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OneCAD/docs/step-import.md
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bherbruckandClaude Opus 5.5 1c10d1e56a STEP import: 65/66 Fusion files; bounded meshing
Meshing (vendored truck-meshalgo) works within a budget so hostile files
cannot hang: bounded edge and surface divisions (point caps, depth and
round limits, NaN-safe), and a grid budget per face shared out per shell.
Surface grids refine only the direction that bends; rulings left undivided
get cells comparable to the other direction, so trimmed cylinders (holes,
tee joints) no longer lose volume to long triangles. The helical sweep
imports in 12 s instead of 7 minutes.

Small sphere patches get poles away from them even when the file runs a
seam through the patch (a pyramid's corner blend). Faces the mesher cannot
mesh are reported as import warnings. Test: wild B-spline and far-off
boundaries import in bounded time.

STEP corpus 65/66 (50-sweep-tight-bend: a horn-torus bend whose inner side
collapses to a point; Fusion's own area for it is also off).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AS5Tn3xieewUSg3uxrMVdL
2026-10-08 01:28:16 +00:00

9.1 KiB

STEP import

SolveCraft reads STEP (ISO 10303-21; AP203, AP214 and AP242 geometry) with its own reader in crates/kernel/src/step_in (written from the public standards; no third-party STEP code). A STEP file becomes an Import base feature on the timeline: it holds the file's B-rep (the STEP text is kept in the design, so the design reopens without the file) and later features — fillets, holes, cuts sketched on its faces, shells — build on its bodies.

  • Open: File → Open (doc.open) accepts .step/.stp in any case and starts a new design; solvecraft part.step; solvecraft-cli eval part.step, solvecraft-cli run script.json --in part.step; the MCP open tool.
  • Insert into the current design: File → Insert STEP… or SOLID → INSERT (FusionImportCommandFromToolbar {path}).
  • Drag and drop a STEP file on the window: inserted when the design has features, opened otherwise.

Read: manifold solid breps (with voids), faceted breps, shell-based surface models; planes, cylinders, cones, spheres, tori, B-spline and rational B-spline surfaces (with knots, Bézier, uniform, quasi-uniform), surfaces of revolution and linear extrusion, trimmed surfaces; lines, circles, ellipses, B-spline curves, polylines, trimmed/surface/seam curves; length and angle units (SI prefixes, conversion-based units such as inches); product names (body names come from the solid's name, else the product's); surface colours; assemblies (next-assembly-usage occurrences placed by item-defined transformations, and mapped items) — the product tree is kept in the feature for the components milestone. Files are untrusted: sizes, entity counts and nesting are capped and every kernel call is guarded. What cannot be read becomes a warning on the feature (a face left out gives an open body); not read yet: offset surfaces, pcurve-only edges.

Fusion corpus

Generated by cargo xtask step-corpus. Each case is a part exported from Fusion as STEP (AP214; kept locally in plan/fusion/oracle/, never committed). SolveCraft opens part.step exactly as File → Open does (an Import base feature) and compares with Fusion's own measurements: body count, volume and area (relative tolerance 1e-3) and the number of faces read from the file.

65 / 66 files pass.

