Girder — BIM clash viewer

A browser BIM coordination viewer: a procedurally generated four-storey building (structural frame, architecture envelope, MEP services) rendered with three.js, and a pure, unit-tested clash-detection engine that finds every place the services run into the structure — the classic clash review, entirely client-side.

Live demo: https://girder.vitaliipopov.dev · no backend, no login

What it shows

• Clash detection as pure logic — src/model/clash.ts intersects AABBs across discipline pairs (structure/architecture vs MEP) with a touch tolerance, returns overlap volume + centroid, severity-sorted. No three.js imports; pinned by unit tests.
• Deterministic model as code — src/model/building.ts generates the building from grid constants and deliberately mis-routes three MEP runs (duct at beam elevation, pipe through a column line, pipe clipping a soffit). Tests assert every planted error is found and every cleanly routed run stays clash-free — the test suite caught a real routing mistake during development.
• Viewer UX from real BIM tools — click a clash: the camera flies to it, the pair lights up red/amber, and the rest of the model turns to glass (isolate-with-ghosted-context, NavisWorks-style). Plus a section plane slider, per-discipline visibility, and a model browser with element counts.
• Imperative 3D behind a small API — src/viewer/scene.ts owns the render loop; React never re-renders on camera moves. The same host/extension split used when building tooling on top of embedded 3D viewers.

Run it

npm install
npm run dev        # vite dev server
npm test           # clash engine + model generator (node --test)
npm run build      # tsc + vite

Background

Generalised from production work extending a web-based BIM viewer (three.js-hosted) with coordination tooling — clash/collision checks, work-set grouping and review UI. This is a clean-room, self-contained reproduction of those patterns: same discipline, none of the original code or data.