    /// Small strain: the stress and its tangent at the (mechanical) strain `strain`
+    /// (engineering shears), from the history `committed` (written, updated, to `updated`);
+    /// `bulk` false keeps the deviatoric part only (what a mixed element takes). St
+    /// Venant–Kirchhoff is linear elasticity here; hyperelastic materials have no small-strain
+    /// form.
+    pub fn small_strain(&self, strain: &[f64; 6], temperature: Option<f64>, committed: &[f64], updated: &mut [f64], bulk: bool) -> Result<Response> {
+        updated.iter_mut().zip(committed).for_each(|(u, c)| *u = *c);
+        match self {
+            MaterialModel::Plastic(j2) => elastoplastic::small(j2, strain, temperature, committed, updated, bulk),
+            MaterialModel::StVenantKirchhoff(d) if bulk => Ok(Response { stress: stress(d, strain), tangent: **d }),
+            _ => Err(Error::NotSupported(format!("the {} material at small strain{}", self.name(), if bulk { "" } else { " in mixed elements" }))),
+        }
+    }
+}
+
+/// The isochoric response of the polynomial energy W̄(Ī₁, Ī₂) with `c` = (C₁₀, C₀₁, C₂₀, C₃₀)
+/// (Holzapfel 2000, §6.5–6.6, in Kirchhoff form): the fictitious stress
+/// τ̄ = 2 (Ψ₁ + Ī₁ Ψ₂) b̄ − 2 Ψ₂ b̄², τ_iso = dev τ̄, and with the fictitious elasticity
+/// c̄ = 4 (Ψ₁₁ + Ψ₂) b̄ ⊗ b̄ − 4 Ψ₂ b̄ ⊙ b̄ (eq. 6.193 pushed forward, Ψ₁₂ = Ψ₂₂ = 0 here),
+/// c_iso = ℙ : c̄ : ℙ + ⅔ tr τ̄ ℙ − ⅔ (τ_iso ⊗ I + I ⊗ τ_iso) (eq. 6.168). With C₁₀ alone it is
+/// the neo-Hookean response.
+fn polynomial_isochoric(c: &[f64; 4], f: &Mat3) -> Result<Response> {
+    let [c10, c01, c20, c30] = *c;
+    let j = jacobian(f)?;
+    let scale = j.powf(-2.0 / 3.0);
+    let b = mul(f, &transpose(f)).map(|row| row.map(|v| scale * v));
+    let b2 = mul(&b, &b);
+    let i1 = b[0][0] + b[1][1] + b[2][2];
+    let x = i1 - 3.0;
+    let (psi1, psi2, psi11) = (c10 + 2.0 * c20 * x + 3.0 * c30 * x * x, c01, 2.0 * c20 + 6.0 * c30 * x);
+    let (bv, b2v) = (voigt(&b), voigt(&b2));
+    let fict: [f64; 6] = std::array::from_fn(|a| 2.0 * (psi1 + i1 * psi2) * bv[a] - 2.0 * psi2 * b2v[a]);
+    let tr = fict[0] + fict[1] + fict[2];
+    let mut tau = fict;
+    for v in tau.iter_mut().take(3) {
+        *v -= tr / 3.0;
+    }
+    let mut cbar = [[0.0; 6]; 6];
+    for (a, &(i, jj)) in PAIRS.iter().enumerate() {
+        for (bb, &(k, l)) in PAIRS.iter().enumerate() {
+            cbar[a][bb] = 4.0 * (psi11 + psi2) * bv[a] * bv[bb] - 2.0 * psi2 * (b[i][k] * b[jj][l] + b[i][l] * b[jj][k]);
+        }
+    }
+    // ℙ : c̄ : ℙ = c̄ − ⅓ I ⊗ (I : c̄) − ⅓ (c̄ : I) ⊗ I + ⅑ (I : c̄ : I) I ⊗ I.
+    let row: [f64; 6] = std::array::from_fn(|a| (0..3).map(|bb| cbar[a][bb]).sum());
+    let col: [f64; 6] = std::array::from_fn(|bb| (0..3).map(|a| cbar[a][bb]).sum());
+    let all: f64 = (0..3).map(|a| row[a]).sum();
+    let i4 = identity4();
+    let mut out = [[0.0; 6]; 6];
+    for a in 0..6 {
+        for bb in 0..6 {
+            let (ia, ib) = (if a < 3 { 1.0 } else { 0.0 }, if bb < 3 { 1.0 } else { 0.0 });
+            let projected = cbar[a][bb] - ia * col[bb] / 3.0 - row[a] * ib / 3.0 + ia * ib * all / 9.0;
+            let projector = i4[a][bb] - ia * ib / 3.0;
+            out[a][bb] = projected + 2.0 / 3.0 * tr * projector - 2.0 / 3.0 * (tau[a] * ib + ia * tau[bb]);
+        }
+    }
+    Ok(Response { stress: tau, tangent: out })
+}
+
+/// An isochoric response with a pressure p acting on dilatation J: τ + J p I, and the tangent
+/// c + J (p̃ I ⊗ I − 2p 𝕀) with p̃ = p + `j_dp` (J dp/dJ, zero when p is held).
+pub fn add_pressure(iso: &Response, j: f64, p: f64, j_dp: f64) -> Response {
+    let mut out = *iso;
+    let i4 = identity4();
+    for a in 0..3 {
+        out.stress[a] += j * p;
+    }
+    for a in 0..6 {
+        for b in 0..6 {
+            let ii = if a < 3 && b < 3 { 1.0 } else { 0.0 };
+            out.tangent[a][b] += j * ((p + j_dp) * ii - 2.0 * p * i4[a][b]);
+        }
+    }
+    out
+}
+
+/// The logarithmic (Hencky) strain ln V = ½ ln b of a deformation gradient, as a strain 6-vector
+/// with engineering shears; `None` when F is not finite or inverted.
+pub fn logarithmic_strain(f: &Mat3) -> Option<[f64; 6]> {
+    let (l, v) = crate::dense::symmetric_eigen(&mul(f, &transpose(f)))?;
+    if !l.iter().all(|x| *x > 0.0) {
+        return None;
+    }
+    let ln = l.map(|x| 0.5 * x.ln());
+    let e = |i: usize, j: usize| (0..3).map(|k| ln[k] * v[i][k] * v[j][k]).sum::<f64>();
+    Some([e(0, 0), e(1, 1), e(2, 2), 2.0 * e(0, 1), 2.0 * e(0, 2), 2.0 * e(1, 2)])
+}
+
+/// The deformation gradient F = I + Σ u_a ⊗ ∇₀N_a of nodal displacements and reference
+/// gradients.
+pub fn deformation_gradient(u: &[[f64; 3]], gradients: &[[f64; 3]]) -> Mat3 {
+    let mut f = IDENTITY;
+    for (ua, g) in u.iter().zip(gradients) {
+        for i in 0..3 {
+            for jj in 0..3 {
+                f[i][jj] += ua[i] * g[jj];
+            }
+        }
+    }
+    f
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::dense::inverse3;
+    use crate::material::isotropic;
+
+    fn deformation() -> Mat3 {
+        [[1.2, 0.15, -0.05], [-0.1, 0.9, 0.2], [0.07, -0.12, 1.05]]
+    }
+
+    /// S = F⁻¹ τ F⁻ᵀ.
+    fn pull_back_stress(f: &Mat3, tau: &[f64; 6]) -> [f64; 6] {
+        crate::rotation::rotate(&inverse3(f).unwrap().0, tau)
+    }
+
+    /// The tangent's consistency: dS = C : dE with C the pull-back of c, checked by central
+    /// differences of S along several directions dF (dE = sym(Fᵀ dF), engineering shears).
+    fn check_tangent(m: &MaterialModel, f: &Mat3) {
+        let r = m.response(f, None, &[], &mut []).unwrap();
+        let (inv, _) = inverse3(f).unwrap();
+        let back = sandwich(&push_forward(&inv), &r.tangent);
+        let scale = back.iter().flatten().fold(0.0f64, |a, v| a.max(v.abs()));
+        let h = 1e-6;
+        for k in 0..9 {
+            let mut df = [[0.0; 3]; 3];
+            df[k / 3][k % 3] = 1.0;
+            df[(k + 1) % 3][(k + 2) % 3] += 0.3;
+            let at = |s: f64| {
+                let fp: Mat3 = std::array::from_fn(|i| std::array::from_fn(|j| f[i][j] + s * df[i][j]));
+                pull_back_stress(&fp, &m.response(&fp, None, &[], &mut []).unwrap().stress)
+            };
+            let (sp, sm) = (at(h), at(-h));
+            let ftdf = mul(&transpose(f), &df);
+            let de = [ftdf[0][0], ftdf[1][1], ftdf[2][2], ftdf[0][1] + ftdf[1][0], ftdf[0][2] + ftdf[2][0], ftdf[1][2] + ftdf[2][1]];
+            for a in 0..6 {
+                let numeric = (sp[a] - sm[a]) / (2.0 * h);
+                let analytic: f64 = (0..6).map(|b| back[a][b] * de[b]).sum();
+                assert!((numeric - analytic).abs() < 1e-6 * scale, "{} {k} {a}: {numeric} vs {analytic}", m.name());
+            }
+        }
+    }
+
+    #[test]
+    fn tangents_are_consistent_with_the_stress() {
+        let d = isotropic(1000.0, 0.3).unwrap();
+        for m in [MaterialModel::StVenantKirchhoff(Box::new(d)), MaterialModel::NeoHookean { shear: 300.0, bulk: 5000.0 }] {
+            check_tangent(&m, &deformation());
+            check_tangent(&m, &IDENTITY);
+            // Symmetric (hyperelastic): major symmetry of c.
+            let c = m.response(&deformation(), None, &[], &mut []).unwrap().tangent;
+            for a in 0..6 {
+                for b in 0..6 {
+                    assert!((c[a][b] - c[b][a]).abs() < 1e-9 * 5000.0, "{a} {b}");
+                }
+            }
+        }
+        // Mooney–Rivlin and Yeoh: consistent and symmetric; with C₁₀ alone the neo-Hookean model.
+        for m in [
+            MaterialModel::Polynomial { name: "Mooney–Rivlin", c: [120.0, 30.0, 0.0, 0.0], bulk: 5000.0 },
+            MaterialModel::Polynomial { name: "Yeoh", c: [150.0, 0.0, -12.0, 1.5], bulk: 5000.0 },
+        ] {
+            check_tangent(&m, &deformation());
+            check_tangent(&m, &IDENTITY);
+            let c = m.response(&deformation(), None, &[], &mut []).unwrap().tangent;
+            assert!((0..36).all(|k| (c[k / 6][k % 6] - c[k % 6][k / 6]).abs() < 1e-9 * 5000.0), "{} symmetric", m.name());
+        }
+        let neo = MaterialModel::NeoHookean { shear: 300.0, bulk: 5000.0 };
+        let poly = MaterialModel::Polynomial { name: "neo", c: [150.0, 0.0, 0.0, 0.0], bulk: 5000.0 };
+        let (a, b) = (neo.response(&deformation(), None, &[], &mut []).unwrap(), poly.response(&deformation(), None, &[], &mut []).unwrap());
+        assert!(a.stress.iter().zip(&b.stress).all(|(x, y)| (x - y).abs() < 1e-11 * 300.0));
+        assert!(a.tangent.iter().flatten().zip(b.tangent.iter().flatten()).all(|(x, y)| (x - y).abs() < 1e-10 * 5000.0));
+        let ortho = crate::material::orthotropic([1000.0, 300.0, 500.0], [0.3, 0.2, 0.25], [100.0, 120.0, 90.0]).unwrap();
+        check_tangent(&MaterialModel::StVenantKirchhoff(Box::new(ortho)), &deformation());
+    }
+
+    #[test]
+    fn small_strain_limit_is_linear_elasticity_and_rotations_do_not_stress() {
+        let (e, nu) = (1000.0, 0.3);
+        let d = isotropic(e, nu).unwrap();
+        let neo = MaterialModel::from_model(&Elastic::Isotropic { young: e, poisson: nu }, Some(&Hyperelastic::NeoHookean {})).unwrap();
+        for m in [MaterialModel::StVenantKirchhoff(Box::new(d)), neo] {
+            let c = m.response(&IDENTITY, None, &[], &mut []).unwrap().tangent;
+            for a in 0..6 {
+                for b in 0..6 {
+                    assert!((c[a][b] - d[a][b]).abs() < 1e-9 * e, "{}: {a} {b}", m.name());
+                }
+            }
+            // A rigid rotation (90° about an inclined axis) leaves the stress at zero.
+            let (s, cth) = (1.0f64, 0.0f64);
+            let axis = [1.0 / 3f64.sqrt(); 3];
+            let k = crate::rotation::skew(&axis);
+            let k2 = mul(&k, &k);
+            let rot: Mat3 = std::array::from_fn(|i| std::array::from_fn(|j| IDENTITY[i][j] + s * k[i][j] + (1.0 - cth) * k2[i][j]));
+            let tau = m.response(&rot, None, &[], &mut []).unwrap().stress;
+            assert!(tau.iter().all(|v| v.abs() < 1e-12 * e), "{}: {tau:?}", m.name());
+        }
+    }
+
+    #[test]
+    fn uniaxial_stretch_of_neo_hookean_and_log_strain() {
+        // Stretch λ along x with the lateral stretch μ chosen so that σ_yy = 0: check σ_xx
+        // against W directly, σ = (μ/J^(5/3)) (λ² − (λ² + 2 l²)/3) + κ (J − 1).
+        let (mu, kappa) = (300.0, 5000.0);
+        let m = MaterialModel::NeoHookean { shear: mu, bulk: kappa };
+        let (lam, l) = (1.5f64, 0.85f64);
+        let f = [[lam, 0.0, 0.0], [0.0, l, 0.0], [0.0, 0.0, l]];
+        let j = lam * l * l;
+        let tau = m.response(&f, None, &[], &mut []).unwrap().stress;
+        let i1 = lam * lam + 2.0 * l * l;
+        let sxx = mu / j.powf(5.0 / 3.0) * (lam * lam - i1 / 3.0) + kappa * (j - 1.0);
+        let syy = mu / j.powf(5.0 / 3.0) * (l * l - i1 / 3.0) + kappa * (j - 1.0);
+        assert!((tau[0] / j - sxx).abs() < 1e-10 * mu && (tau[1] / j - syy).abs() < 1e-10 * mu, "{tau:?}");
+        let e = logarithmic_strain(&f).unwrap();
+        assert!((e[0] - lam.ln()).abs() < 1e-14 && (e[1] - l.ln()).abs() < 1e-14 && e[3].abs() < 1e-14, "{e:?}");
+        assert!(m.response(&[[1.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, -1.0]], None, &[], &mut []).is_err(), "inverted");
+        assert!(MaterialModel::StVenantKirchhoff(Box::new(isotropic(1.0, 0.3).unwrap())).isochoric(&IDENTITY, None, &[], &mut []).is_err());
+    }
+}

crates/fem/src/dense.rs

@@ -106,11 +106,64 @@ pub fn inverse3(m: &[[f64; 3]; 3]) -> Option<([[f64; 3]; 3], f64)> {
 }
 
