Coherent Ray Tracing via Stream Filtering
We introduce an approach to coherent ray tracing based on a new stream filtering algorithm.  This algorithm, which is motivated by breadth-first ray traversal and implicit reordering of ray elements, exploits the coherence exhibited by processing arbitrarily-sized groups of arbitrary rays in SIMD fashion.  These groups are processed by a series of filters that eliminate inactive rays throughout the various stages of the rendering process.  We present results obtained with two detailed simulators, including a cycle accurate simulation of an architecture that supports efficient scatter/gather memory operations and wider-than-four SIMD operations.  Using an appropriate hardware architecture, stream filtering achieves frame rates of 15-25 fps for scenes of high geometric complexity with path tracing and a variety of visual effects, including diffuse interreflection.