OneCAD/docs/step-import.md

STEP import

SolidCraft 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 (file.insert_step {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.

Imported appearances

Imported body colours and face colours are retained through later features. Body colours remain the fallback under explicit design appearances and materials; face colours follow persistent face names. A removed face has no colour assignment to display on the resulting body.

IGES

IGES 5.3 files (.igs/.iges) open, insert and drop the same way: crates/kernel/src/iges_in.rs (written from the published specification) restates the file as STEP and the STEP reader reads it, so the feature holds STEP text. Read: manifold solid B-reps (186) with their shells, faces, loops, edge and vertex lists; trimmed (144) and bounded (143) surfaces, and bare B-spline patches, sewn into a solid by their shared edges (an open body when they do not close); lines, circular arcs, ellipses, composite curves, rational B-spline curves; planes (108, 190), cylinders, cones, spheres, tori, rational B-spline surfaces, surfaces of revolution and tabulated cylinders; transformation matrices; units; colours (314 and the predefined numbers); body names (name properties, else labels). Not read yet: ruled and offset surfaces, curves on surfaces given only in parameter space. Export (file.export to .igs) writes each body as a manifold solid B-rep on the same surfaces a STEP export uses, with its name and colour.

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). SolidCraft 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.

76 / 76 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	3
02-cylinder	pass	Cylinder	35339.429 / 35342.917	6125.845 / 6126.106	3 / 3	87
03-box-through-hole	pass	Box	45738.283 / 45738.053	9327.809 / 9327.788	7 / 7	62
04-revolve-vase	pass	Vase	112488.847 / 112499.479	13156.093 / 13156.615	5 / 5	511
05-taper-extrude	pass	Frustum	61814.826 / 61814.826	9676.915 / 9676.915	6 / 6	2
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	532
08-chamfer	pass	Box	23730.667 / 23730.667	5029.352 / 5029.352	10 / 10	3
09-shell	pass	Box	13632.000 / 13632.000	13992.000 / 13992.000	11 / 11	2
10-rect-pattern-holes	pass	Plate	29803.713 / 29803.540	14652.481 / 14652.389	18 / 18	252
11-circular-pattern-flange	pass	Flange	66758.144 / 66758.844	19320.617 / 19320.795	10 / 10	168
12-mirror-feature	pass	Base	21392.575 / 21392.920	6530.944 / 6530.973	10 / 10	80
13-combine-join	pass	A	45570.295 / 45571.680	8634.196 / 8634.336	9 / 9	43
14-combine-cut	pass	A	42933.034 / 42931.417	9706.783 / 9706.858	7 / 7	402
15-combine-intersect	pass	A	54452.172 / 54454.273	7382.532 / 7382.743	7 / 7	1022
16-sweep	pass	Tube	2584.428 / 2584.724	1779.638 / 1779.698	5 / 5	612
17-loft	pass	Loft	35121.595 / 35125.498	6495.373 / 6495.000	6 / 6	191
18-hole-features	pass	Plate	33890.908 / 33890.710	8568.695 / 8568.696	13 / 13	184
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	15
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	109
23-bracket-multifeature	pass	Bracket	59331.477 / 59331.129	18290.767 / 18290.737	19 / 19	117
24-user-parameters	pass	Block	34822.022 / 34821.903	8114.175 / 8114.159	7 / 7	58
25-sketch-triangle	pass	Triangle	4032.155 / 4032.155	2274.099 / 2274.099	5 / 5	1
26-sketch-belt	pass	Belt	11326.042 / 11326.170	5637.347 / 5637.404	7 / 7	42
27-sketch-trapezoid	pass	Trapezoid	5342.286 / 5342.257	3066.961 / 3066.946	8 / 8	53
28-blind-pocket-fillets	pass	Block	84299.345 / 84299.249	16279.560 / 16279.572	23 / 23	320
29-two-sided-and-partial-revolve	pass	Block	25731.356 / 25731.307	6312.589 / 6312.602	12 / 12	26
30-fillet-after-shell	pass	Box	21745.915 / 21745.876	14968.284 / 14968.332	27 / 27	464
31-fillet-l-all-edges	pass	L	14321.483 / 14321.626	5024.004 / 5024.045	38 / 38	747