 /// The inverse and determinant of a Jacobian that maps a reference element onto a valid one:
-/// `None` unless det J is positive beyond round-off relative to the product of its row norms.
+/// `None` unless it is admissible by FieldCraft's one validity criterion
+/// ([`fieldcraft_model::admissible_jacobian`], the one the meshers' validity gate proves).
 pub fn positive_inverse(j: &[[f64; 3]; 3]) -> Option<([[f64; 3]; 3], f64)> {
-    let (inv, det) = inverse3(j)?;
-    let norms: f64 = j.iter().map(|r| (r[0] * r[0] + r[1] * r[1] + r[2] * r[2]).sqrt()).product();
-    (det > 1e-12 * norms).then_some((inv, det))
+    if !fieldcraft_model::admissible_jacobian(j) {
+        return None;
+    }
+    inverse3(j)
+}
+
+/// The eigenvalues and unit eigenvectors (the columns of the matrix returned) of a symmetric
+/// 3 × 3 matrix, by cyclic Jacobi rotations (G. H. Golub, C. F. Van Loan, *Matrix
+/// Computations*, 4th ed., Johns Hopkins 2013, §8.5): each rotation zeroes one off-diagonal
+/// entry with the stable choice of angle, and the sweeps stop when the off-diagonal part is
+/// round-off relative to the diagonal (at most 32 sweeps; three or four suffice). Accurate to a
+/// few ulps of the largest eigenvalue; `None` for non-finite input.
+pub fn symmetric_eigen(a: &[[f64; 3]; 3]) -> Option<([f64; 3], [[f64; 3]; 3])> {
+    if a.iter().flatten().any(|v| !v.is_finite()) {
+        return None;
+    }
+    let mut m = [[a[0][0], 0.5 * (a[0][1] + a[1][0]), 0.5 * (a[0][2] + a[2][0])], [0.0; 3], [0.0; 3]];
+    m[1] = [m[0][1], a[1][1], 0.5 * (a[1][2] + a[2][1])];
+    m[2] = [m[0][2], m[1][2], a[2][2]];
+    let mut v = [[1.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, 1.0]];
+    for _ in 0..32 {
+        let off = m[0][1] * m[0][1] + m[0][2] * m[0][2] + m[1][2] * m[1][2];
+        let diag = m[0][0] * m[0][0] + m[1][1] * m[1][1] + m[2][2] * m[2][2];
+        if off <= 1e-36 * diag || off == 0.0 {
+            break;
+        }
+        for (p, q) in [(0, 1), (0, 2), (1, 2)] {
+            let apq = m[p][q];
+            if apq == 0.0 {
+                continue;
+            }
+            // tan of the rotation angle, the smaller root of t² + 2θt − 1 = 0.
+            let theta = (m[q][q] - m[p][p]) / (2.0 * apq);
+            let sign = if theta >= 0.0 { 1.0 } else { -1.0 };
+            let t = sign / (theta.abs() + (theta * theta + 1.0).sqrt());
+            let c = 1.0 / (t * t + 1.0).sqrt();
+            let s = t * c;
+            for k in 0..3 {
+                let (mkp, mkq) = (m[k][p], m[k][q]);
+                m[k][p] = c * mkp - s * mkq;
+                m[k][q] = s * mkp + c * mkq;
+            }
+            for k in 0..3 {
+                let (mpk, mqk) = (m[p][k], m[q][k]);
+                m[p][k] = c * mpk - s * mqk;
+                m[q][k] = s * mpk + c * mqk;
+            }
+            for row in &mut v {
+                let (vp, vq) = (row[p], row[q]);
+                row[p] = c * vp - s * vq;
+                row[q] = s * vp + c * vq;
+            }
+        }
+    }
+    Some(([m[0][0], m[1][1], m[2][2]], v))
 }
 
 pub fn det3(m: &[[f64; 3]; 3]) -> f64 {
@@ -143,4 +196,29 @@ mod tests {
         }
         assert!(inverse3(&[[1.0, 2.0, 3.0], [2.0, 4.0, 6.0], [0.0, 0.0, 1.0]]).is_none());
     }
+
+    #[test]
+    fn symmetric_eigen_decomposes() {
+        for a in [
+            [[4.0, 1.0, -2.0], [1.0, 3.0, 0.5], [-2.0, 0.5, 1.0]],
+            [[2.0, 0.0, 0.0], [0.0, 2.0, 0.0], [0.0, 0.0, 5.0]],
+            [[1.0, 1e-9, 0.0], [1e-9, 1.0, 0.0], [0.0, 0.0, 1.0]],
+            [[1e6, 3.0, 2.0], [3.0, 1e-3, 0.0], [2.0, 0.0, -7.0]],
+        ] {
+            let (l, v) = symmetric_eigen(&a).unwrap();
+            let scale = l.iter().fold(0.0f64, |m, x| m.max(x.abs()));
+            for k in 0..3 {
+                // A v_k = λ_k v_k and the v_k are orthonormal.
+                for i in 0..3 {
+                    let av: f64 = (0..3).map(|j| a[i][j] * v[j][k]).sum();
+                    assert!((av - l[k] * v[i][k]).abs() < 1e-12 * scale, "{a:?}: {l:?}");
+                }
+                for m in 0..3 {
+                    let d: f64 = (0..3).map(|i| v[i][k] * v[i][m]).sum();
+                    assert!((d - if k == m { 1.0 } else { 0.0 }).abs() < 1e-13);
+                }
+            }
+        }
+        assert!(symmetric_eigen(&[[f64::NAN, 0.0, 0.0], [0.0; 3], [0.0; 3]]).is_none());
+    }
 }

