SoftForge OCCT add-on

The OpenCASCADE (OCCT) kernel for the SoftForge Electronic Workbench extension (SoftForge.softforge-electronic-workbench, 1.4.0 and newer). It is a separate extension because the kernel — opencascade.js 1.1.1, OCCT 7.4 compiled to WebAssembly — is about 65 MB; the main extension stays small and works without it.

With the add-on installed the MCAD features of the main extension get:

Install

Build the VSIX from the repository root with npm run package:occt (about 14 MB; the wasm is compressed in it), then install it next to the main extension:

code --install-extension softforge-occt-1.4.0.vsix

On start-up the add-on activates the main extension and registers itself with api.system.registerOcct(...). The wasm is loaded lazily on the first OCCT call (about 0.6 s). The SoftForge OCCT output channel logs the load time, each call and errors; SoftForge OCCT: Self test meshes a box and shows the kernel version.

The ewb CLI

ewb runs without VS Code, so it finds the add-on by itself: EWB_OCCT_ADDON (the add-on folder or its out/service.js), else the newest installed softforge.softforge-occt-* under ~/.vscode/extensions, ~/.vscode-server/extensions, ~/.vscode-oss/extensions or ~/.vscode-insiders/extensions. It requires out/service.js and calls createOcctService().

EWB_OCCT_ADDON=/path/to/packages/occt-addon ewb …

Frames

• STEP / MCAD frame: mm, z up, x = KiCad x, y = −KiCad y, z = 0 on the board's bottom face (KiCad's own STEP frame without an origin offset). Every service call works in this frame.
• glb: metres, y up — glb (x, y, z) = MCAD (x, z, −y) / 1000, like kicad-cli.

Service (out/service.js, createOcctService())

• stepToGlb(step, { meshQuality }) — one mesh per solid; linear deflection = bbox diagonal × lerp(0.01, 0.0005, q), angular lerp(0.5, 0.15, q) rad; bounds in mm.
• boardToStep({ outline, holes, thickness, components }) — board prism from z = 0 with the holes cut; components read from their STEP, scaled, rotated about x, then y, then z (degrees) and moved to at. Written as an XCAF assembly "Board" with the part "PCB" and one part per reference (a model used twice is stored once).
• outlineFrom(file, { plane, tolerance }) — .dxf through the TypeScript reader; STEP: the largest planar face with a ±z normal (top-most for top, bottom-most for bottom), curved edges discretised to tolerance (mm); without such a face a section at mid height is chained into loops.
• booleans(a, b, op) — each input set is one region by the even–odd rule; the result is flattened as, for each face, its outer ring (counter-clockwise) followed by its holes (clockwise).
• bossesOf(step) — vertical cylindrical faces with 1 mm ≤ d ≤ 20 mm, merged within 0.1 mm: at = axis x, y and the face's top z; height = the face's z extent.
• assemblyStep(parts) — each part's STEP placed by its column-major 4×4 matrix (rigid), one named STEP assembly.
• version(), available() (the wasm file is present; does not load it).

Limits

• opencascade.js 1.1.1 is single-threaded: large STEP files (100k+ faces) take seconds and block the extension host while they mesh.
• Colours and names are not read from STEP files (shapes only); names are written on export.
• Non-uniform component scales are applied as a general transform (the geometry may become B-splines).
• If the XCAF writer fails, assemblies fall back to one unnamed compound (lastAssemblyMode() reports compound).

License

The SoftForge code is MIT (LICENSE). opencascade.js and OCCT are LGPL-2.1; they ship unmodified as the separate file out/opencascade.wasm.wasm that the add-on loads at run time and that you may replace. See THIRD_PARTY_NOTICES.md.

Development

cd packages/occt-addon
npm install            # opencascade.js 1.1.1 (devDependencies come from the repository root)
npm run typecheck && npm run build
npm run make-enclosure # rewrites fixtures/mcad/enclosure.step
npm run package        # ../../softforge-occt-1.4.0.vsix
cd ../.. && OCCT=1 npx tsx --test test/mcad.occt.test.ts