high performance computing on graphics processing units: hgpu.org

Raytracing dynamic scenes at interactive rates has received a lot of attention recently. We present a few strategies for high performance ray tracing on a commodity GPU. The construction of grids needs sorting, which is fast on GPUs. The grid is thus the acceleration structure of choice for dynamic scenes as per-frame rebuilding is required. We advocate the use of appropriate data structures for each stage of raytracing, resulting in multiple structure building per frame. A perspective grid built for the camera achieves coherence for primary rays. A perspective grid built with respect to each light source provides the best performance for shadow rays. Spherical grids handle lights positioned inside the model and handle spot lights. Uniform grids are best for reflection and refraction rays with little coherence. We propose an Enforced Coherence method to bring coherence to them by rearranging the ray to voxel mapping using sorting. This gives the best performance on GPUs with only user managed caches. We also propose a simple, Independent Voxel Walk method, which performs best by taking advantage of the L1 and L2 caches on recent GPUs. Ideas presented here are likely to give high performance on the future GPUs as well as other manycore architectures.