crates/fem/src/elastoplastic.rs

@@ -0,0 +1,407 @@
+//! Von Mises (J2) elastoplasticity at a material point of implicit (Newton) analysis: the
+//! stress after an increment and its consistent tangent, at finite strain and at small strain.
+//! Both kinematics call the radial return of [`crate::plasticity`], the update explicit
+//! dynamics uses, so the yield surface, the hardening (bilinear isotropic or linear kinematic,
+//! tabulated, Johnson–Cook) and the plastic strain increment of a trial state are one
+//! implementation for both solvers.
+//!
+//! **Finite strain** (J. C. Simo, *Algorithms for static and dynamic multiplicative plasticity
+//! that preserve the classical return mapping schemes of the infinitesimal theory*, CMAME
+//! 99:61–112, 1992; Simo & Hughes 1998, ch. 9): the multiplicative split F = Fₑ Fₚ with the
+//! elastic left Cauchy–Green tensor bₑ = F Cₚ⁻¹ Fᵀ and a Hencky (quadratic in the logarithmic
+//! strain) elastic energy, so the Kirchhoff stress is τ = K ln J I + 2G dev εₑ with
+//! εₑ = ½ ln bₑ. The history is Cₚ⁻¹ (stored as Cₚ⁻¹ − I, so the virgin state is zeros) and the
+//! equivalent plastic strain. An increment freezes Cₚ⁻¹ at its committed value: the trial
+//! bₑᵗʳ = F Cₚ⁻¹ Fᵀ, its principal stretches and directions, the trial logarithmic strains
+//! ε_A = ½ ln λ_A², and then the **return map of the infinitesimal theory on the principal
+//! values** (the exponential map integrates the flow rule exactly in the principal frame, which
+//! the isotropy of the model keeps fixed during the return). The update writes back
+//! bₑ = Σ exp(2 εₑ,A) n_A ⊗ n_A and Cₚ⁻¹ = F⁻¹ bₑ F⁻ᵀ, which keeps det Cₚ = 1 (plastic flow
+//! is isochoric).
+//!
+//! **Its tangent.** With Cₚ⁻¹ frozen, the Lie derivative of bₑᵗʳ vanishes, so for a rate of
+//! deformation d the trial strain changes by dεᵗʳ = ½ (∂ ln b/∂b) : (d b + b d), and
+//! L_v τ = 𝔻ᵉᵖ : dεᵗʳ − (d τ + τ d), with 𝔻ᵉᵖ the algorithmic tangent of the return map
+//! ([`crate::plasticity::J2::tangent`]). In the principal frame of b the derivative of the
+//! logarithm is the Daleckii–Krein divided difference, so dεᵗʳ_AB = θ_AB d_AB with θ_AA = 1 and
+//! θ_AB = ½ (λ²_A + λ²_B) ln(λ²_A/λ²_B)/(λ²_A − λ²_B) = artanh(r)/r, r = (λ²_A − λ²_B)/(λ²_A + λ²_B),
+//! smooth through equal stretches (its series 1 + r²/3 + r⁴/5 + … near r = 0), so uniaxial and
+//! undeformed states need no special case (Simo 1992, §3.3, gives the same tangent in spectral
+//! form; R. Bhatia, *Matrix Analysis*, Springer 1997, §V.3, for the divided differences). The
+//! tangent is symmetric for isotropic hardening: 𝔻ᵉᵖ and the θ scaling share the principal
+//! frame.
+//!
+//! **Kinematic hardening at finite strain** is refused: a back stress is not coaxial with bₑ, so
+//! the principal-frame return no longer holds, and it needs a formulation of its own (for
+//! example the Lagrangian logarithmic strain space of C. Miehe, N. Apel, M. Lambrecht, CMAME
+//! 191:5383–5425, 2002). It works with small strain.
+//!
+//! **Small strain** (Simo & Hughes 1998, §3.3): ε = εₑ + εₚ additively, the history the plastic
+//! strain εₚ, the back stress α and the equivalent plastic strain; the trial εₑ = ε − εₚ,ₙ goes
+//! through the same return, and εₚ advances by √(3/2) Δε̄ₚ n.
+//!
+//! **Mixed (hybrid) elements** take the isochoric part (the deviatoric return, without K) and the
+//! volumetric energy U(J) = K/2 (ln J)², U′ = K ln J / J (finite strain), or U = K/2 (J − 1)² with
+//! J the 1 + tr ε of small strain: J2 plasticity is pressure insensitive and isochoric, so the
+//! split is exact.
+//!
+//! **History layout** per integration point ([`HISTORY`] values): 0–5 Cₚ⁻¹ − I (finite strain,
+//! tensor components) or εₚ (small strain, engineering shears), 6–11 the back stress α, 12 the
+//! equivalent plastic strain.
+
+use crate::constitutive::{Response, Tangent};
+use crate::dense::{inverse3, symmetric_eigen};
+use crate::plasticity::{J2, PointState, Return};
+use crate::rotation::{IDENTITY, Mat3, mul, tensor, transpose, voigt};
+use crate::{Error, Result};
+
+/// History values per integration point.
+pub const HISTORY: usize = 13;
+
+/// Where the equivalent plastic strain is in a point's history.
+pub const PLASTIC_STRAIN: usize = 12;
+
+/// History value `i` (0 when the slice is short).
+pub(crate) fn value(h: &[f64], i: usize) -> f64 {
+    h.get(i).copied().unwrap_or(0.0)
+}
+
+/// Cₚ⁻¹ of a finite-strain history (stored as Cₚ⁻¹ − I).
+fn plastic_stretch(h: &[f64]) -> Mat3 {
+    let stored = tensor(&std::array::from_fn(|k| value(h, k)));
+    std::array::from_fn(|i| std::array::from_fn(|j| IDENTITY[i][j] + stored[i][j]))
+}
+
+/// Store Cₚ⁻¹ as Cₚ⁻¹ − I in the first six history values.
+fn store_plastic_stretch(cp: &Mat3, h: &mut [f64]) {
+    let v = voigt(cp);
+    for (k, slot) in h.iter_mut().take(6).enumerate() {
+        *slot = v[k] - if k < 3 { 1.0 } else { 0.0 };
+    }
+}
+
+/// artanh(r)/r, smooth through r = 0.
+fn log_divided_difference(r: f64) -> f64 {
+    if r.abs() < 1e-4 {
+        let r2 = r * r;
+        1.0 + r2 * (1.0 / 3.0 + r2 * (1.0 / 5.0 + r2 / 7.0))
+    } else {
+        r.atanh() / r
+    }
+}
+
+/// The state a return starts from: the committed back stress and plastic strain, at the point's
+/// temperature (Johnson–Cook softening; room temperature without one).
+fn start(j2: &J2, committed: &[f64], temperature: Option<f64>) -> PointState {
+    let mut s = PointState::new(temperature.unwrap_or_else(|| j2.initial_temperature()));
+    s.back = std::array::from_fn(|k| value(committed, 6 + k));
+    s.plastic_strain = value(committed, PLASTIC_STRAIN);
+    s
+}
+
+fn singular() -> Error {
+    Error::Degenerate("the plastic material point has no tangent: its hardening falls faster than −3G (a softening material localises)".into())
+}
+
+/// The deviatoric trial stress 2G dev ε of a strain 6-vector (engineering shears), as tensor
+/// components.
+fn trial_deviator(j2: &J2, e: &[f64; 6]) -> [f64; 6] {
+    let mean = (e[0] + e[1] + e[2]) / 3.0;
+    let g2 = 2.0 * j2.shear;
+    [g2 * (e[0] - mean), g2 * (e[1] - mean), g2 * (e[2] - mean), j2.shear * e[3], j2.shear * e[4], j2.shear * e[5]]
+}
+
+/// Finite strain: the isochoric (deviatoric) Kirchhoff stress and its spatial tangent at
+/// deformation gradient `f`, from the history `committed` (written, updated, to `updated`). Add
+/// the volumetric part with [`volumetric`] (or the mixed element's pressure) for the whole
+/// response.
+pub fn finite_isochoric(j2: &J2, f: &Mat3, temperature: Option<f64>, committed: &[f64], updated: &mut [f64]) -> Result<Response> {
+    if let Some(crate::plasticity::Flow::Linear { kinematic: true, .. }) = j2.flow {
+        return Err(Error::NotSupported(
+            "kinematic hardening at finite strain (its back stress is not coaxial with the elastic stretch; use nonlinear_geometry false or isotropic hardening)"
+                .into(),
+        ));
+    }
+    let b = mul(&mul(f, &plastic_stretch(committed)), &transpose(f));
+    let (l, q) = symmetric_eigen(&b)
+        .filter(|(l, _)| l.iter().all(|x| *x > 0.0))
+        .ok_or_else(|| Error::Degenerate("the elastic stretch of a plastic material point is not positive (the material is inverted)".into()))?;
+    let eps = l.map(|x| 0.5 * x.ln());
+    let mut state = start(j2, committed, temperature);
+    let mut trial = trial_deviator(j2, &[eps[0], eps[1], eps[2], 0.0, 0.0, 0.0]);
+    let ret: Option<Return> = j2.radial_return(&mut state, &mut trial, 0.0);
+    // Back to the global frame: τ = Σ τ_A q_A ⊗ q_A, n likewise.
+    let spectral = |v: [f64; 3]| -> Mat3 { std::array::from_fn(|i| std::array::from_fn(|j| (0..3).map(|a| v[a] * q[i][a] * q[j][a]).sum())) };
+    let tau = voigt(&spectral([trial[0], trial[1], trial[2]]));
+    let global = ret.map(|r| Return { normal: voigt(&spectral([r.normal[0], r.normal[1], r.normal[2]])), ..r });
+    let d = j2.tangent(global.as_ref(), false).ok_or_else(singular)?;
+    // θ_AB of the logarithm's derivative.
+    let theta: Mat3 =
+        std::array::from_fn(|a| std::array::from_fn(|bb| if a == bb { 1.0 } else { log_divided_difference((l[a] - l[bb]) / (l[a] + l[bb])) }));
+    let tau_m = tensor(&tau);
+    let qt = transpose(&q);
+    let mut c: Tangent = [[0.0; 6]; 6];
+    for (col, &(i, j)) in crate::constitutive::PAIRS.iter().enumerate() {
+        // The unit rate of deformation of this column (engineering shear 1: d_ij = d_ji = ½).
+        let mut dm = [[0.0; 3]; 3];
+        let half = if i == j { 1.0 } else { 0.5 };
+        dm[i][j] = half;
+        dm[j][i] = half;
+        let mut dp = mul(&mul(&qt, &dm), &q);
+        for a in 0..3 {
+            for bb in 0..3 {
+                dp[a][bb] *= theta[a][bb];
+            }
+        }
+        let de = voigt(&mul(&mul(&q, &dp), &qt));
+        let de = [de[0], de[1], de[2], 2.0 * de[3], 2.0 * de[4], 2.0 * de[5]];
+        let spin = voigt(&{
+            let (x, y) = (mul(&dm, &tau_m), mul(&tau_m, &dm));
+            std::array::from_fn(|r| std::array::from_fn(|s| x[r][s] + y[r][s]))
+        });
+        for row in 0..6 {
+            c[row][col] = (0..6).map(|k| d[row][k] * de[k]).sum::<f64>() - spin[row];
+        }
+    }
+    if let Some(r) = ret {
+        // bₑ = Σ exp(2 εₑ,A) q_A ⊗ q_A with εₑ = ε − √(3/2) Δε̄ₚ n, and Cₚ⁻¹ = F⁻¹ bₑ F⁻ᵀ.
+        let dg = (1.5f64).sqrt() * r.plastic_strain;
+        let be = spectral(std::array::from_fn(|a| (2.0 * (eps[a] - dg * r.normal[a])).exp()));
+        let (inv, _) = inverse3(f).ok_or_else(|| Error::Degenerate("the deformation gradient is singular".into()))?;
+        store_plastic_stretch(&mul(&mul(&inv, &be), &transpose(&inv)), updated);
+        if let Some(slot) = updated.get_mut(PLASTIC_STRAIN) {
+            *slot = state.plastic_strain;
+        }
+    }
+    Ok(Response { stress: tau, tangent: c })
+}
+
+/// U′(J) and U″(J) of the Hencky volumetric energy K/2 (ln J)² (finite strain), or of
+/// K/2 (J − 1)² for the dilatation J = 1 + tr ε of small strain.
+pub fn volumetric(j2: &J2, j: f64, small: bool) -> Option<(f64, f64)> {
+    if !(j > 0.0 && j.is_finite()) {
+        return None;
+    }
+    let k = j2.bulk;
+    Some(if small { (k * (j - 1.0), k) } else { (k * j.ln() / j, k * (1.0 - j.ln()) / (j * j)) })
+}
+
+/// Small strain: the stress and the consistent tangent at total (mechanical) strain `strain`
+/// (engineering shears), from the history `committed` (written, updated, to `updated`); with
+/// `bulk` false only the deviatoric part (what a mixed element takes).
+pub fn small(j2: &J2, strain: &[f64; 6], temperature: Option<f64>, committed: &[f64], updated: &mut [f64], bulk: bool) -> Result<Response> {
+    let elastic: [f64; 6] = std::array::from_fn(|k| strain[k] - value(committed, k));
+    let mut state = start(j2, committed, temperature);
+    let mut stress = trial_deviator(j2, &elastic);
+    let ret = j2.radial_return(&mut state, &mut stress, 0.0);
+    if bulk {
+        let p = j2.bulk * (elastic[0] + elastic[1] + elastic[2]);
+        for s in stress.iter_mut().take(3) {
+            *s += p;
+        }
+    }
+    let tangent = j2.tangent(ret.as_ref(), bulk).ok_or_else(singular)?;
+    if let Some(r) = ret {
+        let dg = (1.5f64).sqrt() * r.plastic_strain;
+        for (k, slot) in updated.iter_mut().take(6).enumerate() {
+            *slot = value(committed, k) + dg * r.normal[k] * if k < 3 { 1.0 } else { 2.0 };
+        }
+        for (k, slot) in updated.iter_mut().skip(6).take(6).enumerate() {
+            *slot = state.back[k];
+        }
+        if let Some(slot) = updated.get_mut(PLASTIC_STRAIN) {
+            *slot = state.plastic_strain;
+        }
+    }
+    Ok(Response { stress, tangent })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::constitutive::{add_pressure, push_forward};
+    use fieldcraft_model::{Elastic, Hardening, HardeningPoint, Plastic};
+
+    const E: f64 = 200_000.0;
+    const NU: f64 = 0.3;
+
+    fn j2(plastic: Plastic) -> J2 {
+        J2::from_model(&Elastic::Isotropic { young: E, poisson: NU }, Some(&plastic), None).unwrap()
+    }
+
+    fn bilinear(h: f64, hardening: Hardening) -> J2 {
+        j2(Plastic::Bilinear { yield_stress: 250.0, hardening_modulus: h, hardening })
+    }
+
+    /// The whole finite-strain response, isochoric plus the Hencky volume.
+    fn finite(m: &J2, f: &Mat3, committed: &[f64], updated: &mut [f64]) -> Response {
+        let iso = finite_isochoric(m, f, None, committed, updated).unwrap();
+        let j = crate::dense::det3(f);
+        let (p, dp) = volumetric(m, j, false).unwrap();
+        add_pressure(&iso, j, p, j * dp)
+    }
+
+    /// The pulled-back tangent C (dS = C : dE) against central differences of S along several
+    /// directions of F, as `constitutive::tests::check_tangent` does, from fixed history.
+    fn check_finite_tangent(m: &J2, f: &Mat3, committed: &[f64]) -> f64 {
+        let mut scratch = vec![0.0; HISTORY];
+        let r = finite(m, f, committed, &mut scratch);
+        let (inv, _) = inverse3(f).unwrap();
+        let t = push_forward(&inv);
+        let back: Tangent =
+            std::array::from_fn(|a| std::array::from_fn(|b| (0..6).map(|k| (0..6).map(|l| t[a][k] * r.tangent[k][l] * t[b][l]).sum::<f64>()).sum()));
+        let scale = back.iter().flatten().fold(0.0f64, |a, v| a.max(v.abs()));
+        let h = 1e-7;
+        let mut worst: f64 = 0.0;
+        for k in 0..9 {
+            let mut df = [[0.0; 3]; 3];
+            df[k / 3][k % 3] = 1.0;
+            df[(k + 1) % 3][(k + 2) % 3] += 0.3;
+            let at = |s: f64| {
+                let fp: Mat3 = std::array::from_fn(|i| std::array::from_fn(|j| f[i][j] + s * df[i][j]));
+                let mut scratch = vec![0.0; HISTORY];
+                let tau = finite(m, &fp, committed, &mut scratch).stress;
+                crate::rotation::rotate(&inverse3(&fp).unwrap().0, &tau)
+            };
+            let (sp, sm) = (at(h), at(-h));
+            let ftdf = mul(&transpose(f), &df);
+            let de = [ftdf[0][0], ftdf[1][1], ftdf[2][2], ftdf[0][1] + ftdf[1][0], ftdf[0][2] + ftdf[2][0], ftdf[1][2] + ftdf[2][1]];
+            for a in 0..6 {
+                let numeric = (sp[a] - sm[a]) / (2.0 * h);
+                let analytic: f64 = (0..6).map(|b| back[a][b] * de[b]).sum();
+                worst = worst.max((numeric - analytic).abs() / scale);
+            }
+        }
+        worst
+    }
+
+    #[test]
+    fn finite_strain_tangent_is_consistent_elastic_and_plastic() {
+        let deformations: [Mat3; 3] = [
+            [[1.02, 0.015, -0.005], [-0.01, 0.99, 0.02], [0.007, -0.012, 1.005]],
+            // Large: well into plasticity.
+            [[1.3, 0.15, -0.05], [-0.1, 0.85, 0.2], [0.07, -0.12, 1.05]],
+            // Uniaxial (two equal principal stretches).
+            [[1.2, 0.0, 0.0], [0.0, 0.92, 0.0], [0.0, 0.0, 0.92]],
+        ];
+        let tables = Plastic::Table { points: vec![HardeningPoint { strain: 0.0, stress: 250.0 }, HardeningPoint { strain: 0.5, stress: 600.0 }] };
+        let jc = Plastic::JohnsonCook {
+            a: 350.0,
+            b: 275.0,
+            n: 0.36,
+            c: 0.0,
+            m: 1.0,
+            reference_strain_rate: 1.0,
+            room_temperature: 293.0,
+            melt_temperature: 1356.0,
+            specific_heat: None,
+            taylor_quinney: 0.9,
+        };
+        // A plastic history to start from: a prior stretch committed.
+        let mut prior = vec![0.0; HISTORY];
+        finite(&bilinear(2000.0, Hardening::Isotropic), &[[1.1, 0.02, 0.0], [0.0, 0.95, 0.03], [0.0, 0.0, 0.96]], &[0.0; HISTORY], &mut prior);
+        assert!(prior[PLASTIC_STRAIN] > 0.0);
+        for m in [bilinear(2000.0, Hardening::Isotropic), bilinear(0.0, Hardening::Isotropic), j2(tables), j2(jc)] {
+            for f in &deformations {
+                for committed in [&[0.0; HISTORY][..], &prior[..]] {
+                    let worst = check_finite_tangent(&m, f, committed);
+                    assert!(worst < 1e-7, "{:?} at {f:?}: {worst}", m.flow);
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn finite_strain_tangent_is_symmetric_and_elastic_at_rest() {
+        let m = bilinear(2000.0, Hardening::Isotropic);
+        let mut scratch = vec![0.0; HISTORY];
+        let r = finite(&m, &[[1.3, 0.15, -0.05], [-0.1, 0.85, 0.2], [0.07, -0.12, 1.05]], &[0.0; HISTORY], &mut scratch);
+        for a in 0..6 {
+            for b in 0..6 {
+                assert!((r.tangent[a][b] - r.tangent[b][a]).abs() < 1e-9 * E, "{a} {b}");
+            }
+        }
+        let rest = finite(&m, &IDENTITY, &[0.0; HISTORY], &mut scratch);
+        let d = crate::material::isotropic(E, NU).unwrap();
+        for a in 0..6 {
+            for b in 0..6 {
+                assert!((rest.tangent[a][b] - d[a][b]).abs() < 1e-9 * E);
+            }
+        }
+        assert!(rest.stress.iter().all(|v| *v == 0.0));
+    }
+
+    /// Uniaxial stress along x at finite strain, from a virgin point to a logarithmic strain ε
+    /// in one increment (the lateral stretch found so σ_yy = 0): the Kirchhoff stress is the
+    /// small-strain curve in the logarithmic strain, τ = σ_y + E_t (ε − σ_y/E), because the
+    /// exponential map integrates a proportional path exactly.
+    #[test]
+    fn finite_uniaxial_matches_the_logarithmic_closed_form() {
+        let (y0, h) = (250.0, 2000.0);
+        let m = bilinear(h, Hardening::Isotropic);
+        let strain: f64 = 0.2;
+        let lam = strain.exp();
+        let sigma = |l: f64| {
+            let f = [[lam, 0.0, 0.0], [0.0, l, 0.0], [0.0, 0.0, l]];
+            let mut u = vec![0.0; HISTORY];
+            let r = finite(&m, &f, &[0.0; HISTORY], &mut u);
+            let j = lam * l * l;
+            (r.stress[0] / j, r.stress[1] / j, u)
+        };
+        // Secant on the lateral stretch.
+        let (mut a, mut b) = (1.0, 0.9);
+        for _ in 0..60 {
+            let (fa, fb) = (sigma(a).1, sigma(b).1);
+            if fb.abs() < 1e-11 || fb == fa {
+                break;
+            }
+            (a, b) = (b, b - fb * (b - a) / (fb - fa));
+        }
+        let (sxx, _, u) = sigma(b);
+        let j = lam * b * b;
+        // In Kirchhoff stress τ = J σ: τ = y0 + E_t (ε − y0/E) along the log strain path.
+        let et = E * h / (E + h);
+        let exact = y0 + et * (strain - y0 / E);
+        assert!((sxx * j - exact).abs() < 1e-8 * exact, "{} vs {exact}", sxx * j);
+        assert!((u[PLASTIC_STRAIN] - (exact - y0) / h).abs() < 1e-10);
+        // The plastic deformation is isochoric: det Cₚ⁻¹ = 1.
+        let cp = plastic_stretch(&u);
+        assert!((crate::dense::det3(&cp) - 1.0).abs() < 1e-12);
+    }
+
+    #[test]
+    fn small_strain_tangent_is_consistent_and_cyclic_kinematic_shows_bauschinger() {
+        let m = bilinear(10_000.0, Hardening::Kinematic);
+        let strain = [3e-3, -1e-3, 5e-4, 2e-3, -1e-3, 7e-4];
+        let mut prior = vec![0.0; HISTORY];
+        small(&m, &[2e-3, -1e-3, -1e-3, 0.0, 0.0, 0.0], None, &[0.0; HISTORY], &mut prior, true).unwrap();
+        for committed in [&[0.0; HISTORY][..], &prior[..]] {
+            let mut scratch = vec![0.0; HISTORY];
+            let r = small(&m, &strain, None, committed, &mut scratch, true).unwrap();
+            let h = 1e-9;
+            for b in 0..6 {
+                let at = |s: f64| {
+                    let mut e = strain;
+                    e[b] += s;
+                    small(&m, &e, None, committed, &mut [0.0; HISTORY], true).unwrap().stress
+                };
+                let (p, q) = (at(h), at(-h));
+                for a in 0..6 {
+                    let numeric = (p[a] - q[a]) / (2.0 * h);
+                    assert!((numeric - r.tangent[a][b]).abs() < 1e-5 * E, "{a} {b}: {numeric} vs {}", r.tangent[a][b]);
+                }
+            }
+        }
+        // Kinematic hardening is refused at finite strain, named.
+        assert!(matches!(finite_isochoric(&m, &IDENTITY, None, &[0.0; HISTORY], &mut [0.0; HISTORY]), Err(Error::NotSupported(_))));
+    }
+
+    #[test]
+    fn softening_steeper_than_3g_has_no_tangent() {
+        let g = E / (2.0 * (1.0 + NU));
+        let points = vec![HardeningPoint { strain: 0.0, stress: 250.0 }, HardeningPoint { strain: 1e-4, stress: 250.0 - 4.0 * g * 1e-4 }];
+        let m = j2(Plastic::Table { points });
+        let r = small(&m, &[5e-3, -2.5e-3, -2.5e-3, 0.0, 0.0, 0.0], None, &[0.0; HISTORY], &mut [0.0; HISTORY], true);
+        assert!(matches!(r, Err(Error::Degenerate(_))), "{r:?}");
+    }
+}

crates/fem/src/element.rs

@@ -35,7 +35,7 @@
 use fieldcraft_model::ElementKind;
 
 use crate::basis::Basis;
-use crate::dense::{Cholesky, Matrix, inverse3, positive_inverse};
+use crate::dense::{Cholesky, Matrix, positive_inverse};
 use crate::dof::{DofSet, ElementDofs, Internal};
 use crate::material::{Elasticity, stress};
 use crate::quadrature::{Point, Rule};
@@ -356,7 +356,7 @@ impl<'a> Solid<'a> {
 
     fn centre_jacobian(&self) -> Result<([[f64; 3]; 3], f64)> {
         let s = (self.ty.shape)([0.0; 3]);
-        inverse3(&self.jacobian(&s)).filter(|(_, d)| *d > 0.0).ok_or_else(|| self.degenerate())
+        positive_inverse(&self.jacobian(&s)).ok_or_else(|| self.degenerate())
     }
 
     /// The parts of the stiffness with the incompatible modes: K_uu (when `with_uu`), K_ua

crates/fem/src/face.rs

@@ -21,6 +21,113 @@ pub fn pressure(xyz: &[[f64; 3]], magnitude: f64) -> Result<Vec<[f64; 3]>> {
     Ok(normal_weights(xyz)?.into_iter().map(|w| w.map(|c| -magnitude * c)).collect())
 }
 
