Research on Fast Soft Shadow Algorithm Based on 4D Rasterization

摘要

This paper introduces an algorithm that extends traditional 2D projection and rasterization to 4D space for fast soft shadow rendering. First, the rectangular area light source is seen as a point light source that translates with two degrees of freedom. As the point light source moving, the projections of the triangles and the output image samples on the projection plane are also moving. The locus of the projection is called the 4D projection. 4D projections are rasterized, and a conservative set of output image sample/triangle pairs can be obtained. The set is then examined to derive light mask for each sample. Since all potentially blocking triangles are considered, the algorithm is an accurate algorithm. And, the algorithm does not require any type of precomputation, so it supports fully dynamic scene. We have tested our algorithm on several scenes to render complex soft shadows accurately at interactive rates.