Geometry Pipeline

The geometry pipeline converts user configurations into renderable 3D meshes and exportable 3MF files.

Data Flow

User changes bin config
  → Zustand store updates
  → Web Worker receives config
  → Manifold WASM generates CSG mesh
  → Mesh transferred back to main thread
  → Converted to Three.js BufferGeometry
  → 3D viewport updates in real-time

Web Worker

Heavy CSG operations run in a Web Worker (manifoldWorker.ts) to keep the UI thread responsive. The worker:

1. Initializes the Manifold WASM module once, sharing an initialization promise across concurrent requests
2. Receives bin or baseplate configurations via postMessage
3. Runs CSG operations (boolean subtract, add)
4. Rejects empty or invalid solids, extracts XYZ positions and triangle indices, and transfers the arrays to the main thread

Caching

Generated meshes are cached by mode and configuration in a bounded LRU cache. A new preview request cancels an older pending result for that bin, even when the new configuration is cached. The viewport clones cached arrays before its Y↔Z coordinate swap; exports keep Z-up coordinates.

Coordinate Systems

System	Up Axis	Used By
Manifold	Z-up	CSG operations
Three.js	Y-up	3D rendering
3MF	Z-up	Export files

When converting from Manifold to Three.js:

1. Swap Y and Z vertex coordinates
2. Reverse triangle winding order (to fix normals)

Performance

• One geometry for preview and export: what you see is what you print (feet, stacking lip, chamfers). Preview uses coarser curve tessellation for speed; export renders full resolution.
• Web Worker: all CSG (preview and 3MF export) runs off the main thread
• Mesh caching: avoids redundant CSG operations

Fit Verification

mating.test.ts compares cross-sections against independent numerical reference dimensions and checks bin/baseplate intersections. export3mf.test.ts reconstructs the three fit-kit solids from the serialized archive and checks dimensions, connectivity, placement, and assembled interference. These checks do not replace a physical print or a slicer smoke test. See Print a Fit Test.

The change verification record records commands, browser scenarios, rollback boundaries, and remaining validation limits.