+/// A pressure that follows the deformed face (positive pushes in): the nodal forces
+/// fᵢ = −p ∫ Nᵢ (x,ξ × x,η) dξ dη on the current positions x = X + u (reference coordinates `xyz`,
+/// displacements `u`, in the face's node order), and the load stiffness K = −∂f/∂u, 3n × 3n
+/// row-major, from Δ(x,ξ × x,η) = [x,ξ]× Δx,η − [x,η]× Δx,ξ:
+/// K_ab = p ∫ N_a (N_b,η [x,ξ]× − N_b,ξ [x,η]×) dξ dη (K. Schweizerhof, E. Ramm, *Displacement
+/// dependent pressure loads in nonlinear finite element analyses*, Comput. Struct.
+/// 18(6):1099–1114, 1984). K is not symmetric on its own; over a closed surface, or one whose
+/// boundary is held, the assembled skew parts cancel. Same rule as [`pressure`], so at u = 0 the
+/// forces are its forces.
+pub fn follower_pressure(xyz: &[[f64; 3]], u: &[[f64; 3]], magnitude: f64) -> Result<(Vec<[f64; 3]>, Vec<f64>)> {
+    let n = xyz.len();
+    if u.len() != n {
+        return Err(Error::Invalid(format!("{} displacements for a {n}-node face", u.len())));
+    }
+    let x: Vec<[f64; 3]> = xyz.iter().zip(u).map(|(a, b)| [a[0] + b[0], a[1] + b[1], a[2] + b[2]]).collect();
+    if x.iter().flatten().any(|c| !c.is_finite()) || !magnitude.is_finite() {
+        return Err(Error::Invalid("face positions and pressure must be finite".into()));
+    }
+    let points = fieldcraft_model::nodal::face_points(n).map_err(|e| Error::Invalid(e.to_string()))?;
+    let mut f = vec![[0.0; 3]; n];
+    let mut k = vec![0.0; 9 * n * n];
+    for q in &points {
+        let (mut tx, mut te) = ([0.0; 3], [0.0; 3]);
+        for ((p, dx), de) in x.iter().zip(&q.dxi).zip(&q.deta) {
+            for c in 0..3 {
+                tx[c] += dx * p[c];
+                te[c] += de * p[c];
+            }
+        }
+        let normal = [tx[1] * te[2] - tx[2] * te[1], tx[2] * te[0] - tx[0] * te[2], tx[0] * te[1] - tx[1] * te[0]];
+        let (sx, se) = (crate::rotation::skew(&tx), crate::rotation::skew(&te));
+        for (a, na) in q.n.iter().enumerate() {
+            if let Some(fa) = f.get_mut(a) {
+                for c in 0..3 {
+                    fa[c] -= magnitude * q.weight * na * normal[c];
+                }
+            }
+            for (b, (db_xi, db_eta)) in q.dxi.iter().zip(&q.deta).enumerate() {
+                for r in 0..3 {
+                    for c in 0..3 {
+                        let v = magnitude * q.weight * na * (db_eta * sx[r][c] - db_xi * se[r][c]);
+                        if let Some(e) = k.get_mut((3 * a + r) * 3 * n + 3 * b + c) {
+                            *e += v;
+                        }
+                    }
+                }
+            }
+        }
+    }
+    Ok((f, k))
+}
+
+/// A pressure that follows a deformed edge of a 2D element (positive pushes into a
+/// counter-clockwise element): the nodal forces (x, y) fᵢ = −p ∫ Nᵢ e (t_y, −t_x) ds on the
+/// current positions, with t the tangent and e the out-of-plane extent (a thickness, or 2π r at
+/// the current radius when revolved), and the load stiffness K = −∂f/∂u, 2n × 2n row-major (the
+/// revolved extent depends on the radial motion too).
+pub fn follower_edge_pressure(
+    xyz: &[[f64; 3]],
+    u: &[[f64; 2]],
+    extent: fieldcraft_model::Extent,
+    magnitude: f64,
+) -> Result<(Vec<[f64; 2]>, Vec<f64>)> {
+    let n = xyz.len();
+    if u.len() != n {
+        return Err(Error::Invalid(format!("{} displacements for a {n}-node edge", u.len())));
+    }
+    let x: Vec<[f64; 2]> = xyz.iter().zip(u).map(|(a, b)| [a[0] + b[0], a[1] + b[1]]).collect();
+    if x.iter().flatten().any(|c| !c.is_finite()) || !magnitude.is_finite() {
+        return Err(Error::Invalid("edge positions and pressure must be finite".into()));
+    }
+    let revolved = matches!(extent, fieldcraft_model::Extent::Revolved);
+    let points = fieldcraft_model::nodal::edge_points(n).map_err(|e| Error::Invalid(e.to_string()))?;
+    let mut f = vec![[0.0; 2]; n];
+    let mut k = vec![0.0; 4 * n * n];
+    let two_pi = 2.0 * std::f64::consts::PI;
+    for q in &points {
+        let (mut t, mut pos) = ([0.0; 2], [0.0; 2]);
+        for ((p, dn), ni) in x.iter().zip(&q.dxi).zip(&q.n) {
+            for c in 0..2 {
+                t[c] += dn * p[c];
+                pos[c] += ni * p[c];
+            }
+        }
+        let e = extent.at([pos[0], pos[1], 0.0]);
+        let w = magnitude * q.weight;
+        for (a, na) in q.n.iter().enumerate() {
+            if let Some(fa) = f.get_mut(a) {
+                fa[0] -= w * na * e * t[1];
+                fa[1] += w * na * e * t[0];
+            }
+            for (b, (nb, db)) in q.n.iter().zip(&q.dxi).enumerate() {
+                // ∂e/∂u_b (radial) = 2π N_b when revolved.
+                let de = if revolved { two_pi * nb } else { 0.0 };
+                // K = −∂f/∂u.
+                let entries = [(0, 0, w * na * de * t[1]), (0, 1, w * na * e * db), (1, 0, -w * na * (e * db + de * t[0])), (1, 1, 0.0)];
+                for (r, c, v) in entries {
+                    if let Some(x) = k.get_mut((2 * a + r) * 2 * n + 2 * b + c) {
+                        *x += v;
+                    }
+                }
+            }
+        }
+    }
+    Ok((f, k))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -57,6 +164,51 @@ mod tests {
         assert!(pressure(&tri[..2], 1.0).is_err());
     }
 
+    /// Central differences of the follower forces against the load stiffness, on a distorted
+    /// quadratic face and a revolved quadratic edge; at u = 0 the forces are the dead ones.
+    #[test]
+    fn follower_pressure_stiffness_is_the_derivative_of_its_forces() {
+        let face = [[0., 0., 0.], [2., 0., 0.1], [2.2, 3., 0.], [0., 3., -0.2], [1., -0.1, 0.], [2.1, 1.5, 0.], [1., 3.1, 0.1], [0.1, 1.5, 0.]];
+        let u: Vec<[f64; 3]> = (0..8).map(|i| [0.1 * (i as f64).sin(), 0.05 * (i as f64).cos(), 0.2 * ((i * i) as f64).sin()]).collect();
+        let (f0, _) = follower_pressure(&face, &[[0.0; 3]; 8], 3.0).unwrap();
+        let dead = pressure(&face, 3.0).unwrap();
+        assert!(f0.iter().flatten().zip(dead.iter().flatten()).all(|(a, b)| (a - b).abs() < 1e-13), "{f0:?}");
+        let (_, k) = follower_pressure(&face, &u, 3.0).unwrap();
+        let h = 1e-6;
+        for j in 0..24 {
+            let shifted = |s: f64| {
+                let mut v = u.clone();
+                v[j / 3][j % 3] += s;
+                follower_pressure(&face, &v, 3.0).unwrap().0
+            };
+            let (p, m) = (shifted(h), shifted(-h));
+            for i in 0..24 {
+                let numeric = -(p[i / 3][i % 3] - m[i / 3][i % 3]) / (2.0 * h);
+                assert!((numeric - k[i * 24 + j]).abs() < 1e-7, "{i} {j}: {numeric} vs {}", k[i * 24 + j]);
+            }
+        }
+        let edge = [[1.0, 0.0, 0.0], [1.5, 2.0, 0.0], [1.3, 1.0, 0.0]];
+        let ue = [[0.1, 0.05], [-0.2, 0.1], [0.05, -0.03]];
+        for extent in [fieldcraft_model::Extent::Revolved, fieldcraft_model::Extent::Thickness(2.0)] {
+            let (f0, _) = follower_edge_pressure(&edge, &[[0.0; 2]; 3], extent, 2.0).unwrap();
+            let dead = fieldcraft_model::nodal::edge_pressure(&edge, extent, 2.0).unwrap();
+            assert!(f0.iter().zip(&dead).all(|(a, b)| (a[0] - b[0]).abs() < 1e-12 && (a[1] - b[1]).abs() < 1e-12));
+            let (_, k) = follower_edge_pressure(&edge, &ue, extent, 2.0).unwrap();
+            for j in 0..6 {
+                let shifted = |s: f64| {
+                    let mut v = ue;
+                    v[j / 2][j % 2] += s;
+                    follower_edge_pressure(&edge, &v, extent, 2.0).unwrap().0
+                };
+                let (p, m) = (shifted(h), shifted(-h));
+                for i in 0..6 {
+                    let numeric = -(p[i / 2][i % 2] - m[i / 2][i % 2]) / (2.0 * h);
+                    assert!((numeric - k[i * 6 + j]).abs() < 1e-7, "{extent:?} {i} {j}: {numeric} vs {}", k[i * 6 + j]);
+                }
+            }
+        }
+    }
+
     #[test]
     fn pressure_on_a_curved_face_sums_to_the_projected_area() {
         // A quadratic face on a quarter cylinder r = 2, z in 0..1, normal outward: the total

