Chapter 8. Summed-Area Variance Shadow Maps Andrew Lauritzen University of Waterloo In this chapter, we discuss shadow-map filtering and soft shadows. We review the variance shadow-mapping algorithm and explain how it can help solve many common shadowmapping problems. We also present a simple but effective technique for significantly reducing the light-bleeding artifacts associated with variance shadow maps (VSMs). Finally, we introduce a real-time shadowing algorithm based on VSMs and summedarea tables (SATs). We achieve efficient computation of shadow contributions for arbitrary rectangular filter regions, which makes summed-area variance shadow mapping (SAVSM) an ideal algorithm for soft shadows without aliasing. 8.1 Introduction Shadow mapping (Williams 1978) is a popular shadowing algorithm that offers several important advantages over shadow volumes (Crow 1977). In particular, shadow maps can be queried at arbitrary locations and are less sensitive to geometric complexity. Unfortunately, standard shadow…