forked from 1b-agent/opencadstudio-upstream
Hakan SevenandClaude Opus 5.5
f537aff75c
The codec and kernel repositories and crates are renamed opencadcodec and opencadkernel. Inside OCS they are depended on under short keys, so code reads `codec::`, `kernel::` and the new `graph::` (opencadgraph, the node graph engine). File-format and protocol spellings stay as they were: the ACIS product id `acadrust`, the ACADRUST_* switches and the plugin version keys `acadrust_version` / `acadrust_source`. A button left of MCP on the command line opens a translucent node graph over the viewport, with a palette of object, input, math, logic, list, text and geometry nodes added by click or drag. An object node owns drawing entities and its rows are the Properties panel's own rows for them: the single-object page is extracted from refresh_properties as entity_property_sections, values use the control protocol's property_json, and writes go through set_property_value with a property target override, so the panel, MCP and the graph share one read/write path. A list reaching an object row makes one entity per element. Each graph action is one undo step; the canvas pans and zooms. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
99 lines
6.5 KiB
Markdown
99 lines
6.5 KiB
Markdown
# Entity tessellation paths
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How each opencadcodec `EntityType` becomes drawable geometry in OpenCADStudio.
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There are **three ways** an entity gets there, and they must not be conflated:
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1. **Kernel B-rep mesh** — the ACIS document is lifted into a opencadkernel `Body`
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and each face triangulated in its own surface's parameter space. The only
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path that produces filled *mesh* triangles from analytic surfaces.
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2. **Curve-sampled** — the entity's geometry is read through
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`entities::curve::entity_curve`, which is where each type's curve is defined
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once, and tessellated to a chord tolerance. Output is a polyline; no surface
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is involved.
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3. **Direct** — points, segments or triangles emitted straight from the
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entity's own fields.
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The distinction between (2) and (3) is worth keeping because (2) is a single
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definition shared with everything else that needs an entity's geometry — snap
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candidates, EXTRUDE and REVOLVE profiles, hatch boundaries, clip outlines. A
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circle drawn on screen and a circle handed to the Model tab come from the same
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place and cannot disagree.
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Entry points: `src/scene/convert/tess.rs` (`tessellate_entity`, the per-entity
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dispatcher) → `src/scene/convert/tessellate.rs` (`tessellate`, the
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`RenderObject` router), `src/entities/curve.rs` (curve definitions and
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sampling) and `src/scene/convert/curve_tol.rs` (the per-frame chord tolerance).
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## Summary
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| Path | Entities |
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|---|---|
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| **Kernel B-rep mesh** (lift → per-face triangulation, with a direct per-surface fallback) | `Solid3D`, `Region`, `Body`, `Surface` |
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| **Curve-sampled** (`entity_curve` → chord-tolerance tessellation) | `Line`, `Arc`, `Circle`, `Ellipse`, `Spline`, `LwPolyline`, `Polyline`, `Polyline2D`, `Polyline3D` — *non-thick variants only* |
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| **Direct** (segments/triangles emitted straight) | everything else |
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> The Model/Design-tab primitives (BOX, SPHERE, CYLINDER, CONE, WEDGE, TORUS,
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> PYRAMID, EXTRUDE, REVOLVE) are true kernel B-reps too, cached on the Scene as
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> `Body` and meshed the same way — but they are created as `Solid3D`
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> placeholders carrying that body, not as their own `EntityType`. SWEEP and
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> LOFT produce a mesh only, with no B-rep behind it.
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ACIS solids dispatch through `solid3d_tess::tessellate_acis`, which lifts the
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document into the kernel first (`acis_kernel::tessellate_sat`) and falls back
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to a bespoke per-surface LOD sampler (`tessellate_sat_lods`) when the kernel
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cannot express a face — so their path is **kernel-with-direct-fallback**. The
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fallback is not silent: a mesh whose faces did not all lift is marked
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incomplete, because one missing wall looks exactly like a finished solid.
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Curved-surface tessellation density is radius-relative (`CURVE_REL_TOL`, a
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fraction of the surface radius) so a cylinder's facet count matches the
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circle/arc wire tessellation instead of exploding on large radii.
