ABSTRACT
This chapter discusses a class of algorithms for computing global illumination pictures known as path-tracing algorithms. The common aspect of these algorithms is that they generate light transport paths between light sources and the points in the scene for which we want to compute radiance values. This chapter explains the light-tracing algorithm that proceeds exactly along those lines. Light tracing is the dual algorithm of ray tracing, and many of the optimizations used in ray tracing can also be used in light tracing. Stochastic light tracing and ray tracing are dual algorithms and, in theory, solve the same transport problem. The camera acts as a source of importance during light tracing, while the light sources are the source of radiance in stochastic ray tracing. Shadow rays and contribution rays are each other’s dual mechanism for optimizing the computations of final flux through a pixel.
