OneCAD-Simulation/docs/parity.md

Capability checklist (reference: Abaqus/CAE)

What an analyst does in a full CAE pre-processor, grouped by milestone, with ModelCraft's status. Scope comes from the public documentation of Abaqus/CAE and public analyst discussion, described in our own words; nothing was taken from the product itself (AGENTS.md: no commercial products are run, no documentation text is copied). Status: done, started, planned. HEX marks items centred on hexahedral meshing, the core goal.

Where we aim to be better

#	Opportunity	Why analysts want it	ModelCraft approach
1	Hex meshes without manual partitioning	Partitioning a part into sweepable cells by hand is the most cited chore	Sweep and mapped meshing with automatic decomposition that proposes SolidCraft splits (M5); octree all-hex for anything else (M6)
2	Undo, redo, replay, crash recovery	No general undo; replay files are hard to reuse; corrupted model files	Every action is a journalled command with rollback, undo and redo; autosave with recovery after a crash
3	Sets that survive changes	Sets and loads break when geometry regenerates or is remeshed	Sets bind to SolidCraft's persistent face, edge and body names and resolve after meshing (M3)
4	An API that is not a bundled scripting runtime	Version breakage, slow scripts, geometry picked by position	JSON commands over CLI, control channel and MCP
5	Located diagnostics	Generic error messages	Errors name the element, face or keyword; mesh.quality lists failing elements
6	Lossless deck round trip	Unsupported keywords dropped on import	Deck readers keep unknown keywords and write them back (M9)
7	Safe, diffable model files	Binary model databases that corrupt or lock to a version	.modelcraft: text, line-diffable definition and journal, checksummed binary mesh, versioned format tag, atomic saves with backup, autosave (M3, done)
8	Geometry checked before meshing	Slivers and tiny faces fail late	Surface preparation reports defects with their location (M1)
9	No size caps, any solver	Node limits in learning editions; one solver per tool	Free, open source, three deck formats
10	Clear step history	Loads and BCs propagate between steps implicitly	An explicit step × load/BC table (M3)

Checklist

Area	Capability	Milestone	HEX	Status
Geometry	Open SolidCraft designs, bodies, persistent face names, assemblies placed	M1		done
Geometry	Face-tagged mesh import (3MF)	M1		done
Geometry	Weld, closed/manifold/orientation and self-intersection checks, feature edges	M1	yes	started
Geometry	Partitions and datums as SolidCraft features (split body/face, construction planes)	M5	yes	planned
Geometry	Midsurface extraction for shells	M8		planned
Mesh	Size field: global, per face and edge seeds, bias, curvature and proximity refinement	M2	yes	planned
Mesh	Free tet meshing (tet4, tet10 with mid-side nodes on the geometry)	M2		started
Mesh	Quality metrics, certified validity, verify per set	M1–M2	yes	done (metrics, gate)
Mesh	2D quad meshing of faces	M5	yes	planned
Mesh	Mapped hex of six-sided regions	M5	yes	planned
Mesh	Sweep hex (extrusions, revolutions)	M5	yes	planned
Mesh	Automatic decomposition into sweepable and mappable regions	M5	yes	planned
Mesh	Conforming interfaces, tet–hex transition with pyramids	M5	yes	planned
Mesh	Octree/grid-dual all-hex for any part	M6	yes	planned
Mesh	Hex-dominant by recombination; polycube	M6	yes	planned
Mesh	Smoothing, untangling, boundary padding, layers through thin walls	M6	yes	planned
Mesh	Mesh editing (move, merge, split, collapse, remesh region), imported orphan meshes	M6	yes	started (node/element add/remove)
Model	Sets and surfaces bound to geometry names	M3	yes	done
Model	Materials: elastic (isotropic, orthotropic), density, unit-system check	M3		done
Model	Materials: plasticity, hyperelasticity, damage, thermal	M8		planned
Model	Sections: solid, shell, beam profiles; assignment by set	M3		done
Model	Composite layups, material orientations, continuum shells	M8	yes	planned
Model	Element formulation per region (integration, incompatible modes, hybrid) mapped per solver	M3	yes	done (model; per-solver mapping with the deck writers)
Model	Boundary conditions: fixed, displacement, symmetry	M3		done
Model	Loads: force and moment, pressure, gravity, body force	M3		done
Model	Reference points, kinematic and distributing coupling	M3		done
Model	Steps: linear static, frequency; output presets	M3		done
Model	Steps: nonlinear static, explicit dynamics, heat transfer; amplitudes	M7–M8		planned
Interaction	Tie between non-matching meshes	M7		planned
Interaction	Contact (general and pairs), friction, automatic pair detection	M7		planned
Interaction	Bolt pretension, springs, point masses, connectors	M7		planned
Decks	Abaqus input writer (deck.write, flat deck; reports what Abaqus cannot express)	M3		done
Decks	Nastran bulk data writer (deck.write, SOL 101 or 103 per deck; reports what Nastran cannot express)	M3		done
Decks	LS-DYNA keyword writer (implicit; explicit in M8)	M3		done (implicit static and eigenvalue; beam sections planned)
Decks	Readers keeping unknown keywords	M9		planned
Solve	Own linear static and modal solver, verified against analytic solutions	M4	yes	started (solid elements: tet4, tet10, wedge6, hex8, hex20; reference points, kinematic and distributing couplings, moments)
Solve	Own explicit dynamics solver (central differences, one-point hex8 with hourglass control, nodal-pressure tet4, bulk viscosity, energy balance), verified against analytic wave and impact solutions	M10	yes	started (X1 core: small-strain elastic, rigid walls; large deformation, plasticity and contact planned)
Results	Deformed shape, contours, mode shapes, probes, reaction sums	M4		started (results in the session, solve.probe, reaction sums; display planned)
Results	XY and path plots, cuts, display groups, free-body forces, animation	M9		planned
Results	Readers for public result formats (Nastran OP2, LS-DYNA d3plot, Abaqus .fil)	M9		planned
Results	Mesh convergence studies	M9		planned
App	Desktop viewport, model tree, commands, control channel	continuous		done
App	Undo/redo on the command journal, autosave, .modelcraft file	M3		done
App	MCP server, browser build	continuous		planned

