CAD-Preview

A Visual Studio Code extension that previews 3D CAD and mesh files directly in the editor. Open a supported file and CAD-Preview renders an interactive 3D view (orbit / pan / zoom) in a read-only custom editor.

B-rep (boundary-representation) formats are parsed and tessellated with OpenCascade.js (the OCCT CAD kernel compiled to WebAssembly). Already-triangulated mesh formats are loaded with native Three.js loaders. Rendering is always Three.js.

Supported formats

Format	Extensions	Pipeline
STEP	`.step`, `.stp`	OpenCascade.js → `BRepMesh` tessellation
IGES	`.iges`, `.igs`	OpenCascade.js → `BRepMesh` tessellation
BREP	`.brep`	OpenCascade.js → `BRepMesh` tessellation
STL	`.stl`	Three.js `STLLoader`
OBJ	`.obj`	Three.js `OBJLoader`
PLY	`.ply`	Three.js `PLYLoader`
glTF	`.gltf`, `.glb`	Three.js `GLTFLoader`

Features

Interactive camera: orbit, pan, zoom (OrbitControls with damping)
Fit-to-view on open and on demand via toolbar button
Shaded / wireframe toggle
Axes and grid helpers
Loading status indicator and error reporting

Architecture

OpenCascade.js (the WASM kernel) runs in the Node extension host, not in the webview. The host reads the file, tessellates B-rep shapes, and sends plain geometry buffers (base64-encoded typed arrays) to the webview. The webview runs only Three.js and is responsible for rendering and camera interaction. This keeps the WASM out of the webview (no CSP issues), keeps activation fast (the kernel is lazy-loaded only on the first B-rep open), and means pure-mesh files never load the WASM at all.

Extension host (Node)                    Webview (Chromium)
  read file bytes                          Three.js scene + OrbitControls
  OpenCascade.js parse + tessellate  ───▶  build BufferGeometry from buffers
  → base64 {positions, indices}            render, orbit/pan/zoom, toolbar
             — or —
  asWebviewUri(file)                 ───▶  STL/OBJ/PLY/GLTFLoader.loadAsync(url)

Development

npm install        # install dependencies
npm run build      # build extension host + webview bundles (esbuild) and type-check
npm run watch      # rebuild on change
npm test           # run unit tests (vitest)

Press F5 in VS Code to launch an Extension Development Host, then open any supported file from examples/:

Fixture	Format
`examples/STP/bull.stp`	STEP (B-rep, OCCT pipeline)
`examples/STL/cube.stl`	STL mesh
`examples/OBJ/cube.obj`	OBJ mesh
`examples/PLY/cube.ply`	PLY mesh
`examples/GLTF/cube.gltf`	glTF mesh

Packaging

npm run package    # produces cad-preview.vsix
code --install-extension cad-preview.vsix

CI

GitHub Actions runs on every push and pull request to master: builds the extension, runs unit tests, and uploads a .vsix artifact. See .github/workflows/ci.yml.

License

See LICENSE.

CAD Preview

kratos-multiphysics