crates/fem/src/finite.rs

@@ -0,0 +1,961 @@
+//! Solid and 2D elements of nonlinear steps: total Lagrangian (finite strain) or with small
+//! strain and an inelastic material; internal forces and the consistent tangent stiffness for
+//! nodal displacements u, and the Cauchy stress and the strain at the integration points.
+//!
+//! **Formulation.** Total Lagrangian: the integrals run over the reference (undeformed) element
+//! with its own quadrature, F = I + Σ u_a ⊗ ∇₀N_a at each point, and the material returns the
+//! Kirchhoff stress τ and its spatial tangent c ([`crate::constitutive`]). With the shape
+//! function gradients of the current configuration ∇ₓN_a = F⁻ᵀ ∇₀N_a,
+//! - internal forces f_a = ∫ Bₓ,aᵀ τ dV₀,
+//! - tangent K_ab = ∫ (Bₓ,aᵀ c Bₓ,b + (∇ₓN_a · τ ∇ₓN_b) I) dV₀ (material plus geometric, or
+//!   initial-stress, stiffness),
+//!
+//! with Bₓ the small-strain operator of the current gradients. This is the push-forward of the
+//! textbook ∫ B₀ᵀ S dV₀ and ∫ (B₀ᵀ C B₀ + ∇₀N·S∇₀N I) dV₀, identical term by term (Bonet & Wood
+//! 2008, §9.2–9.4; K.-J. Bathe, *Finite Element Procedures*, 2nd ed. 2014, §6.3). A rigid motion
+//! leaves τ at zero exactly, whatever its size.
+//!
+//! **Hybrid (mixed u–p) solids** with a decoupled material W = W̄(C̄) + U(J): the three-field
+//! formulation of J. C. Simo, R. L. Taylor, K. S. Pister, *Variational and projection methods
+//! for the volume constraint in finite deformation elasto-plasticity*, CMAME 51:177–208, 1985,
+//! with the element's discontinuous pressure functions N_p (the linear hybrid elements' fields,
+//! [`crate::hybrid`]): the dilatation θ = N_p·θ̂ is the projection of J, M θ̂ = ∫ N_p J dV₀ with
+//! M = ∫ N_p N_pᵀ dV₀; the pressure p = N_p·p̂ the projection of U′(θ), M p̂ = ∫ N_p U′(θ) dV₀.
+//! Then τ = τ_iso(F) + J p I, and with G = ∫ N_p J (∇ₓN)ᵀ dV₀ and H = ∫ N_p U″(θ) N_pᵀ dV₀,
+//! K = ∫ (Bₓᵀ c* Bₓ + ∇ₓN·τ∇ₓN I) dV₀ + Gᵀ M⁻¹ H M⁻¹ G with c* = c_iso + J p (I ⊗ I − 2𝕀),
+//! symmetric; at u = 0 it is the linear hybrid stiffness K_dev + κ G M⁻¹ Gᵀ. The constant
+//! pressure case is the mean dilatation method of J. C. Nagtegaal, D. M. Parks, J. R. Rice
+//! (CMAME 4:153–177, 1974) at finite strain. St Venant–Kirchhoff has no such split, so hybrid
+//! elements of an elastic material are refused in nonlinear steps; J2 plasticity has it exactly
+//! (the return is deviatoric, the volume Hencky's K/2 (ln J)², [`crate::elastoplastic`]).
+//!
+//! **Thermal strain** ([`Temperature`]): at finite strain the multiplicative split F = F_m F_θ
+//! with the thermal stretches F_θ = diag(1 + αᵢ (T − T_ref)) at each point (T interpolated from
+//! the nodes; V. A. Lubarda, *Constitutive theories based on the multiplicative decomposition of
+//! deformation gradient: thermoelasticity, elastoplasticity, and biomechanics*, Appl. Mech. Rev.
+//! 57(2):95–108, 2004): the material sees
+//! F_m, the stress per reference volume is J_θ τ_m(F_m), and since F_θ is fixed over an
+//! iteration the spatial tangent is J_θ c_m, so the loops run unchanged on the thermally
+//! expanded volume J_θ dV₀ (the mixed elements project det F_m on it). The linear stretch
+//! 1 + α ΔT is the engineering definition of α, so a free body grows by exactly α ΔT. At small
+//! strain the split is additive, ε_m = ε − α ΔT. Reported strains are the total ones.
+//!
+//! **Small strain** ([`Kinematics::Small`], a step without nonlinear geometry with an inelastic
+//! material): the same loops on the linear kinematics, ε = sym ∇u with the reference gradients,
+//! f = ∫ Bᵀ σ dV₀ and K = ∫ Bᵀ 𝔻 B dV₀ with the material's consistent tangent 𝔻, and no
+//! geometric stiffness. Mixed elements project the dilatation 1 + tr ε and the pressure K tr ε
+//! the same way, which is the linear hybrid element of [`crate::hybrid`] while the material is
+//! elastic.
+//!
+//! **2D elements**: plane strain (F₃₃ = 1) and axisymmetric (F₃₃ = r/R, the hoop stretch, with
+//! the hoop column N/r of the current radius in Bₓ and a geometric term τ_θθ N_a N_b / r² on the
+//! radial motion; Bonet & Wood 2008, §9.5). Plane stress (whose thickness change needs a local
+//! iteration for σ_zz = 0) is refused.
+//!
+//! **Incompatible modes** (hex8, quad4) are refused in nonlinear steps: their finite-strain form
+//! (enhanced assumed strain, J. C. Simo, F. Armero, IJNME 33:1413–1449, 1992) needs the internal
+//! modes as element unknowns carried between iterations, and it develops spurious hourglass
+//! modes in large compression (P. Wriggers, S. Reese, CMAME 135:201–209, 1996), which want a
+//! stabilised variant of their own. With small strain they are refused for inelastic materials
+//! too: their internal modes would carry the plastic history between iterations.
+
+use crate::constitutive::{MaterialModel, Response, add_pressure, logarithmic_strain};
+use crate::dense::{Cholesky, Matrix, inverse3};
+use crate::element::{Formulation, PointStress, Solid, accumulate_symmetric, b_block};
+use crate::hybrid::pressure_basis;
+use crate::plane::{Plane, Theory};
+use crate::rotation::{IDENTITY, Mat3};
+use crate::{Error, Result};
+
+/// Internal forces (element degrees of freedom, node by node) and, when asked for, the tangent.
+#[derive(Debug, Clone, PartialEq)]
+pub struct Finite {
+    pub force: Vec<f64>,
+    pub tangent: Option<Matrix>,
+}
+
+/// The kinematics of an evaluation.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Kinematics {
+    /// Total Lagrangian, large displacements, rotations and strains.
+    Finite,
+    /// Small displacements and strains (ε = sym ∇u, the reference gradients, no geometric
+    /// stiffness): only the material is nonlinear.
+    Small,
+}
+
+/// The temperatures of an element in a nonlinear step: the linear expansion coefficients along
+/// X, Y, Z (zero for a material that does not expand), the reference temperature at which the
+/// thermal strain is zero, and the temperature at each node.
+#[derive(Debug, Clone, PartialEq)]
+pub struct Temperature {
+    pub alpha: [f64; 3],
+    pub reference: f64,
+    pub nodal: Vec<f64>,
+}
+
+impl Temperature {
+    fn check(&self, nodes: usize) -> Result<()> {
+        if self.nodal.len() != nodes {
+            return Err(Error::Invalid(format!("{} temperatures for a {nodes}-node element", self.nodal.len())));
+        }
+        if self.alpha.iter().chain(&self.nodal).chain([&self.reference]).any(|v| !v.is_finite()) {
+            return Err(Error::Invalid("temperatures and expansion coefficients must be finite".into()));
+        }
+        Ok(())
+    }
+}
+
+/// The temperature at a point and its thermal stretches ϑᵢ = 1 + αᵢ (T − T_ref).
+#[derive(Debug, Clone, Copy)]
+struct Heat {
+    temperature: Option<f64>,
+    stretch: [f64; 3],
+}
+
+impl Heat {
+    /// At a point of shape function values `n`.
+    fn at(t: Option<&Temperature>, n: &[f64]) -> Result<Heat> {
+        let Some(t) = t else { return Ok(Heat { temperature: None, stretch: [1.0; 3] }) };
+        let temperature: f64 = t.nodal.iter().zip(n).map(|(a, b)| a * b).sum();
+        let stretch = t.alpha.map(|a| 1.0 + a * (temperature - t.reference));
+        if !stretch.iter().all(|v| *v > 0.0 && v.is_finite()) {
+            return Err(Error::Degenerate(format!("the thermal stretches {stretch:?} at T = {temperature} are not positive")));
+        }
+        Ok(Heat { temperature: Some(temperature), stretch })
+    }
+
+    /// J_θ = ϑ₁ ϑ₂ ϑ₃.
+    fn volume(&self) -> f64 {
+        self.stretch.iter().product()
+    }
+
+    /// The mechanical part F_m = F F_θ⁻¹ of a deformation gradient.
+    fn mechanical(&self, f: &Mat3) -> Mat3 {
+        std::array::from_fn(|i| std::array::from_fn(|j| f[i][j] / self.stretch[j]))
+    }
+
+    /// The mechanical part ε − α (T − T_ref) of a small strain.
+    fn mechanical_strain(&self, e: &[f64; 6]) -> [f64; 6] {
+        std::array::from_fn(|k| if k < 3 { e[k] - (self.stretch[k] - 1.0) } else { e[k] })
+    }
+}
+
+/// What one integration point gives the element.
+struct PointKinematics {
+    /// The point's share of the reference volume (of the thermally expanded volume J_θ dV₀ at
+    /// finite strain).
+    weight: f64,
+    /// The deformation gradient, and its mechanical part F_m = F F_θ⁻¹ the material sees.
+    total: Mat3,
+    f: Mat3,
+    /// det F_m, or the dilatation 1 + tr ε_m of small strain (what a mixed element projects).
+    j: f64,
+    /// The mechanical small strain ε − ε_th (engineering shears); zero at finite strain.
+    strain: [f64; 6],
+    temperature: Option<f64>,
+    /// ∇ₓN of every node (∇₀N at small strain).
+    gradients: Vec<[f64; 3]>,
+    /// Reference position.
+    x0: [f64; 3],
+}
+
+/// The checked history slice of one integration point.
+fn point_history(history: &[f64], len: usize, point: usize) -> &[f64] {
+    history.get(point * len..(point + 1) * len).unwrap_or_default()
+}
+
+/// The small strain of a displacement gradient F − I (engineering shears).
+fn small_strain(f: &Mat3) -> [f64; 6] {
+    [f[0][0] - 1.0, f[1][1] - 1.0, f[2][2] - 1.0, f[0][1] + f[1][0], f[0][2] + f[2][0], f[1][2] + f[2][1]]
+}
+
+/// The response of one point's material with its history slices.
+fn point_response(m: &MaterialModel, kin: Kinematics, p: &PointKinematics, committed: &[f64], updated: &mut [f64]) -> Result<Response> {
+    match kin {
+        Kinematics::Finite => m.response(&p.f, p.temperature, committed, updated),
+        Kinematics::Small => m.small_strain(&p.strain, p.temperature, committed, updated, true),
+    }
+}
+
+/// Add f_a += w Bₓ,aᵀ τ and, with `k`, the material tangent and (with `geometric`) the
+/// geometric one.
+fn add_point(force: &mut [f64], k: Option<&mut Matrix>, gradients: &[[f64; 3]], r: &Response, w: f64, geometric: bool) {
+    for (a, g) in gradients.iter().enumerate() {
+        let b = b_block(g);
+        for c in 0..3 {
+            if let Some(x) = force.get_mut(3 * a + c) {
+                *x += w * (0..6).map(|s| b[s][c] * r.stress[s]).sum::<f64>();
+            }
+        }
+    }
+    let Some(k) = k else { return };
+    accumulate_symmetric(&mut k.data, gradients, &r.tangent, w);
+    if !geometric {
+        return;
+    }
+    let tau = crate::rotation::tensor(&r.stress);
+    let n = k.n;
+    for (a, ga) in gradients.iter().enumerate() {
+        let tg: [f64; 3] = std::array::from_fn(|i| (0..3).map(|jj| tau[i][jj] * ga[jj]).sum());
+        for (b, gb) in gradients.iter().enumerate() {
+            let s = w * (tg[0] * gb[0] + tg[1] * gb[1] + tg[2] * gb[2]);
+            for c in 0..3 {
+                if let Some(x) = k.data.get_mut((3 * a + c) * n + 3 * b + c) {
+                    *x += s;
+                }
+            }
+        }
+    }
+}
+
+fn inverted(kind: &str, j: f64) -> Error {
+    Error::Degenerate(format!("a {kind} element is inverted at an integration point (J = det F = {j:.3e})"))
+}
+
+/// One displacement vector per node, all finite.
+fn check_displacements<const N: usize>(u: &[[f64; N]], nodes: usize) -> Result<()> {
+    if u.len() != nodes {
+        return Err(Error::Invalid(format!("{} displacements for a {nodes}-node element", u.len())));
+    }
+    if u.iter().flatten().any(|v| !v.is_finite()) {
+        return Err(Error::Invalid("displacements must be finite".into()));
+    }
+    Ok(())
+}
+
+/// Check the element's history slices against the material and its points.
+fn check_history(m: &MaterialModel, points: usize, committed: &[f64], updated: &[f64]) -> Result<usize> {
+    let len = m.history_len();
+    if committed.len() != points * len || updated.len() != points * len {
+        return Err(Error::Invalid(format!("{} history values for {points} points of {len}", committed.len())));
+    }
+    Ok(len)
+}
+
+impl Solid<'_> {
+    /// Refuse what has no form here.
+    fn check_nonlinear(&self, m: &MaterialModel, u: &[[f64; 3]], kin: Kinematics) -> Result<()> {
+        check_displacements(u, self.ty.nodes)?;
+        match self.formulation {
+            Formulation::IncompatibleModes => {
+                let why = match kin {
+                    Kinematics::Finite => "in nonlinear steps (their finite-strain form, enhanced assumed strain, is not implemented",
+                    Kinematics::Small => "with an inelastic material (their internal modes would carry the plastic history",
+                };
+                Err(Error::NotSupported(format!("{} incompatible modes {why}; use full integration, hybrid or hex20)", self.ty.kind.name())))
+            }
+            Formulation::Hybrid { .. } if !m.is_decoupled() => Err(Error::NotSupported(format!(
+                "hybrid elements of a {} material in nonlinear steps (the mixed formulation needs a volumetric–isochoric split of the strain energy; give the material the neo-Hookean option)",
+                m.name()
+            ))),
+            _ => Ok(()),
+        }
+    }
+
+    /// F, J and the gradients at every stiffness point: the current ones at finite strain, the
+    /// reference ones at small strain.
+    fn kinematics(&self, u: &[[f64; 3]], kin: Kinematics, thermal: Option<&Temperature>) -> Result<Vec<PointKinematics>> {
+        let n = self.ty.nodes;
+        if let Some(t) = thermal {
+            t.check(n)?;
+        }
+        let mut out = Vec::new();
+        for p in self.rule().points() {
+            let g = self.gradients(p.xi)?;
+            let reference = g.dx.get(..n).unwrap_or_default();
+            let total = crate::constitutive::deformation_gradient(u, reference);
+            let (weight, x0) = (g.det * p.weight, self.position_of(g.shape.values()));
+            let heat = Heat::at(thermal, g.shape.values())?;
+            if kin == Kinematics::Small {
+                let strain = heat.mechanical_strain(&small_strain(&total));
+                let j = 1.0 + strain[0] + strain[1] + strain[2];
+                let gradients = reference.to_vec();
+                out.push(PointKinematics { weight, total, f: total, j, strain, temperature: heat.temperature, gradients, x0 });
+                continue;
+            }
+            let (inv, det) = inverse3(&total).ok_or_else(|| inverted(self.ty.kind.name(), 0.0))?;
+            let j = det / heat.volume();
+            if !(det > 0.0 && j.is_finite()) {
+                return Err(inverted(self.ty.kind.name(), det));
+            }
+            let gradients = reference.iter().map(|d| std::array::from_fn(|i| (0..3).map(|jj| d[jj] * inv[jj][i]).sum())).collect();
+            let f = heat.mechanical(&total);
+            out.push(PointKinematics { weight: weight * heat.volume(), total, f, j, strain: [0.0; 6], temperature: heat.temperature, gradients, x0 });
+        }
+        Ok(out)
+    }
+
+    /// The effective response (Kirchhoff stress and tangent, or the stress of small strain) at
+    /// every point, the forces, and the tangent when `tangent`.
+    #[allow(clippy::too_many_arguments)]
+    fn nonlinear_points(
+        &self,
+        m: &MaterialModel,
+        u: &[[f64; 3]],
+        kin: Kinematics,
+        thermal: Option<&Temperature>,
+        committed: &[f64],
+        updated: &mut [f64],
+        tangent: bool,
+    ) -> Result<(Finite, Vec<(PointKinematics, Response)>)> {
+        self.check_nonlinear(m, u, kin)?;
+        let points = self.kinematics(u, kin, thermal)?;
+        let len = check_history(m, points.len(), committed, updated)?;
+        let ndof = 3 * self.ty.nodes;
+        let mut force = vec![0.0; ndof];
+        let mut k = tangent.then(|| Matrix::zeros(ndof));
+        let responses: Vec<Response> = if let Formulation::Hybrid { .. } = self.formulation {
+            self.mixed_responses(m, &points, kin, committed, updated, k.as_mut())?
+        } else {
+            let mut out = Vec::with_capacity(points.len());
+            for (i, p) in points.iter().enumerate() {
+                let updated_point = updated.get_mut(i * len..(i + 1) * len).unwrap_or_default();
+                out.push(point_response(m, kin, p, point_history(committed, len, i), updated_point)?);
+            }
+            out
+        };
+        for (p, r) in points.iter().zip(&responses) {
+            add_point(&mut force, k.as_mut(), &p.gradients, r, p.weight, kin == Kinematics::Finite);
+        }
+        Ok((Finite { force, tangent: k }, points.into_iter().zip(responses).collect()))
+    }
+
+    /// The three-field mixed responses τ_iso + J p I with their tangents (small strain:
+    /// s + p I), and the dilatation stiffness Gᵀ M⁻¹ H M⁻¹ G added to `k`.
+    fn mixed_responses(
+        &self,
+        m: &MaterialModel,
+        points: &[PointKinematics],
+        kin: Kinematics,
+        committed: &[f64],
+        updated: &mut [f64],
+        k: Option<&mut Matrix>,
+    ) -> Result<Vec<Response>> {
+        let small = kin == Kinematics::Small;
+        let len = m.history_len();
+        let (np, frame) = (self.np(), self.frame());
+        let basis: Vec<[f64; 4]> = points.iter().map(|p| pressure_basis(np, p.x0, &frame)).collect();
+        let mut mm = Matrix::zeros(np);
+        let mut theta = vec![0.0; np];
+        for (p, nb) in points.iter().zip(&basis) {
+            for a in 0..np {
+                theta[a] += p.weight * nb[a] * p.j;
+                for b in 0..np {
+                    mm.add(a, b, p.weight * nb[a] * nb[b]);
+                }
+            }
+        }
+        let chol = Cholesky::new(&mm)?;
+        chol.solve(&mut theta);
+        let mut pressure = vec![0.0; np];
+        let mut h = Matrix::zeros(np);
+        for (p, nb) in points.iter().zip(&basis) {
+            let th: f64 = (0..np).map(|a| nb[a] * theta[a]).sum();
+            if !(th > 0.0 && th.is_finite()) {
+                return Err(inverted(self.ty.kind.name(), th));
+            }
+            let (dp, ddp) = m.volumetric(th, small).ok_or_else(|| Error::Invalid("volumetric response".into()))?;
+            for a in 0..np {
+                pressure[a] += p.weight * nb[a] * dp;
+                for b in 0..np {
+                    h.add(a, b, p.weight * ddp * nb[a] * nb[b]);
+                }
+            }
+        }
+        chol.solve(&mut pressure);
+        let mut out = Vec::with_capacity(points.len());
+        for (i, (p, nb)) in points.iter().zip(&basis).enumerate() {
+            let pr: f64 = (0..np).map(|a| nb[a] * pressure[a]).sum();
+            let (c, u) = (point_history(committed, len, i), updated.get_mut(i * len..(i + 1) * len).unwrap_or_default());
+            out.push(if small {
+                let mut r = m.small_strain(&p.strain, p.temperature, c, u, false)?;
+                r.stress.iter_mut().take(3).for_each(|s| *s += pr);
+                r
+            } else {
+                add_pressure(&m.isochoric(&p.f, p.temperature, c, u)?, p.j, pr, 0.0)
+            });
+        }
+        if let Some(k) = k {
+            // A = M⁻¹ G, np × ndof; K += Aᵀ H A. At small strain G = ∫ N_p ∇₀N dV₀.
+            let ndof = k.n;
+            let mut a_cols = vec![vec![0.0; np]; ndof];
+            for (p, nb) in points.iter().zip(&basis) {
+                let jw = p.weight * if small { 1.0 } else { p.j };
+                for (node, g) in p.gradients.iter().enumerate() {
+                    for c in 0..3 {
+                        if let Some(col) = a_cols.get_mut(3 * node + c) {
+                            for (x, n) in col.iter_mut().zip(nb) {
+                                *x += jw * n * g[c];
+                            }
+                        }
+                    }
+                }
+            }
+            for col in &mut a_cols {
+                chol.solve(col);
+            }
+            let ha: Vec<Vec<f64>> = a_cols.iter().map(|col| h.mul_vec(col)).collect();
+            for i in 0..ndof {
+                for jj in i..ndof {
+                    let v: f64 = a_cols.get(i).zip(ha.get(jj)).map_or(0.0, |(x, y)| x.iter().zip(y).map(|(p, q)| p * q).sum());
+                    k.add(i, jj, v);
+                    if i != jj {
+                        k.add(jj, i, v);
+                    }
+                }
+            }
+        }
+        Ok(out)
+    }
+
+    /// Internal forces and (with `tangent`) the tangent stiffness at nodal displacements `u`,
+    /// with the material history `committed` at the start of the increment (points × the
+    /// material's history length) written, updated, to `updated`.
+    pub fn finite_strain(&self, m: &MaterialModel, u: &[[f64; 3]], committed: &[f64], updated: &mut [f64], tangent: bool) -> Result<Finite> {
+        Ok(self.nonlinear_points(m, u, Kinematics::Finite, None, committed, updated, tangent)?.0)
+    }
+
+    /// As [`Self::finite_strain`] with either kinematics and the element's temperatures when
+    /// it has some; with small strain an inelastic material on the linear kinematics,
+    /// f = ∫ Bᵀ σ dV and K = ∫ Bᵀ 𝔻 B dV with the material's consistent tangent 𝔻.
+    #[allow(clippy::too_many_arguments)]
+    pub fn nonlinear(
+        &self,
+        m: &MaterialModel,
+        u: &[[f64; 3]],
+        kin: Kinematics,
+        thermal: Option<&Temperature>,
+        committed: &[f64],
+        updated: &mut [f64],
+        tangent: bool,
+    ) -> Result<Finite> {
+        Ok(self.nonlinear_points(m, u, kin, thermal, committed, updated, tangent)?.0)
+    }
+
+    /// The Cauchy stress and the total strain (logarithmic at finite strain, ε at small strain)
+    /// at every integration point (at its reference position).
+    pub fn nonlinear_stresses(
+        &self,
+        m: &MaterialModel,
+        u: &[[f64; 3]],
+        kin: Kinematics,
+        thermal: Option<&Temperature>,
+        committed: &[f64],
+    ) -> Result<Vec<PointStress>> {
+        let mut scratch = committed.to_vec();
+        let (_, points) = self.nonlinear_points(m, u, kin, thermal, committed, &mut scratch, false)?;
+        points
+            .iter()
+            .map(|(p, r)| {
+                if kin == Kinematics::Small {
+                    return Ok(PointStress { xyz: p.x0, strain: small_strain(&p.total), stress: r.stress });
+                }
+                let strain = logarithmic_strain(&p.total).ok_or_else(|| inverted(self.ty.kind.name(), p.j))?;
+                Ok(PointStress { xyz: p.x0, strain, stress: r.stress.map(|v| v / p.j) })
+            })
+            .collect()
+    }
+}
+
+/// One integration point of a 2D element in a nonlinear step: the total deformation gradient,
+/// det F_m, the reference position and the response.
+struct PlanePoint {
+    f: Mat3,
+    j: f64,
+    x: [f64; 3],
+    response: Response,
+}
+
+impl Plane<'_> {
+    fn check_nonlinear(&self, u: &[[f64; 2]], kin: Kinematics) -> Result<()> {
+        check_displacements(u, self.ty.nodes)?;
+        if let Theory::PlaneStress { .. } = self.theory {
+            let why = match kin {
+                Kinematics::Finite => "the thickness change needs a local iteration",
+                Kinematics::Small => "σ_zz = 0 needs a local iteration of the inelastic material",
+            };
+            return Err(Error::NotSupported(format!(
+                "plane stress elements in nonlinear steps ({why}; use plane strain, axisymmetric or solid elements)"
+            )));
+        }
+        if self.formulation == Formulation::IncompatibleModes {
+            return Err(Error::NotSupported(format!(
+                "2D {} incompatible modes in nonlinear steps (their finite-strain form, enhanced assumed strain, is not implemented; use full integration or quad8)",
+                self.ty.kind.name()
+            )));
+        }
+        Ok(())
+    }
+
+    /// Per point: F, J, the reference position, the small strain and the response; the forces
+    /// and the tangent.
+    #[allow(clippy::too_many_arguments)]
+    fn nonlinear_points(
+        &self,
+        m: &MaterialModel,
+        u: &[[f64; 2]],
+        kin: Kinematics,
+        thermal: Option<&Temperature>,
+        committed: &[f64],
+        updated: &mut [f64],
+        tangent: bool,
+    ) -> Result<(Finite, Vec<PlanePoint>)> {
+        self.check_nonlinear(u, kin)?;
+        let n = self.ty.nodes;
+        if let Some(t) = thermal {
+            t.check(n)?;
+        }
+        let rule = self.rule().points();
+        let len = check_history(m, rule.len(), committed, updated)?;
