Compiling Open CASCADE to WebAssembly: Building Custom Web-Based CAD Kernels
Bridging native C++ geometric modeling engines with modern web browsers to perform high-precision B-Rep operations, STEP parsing, and mesh generation via Emscripten.
While WebGL and WebGPU handle visual rendering, true parametric CAD applications require robust geometry modeling kernels (B-Rep) to compute exact NURBS surfaces, boolean operations, and STEP file parsing directly in client-side memory.
1. Why WebAssembly for CAD Kernels?
JavaScript engines excel at DOM manipulation and reactive state management, but struggle with complex linear algebra, ray-triangle intersection, and topology stitching. Cross-compiling Open CASCADE Technology (OCCT) using Emscripten provides near-native C++ performance inside modern browsers.
2. Memory Management & WebWorker Threads
Heavy CAD operations can easily freeze the main UI thread. Executing WebAssembly OCCT instances inside dedicated WebWorkers ensures smooth 60 FPS viewport navigation while background threads calculate complex chamfers and fillets.
3. Converting B-Rep Geometry to Triangulated Meshes
Parametric geometry represented as NURBS faces must be triangulated before sending to GPU buffers. Utilizing Open CASCADE’s BRepMesh_IncrementalMesh allows developers to set adaptive deflection tolerances based on camera distance.