Deck notes for the writers

• Node order: the model stores Abaqus/VTK order. Nastran orders the mid-side nodes of 20-node hexes and 15-node wedges differently; LS-DYNA takes tets and wedges as degenerate hexes and triangles as degenerate quads. Every mapping is tested by the sign of the element Jacobian after writing.
• Each format's field widths, continuation rules, number forms and label limits are respected by the writer and checked by golden-file tests on our own examples.
• Abaqus: the model's node order and face numbers are Abaqus's, so connectivity passes through; element types come from the element kind, the section and its formulation (table in crates/decks/src/abaqus.rs). The step table is bridged to Abaqus's propagation: zero-valued boundary conditions active in every step go to the initial state, and steps restate their boundary conditions and loads with OP=NEW when the active set changes.
• Nastran (modelcraft_decks::nastran): entries with a real use large (16-column) fields, the rest small fields; a real is exact when its shortest round-trip form fits 16 columns, else rounded to at least ten significant digits. Linear solids map full integration to PSOLID TWO/THREE + FULL, hex20 reduced to TWO + FULL, hex8 incompatible modes to BUBBLE; one-point reduced linear solids, hybrid solids, reduced-integration or one-point shells, body forces, gravity on part of the model, orthotropic beams and rods, and orthotropic shells off planes of constant Z are reported as unsupported. Static and frequency steps need separate decks (deck.write steps).
• LS-DYNA (modelcraft_decks::lsdyna, deck.write {"format": "lsdyna"}): long format (20-column fields; every value with up to 13 significant digits, and 17-digit values from 0.01 to 1e17, are written exactly; the rest is rounded to at least 13 digits and counted). The 10-node tetrahedron follows the manual's figure: mid-side nodes 8, 9, 10 on edges 2-4, 3-4, 1-4 (the model has them on 1-4, 2-4, 3-4). Incompatible modes map to ELFORM −18 (eight-point enhanced strain). Several steps are written as *CASE analyses. Refused with the item named: beam sections (not yet), body forces per volume, partial-DOF kinematic couplings, constraints on a coupled reference point, gravity on different sets or on parts of sections, hybrid other than tet4, reduced quadratic elements, materials without density, more than 10 shell integration points.
• Open item (LS-DYNA tet10 node order): the writer follows the manual's figure (mid-side nodes 8, 9, 10 on edges 2-4, 3-4, 1-4), which disagrees with an earlier reading as the Abaqus order. It needs one confirmation run by a licensed user; agents never run commercial solvers.