+        let ndof = 2 * n;
+        let mut force = vec![0.0; ndof];
+        let mut k = tangent.then(|| Matrix::zeros(ndof));
+        let axisymmetric = self.theory == Theory::Axisymmetric;
+        let small = kin == Kinematics::Small;
+        let mut out = Vec::with_capacity(rule.len());
+        for (i, p) in rule.iter().enumerate() {
+            let at = self.at(p)?;
+            let cols = at.g.get(..n).unwrap_or_default();
+            let mut f = IDENTITY;
+            for (ua, g) in u.iter().zip(cols) {
+                for r in 0..2 {
+                    for c in 0..2 {
+                        f[r][c] += ua[r] * g[c];
+                    }
+                }
+                if axisymmetric {
+                    f[2][2] += ua[0] * g[2];
+                }
+            }
+            let updated_point = updated.get_mut(i * len..(i + 1) * len).unwrap_or_default();
+            let heat = Heat::at(thermal, at.shape.values())?;
+            let (j, dv, current, r) = if small {
+                let strain = heat.mechanical_strain(&small_strain(&f));
+                let r = m.small_strain(&strain, heat.temperature, point_history(committed, len, i), updated_point, true)?;
+                (1.0, at.dv, cols.to_vec(), r)
+            } else {
+                let det2 = f[0][0] * f[1][1] - f[0][1] * f[1][0];
+                let j = det2 * f[2][2];
+                if !(j > 0.0 && j.is_finite() && f[2][2] > 0.0) {
+                    return Err(inverted(&format!("2D {}", self.ty.kind.name()), j));
+                }
+                let inv = [[f[1][1] / det2, -f[0][1] / det2], [-f[1][0] / det2, f[0][0] / det2]];
+                let current: Vec<[f64; 3]> =
+                    cols.iter().map(|g| [g[0] * inv[0][0] + g[1] * inv[1][0], g[0] * inv[0][1] + g[1] * inv[1][1], g[2] / f[2][2]]).collect();
+                let r = m.response(&heat.mechanical(&f), heat.temperature, point_history(committed, len, i), updated_point)?;
+                (j / heat.volume(), at.dv * heat.volume(), current, r)
+            };
+            let tau = [r.stress[0], r.stress[1], r.stress[2], r.stress[3]];
+            for (a, g) in current.iter().enumerate() {
+                if let Some(x) = force.get_mut(2 * a) {
+                    *x += dv * (g[0] * tau[0] + g[2] * tau[2] + g[1] * tau[3]);
+                }
+                if let Some(x) = force.get_mut(2 * a + 1) {
+                    *x += dv * (g[1] * tau[1] + g[0] * tau[3]);
+                }
+            }
+            if let Some(k) = k.as_mut() {
+                let c4: [[f64; 4]; 4] = std::array::from_fn(|a| std::array::from_fn(|b| r.tangent[a][b]));
+                crate::plane::accumulate(&mut k.data, &current, &c4, dv);
+                if !small {
+                    for (a, ga) in current.iter().enumerate() {
+                        for (b, gb) in current.iter().enumerate() {
+                            let s = ga[0] * gb[0] * tau[0] + ga[1] * gb[1] * tau[1] + (ga[0] * gb[1] + ga[1] * gb[0]) * tau[3];
+                            k.add(2 * a, 2 * b, dv * (s + tau[2] * ga[2] * gb[2]));
+                            k.add(2 * a + 1, 2 * b + 1, dv * s);
+                        }
+                    }
+                }
+            }
+            out.push(PlanePoint { f, j, x: at.x, response: r });
+        }
+        Ok((Finite { force, tangent: k }, out))
+    }
+
+    /// Internal forces (u, v per node) and (with `tangent`) the tangent stiffness at nodal
+    /// displacements `u`, as for [`Solid::finite_strain`].
+    pub fn finite_strain(&self, m: &MaterialModel, u: &[[f64; 2]], committed: &[f64], updated: &mut [f64], tangent: bool) -> Result<Finite> {
+        Ok(self.nonlinear_points(m, u, Kinematics::Finite, None, committed, updated, tangent)?.0)
+    }
+
+    /// As [`Solid::nonlinear`], on the 2D element.
+    #[allow(clippy::too_many_arguments)]
+    pub fn nonlinear(
+        &self,
+        m: &MaterialModel,
+        u: &[[f64; 2]],
+        kin: Kinematics,
+        thermal: Option<&Temperature>,
+        committed: &[f64],
+        updated: &mut [f64],
+        tangent: bool,
+    ) -> Result<Finite> {
+        Ok(self.nonlinear_points(m, u, kin, thermal, committed, updated, tangent)?.0)
+    }
+
+    /// The Cauchy stress and the total strain at every integration point, as the solid
+    /// elements' 6-vectors (axisymmetric: rr, axial, hoop, r-axial).
+    pub fn nonlinear_stresses(
+        &self,
+        m: &MaterialModel,
+        u: &[[f64; 2]],
+        kin: Kinematics,
+        thermal: Option<&Temperature>,
+        committed: &[f64],
+    ) -> Result<Vec<PointStress>> {
+        let mut scratch = committed.to_vec();
+        let (_, points) = self.nonlinear_points(m, u, kin, thermal, committed, &mut scratch, false)?;
+        points
+            .iter()
+            .map(|p| {
+                if kin == Kinematics::Small {
+                    return Ok(PointStress { xyz: p.x, strain: small_strain(&p.f), stress: p.response.stress });
+                }
+                let strain = logarithmic_strain(&p.f).ok_or_else(|| inverted(&format!("2D {}", self.ty.kind.name()), p.j))?;
+                Ok(PointStress { xyz: p.x, strain, stress: p.response.stress.map(|v| v / p.j) })
+            })
+            .collect()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::material::isotropic;
+    use fieldcraft_model::ElementKind;
+
+    fn hex20() -> Vec<[f64; 3]> {
+        let mut x: Vec<[f64; 3]> = crate::shape::HEX_CORNERS.iter().map(|c| [c[0] + 1.0, 0.5 * c[1] + 1.0, 0.8 * c[2]]).collect();
+        let edges = [(0, 1), (1, 2), (2, 3), (3, 0), (4, 5), (5, 6), (6, 7), (7, 4), (0, 4), (1, 5), (2, 6), (3, 7)];
+        for (a, b) in edges {
+            x.push(std::array::from_fn(|k| 0.5 * (x[a][k] + x[b][k])));
+        }
+        // Distort a corner and a mid-side node.
+        x[6][0] += 0.2;
+        x[9][2] += 0.05;
+        x
+    }
+
+    fn tet10() -> Vec<[f64; 3]> {
+        let c = [[0.0, 0.0, 0.0], [1.2, 0.1, 0.0], [0.2, 1.0, 0.1], [0.1, 0.2, 0.9]];
+        let mut x = c.to_vec();
+        for (a, b) in [(0, 1), (1, 2), (2, 0), (0, 3), (1, 3), (2, 3)] {
+            x.push(std::array::from_fn(|k| 0.5 * (c[a][k] + c[b][k])));
+        }
+        x
+    }
+
+    fn displacement(n: usize, scale: f64) -> Vec<[f64; 3]> {
+        (0..n).map(|i| [scale * (i as f64 * 1.3).sin(), scale * (i as f64 * 0.7).cos(), scale * (i as f64 * 2.1).sin()]).collect()
+    }
+
+    /// Central differences of the internal forces against the tangent.
+    fn check_tangent(solid: &Solid, m: &MaterialModel, u: &[[f64; 3]]) {
+        check_tangent_from(solid, m, u, Kinematics::Finite, &[], 1e-6);
+    }
+
+    /// The same from a committed history, with either kinematics.
+    fn check_tangent_from(solid: &Solid, m: &MaterialModel, u: &[[f64; 3]], kin: Kinematics, committed: &[f64], tol: f64) {
+        let mut scratch = committed.to_vec();
+        let k = solid.nonlinear_points(m, u, kin, None, committed, &mut scratch, true).unwrap().0.tangent.unwrap();
+        let scale = k.data.iter().fold(0.0f64, |a, v| a.max(v.abs()));
+        let n = 3 * u.len();
+        let h = if kin == Kinematics::Small { 1e-9 } else { 1e-6 };
+        for j in 0..n {
+            let shifted = |s: f64| {
+                let mut v = u.to_vec();
+                v[j / 3][j % 3] += s;
+                solid.nonlinear_points(m, &v, kin, None, committed, &mut committed.to_vec(), false).unwrap().0.force
+            };
+            let (p, q) = (shifted(h), shifted(-h));
+            for i in 0..n {
+                let numeric = (p[i] - q[i]) / (2.0 * h);
+                assert!((numeric - k.get(i, j)).abs() < tol * scale, "{:?} {kin:?} {i} {j}: {numeric} vs {}", solid.ty.kind, k.get(i, j));
+            }
+        }
+        for i in 0..n {
+            for j in 0..n {
+                assert!((k.get(i, j) - k.get(j, i)).abs() <= 1e-12 * scale, "symmetric");
+            }
+        }
+    }
+
+    #[test]
+    fn solid_tangents_are_the_derivative_of_the_forces() {
+        let d = isotropic(1000.0, 0.3).unwrap();
+        let neo = MaterialModel::NeoHookean { shear: 300.0, bulk: 3000.0 };
+        let svk = MaterialModel::StVenantKirchhoff(Box::new(d));
+        let (x20, x10) = (hex20(), tet10());
+        let x8: Vec<[f64; 3]> = x20[..8].to_vec();
+        let x6 = vec![[0., 0., 0.], [1., 0., 0.], [0., 1., 0.1], [0., 0., 1.], [1.1, 0., 1.], [0., 1., 1.2]];
+        let x4 = vec![x10[0], x10[1], x10[2], x10[3]];
+        for (kind, x) in
+            [(ElementKind::Tet4, &x4), (ElementKind::Tet10, &x10), (ElementKind::Wedge6, &x6), (ElementKind::Hex8, &x8), (ElementKind::Hex20, &x20)]
+        {
+            for m in [&svk, &neo] {
+                let solid = Solid::new(kind, x, Formulation::Full).unwrap();
+                check_tangent(&solid, m, &displacement(x.len(), 0.08));
+            }
+        }
+        let reduced = Solid::new(ElementKind::Hex20, &x20, Formulation::Reduced).unwrap();
+        check_tangent(&reduced, &neo, &displacement(20, 0.08));
+        for (kind, x, np) in [(ElementKind::Hex8, &x8, 1), (ElementKind::Hex20, &x20, 4), (ElementKind::Tet10, &x10, 1)] {
+            let hybrid = Solid::new(kind, x, Formulation::Hybrid { pressures: np }).unwrap();
+            check_tangent(&hybrid, &neo, &displacement(x.len(), 0.08));
+            let mr = MaterialModel::Polynomial { name: "Mooney–Rivlin", c: [100.0, 50.0, 0.0, 0.0], bulk: 3000.0 };
+            let yeoh = MaterialModel::Polynomial { name: "Yeoh", c: [150.0, 0.0, -10.0, 2.0], bulk: 3000.0 };
+            check_tangent(&hybrid, &mr, &displacement(x.len(), 0.08));
+            check_tangent(&hybrid, &yeoh, &displacement(x.len(), 0.08));
+            assert!(hybrid.finite_strain(&svk, &displacement(x.len(), 0.0), &[], &mut [], false).is_err(), "SVK has no split");
+        }
+        let im = Solid::new(ElementKind::Hex8, &x8, Formulation::IncompatibleModes).unwrap();
+        assert!(matches!(im.finite_strain(&svk, &displacement(8, 0.0), &[], &mut [], true), Err(Error::NotSupported(_))));
+    }
+
+    #[test]
+    fn at_zero_displacement_the_tangent_is_the_linear_stiffness() {
+        let (e, nu) = (1000.0, 0.45);
+        let d = isotropic(e, nu).unwrap();
+        let neo = MaterialModel::NeoHookean { shear: e / (2.0 * (1.0 + nu)), bulk: e / (3.0 * (1.0 - 2.0 * nu)) };
+        let x20 = hex20();
+        for (f, m) in [
+            (Formulation::Full, MaterialModel::StVenantKirchhoff(Box::new(d))),
+            (Formulation::Full, neo.clone()),
+            (Formulation::Hybrid { pressures: 4 }, neo),
+        ] {
+            let solid = Solid::new(ElementKind::Hex20, &x20, f).unwrap();
+            let r = solid.finite_strain(&m, &vec![[0.0; 3]; 20], &[], &mut [], true).unwrap();
+            let linear = solid.stiffness(&d).unwrap();
+            let k = r.tangent.unwrap();
+            for (a, b) in k.data.iter().zip(&linear.data) {
+                assert!((a - b).abs() < 1e-9 * e, "{f:?}: {a} vs {b}");
+            }
+            assert!(r.force.iter().all(|v| v.abs() < 1e-12 * e));
+        }
+    }
+
+    /// J2 plasticity in full and hybrid elements, at finite and small strain: the tangent is
+    /// the derivative of the forces from a plastic history too, and the plastic points are
+    /// really plastic.
+    #[test]
+    fn plastic_tangents_are_the_derivative_of_the_forces() {
+        use crate::elastoplastic::{HISTORY, PLASTIC_STRAIN};
+        use fieldcraft_model::{Elastic, Hardening, Plastic};
+        let j2 = crate::plasticity::J2::from_model(
+            &Elastic::Isotropic { young: 1000.0, poisson: 0.3 },
+            Some(&Plastic::Bilinear { yield_stress: 5.0, hardening_modulus: 50.0, hardening: Hardening::Isotropic }),
+            None,
+        )
+        .unwrap();
+        let m = MaterialModel::Plastic(std::sync::Arc::new(j2));
+        let (x20, x10) = (hex20(), tet10());
+        let x8: Vec<[f64; 3]> = x20[..8].to_vec();
+        for (kind, x, f) in [
+            (ElementKind::Hex8, &x8, Formulation::Full),
+            (ElementKind::Tet10, &x10, Formulation::Full),
+            (ElementKind::Hex20, &x20, Formulation::Reduced),
+            (ElementKind::Hex8, &x8, Formulation::Hybrid { pressures: 1 }),
+            (ElementKind::Hex20, &x20, Formulation::Hybrid { pressures: 4 }),
+        ] {
+            let solid = Solid::new(kind, x, f).unwrap();
+            let points = solid.rule().points().len();
+            for (kin, scale) in [(Kinematics::Finite, 0.05), (Kinematics::Small, 0.05)] {
+                // A first increment from the virgin state, committed, then a second from it.
+                let mut committed = vec![0.0; points * HISTORY];
+                let first = displacement(x.len(), 0.5 * scale);
+                solid.nonlinear_points(&m, &first, kin, None, &vec![0.0; points * HISTORY], &mut committed, false).unwrap();
+                assert!((0..points).all(|p| committed[p * HISTORY + PLASTIC_STRAIN] > 0.0), "{kind:?} {f:?} {kin:?} yields everywhere");
+                check_tangent_from(&solid, &m, &displacement(x.len(), scale), kin, &committed, 1e-6);
+            }
+        }
+        // Incompatible modes have no inelastic form.
+        let im = Solid::new(ElementKind::Hex8, &x8, Formulation::IncompatibleModes).unwrap();
+        assert!(matches!(
+            im.nonlinear(&m, &displacement(8, 0.0), Kinematics::Small, None, &[0.0; 8 * HISTORY], &mut [0.0; 8 * HISTORY], true),
+            Err(Error::NotSupported(_))
+        ));
+    }
+
+    #[test]
+    fn plastic_plane_strain_and_axisymmetric_tangents_are_the_derivative_of_the_forces() {
+        use crate::elastoplastic::{HISTORY, PLASTIC_STRAIN};
+        use fieldcraft_model::{Elastic, Hardening, Plastic};
+        let j2 = crate::plasticity::J2::from_model(
+            &Elastic::Isotropic { young: 1000.0, poisson: 0.3 },
+            Some(&Plastic::Bilinear { yield_stress: 5.0, hardening_modulus: 50.0, hardening: Hardening::Isotropic }),
+            None,
+        )
+        .unwrap();
+        let m = MaterialModel::Plastic(std::sync::Arc::new(j2));
+        let quad8 = [
+            [1.0, 0.0, 0.0],
+            [2.0, 0.1, 0.0],
+            [2.2, 1.0, 0.0],
+            [0.9, 1.1, 0.0],
+            [1.5, 0.0, 0.0],
+            [2.1, 0.55, 0.0],
+            [1.5, 1.1, 0.0],
+            [0.95, 0.5, 0.0],
+        ];
+        for theory in [Theory::PlaneStrain { thickness: 2.0 }, Theory::Axisymmetric] {
+            for (kind, x) in [(ElementKind::Quad8, &quad8[..]), (ElementKind::Tri3, &quad8[..3])] {
+                let plane = Plane::new(kind, x, Formulation::Full, theory).unwrap();
+                let points = plane.rule().points().len();
+                for kin in [Kinematics::Finite, Kinematics::Small] {
+                    let u = |scale: f64| -> Vec<[f64; 2]> { displacement(x.len(), scale).iter().map(|v| [v[0], v[1]]).collect() };
+                    let mut committed = vec![0.0; points * HISTORY];
+                    plane.nonlinear_points(&m, &u(0.03), kin, None, &vec![0.0; points * HISTORY], &mut committed, false).unwrap();
+                    assert!((0..points).all(|p| committed[p * HISTORY + PLASTIC_STRAIN] > 0.0), "{theory:?} {kind:?} {kin:?}");
+                    let at = u(0.06);
+                    let k = plane.nonlinear_points(&m, &at, kin, None, &committed, &mut committed.clone(), true).unwrap().0.tangent.unwrap();
+                    let scale = k.data.iter().fold(0.0f64, |a, v| a.max(v.abs()));
+                    let h = 1e-8;
+                    for j in 0..2 * x.len() {
+                        let shifted = |s: f64| {
+                            let mut v = at.clone();
+                            v[j / 2][j % 2] += s;
+                            plane.nonlinear_points(&m, &v, kin, None, &committed, &mut committed.clone(), false).unwrap().0.force
+                        };
+                        let (p, q) = (shifted(h), shifted(-h));
+                        for i in 0..2 * x.len() {
+                            let numeric = (p[i] - q[i]) / (2.0 * h);
+                            assert!(
+                                (numeric - k.get(i, j)).abs() < 1e-6 * scale,
+                                "{theory:?} {kind:?} {kin:?} {i} {j}: {numeric} vs {}",
+                                k.get(i, j)
+                            );
+                        }
+                    }
+                }
+            }
+        }
+        let stress = Plane::new(ElementKind::Quad4, &quad8[..4], Formulation::Full, Theory::PlaneStress { thickness: 1.0 }).unwrap();
+        assert!(matches!(
+            stress.nonlinear(&m, &[[0.0; 2]; 4], Kinematics::Small, None, &[0.0; 4 * HISTORY], &mut [0.0; 4 * HISTORY], true),
+            Err(Error::NotSupported(_))
+        ));
+    }
+
+    /// A temperature field: the tangent is the derivative of the forces (finite and small strain,
+    /// full and hybrid, elastic and plastic), and a free expansion u = (F_θ − I) X of a uniform
+    /// temperature stresses nothing.
+    #[test]
+    fn thermal_tangents_and_free_expansion() {
+        use crate::elastoplastic::HISTORY;
+        use fieldcraft_model::{Elastic, Hardening, Plastic};
+        let j2 = crate::plasticity::J2::from_model(
+            &Elastic::Isotropic { young: 1000.0, poisson: 0.3 },
+            Some(&Plastic::Bilinear { yield_stress: 5.0, hardening_modulus: 50.0, hardening: Hardening::Isotropic }),
+            None,
+        )
+        .unwrap();
+        let plastic = MaterialModel::Plastic(std::sync::Arc::new(j2));
+        let neo = MaterialModel::NeoHookean { shear: 300.0, bulk: 3000.0 };
+        let x20 = hex20();
+        let field = |n: usize| Temperature {
+            alpha: [1e-3, 2e-3, 1.5e-3],
+            reference: 20.0,
+            nodal: (0..n).map(|i| 20.0 + 40.0 * (i as f64 * 0.37).sin()).collect(),
+        };
+        for f in [Formulation::Full, Formulation::Hybrid { pressures: 4 }] {
+            let solid = Solid::new(ElementKind::Hex20, &x20, f).unwrap();
+            let points = solid.rule().points().len();
+            let t = field(20);
+            for (m, kin, len) in [(&neo, Kinematics::Finite, 0), (&plastic, Kinematics::Finite, HISTORY), (&plastic, Kinematics::Small, HISTORY)] {
+                let u = displacement(20, 0.03);
+                let committed = vec![0.0; points * len];
+                let k = solid.nonlinear(m, &u, kin, Some(&t), &committed, &mut committed.clone(), true).unwrap().tangent.unwrap();
+                let scale = k.data.iter().fold(0.0f64, |a, v| a.max(v.abs()));
+                let h = if kin == Kinematics::Small { 1e-9 } else { 1e-7 };
+                for j in 0..60 {
+                    let shifted = |s: f64| {
+                        let mut v = u.clone();
+                        v[j / 3][j % 3] += s;
+                        solid.nonlinear(m, &v, kin, Some(&t), &committed, &mut committed.clone(), false).unwrap().force
+                    };
+                    let (p, q) = (shifted(h), shifted(-h));
+                    for i in 0..60 {
+                        let numeric = (p[i] - q[i]) / (2.0 * h);
+                        assert!((numeric - k.get(i, j)).abs() < 1e-6 * scale, "{f:?} {} {kin:?} {i} {j}: {numeric} vs {}", m.name(), k.get(i, j));
+                    }
+                }
+            }
+            // Free expansion by a uniform 150 degrees: no force, no stress.
+            let uniform = Temperature { alpha: [1e-3, 2e-3, 1.5e-3], reference: 20.0, nodal: vec![170.0; 20] };
+            let stretch = uniform.alpha.map(|a| 1.0 + 150.0 * a);
+            let u: Vec<[f64; 3]> = x20.iter().map(|x| std::array::from_fn(|k| (stretch[k] - 1.0) * x[k])).collect();
+            let r = solid.nonlinear(&neo, &u, Kinematics::Finite, Some(&uniform), &[], &mut [], false).unwrap();
+            assert!(r.force.iter().all(|v| v.abs() < 1e-10 * 3000.0), "{f:?}: {:?}", r.force);
+            let s = solid.nonlinear_stresses(&neo, &u, Kinematics::Finite, Some(&uniform), &[]).unwrap();
+            assert!(s.iter().all(|p| p.stress.iter().all(|v| v.abs() < 1e-10 * 3000.0)), "{f:?}");
+            assert!((s[0].strain[1] - stretch[1].ln()).abs() < 1e-12, "total logarithmic strain: {:?}", s[0].strain);
+        }
+    }
+
+    #[test]
+    fn rigid_rotation_strains_and_stresses_nothing() {
+        let x20 = hex20();
+        let rot = [[0.0, -0.6, 0.8], [0.6, 0.64, 0.48], [-0.8, 0.48, 0.36]];
+        let u: Vec<[f64; 3]> = x20.iter().map(|p| std::array::from_fn(|i| (0..3).map(|jj| rot[i][jj] * p[jj]).sum::<f64>() + 5.0 - p[i])).collect();
+        let neo = MaterialModel::NeoHookean { shear: 300.0, bulk: 3000.0 };
+        for f in [Formulation::Full, Formulation::Hybrid { pressures: 4 }] {
+            let solid = Solid::new(ElementKind::Hex20, &x20, f).unwrap();
+            let s = solid.nonlinear_stresses(&neo, &u, Kinematics::Finite, None, &[]).unwrap();
+            assert!(s.iter().all(|p| p.stress.iter().chain(&p.strain).all(|v| v.abs() < 1e-12 * 3000.0)), "{f:?}: {:?}", s[0]);
+            let r = solid.finite_strain(&neo, &u, &[], &mut [], false).unwrap();
+            assert!(r.force.iter().all(|v| v.abs() < 1e-11 * 3000.0));
+        }
+        // A rotation that inverts the element is refused.
+        let flip: Vec<[f64; 3]> = x20.iter().map(|p| [-2.0 * p[0], 0.0, 0.0]).collect();
+        let solid = Solid::new(ElementKind::Hex20, &x20, Formulation::Full).unwrap();
+        assert!(matches!(solid.finite_strain(&neo, &flip, &[], &mut [], false), Err(Error::Degenerate(_))));
+    }
+
+    #[test]
+    fn plane_strain_and_axisymmetric_tangents_are_the_derivative_of_the_forces() {
+        let quad8 = [
+            [1.0, 0.0, 0.0],
+            [2.0, 0.1, 0.0],
+            [2.2, 1.0, 0.0],
+            [0.9, 1.1, 0.0],
+            [1.5, 0.0, 0.0],
+            [2.1, 0.55, 0.0],
+            [1.5, 1.1, 0.0],
+            [0.95, 0.5, 0.0],
+        ];
+        let neo = MaterialModel::NeoHookean { shear: 300.0, bulk: 3000.0 };
+        let svk = MaterialModel::StVenantKirchhoff(Box::new(isotropic(1000.0, 0.3).unwrap()));
+        for theory in [Theory::PlaneStrain { thickness: 2.0 }, Theory::Axisymmetric] {
+            for (kind, x) in [(ElementKind::Quad8, &quad8[..]), (ElementKind::Quad4, &quad8[..4]), (ElementKind::Tri3, &quad8[..3])] {
+                let plane = Plane::new(kind, x, Formulation::Full, theory).unwrap();
+                for m in [&neo, &svk] {
+                    let u: Vec<[f64; 2]> = displacement(x.len(), 0.06).iter().map(|v| [v[0], v[1]]).collect();
+                    let k = plane.finite_strain(m, &u, &[], &mut [], true).unwrap().tangent.unwrap();
+                    let scale = k.data.iter().fold(0.0f64, |a, v| a.max(v.abs()));
+                    let h = 1e-6;
+                    for j in 0..2 * x.len() {
+                        let shifted = |s: f64| {
+                            let mut v = u.clone();
+                            v[j / 2][j % 2] += s;
+                            plane.finite_strain(m, &v, &[], &mut [], false).unwrap().force
+                        };
+                        let (p, q) = (shifted(h), shifted(-h));
+                        for i in 0..2 * x.len() {
+                            let numeric = (p[i] - q[i]) / (2.0 * h);
+                            assert!((numeric - k.get(i, j)).abs() < 1e-6 * scale, "{theory:?} {kind:?} {i} {j}: {numeric} vs {}", k.get(i, j));
+                        }
+                    }
+                }
+                // At rest the tangent is the linear stiffness.
+                let d = isotropic(1000.0, 0.3).unwrap();
+                let k = plane.finite_strain(&svk, &vec![[0.0; 2]; x.len()], &[], &mut [], true).unwrap().tangent.unwrap();
+                for (a, b) in k.data.iter().zip(&plane.stiffness(&d).unwrap().data) {
+                    assert!((a - b).abs() < 1e-9 * 1000.0);
+                }
+            }
+        }
+        let stress = Plane::new(ElementKind::Quad4, &quad8[..4], Formulation::Full, Theory::PlaneStress { thickness: 1.0 }).unwrap();
+        assert!(matches!(stress.finite_strain(&svk, &[[0.0; 2]; 4], &[], &mut [], true), Err(Error::NotSupported(_))));
+    }
+}

