A Cost Metric for Scene-Interior Ray Origins

Acceleration structures reducing the number of intersection tests are crucial for high ray tracing performance. The best acceleration structures are currently obtained using the surface area heuristic (SAH) which greedily optimizes a cost metric based on a series of heuristic assumptions about the rays. Noting that rays in many cases originate within the scene’s bounding box, we assume a uniform distribution of their origins throughout the scene and derive alternative cost metrics. Our experimental results show that at a slight increase in acceleration structure build time, an improvement in ray tracing speed over the SAH is achieved for most scenes. A more accurate metric based on our assumptions yields even more reliable speed-ups at the cost of higher construction time. We conclude that making more realistic assumptions than the SAH is a promising route for better ray tracing acceleration.