Non-Self-Adjacent Ray Classes for Parallelizable Shooting–Bouncing Ray Tracing Double Count Removal

We propose and experimentally validate a new ray spawning and associated double count removal (DCR) technique for shooting-bouncing ray tracing (SBR). This technique allows, for the first time, efficient parallelization of ray DCR, the major bottleneck and least parallel aspect of modern SBR ray-tracing relying on the ray-cone approximation (RCA). We define non-self-adjacent (NSA) ray classes on a recursively sampled icosahedron, guaranteeing removal of mutual adjacency data dependencies between rays that previously prevented efficient parallelization of ray DCR and, by extension, SBR. Using a GPU-parallelized implementation of the technique, we demonstrate speedups of DCR over 300×, limited in our testing only by the available hardware. As DCR is the asymptotically dominant contributor to the computation time of SBR-RCA, with respect to the number of parallel processes available, the achieved speedup applies to parallel SBR-RCA as a whole.