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

Features

• File menu: a top menu bar with a File ▾ dropdown — Open… (open another CAD/mesh file), Save (flush the parts/edits/mesh sidecars now; the CAD file itself stays read-only), Save As… and Export… (both run the Export flow). Every item is also a VS Code command with a keyboard shortcut (Ctrl+O / Ctrl+S / Ctrl+Shift+S / Ctrl+E, scoped to a focused CAD Preview tab).
• Interactive camera: orbit, pan, zoom (OrbitControls with damping)
• View-manipulation panel: stepped rotate (15° / 45° / 90°), pan, zoom, Fit (reframe in place) and Ctr (reset to the default isometric view). The panel is collapsible — use the ⌄ / ⌃ button to hide or show it.
• Orientation cube: a labeled gizmo in the top-left corner that mirrors the current view; click a face to snap to that standard view
• Fit-to-view on open and on demand
• Shaded / wireframe toggle
• Axes and grid helpers
• Loading status indicator and error reporting
• Parts: define named groups by clicking volumes / surfaces / lines / points in the 3D view and assigning them to a part; assignments are colour-highlighted, listed in a tree panel, and saved to a <model>.parts.json sidecar (the CAD file stays read-only)
• Edits: apply non-destructive operations — transforms (move / rotate / scale / mirror), booleans (unite / subtract / intersect), fillet/chamfer, feature modeling (extrude / revolve / sweep / loft), assembly (explode / mate), primitive creation (box/cube, sphere, cylinder, cone, torus, N-sided prism), 2D profile sketches (circle, rectangle, N-sided polygon — pick one later as an extrude/revolve/sweep/loft profile), and bottom-up wireframe modeling (points, lines, arcs → build a surface from a set of lines → build a volume from a set of surfaces); operations are undoable, replayable, and saved to a <model>.edits.json sidecar — the CAD file stays read-only, and edits are baked in only on Export. (Transforms, booleans, explode, and primitive creation work on both B-rep and mesh; fillet/chamfer, feature modeling, mate, 2D profile sketches, and the wireframe/build ops are B-rep only.)
• Export: convert the open model to a compatible format and save it via a native Save dialog — see Export below
• FE Meshing: generate a finite-element mesh (nodes + triangles/tetrahedra) of the open model with Gmsh compiled to WebAssembly, shown as an overlay on top of the existing view. Options (dimension, element size, algorithm, element order) are set in the FE Mesh panel and autosaved to a <model>.mesh.json sidecar alongside a generated, editable <model>.geo script; 📤 Export saves the mesh to disk in any format the panel's dropdown offers, defaulting to Kratos MDPA (hand-written, in either an Elements+Conditions or a Geometries layout, preserving named Parts as Kratos SubModelParts), or Gmsh .msh/.msh2/.geo_unrolled, VTK, I-DEAS Universal, Abaqus, Nastran, SU2, INRIA Medit, STL, Diffpack, OFF. The CAD file stays read-only. See GMSH Integration for details.

Export

The File ▸ Export… menu item (or Ctrl+E) converts the currently displayed model to a compatible format. Available targets depend on the source file's pipeline:

The source format itself is never offered. B-rep targets are written entirely in the extension host via OCCT; mesh targets are serialized in the webview from the already-tessellated Three.js model (there is no way to promote a triangle mesh back into a B-rep). glTF export always produces a single binary .glb file. See File Formats → Export for details.

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/:

Packaging

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

Documentation

Full documentation is available at https://loumalouomega.github.io/CAD-Preview/

Source lives in the doc/ folder, built with VitePress and deployed automatically to GitHub Pages on every push to master. See .github/workflows/docs.yml.

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.

Licensing

CAD-Preview bundles @loumalouomega/gmsh-wasm, which compiles the Gmsh mesh generator and statically links it (together with OpenCASCADE Technology) into a single WebAssembly binary. Gmsh is distributed under the GNU General Public License, version 2 or later (GPL-2.0-or-later), with a linking exception that covers Netgen, METIS, OpenCASCADE, and ParaView. Because CAD-Preview ships that compiled binary as part of the extension, CAD-Preview itself is distributed under the GPL-2.0-or-later — see LICENSE for the full text.

OpenCASCADE Technology (OCCT) is used in two places in this extension: directly, via opencascade.js, for the native B-rep read/export pipeline, and indirectly, inside gmsh-wasm's meshing pipeline. OCCT is licensed under the GNU Lesser General Public License, version 2.1, with an additional exception granted by its authors.

Anyone who needs to use Gmsh under terms other than the GPL can obtain a separate commercial license directly from its authors at gmsh.info.

Attribution

• Gmsh — C. Geuzaine and J.-F. Remacle. https://gmsh.info
• OpenCASCADE Technology (OCCT) — https://dev.opencascade.org

License

See LICENSE.