Accelerated Single Ray Tracing for Wide Vector Units

Abstract

Utilizing the vector units of current processors for ray tracing single rays through Bounding Volume Hierarchies has been accomplished by increasing the branching factor of the acceleration structure to match the vector width. A high branching factor allows vectorized bounding box tests but requires a complex control flow for the calculation of a front-to-back traversal order. We propose a novel algorithm for single rays entirely based on vector operations that performs a complete traversal iteration in constant time, ideally suited for current and future micro architectures featuring wide vector units. In addition we use our single ray technique as a building block to construct a fast packet traversal for coherent rays. We validate our algorithms with implementations utilizing the AVX2 and AVX-512 instruction sets and demonstrate significant performance gains over state-of-the-art solutions.