taucad/opencascade.js: Port of the OpenCascade CAD library to JavaScript and WebAssembly via Emscripten. · GitHub

The OpenCASCADE 3D CAD kernel, compiled to WebAssembly with TypeScript bindings.
Documentation · Issues

Build solids, run booleans, fillet edges, mesh, and read/write STEP — in a browser tab, a Node CLI, or an LLM tool call. Source lives in taucad/opencascade.js; this is not an official Open CASCADE Technology distribution.

npm install libcascade

import oc from 'libcascade';

using box = new oc.BRepPrimAPI_MakeBox(10, 10, 10);
const shape = box.Shape();

The root export is an initialised instance, selected for the variant the host supports. Every bound symbol is also a named export.

Pass options through a fixed initializer when the variant is known:

// Vite / browser, with a relocated wasm asset
import { createInstance } from 'libcascade/single/init';
import wasmUrl from 'libcascade/single/wasm?url';

const oc = await createInstance({ locateFile: () => wasmUrl });

The package is ESM-only. The WASM resolves on its own — reach for locateFile only when a bundler or deployment moves the binary. Deep imports into dist/ are not a supported surface.

The tarball ships dist/opencascade_single.{wasm,js} and dist/opencascade_multi.{wasm,js}, each with a provenance.json sidecar naming the exact toolchain and source commits. Both variants share one assembled types.d.ts surface. Releases publish through GitHub OIDC Trusted Publishing with Sigstore provenance — see the release flow.

For batch meshing, boolean grids, and STEP→glTF pipelines that use OCCT's internal thread pool, ask for the pthread build:

import { createInstance } from 'libcascade/multi/init';

const oc = await createInstance();

// Run once after init — flip OCCT global parallel defaults.
oc.BOPAlgo_Options.SetParallelMode(true); // booleans fan out
oc.BRepMesh_IncrementalMesh.SetParallelDefault(true); // meshing fans out

createInstance owns the pthread plumbing: worker self-reference, Node path conversion, and thread-pool sizing. Under Vite, set worker: { format: 'es' } — Emscripten's workers are ES modules.

Browsers need Cross-Origin-Opener-Policy: same-origin and Cross-Origin-Embedder-Policy: require-corp on every page that loads the threaded binary. The multi-threading guide covers activation, measured speedups, and when not to ship threaded.

Reach for @libcascade/toolchain when you need a binary the prebuilt one is not: a trimmed symbol set, your own C++ wrappers, or different Emscripten link settings. It drives digest-pinned Docker images for you, so there is no docker run string to maintain. A container engine must be installed and running.

npm install --save-dev @libcascade/toolchain

// libcascade.config.ts
import { defineBuild } from '@libcascade/toolchain';

export default defineBuild({
  name: 'myapp',
  bindings: ['BRepPrimAPI_MakeBox', 'TopoDS_Shape', 'gp_Pnt'],
  settings: { MODULARIZE: true, EXPORT_ES6: true, ALLOW_MEMORY_GROWTH: true },
  compilerFlags: { optimize: 'O3', simd: true, exceptions: 'wasm', noEntry: true },
  variants: [{ name: 'single' }],
});

npx libcascade build       # link each variant through the pinned image → dist/
npx libcascade assemble    # shared types.d.ts + ./init entry + exports map
npx libcascade check src   # CI drift guard: referenced symbols ⊆ bound symbols

Symbol names and -s settings are compile-checked against unions generated from the pinned image, so a typo is a TypeScript error rather than a runtime BindingError.

• Toolchain quickstart
• Config reference
• Migrate from a yml build

Images publish to ghcr.io/taucad/opencascade.js as multi-arch manifest lists (linux/amd64 + linux/arm64). Docker resolves the architecture itself, Apple Silicon runs natively, and no --platform flag is needed.

Building the image, or driving it directly, is covered in MAINTAINER.md.

Overload dispatch measures ~264 ns/call, under 0.011% of wall time on typical CAD models. BENCHMARKS.md carries the evidence: CAD wall-clock against native C++, threading speedup, embind dispatch cost, and RBV overhead. CHANGELOG.md has the full entry.

• ArchiYou — library, code-CAD design tool, community hub
• BitByBit — code- and node-based CAD tool
• CascadeStudio — library and code-CAD design tool
• Replicad — library and code-CAD design tool
• Tau — AI-native CAD platform for the web

Start with CONTRIBUTING.md, check TODO.md for the backlog, and use MAINTAINER.md to build from source.

See LICENSE.