Computing caustic effects by backward beam tracing

Caustic effects produced by the transport of light from specular surfaces to diffuse surfaces are a common type of optical effect that cannot be modeled by ray tracing. We propose a two-pass algorithm to model caustic effects efficiently and reliably. In the proposed method, information on transmitted light beams is collected in a tree structure, which is used to compute the intensity efficiently. The method does not require the polygonization of diffuse surfaces and can easily be combined with any rendering algorithm.