Analysis of Cache Behavior and Performance of Different BVH Memory Layouts for Tracing Incoherent Rays

Abstract

With CPUs moving towards many-core architectures and GPUs becoming more general purpose architectures, path tracing can now be well parallelized on commodity hardware. While parallelization is trivial in theory, properties of real hardware make efficient parallelization difficult, especially when tracing incoherent rays. We investigate how different bounding volume hierarchy (BVH) and node memory layouts as well as storing the BVH in different memory areas impacts the ray tracing performance of a GPU path tracer. We optimize the BVH layout using information gathered in a pre-processing pass applying a number of different BVH reordering techniques. Depending on the memory area and scene complexity, we achieve moderate speedups.