1. A method of performing ray tracing, comprising: issuing a ray into a three-dimensional scene; if the ray intersects a primitive contained within the three-dimensional scene, generating a first plurality of secondary rays; by operation of one or more computer processors, determining a respective culling probability to assign to each of the secondary rays, based on a depth of recursion from which the respective secondary ray is generated, relative to the issued ray, wherein the culling probability assigned to at least a first one of the secondary rays is determined based further on a type of the first secondary ray and a workload being experienced by at least one of the one or more computer processors; and issuing a limited subset of the secondary rays into the three-dimensional scene, wherein the limited subset of the secondary rays is determined by stochastically deleting at least one of the secondary rays based at least in part on the determined culling probability of the at least one of the secondary rays.