Hemispherical Rasterization for Self-Shadowing of Dynamic Objects

Abstract

We present a method for interactive rendering of dynamic models with self-shadows due to time-varying, lowfrequency lighting environments. In contrast to previous techniques, the method is not limited to static or preanimated models. Our main contribution is a hemispherical rasterizer, which rapidly computes visibility by rendering blocker geometry into a 2D occlusion mask with correct occluder fusion. The response of an object to the lighting is found by integrating the visibility function at each of the vertices against the spherical harmonic functions and the BRDF. This yields transfer coefficients that are then multiplied by the lighting coefficients to obtain the final, shadowed exitant radiance. No precomputation is necessary and memory requirements are modest. The method supports both diffuse and glossy BRDFs.