Case Result Bodies Volume mm³ (got / Fusion) Area mm² (got / Fusion) Faces (got / Fusion) ms Notes
01-box pass Box 24000.000 / 24000.000 5200.000 / 5200.000 6 / 6 8
02-cylinder pass Cylinder 35339.429 / 35342.917 6125.845 / 6126.106 3 / 3 89
03-box-through-hole pass Box 45738.283 / 45738.053 9327.809 / 9327.788 7 / 7 147
04-revolve-vase pass Vase 112488.811 / 112499.479 13156.092 / 13156.615 5 / 5 502
05-taper-extrude pass Frustum 61814.826 / 61814.826 9676.915 / 9676.915 6 / 6 10
06-symmetric-extrude pass Block 30000.000 / 30000.000 6200.000 / 6200.000 6 / 6 1
07-fillet-all-edges pass Box 23340.621 / 23340.849 4726.220 / 4726.265 26 / 26 286
08-chamfer pass Box 23730.667 / 23730.667 5029.352 / 5029.352 10 / 10 14
09-shell pass Box 13632.000 / 13632.000 13992.000 / 13992.000 11 / 11 17
10-rect-pattern-holes pass Plate 29803.713 / 29803.540 14652.481 / 14652.389 18 / 18 282
11-circular-pattern-flange pass Flange 66758.144 / 66758.844 19320.617 / 19320.795 10 / 10 236
12-mirror-feature pass Base 21392.575 / 21392.920 6530.944 / 6530.973 10 / 10 179
13-combine-join pass A 45570.295 / 45571.680 8634.196 / 8634.336 9 / 9 105
14-combine-cut pass A 42933.034 / 42931.417 9706.783 / 9706.858 7 / 7 823
15-combine-intersect pass A 54452.172 / 54454.273 7382.532 / 7382.743 7 / 7 1957
16-sweep pass Tube 2584.428 / 2584.724 1779.638 / 1779.698 5 / 5 1379
17-loft pass Loft 35121.851 / 35125.498 6497.868 / 6495.000 6 / 6 140
18-hole-features pass Plate 33890.921 / 33890.710 8568.694 / 8568.696 13 / 13 287
19-l-bracket-constrained pass LBracket 14720.000 / 14720.000 5472.000 / 5472.000 8 / 8 2
20-slot-constrained pass Slot 2965.428 / 2965.487 1774.644 / 1774.690 6 / 6 51
21-draft pass Box 54574.737 / 54574.737 8781.998 / 8781.998 6 / 6 1
22-split-body pass Cyl, Cyl (1) 75390.813 / 75398.224 12954.440 / 12955.175 6 / 6 302
23-bracket-multifeature pass Bracket 59331.477 / 59331.129 18290.767 / 18290.737 19 / 19 190
24-user-parameters pass Block 34822.022 / 34821.903 8114.175 / 8114.159 7 / 7 113
25-sketch-triangle pass Triangle 4032.155 / 4032.155 2274.099 / 2274.099 5 / 5 11
26-sketch-belt pass Belt 11326.042 / 11326.170 5637.347 / 5637.404 7 / 7 91
27-sketch-trapezoid pass Trapezoid 5342.286 / 5342.257 3066.961 / 3066.946 8 / 8 148
28-blind-pocket-fillets pass Block 84299.345 / 84299.249 16279.560 / 16279.572 23 / 23 280
29-two-sided-and-partial-revolve pass Block 25731.356 / 25731.307 6312.589 / 6312.602 12 / 12 64
30-fillet-after-shell pass Box 21745.915 / 21745.876 14968.284 / 14968.332 27 / 27 273
31-fillet-l-all-edges pass L 14321.482 / 14321.626 5024.003 / 5024.045 38 / 38 335
32-boss-plate-fillets pass Part 33590.273 / 33590.350 9929.854 / 9929.864 10 / 10 3052
33-fillet-tangent-chain pass Slot 8237.030 / 8237.122 2793.540 / 2793.569 14 / 14 449
34-chamfer-then-fillet pass Box 22892.383 / 22892.421 4753.677 / 4753.688 18 / 18 46
35-fillet-curved-curved pass Tee 63169.683 / 63171.443 10269.167 / 10269.348 6 / 6 1868
36-corner-blend-two-radii pass Box 57799.502 / 57800.240 8585.435 / 8585.524 18 / 18 454
37-pyramid-apex-blend pass Pyramid 15465.376 / 15465.575 3914.529 / 3914.581 18 / 18 322
38-coincident-cylinders pass A 15706.406 / 15707.963 3769.760 / 3769.911 3 / 3 182
39-tee-pipe pass Tee 24095.763 / 24096.237 16709.772 / 16710.048 7 / 7 426
40-box-sphere-torus pass A 36287.563 / 36287.433 10696.145 / 10696.165 10 / 10 5171
41-tube-radial-holes pass Tube 20243.046 / 20243.981 14873.689 / 14873.773 22 / 22 2199
42-overlapping-patterns pass Plate 38488.411 / 38487.064 21687.215 / 21686.603 43 / 43 1012 solid 'Plate': imported as an open body (the shell is not closed)
43-cut-splits-body pass Bar, Bar (1) 28000.000 / 28000.000 7200.000 / 7200.000 12 / 12 32
44-shell-l-bracket pass L 8384.000 / 8384.000 8784.000 / 8784.000 15 / 15 9
45-shell-boss-plate pass Part 13676.354 / 13676.602 14156.531 / 14156.602 15 / 15 149
46-shell-two-open-faces pass Box 16044.000 / 16044.000 11398.000 / 11398.000 10 / 10 22
47-draft-curved-pocket pass Block 111387.999 / 111387.712 17700.336 / 17700.361 11 / 11 16
48-pulley pass Pulley 168507.231 / 168510.841 23718.208 / 23718.644 12 / 12 235
49-helical-sweep pass Spring 4733.931 / 4738.099 4765.903 / 4767.652 3 / 3 11850 solid 'Spring': face wrapping around a closed surface kept whole: split line does not reach the rings
50-sweep-tight-bend FAIL Bend 3822.427 / 3758.443 1708.948 / 2153.937 5 / 5 605
51-loft-rect-circle-offset pass Loft 61130.904 / 61133.116 9416.313 / 9411.655 6 / 6 39
52-circular-pattern-fillet pass Hub 47206.182 / 47206.850 14141.988 / 14142.171 21 / 21 526
53-path-pattern pass Plate 35010.499 / 35010.398 16463.947 / 16463.894 13 / 13 46
54-mirror-body-fillets pass Bracket 22780.113 / 22780.089 6972.831 / 6972.832 12 / 12 38
55-tapped-hole-cosmetic pass Plate 17542.366 / 17542.314 4761.590 / 4761.596 8 / 8 33
56-holes-on-curved-face pass Cyl 77941.179 / 77942.388 10592.950 / 10593.139 7 / 7 178
57-hole-pattern-sketch-points pass Plate 36767.029 / 36766.712 11818.165 / 11818.153 24 / 24 69
58-phone-stand pass Stand 74559.442 / 74559.177 29148.741 / 29148.785 19 / 19 11
59-enclosure-base pass Enclosure 34309.038 / 34309.486 33795.405 / 33795.610 39 / 39 81
60-pipe-flange pass Flange 323661.056 / 323660.979 56984.269 / 56984.564 16 / 16 463
61-shaft-keyway pass Shaft 47521.487 / 47525.946 9676.780 / 9677.096 14 / 14 80
62-heat-sink pass HeatSink 43125.000 / 43125.000 45725.000 / 45725.000 66 / 66 7
63-hinge-knuckle pass Hinge 4783.029 / 4783.117 4110.255 / 4110.287 14 / 14 55
64-sketch-tangent-arc-chain pass Wave 4800.000 / 4800.000 3843.701 / 3843.712 9 / 9 7
65-sketch-gear-tooth pass Tooth 3987.831 / 3988.084 1945.416 / 1945.485 9 / 9 5
66-sketch-linkage pass Link 8045.410 / 8045.386 4308.172 / 4308.175 10 / 10 49