Automatic Creation of Object Hierarchies for Ray Tracing

Abstract

Intersection calculations dominate the run time of canonical ray tracers. A common algorithm to reduce the number of intersection tests required is the intersection of rays with a tree of extents, rather than the whole database of objects. A shortcoming of this method is that these trees are difficult to generate. Additionally, manually generated trees can be poor, greatly reducing the run-time improvement available. We present methods for evaluation of these trees in approximate number of intersection calculations required and for automatic generation of good trees. These methods run in O(nlogn) expected time where n is the number of objects in the scene. We report some examples of speedups.