Packet-based Ray Tracing of Catmull-Clark Subdivision Surfaces

Efficient ray tracing of subdivision surfaces is an important problem in production rendering, and for interactive applications in the near future. The current hardware trends for both CPUs and GPUs suggest that compute power is outpacing bandwidth. Despite this, current approaches for ray tracing subdivision surfaces favor geometry caches or full pre-tessellation. We demonstrate that directly ray tracing subdivision surfaces using ray packets uses much less bandwidth, while still providing amortization benefits. Our proposed method performs competitively with pre-tessellation even on current hardware, outperforms a single-ray implementation by up to 16× and Pixar’s PRMan 13.0 geometry caching by up to 11×.