STL Preview for BB

Inspect 3D models without leaving your BB thread. Click an STL file to rotate, pan, zoom, or switch to wireframe in the side panel.

Install

bb plugin install git:https://github.com/obostjancic/bb-plugin-stl-preview.git@^0.1.0

Requires BB 0.46+, Plugin SDK 0.6.49+, and a WebGL2-capable browser or desktop client. No separate viewer, account, or API key.

Click an .stl file link in chat or use the file picker. From an agent thread:

bb thread open path/to/model.stl

If another opener is pinned, choose STL Preview under Settings → File openers, or right-click a file link and choose Open with.

Inspect the mesh

• Orbit, pan, zoom: drag to orbit, right-drag to pan, scroll to zoom. On touch screens, one finger orbits; two fingers pan and pinch to zoom.
• Reset view: fit the whole model back into view.
• Wireframe: inspect the STL's triangle mesh.
• Dimensions: read X/Y/Z bounding dimensions and the triangle count in the footer.
• Reload: fetch the latest file after an agent changes it.
• Open original preview: switch back to BB's built-in preview.

STL files contain no unit metadata. Dimensions are shown in model units, not assumed millimeters.

Try the sample

Open examples/showcase-bracket.stl after cloning the repository. The original demo includes rounded edges, counterbored mounting holes, an arched upright, and reinforcing ribs with openings.

The sample measures 96 × 72 × 75 mm and is one watertight, consistently wound mesh. It is a display sample, not a load-rated bracket or a verified print profile. The parametric source is included under the same MIT license.

To regenerate the sample with uv:

uvx --no-config --managed-python --python 3.13 --from cadgen==0.7.15 python examples/showcase-bracket.py

Python and cadgen are needed only to regenerate the sample, not to use the viewer.

File access and limits

Supports binary and ASCII STL, up to 64 MiB and one million triangles.

Workspace, project, host, and thread-storage files load through BB's existing authenticated file routes, including selected remote hosts. Models are rendered in your client; the plugin does not upload them to an external service or open another server port.

Files load when opened. Use Reload after changes; automatic file watching is not included. Malformed, empty, nonfinite, and oversized files show an error with retry and original-preview controls. Parsing happens on the client's main thread, so large meshes can briefly pause the interface.

This is a viewer, not a model editor, repair tool, or slicer.

Development

npm ci
npm test
npm run typecheck
npm run format:check
bb plugin build .
bb plugin install . --yes

After editing, rebuild and run bb plugin reload stl-preview. React and the BB SDK are provided by the host. Three.js is bundled into the viewer; rendering is on demand, with graphics resources and file requests cleaned up on close or reload.

License

MIT. Built with Three.js, also MIT licensed.