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## Full table
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| Entity | Output | Path | Notes |
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|---|---|---|---|
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| Arc | wire | curve-sampled | non-thick: sampled from the arc's own curve; thick: direct `Lines` plus the swept wall |
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| AttributeDefinition | wire | direct | routes through the Text/MText LFF glyph stroke pipeline |
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| AttributeEntity | wire | direct | same as AttributeDefinition; values supplied per Insert |
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| Block | none | n/a | block-definition sentinel; not tessellated (referenced via Insert) |
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| BlockEnd | none | n/a | block-definition end marker; no output |
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| Body | mesh | kernel-with-direct-fallback | 3D ACIS body lifted into a kernel `Body`; fallback per-surface sampler |
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| Circle | wire | curve-sampled | non-thick: sampled from the circle's own curve; thick: direct `Lines` |
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| Dimension | wire | direct | baked-block path recurses on `D###` sub-entities; synthesis path emits lines/arrows/LFF text |
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| Ellipse | wire | curve-sampled | sampled from the ellipse's own curve |
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| Face3D | both | direct | edge `Lines` + direct fan-triangulated `fill_tris`; no B-rep |
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| Hatch | both | direct | boundary outline not emitted to the wire set (#131 OOM); fill rasterized on GPU |
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| Insert | wire | direct | expands block children and tessellates each via its own path; XCLIP filter applied |
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| Leader | wire | direct | leader path + arrowhead + landing, direct `Lines` |
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| Line | wire | curve-sampled | non-thick: its two ends; thick: direct `Lines` plus the swept wall |
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| LwPolyline | wire | curve-sampled | `plinegen` true: sampled from its own curve, bulges kept as arcs; else direct `SegmentedLines` |
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| Mesh | both | direct | SubD mesh: edge `Lines` + direct fan-triangulated `fill_tris` |
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| MLine | wire | direct | spine + offset lines + caps, direct `Lines` |
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| MText | wire | direct | wrap-aware multi-line LFF glyph layout; inline formatting codes |
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| MultiLeader | wire | direct | leader + landing + LFF text + frame + fill |
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| Ole2Frame | wire | direct | bounding rectangle + diagonal cross |
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| Point | wire | direct | a position → dot or cross marker sized by PDSIZE |
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| PolyfaceMesh | both | direct | face list: closed-polyline edges + direct fan-triangulated `fill_tris` |
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| PolygonMesh | both | direct | M×N grid wireframe + direct fan-triangulated `fill_tris` |
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| Polyline | wire | curve-sampled | heavy 3D polyline; sampled from its own curve, bulges kept as arcs |
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| Polyline2D | wire | curve-sampled | 2D polyline with bulge; sampled from its own curve |
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| Polyline3D | wire | curve-sampled | straight edges, no bulge or thickness |
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| RasterImage | wire | direct | boundary rectangle / clipping polygon |
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| Ray | wire | direct | two-point `[base, base + dir×1e6]`, no sampling |
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| Region | mesh | kernel-with-direct-fallback | 2D planar ACIS body; same kernel path as Solid3D |
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| Seqend | none | n/a | vertex-sequence terminator sentinel; no output |
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| Shape | wire | direct | small diamond marker at the insertion point |
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| Solid | wire | direct | 2D SOLID: four quad edges as direct `Lines` |
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| Solid3D | mesh | kernel-with-direct-fallback | 3DSOLID: parse SAT/SAB → lift into a kernel `Body`; fallback sampler |
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| Spline | wire | curve-sampled | NURBS sampled through the kernel's space curve, refined where it bends |
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| Table | both | direct | cell fills (`fill_tris`) + LFF cell text + grid lines |
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| Text | wire | direct | LFF-font stroked glyph polylines |
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| Tolerance | wire | direct | feature-control frame grid + per-cell LFF symbols |
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| Underlay | wire | direct | boundary rectangle of the PDF/DWF reference |
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| Unknown | none | n/a | unrecognized-entity sentinel; no output |
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| Viewport | wire | direct | content-viewport frame rectangle (sheet viewport skipped) |
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| Wipeout | wire | direct | boundary rectangle / clipping polygon |
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| XLine | wire | direct | three-point infinite line, no sampling |
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