RDH: Ray Distribution Heuristics for Construction of Spatial Data Structures

Surface area heuristics is currently the most popular method for view independent construction of spatial hierarchies for ray tracing. We present a method which modifies the surface area heuristics by taking into account the actual distribution of rays in the scene. This is achieved by subsampling the rays to be cast and using these rays in order to estimate the probabilities of rays traversing through nodes of the constructed hierarchy. The main aim of our paper is to analyze the potential of taking the ray distribution into account. The results indicate that we can achieve a minor speedup of ray traversal compared to standard SAH. For large densely occluded scene we can also save the construction time and memory consumption of the hierarchy by not subdividing parts of the scene where no rays are traced.