Coupled Use of BSP and BVH Trees in Order to Exploit Ray Bundle Performance

The use of SIMD ray packets has been an important step forward in ray tracing performance. It is the first significant acceleration process based on a strategy that deals with "small" ray bundles. In order to improve the outcome for wider bundles, very powerful data structures have been used. However, these new data structures are not the most powerful when dealing with single rays or SIMD rays. They are therefore unsuitable, and this incompatibility raised the problem of incoherent rays which, such as secondary rays or global illumination rays (i.e. most the rays traced in real life ray tracing) are impossible to process efficiently. An original coupled use of BSP and BVH trees is proposed to overcome this disadvantage. Each tree, used individually, can efficiently boost both small ray bundles and wide ray bundles. Used together in a coupled strategy, they can achieve a global speedup of +50%.