SIMD for Collision
8 hours ago
- The author applies 'wide SIMD' to collision detection by processing multiple edge-edge tests simultaneously, similar to previous work on the contact solver.
- 'Wide SIMD' processes multiple work units (like 4 edges) at once, differing from 'narrow SIMD' which vectorizes single 3-vector operations.
- The Separating Axis Test (SAT) for convex hull collision in 3D has quadratic complexity, especially edge-edge tests which dominate for complex hulls.
- With many edges (e.g., 89 edges in a boulder hull), SIMD using SSE2 gives over 2x speed improvement in the full simulation.
- The optimization primarily benefits complex hulls; it has negligible effect on box-box collisions.
- Box3D uses SAT instead of GJK+EPA, avoiding collision margins and numerical brittleness.