RESEARCH ON METHODS FOR TRAVERSING TWO-LEVEL BVH TREES ON GRAPHICS PROCESSORS

A key part of the most common ray tracing methods is the traversal/search for intersections with a hierarchical structure - BVH, which describes the scene geometry. This paper presents a comparative analysis of the performance of several BVH tree traversal methods on stationary and mobile graphics processors. We investigated BVH trees with varying depths and numbers of child nodes, implemented several stack-based traversal algorithms, and two different stackless traversal algorithms; we proposed our own stackless traversal variant, which is more performant than existing ones in some cases. We proposed our own compression method for BVH trees with 2 nodes, losing no more than 15% performance. We identified a common problem that occurs in almost all algorithms when implemented on graphics processors. We believe that our analysis will help developers of ray tracing hardware accelerators create more economical hardware solutions, not limited solely to ray tracing. More specifically, our experimental results suggest that up to a 5x speedup can be achieved by changing the L2 cache mechanism, and this has likely already been implemented in stationary GPUs with hardware-accelerated ray tracing, not only within the ray tracing mechanism itself but also in a more general context.