Distribution Ray Tracing: Theory and Practice

Distribution ray tracing uses Monte Carlo integration to solve the rendering equation. This technique was introduced by Cook et. al, and was notable because of its simplicity and its ability to simulate areal luminaires, camera lens e ects, motion blur, and imperfect specular re ection[5]. Distribution ray tracing has been extended and modi ed by many researchers, most notably by Kajiya who added true indirect illumination[12]. Distribution ray tracing has also been used as the viewing component of radiosity systems (e.g [37, 3]). In this paper we examine some of the central issues of distribution ray tracing that have been overlooked in the literature but are still of importance. Our interest in distribution ray tracing arises for three basic reasons. The rst reason is that we believe any rendering system that has imperfect specular re ection (e.g. brushed steel) will use distribution ray tracing as a viewing method. Second, distribution ray tracing is a natural way to render outdoor scenes, where the e ects of single and double re ection dominate color, and where the geometry is extremely complex. Third, it is possible to run ray tracing on large distributed memory multiprocessors[25]. Although the implementation of a simple distribution ray tracer is usually implied to be straightforward, there are several important implementational