MBVH Child Node Sorting for Fast Occlusion Test

Abstract

Optimal BVH layout differs among ray types. To accelerate shadow rays, the use of a specialized traversal order, optionally with an additional data structure has been proposed. In this paper we show how sorting child nodes of MBVH (Multi Bounding Volume Hierarchy) improves the performance of occlusion test without changing the topology of the data structure.We introduce a cost metric suitable for MBVH which takes into account the distribution of representative rays, and prove that the cost can be minimized by sorting child nodes based on a very simple criterion. Our method is very easy to implement and requires only small amounts of storage and preprocessing time for sorting. We also demonstrate how rendering performance can be improved by up to 10% in conjunction with various algorithms.