crates/fem/src/hybrid.rs

@@ -111,7 +111,7 @@ impl PressureField {
 
 /// The pressure functions at a point: 1, then (x − c)/h, (y − c)/h, (z − c)/h for the linear
 /// field (`np` = 4).
-fn pressure_basis(np: usize, x: [f64; 3], frame: &([f64; 3], f64)) -> [f64; 4] {
+pub(crate) fn pressure_basis(np: usize, x: [f64; 3], frame: &([f64; 3], f64)) -> [f64; 4] {
     let (c, h) = frame;
     let mut out = [1.0, 0.0, 0.0, 0.0];
     if np == 4 && *h > 0.0 {
@@ -124,7 +124,7 @@ fn pressure_basis(np: usize, x: [f64; 3], frame: &([f64; 3], f64)) -> [f64; 4] {
 
 impl Solid<'_> {
     /// The pressure unknowns of this (hybrid) element.
-    fn np(&self) -> usize {
+    pub(crate) fn np(&self) -> usize {
         match self.formulation {
             Formulation::Hybrid { pressures } => pressures.min(4),
             _ => 0,
@@ -133,7 +133,7 @@ impl Solid<'_> {
 
     /// The element's centre (mean of its corners) and size (largest corner distance from it),
     /// which scale the linear pressure functions.
-    fn frame(&self) -> ([f64; 3], f64) {
+    pub(crate) fn frame(&self) -> ([f64; 3], f64) {
         let corners = self.xyz.get(..self.ty.corners).unwrap_or_default();
         let n = corners.len().max(1) as f64;
         let c = corners.iter().fold([0.0; 3], |a, x| [a[0] + x[0] / n, a[1] + x[1] / n, a[2] + x[2] / n]);

crates/fem/src/lib.rs

@@ -13,8 +13,14 @@
 //! - [`shape`]: the hand-written first-order functions of tet4, tet10, wedge6, hex8, hex20 that
 //!   the solid kernels evaluate;
 //! - [`material`]: isotropic and orthotropic elasticity matrices, von Mises stress;
+//! - [`constitutive`]: the material point of finite-strain analysis (Kirchhoff stress and
+//!   spatial tangent from the deformation gradient, with history): St Venant–Kirchhoff,
+//!   neo-Hookean and J2 plasticity;
 //! - [`element`]: the element table, stiffness (full, reduced, incompatible modes), consistent
 //!   and lumped mass, body forces, integration-point stresses and their extrapolation to nodes;
+//! - [`finite`]: total Lagrangian solid and 2D elements (internal forces, the consistent tangent
+//!   with its geometric part, mixed u–p at finite strain, Cauchy stress and logarithmic strain),
+//!   and the same with small strain for inelastic materials;
 //! - [`plane`]: 2D elements (plane stress, plane strain, axisymmetric) on tri3, tri6, quad4 and
 //!   quad8, with two displacement components per node;
 //! - [`shell`]: flat MITC4 quadrilateral and MITC3 triangle shells with a drilling rotation, six
@@ -28,6 +34,9 @@
 //!   shape vectors and element frequency bounds for explicit dynamics;
 //! - [`rotation`]: incrementally objective stress updates (Hughes–Winget Jaumann, Flanagan–Taylor
 //!   Green–Naghdi);
+//! - [`elastoplastic`]: J2 plasticity at a material point of implicit analysis, at finite strain
+//!   (Simo's exponential map in the principal logarithmic strains) and at small strain, with the
+//!   consistent tangents, on the radial return of [`plasticity`];
 //! - [`plasticity`]: J2 radial return with isotropic, kinematic and Johnson–Cook hardening,
 //!   Johnson–Cook damage;
 //! - [`truss`]: two- and three-node trusses (straight or curved), their stiffness, mass, body
@@ -44,10 +53,13 @@
 
 pub mod basis;
 pub mod beam;
+pub mod constitutive;
 pub mod dense;
 pub mod dof;
+pub mod elastoplastic;
 pub mod element;
 pub mod face;
+pub mod finite;
 pub mod frame;
 pub mod heat;
 pub mod hybrid;

crates/fem/src/plane.rs

@@ -189,18 +189,18 @@ pub fn formulation(kind: ElementKind, f: &fieldcraft_model::Formulation) -> Resu
 }
 
