Bounding volume hierarchy-tetrahedralization hybrid acceleration structure for ray tracing

Abstract

The computational cost of the ray-tracing method is directly proportional to the number of ray-surface intersection tests. The naive ray-tracing algorithm requires O(N) computational cost for the ray-surface intersection calculations where N is the number of primitives in the scene. Ray tracing acceleration data structures like the regular grid, bounding volume hierarchy (BVH), kd-tree, constrained tetrahedralization, has been developed to reduce the number of rayobject intersection tests to speed-up ray tracing. We propose a hybrid acceleration structure, the Bounding Volume HierarchyTetrahedral mesh hybrid (BTH) acceleration structure, that can be used to speedup ray tracing. BTH structure is composed of a BVH hierarchy where some of the leaves of the BVH hierarchy contain tetrahedralizations. We propose an algorithm for the construction of the BTH structure. We describe methods for approximating the average nearest-hit cost of a tetrahedralization, which we use for the construction of BTH. Besides, we can adapt the proposed BTH structure for dynamic scenes with hierarchical motion. We describe a two-level BVH-BTH acceleration structure for rendering animated scenes. We test the proposed BTH structure using various scenes. For some of the experiments, the BTH structure performs better against other acceleration structures in terms of rendering times. We perform experiments for animated scenes. We show that the two-level BTH structure outperforms the two-level BVH structure for the tested dynamic scenes.