Real-Time Shadow Generation Using BSP Trees and Stencil Buffers

This paper describes a real-time shadow generation algorithm for polygonal environments illuminated by movable point light sources. The main goal is to quickly reduce the number of hidden shadow volumes, by using a technique of volumetric shadow rendering using stencil buffers with a modified BSP tree, i.e. a simplified version of a SVBSP (Shadow Volume BSP) tree. It also provides new easy-to-implement approaches to improvement techniques used in shadow volume algorithms, such as silhouette detection to reduce the number of redundant shadow polygons and the computation of capping polygons to handle cases where the shadow volumes are clipped by the eye-view near clipping plane. Such hybrid approach solves important limitations on the original shadow rendering algorithm, as well as achieves real-time frame rates when using modest size scenes (about 500 shadow polygons), according to measurements performed on personal computers using current graphics hardware. Per-phase timing results from the implementation are provided along the text and compared with those of the standard algorithm.