Bandwidth-Efficient BVH Layout for Incremental Hardware Traversal

Abstract

The memory footprint of bounding volume hierarchies (BVHs) can be significantly reduced using incremental encoding, which enables the coarse quantization of bounding volumes. However, this compression alone does not necessarily yield a comparable improvement in memory bandwidth. While the bounding volumes of the BVH nodes can be aggressively quantized, the size of the child node pointers remains a significant overhead. Moreover, as BVH nodes become comparably small to practical cache line sizes, the BVH is cached less efficiently. In this paper we introduce a novel memory layout and node addressing scheme and map it to a system architecture for fixed-function ray traversal. We evaluate this scheme using an architecture simulator and demonstrate a significant reduction in memory bandwidth, compared to previous approaches.