32-boss-plate-fillets	pass	Part	33590.273 / 33590.350	9929.854 / 9929.864	10 / 10	1214
33-fillet-tangent-chain	pass	Slot	8237.037 / 8237.122	2793.541 / 2793.569	14 / 14	555
34-chamfer-then-fillet	pass	Box	22892.383 / 22892.421	4753.677 / 4753.688	18 / 18	54
35-fillet-curved-curved	pass	Tee	63169.685 / 63171.443	10269.168 / 10269.348	6 / 6	904
36-corner-blend-two-radii	pass	Box	57799.504 / 57800.240	8585.437 / 8585.524	18 / 18	519
37-pyramid-apex-blend	pass	Pyramid	15465.376 / 15465.575	3914.529 / 3914.581	18 / 18	312
38-coincident-cylinders	pass	A	15706.406 / 15707.963	3769.760 / 3769.911	3 / 3	67
39-tee-pipe	pass	Tee	24095.763 / 24096.237	16709.772 / 16710.048	7 / 7	182
40-box-sphere-torus	pass	A	36287.558 / 36287.433	10696.143 / 10696.165	10 / 10	2393
41-tube-radial-holes	pass	Tube	20243.046 / 20243.981	14873.689 / 14873.773	22 / 22	1409
42-overlapping-patterns	pass	Plate	38488.411 / 38487.064	21687.215 / 21686.603	43 / 43	533	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	5
44-shell-l-bracket	pass	L	8384.000 / 8384.000	8784.000 / 8784.000	15 / 15	3
45-shell-boss-plate	pass	Part	13676.354 / 13676.602	14156.531 / 14156.602	15 / 15	69
46-shell-two-open-faces	pass	Box	16044.000 / 16044.000	11398.000 / 11398.000	10 / 10	3
47-draft-curved-pocket	pass	Block	111387.998 / 111387.712	17700.336 / 17700.361	11 / 11	27
48-pulley	pass	Pulley	168508.160 / 168510.841	23718.215 / 23718.644	12 / 12	321
49-helical-sweep	pass	Spring	4733.931 / 4738.099	4765.903 / 4767.652	3 / 3	10552	solid 'Spring': face wrapping around a closed surface kept whole: split line does not reach the rings
50-sweep-tight-bend	pass	Bend	3758.025 / 3758.443	– / –	5 / 5	405
51-loft-rect-circle-offset	pass	Loft	61129.957 / 61133.116	9412.473 / 9411.655	6 / 6	251
52-circular-pattern-fillet	pass	Hub	47206.182 / 47206.850	14141.988 / 14142.171	21 / 21	820
53-path-pattern	pass	Plate	35010.499 / 35010.398	16463.947 / 16463.894	13 / 13	130
54-mirror-body-fillets	pass	Bracket	22780.113 / 22780.089	6972.831 / 6972.832	12 / 12	98
55-tapped-hole-cosmetic	pass	Plate	17542.360 / 17542.314	4761.590 / 4761.596	8 / 8	84
56-holes-on-curved-face	pass	Cyl	77941.171 / 77942.388	10592.951 / 10593.139	7 / 7	378
57-hole-pattern-sketch-points	pass	Plate	36767.029 / 36766.712	11818.165 / 11818.153	24 / 24	197
58-phone-stand	pass	Stand	74559.442 / 74559.177	29148.741 / 29148.785	19 / 19	24
59-enclosure-base	pass	Enclosure	34309.038 / 34309.486	33795.405 / 33795.610	39 / 39	286
60-pipe-flange	pass	Flange	323661.027 / 323660.979	56984.270 / 56984.564	16 / 16	993
61-shaft-keyway	pass	Shaft	47521.504 / 47525.946	9676.781 / 9677.096	14 / 14	182
62-heat-sink	pass	HeatSink	43125.000 / 43125.000	45725.000 / 45725.000	66 / 66	8
63-hinge-knuckle	pass	Hinge	4783.029 / 4783.117	4110.255 / 4110.287	14 / 14	118
64-sketch-tangent-arc-chain	pass	Wave	4800.000 / 4800.000	3843.701 / 3843.712	9 / 9	10
65-sketch-gear-tooth	pass	Tooth	3987.831 / 3988.084	1945.416 / 1945.485	9 / 9	8
66-sketch-linkage	pass	Link	8045.410 / 8045.386	4308.172 / 4308.175	10 / 10	129
67-sm-base-flange	pass	Body1	15000.000 / 15000.000	12800.000 / 12800.000	6 / 6	2
68-sm-edge-flange	pass	Body1	18972.476 / 18972.622	16057.518 / 16057.550	14 / 14	26
69-sm-tray	pass	Body1	29665.828 / 29666.234	24979.993 / 24980.086	46 / 46	66
70-sm-flange-45	pass	Body1	18450.704 / 18450.777	15629.621 / 15629.637	14 / 14	14
71-sm-custom-rule	pass	Body1	10053.579 / 10053.717	13896.249 / 13896.299	22 / 22	38
72-sm-contour-flange	pass	Body1	12097.478 / 12097.622	10411.968 / 10412.002	22 / 22	36
73-sm-hem	pass	Body1	21334.478 / 21334.723	17994.397 / 17994.473	22 / 22	60
74-sm-unfold-refold	pass	Body1	15800.086 / 15800.304	13610.275 / 13610.326	32 / 32	84
75-sm-bracket-holes	pass	Body1	13915.866 / 13916.012	12035.934 / 12035.962	25 / 25	100
76-sm-thickness-variant	pass	Body1	22520.368 / 22520.575	16064.089 / 16064.128	14 / 14	31