 /// One column of the strain operator: (∂N/∂x, ∂N/∂y, hoop N/r), for a node or an internal mode.
-type Column = [f64; 3];
+pub(crate) type Column = [f64; 3];
 
 /// What the kernels need at one integration point.
-struct At {
-    shape: Shape,
+pub(crate) struct At {
+    pub(crate) shape: Shape,
     /// Strain columns of the nodes.
-    g: [Column; MAX_NODES],
-    det: f64,
-    x: [f64; 3],
+    pub(crate) g: [Column; MAX_NODES],
+    pub(crate) det: f64,
+    pub(crate) x: [f64; 3],
     /// det J times the point's weight times the out-of-plane extent: the point's share of the
     /// volume.
-    dv: f64,
+    pub(crate) dv: f64,
 }
 
 /// The incompatible modes' count of internal degrees of freedom: two modes, two directions.
@@ -210,14 +210,14 @@ const INCOMPATIBLE_DOFS: usize = 4;
 #[derive(Debug, Clone, Copy)]
 pub struct Plane<'a> {
     pub ty: &'static ElementType,
-    xyz: &'a [[f64; 3]],
-    formulation: Formulation,
-    theory: Theory,
+    pub(crate) xyz: &'a [[f64; 3]],
+    pub(crate) formulation: Formulation,
+    pub(crate) theory: Theory,
 }
 
 /// out[2i + r][2j + c] += w (Bᵢᵀ D Bⱼ)[r][c] over every pair of columns (row-major, `cols` wide),
 /// computed for j ≥ i and mirrored, so the result is exactly symmetric.
-fn accumulate(out: &mut [f64], columns: &[Column], d: &Elasticity2, w: f64) {
+pub(crate) fn accumulate(out: &mut [f64], columns: &[Column], d: &Elasticity2, w: f64) {
     let cols = 2 * columns.len();
     let block = |g: &Column| -> [[f64; 2]; 4] { [[g[0], 0.0], [0.0, g[1]], [g[2], 0.0], [g[1], g[0]]] };
     for (j, gj) in columns.iter().enumerate() {
@@ -293,7 +293,7 @@ impl<'a> Plane<'a> {
         }
     }
 
-    fn degenerate(&self) -> Error {
+    pub(crate) fn degenerate(&self) -> Error {
         Error::Degenerate(format!("a 2D {} element is inverted, clockwise or degenerate (its Jacobian is not positive)", self.ty.kind.name()))
     }
 
@@ -310,7 +310,7 @@ impl<'a> Plane<'a> {
         (j, j[0][0] * j[1][1] - j[0][1] * j[1][0])
     }
 
-    fn at(&self, p: &Point) -> Result<At> {
+    pub(crate) fn at(&self, p: &Point) -> Result<At> {
         let basis = Basis::of(self.ty.kind);
         let shape = basis.eval(p.xi);
         let grads = basis.gradients(&shape, self.xyz).map_err(|_| self.degenerate())?;

crates/fem/src/plasticity.rs

@@ -30,6 +30,11 @@
 //! [`MIN_FRACTURE_STRAIN`] counts as that (some published sets give negative values at high
 //! triaxiality, where the point fails at once). The point has failed at D ≥ 1.
 //!
+//! **One return map for both solvers.** [`J2::radial_return`] is the return above; explicit
+//! dynamics calls it through [`J2::update`] on its hypoelastic stress, the implicit material
+//! point ([`crate::elastoplastic`]) on its trial elastic strain, small or logarithmic, and adds
+//! the consistent tangent [`J2::tangent`].
+//!
 //! The strain increment the update takes is the **mechanical** one: a caller with initial or
 //! thermal strains subtracts their increment first.
 //!
@@ -98,6 +103,21 @@ impl PointState {
     }
 }
 
+/// What a radial return did: what the consistent tangent needs.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct Return {
+    /// The equivalent plastic strain increment Δε_p.
+    pub plastic_strain: f64,
+    /// The trial von Mises stress of ξ* = s* − α, q* = √(3/2)‖ξ*‖.
+    pub trial: f64,
+    /// The flow direction ξ*/‖ξ*‖ (tensor components).
+    pub normal: [f64; 6],
+    /// The kinematic hardening modulus H_k.
+    pub kinematic: f64,
+    /// The slope of the flow stress against the plastic strain at the end of the increment.
+    pub slope: f64,
+}
+
 /// What one update did.
 #[derive(Debug, Clone, Copy, Default, PartialEq)]
 pub struct Increment {
@@ -209,6 +229,11 @@ impl J2 {
         Ok(J2 { shear, bulk, flow, damage, heating })
     }
 
+    /// Whether the flow stress depends on the temperature (Johnson–Cook softening).
+    pub fn is_temperature_dependent(&self) -> bool {
+        matches!(self.flow, Some(Flow::JohnsonCook { .. }))
+    }
+
     /// The temperature a point starts at.
     pub fn initial_temperature(&self) -> f64 {
         match self.flow {
@@ -232,27 +257,11 @@ impl J2 {
         }
         let pressure = mean + self.bulk * vol;
         let mut out = Increment::default();
-        if let Some(flow) = &self.flow {
-            let xi: [f64; 6] = std::array::from_fn(|k| trial[k] - state.back[k]);
-            let norm = norm2(&xi).sqrt();
-            let q = (1.5f64).sqrt() * norm;
-            let (yield_now, _) = flow.stress(state.plastic_strain, 0.0, state.temperature, dt);
-            if q > yield_now && norm > 0.0 {
-                let hk = flow.kinematic();
-                let de = self.plastic_increment(flow, state, q, yield_now, hk, dt);
-                let n: [f64; 6] = xi.map(|x| x / norm);
-                let radial = g2 * (1.5f64).sqrt() * de;
-                let shift = (2.0f64 / 3.0).sqrt() * hk * de;
-                for k in 0..6 {
-                    trial[k] -= radial * n[k];
-                    state.back[k] += shift * n[k];
-                }
-                state.plastic_strain += de;
-                let q_new = q - (3.0 * self.shear + hk) * de;
-                out = Increment { plastic_strain: de, plastic_work: q_new * de };
-                if self.heating > 0.0 && density > 0.0 {
-                    state.temperature += self.heating * out.plastic_work / density;
-                }
+        if let Some(r) = self.radial_return(state, &mut trial, dt) {
+            let q_new = r.trial - (3.0 * self.shear + r.kinematic) * r.plastic_strain;
+            out = Increment { plastic_strain: r.plastic_strain, plastic_work: q_new * r.plastic_strain };
+            if self.heating > 0.0 && density > 0.0 {
+                state.temperature += self.heating * out.plastic_work / density;
             }
         }
         for k in 0..3 {
@@ -273,6 +282,68 @@ impl J2 {
         out
     }
 
+    /// The radial return of a trial deviator `trial` (tensor components) from `state`: when the
+    /// trial von Mises stress exceeds the yield stress, `trial` is moved back to the yield
+    /// surface, the back stress and the equivalent plastic strain of `state` are advanced, and
+    /// what the consistent tangent needs is returned; `None` when the point stays elastic.
+    pub fn radial_return(&self, state: &mut PointState, trial: &mut [f64; 6], dt: f64) -> Option<Return> {
+        let flow = self.flow.as_ref()?;
+        let xi: [f64; 6] = std::array::from_fn(|k| trial[k] - state.back[k]);
+        let norm = norm2(&xi).sqrt();
+        let q = (1.5f64).sqrt() * norm;
+        let (yield_now, _) = flow.stress(state.plastic_strain, 0.0, state.temperature, dt);
+        if !(q > yield_now && norm > 0.0) {
+            return None;
+        }
+        let hk = flow.kinematic();
+        let de = self.plastic_increment(flow, state, q, yield_now, hk, dt);
+        let n: [f64; 6] = xi.map(|x| x / norm);
+        let radial = 2.0 * self.shear * (1.5f64).sqrt() * de;
+        let shift = (2.0f64 / 3.0).sqrt() * hk * de;
+        for k in 0..6 {
+            trial[k] -= radial * n[k];
+            state.back[k] += shift * n[k];
+        }
+        let rate = if dt > 0.0 { de / dt } else { 0.0 };
+        let (_, slope) = flow.stress(state.plastic_strain + de, rate, state.temperature, dt);
+        state.plastic_strain += de;
+        Some(Return { plastic_strain: de, trial: q, normal: n, kinematic: hk, slope })
+    }
+
+    /// The consistent (algorithmic) tangent of the return map, dσ/dε of the stress after the
+    /// update against the total strain of the increment (engineering-shear columns): the
+    /// elasticity K I ⊗ I + 2G ℙ while elastic, and after a return
+    /// K I ⊗ I + 2G θ ℙ − 2G θ̄ n ⊗ n with θ = 1 − 3G Δε_p / q*, θ̄ = 1/(1 + H/3G) − (1 − θ) and
+    /// H the slope of the flow stress plus the kinematic modulus at the end of the increment
+    /// (Simo & Hughes 1998, Box 3.2, eq. 3.3.10, in the equivalent plastic strain). `bulk`
+    /// leaves out the volumetric part K I ⊗ I when false (the isochoric part a mixed element
+    /// takes). `None` when 3G + H is not positive: the point softens faster than it unloads
+    /// elastically and has no tangent.
+    pub fn tangent(&self, r: Option<&Return>, bulk: bool) -> Option<[[f64; 6]; 6]> {
+        let g = self.shear;
+        let (theta, theta_bar, n) = match r {
+            None => (1.0, 0.0, [0.0; 6]),
+            Some(r) => {
+                let stiff = 3.0 * g + r.slope + r.kinematic;
+                if !(stiff > 0.0 && stiff.is_finite() && r.trial > 0.0) {
+                    return None;
+                }
+                let theta = 1.0 - 3.0 * g * r.plastic_strain / r.trial;
+                (theta, 3.0 * g / stiff - (1.0 - theta), r.normal)
+            }
+        };
+        let k = if bulk { self.bulk } else { 0.0 };
+        let identity = crate::constitutive::identity4();
+        let mut d = [[0.0; 6]; 6];
+        for a in 0..6 {
+            for b in 0..6 {
+                let (ia, ib) = (if a < 3 { 1.0 } else { 0.0 }, if b < 3 { 1.0 } else { 0.0 });
+                d[a][b] = k * ia * ib + 2.0 * g * theta * (identity[a][b] - ia * ib / 3.0) - 2.0 * g * theta_bar * n[a] * n[b];
+            }
+        }
+        Some(d)
+    }
+
     /// The plastic strain increment of a trial state that yields.
     fn plastic_increment(&self, flow: &Flow, state: &PointState, q: f64, yield_now: f64, hk: f64, dt: f64) -> f64 {
         let g3 = 3.0 * self.shear;

crates/fem/src/uniform.rs

@@ -30,7 +30,7 @@
 
 use fieldcraft_model::Elastic;
 
-use crate::dense::inverse3;
+use crate::dense::positive_inverse;
 use crate::material::Elasticity;
 use crate::quadrature::Rule;
 use crate::shape::{self, HEX_CORNERS};
@@ -72,11 +72,7 @@ impl UniformStrain<8> {
                     }
                 }
             }
-            let (inv, det) = inverse3(&j).ok_or_else(|| degenerate("hex8"))?;
-            let norms: f64 = j.iter().map(|r| (r[0] * r[0] + r[1] * r[1] + r[2] * r[2]).sqrt()).product();
-            if !(det > 1e-12 * norms) {
-                return Err(degenerate("hex8"));
-            }
+            let (inv, det) = positive_inverse(&j).ok_or_else(|| degenerate("hex8"))?;
             let w = det * p.weight;
             volume += w;
             for (((bi, vi), d), n) in b.iter_mut().zip(nodal_volume.iter_mut()).zip(s.derivatives()).zip(s.values()) {
@@ -172,15 +168,9 @@ impl UniformStrain<4> {
     /// The linear tetrahedron of corners `xyz` (the model's tet4 node order).
     pub fn tet4(xyz: &[[f64; 3]; 4]) -> Result<Tet4> {
         fieldcraft_model::check_coordinates(xyz.as_flattened()).map_err(|e| Error::Invalid(e.to_string()))?;
-        let [x0, x1, x2, x3] = *xyz;
-        let e = |x: [f64; 3]| [x[0] - x0[0], x[1] - x0[1], x[2] - x0[2]];
         // J[a][c] = ∂x_c/∂ξ_a: the edges from corner 1.
-        let j = [e(x1), e(x2), e(x3)];
-        let (inv, det) = inverse3(&j).ok_or_else(|| degenerate("tet4"))?;
-        let norms: f64 = j.iter().map(|r| (r[0] * r[0] + r[1] * r[1] + r[2] * r[2]).sqrt()).product();
-        if !(det > 1e-12 * norms) {
-            return Err(degenerate("tet4"));
-        }
+        let j = fieldcraft_model::tet4_jacobian(xyz);
+        let (inv, det) = positive_inverse(&j).ok_or_else(|| degenerate("tet4"))?;
         let volume = det / 6.0;
         let s = shape::tet4([0.25; 3]);
         let mut b = [[0.0; 3]; 4];

crates/geometry/src/design.rs

@@ -2,9 +2,8 @@
 //! with SolidCraft, and hand back its bodies with persistent face names.
 //!
 //! The design is rebuilt from its authoritative inputs (sketches, features, parameters); cached
-//! display meshes in the file are never used. [`open_design`] takes bytes; [`open_design_file`]
-//! reads a path through SolidCraft's file access, which in the browser is the in-memory files the
-//! web host loaded.
+//! display meshes in the file are never used. [`open_design`] takes the file's bytes (reading
+//! files is `fieldcraft_io::fs`'s job, which in the browser holds the page's files).
 
 use solidcraft_doc::{Document, Model, naming};
 use solidcraft_kernel::{KernelError, guard};
@@ -45,11 +44,6 @@ pub fn open_design(bytes: &[u8]) -> Result<Design> {
     rebuild(&doc)
 }
 
-/// Read a design file (a regular file of at most [`MAX_DESIGN_BYTES`]) and rebuild it.
-pub fn open_design_file(path: &str) -> Result<Design> {
-    open_design(&crate::read_file(path, MAX_DESIGN_BYTES)?)
-}
-
 /// Rebuild an in-memory document (the design half of [`open_design`]).
 pub(crate) fn rebuild(doc: &Document) -> Result<Design> {
     let model = guard("rebuild design", || {
@@ -165,8 +159,5 @@ mod tests {
             assert!(open_design(bytes).is_err(), "{bytes:?}");
         }
         assert!(open_design(&vec![b' '; MAX_DESIGN_BYTES + 1]).is_err());
-        for path in ["", "/", "/dev/zero", "/no/such/design.solidcraft"] {
-            assert!(open_design_file(path).is_err(), "{path}");
-        }
     }
 }

crates/geometry/src/lib.rs

@@ -22,7 +22,7 @@ pub mod sample;
 #[cfg(feature = "scripts")]
 mod script;
 
-pub use design::{Design, FeatureError, MAX_DESIGN_BYTES, open_design, open_design_file};
+pub use design::{Design, FeatureError, MAX_DESIGN_BYTES, open_design};
 pub mod tagged_mesh;
 #[cfg(feature = "scripts")]
 pub use script::{MAX_SCRIPT_BYTES, script_design};
@@ -47,14 +47,6 @@ impl From<KernelError> for Error {
     }
 }
 
-/// Read a regular file of at most `max_bytes` through SolidCraft's file access (in the browser,
-/// the in-memory files the web host loaded). Opening a design or a 3MF package from these bytes
-/// ([`open_design`], [`tagged_mesh::read_3mf`]) lets the caller record a hash of exactly what it
-/// opened.
-pub fn read_file(path: &str, max_bytes: usize) -> Result<Vec<u8>> {
-    solidcraft_io::vfs::read(path, max_bytes).map_err(|e| Error::Invalid(format!("cannot read `{path}`: {e}")))
-}
-
 /// SolidCraft's linear modelling tolerance (mm): points closer than this are the same point.
 const LINEAR_TOLERANCE: f64 = solidcraft_geom::LINEAR_TOL;