Abstract: The problem of computing soft shadows with area light sources has received considerable attention in computer graphics. Most of the solutions proposed have been limited to polygonal environments, and require a full visibility determination preprocessing step. The result is typically a partitioning of the environment into regions that have a similar view of the light source.

We propose a new approach that can be successfully applied to polygonal as well as non-polygonal environments. This approach is based on the observation that the primary difficulty in computing the contribution of an area light source in the presence of occluders is that of determining the discontinuities in the integrand, that is, determining the domain of the integrand that is not occluded. We extend previous work on an algorithm for linear light sources to calculate a polygonal approximation to the visible portion of the source. We demonstrate that for an important class of shadowing problems, namely those with at most two discontinuities in the domain of integration (e.g., with a convex occluder), the location of the discontinuity only needs to be roughly approximated by a linear boundary. We then use these boundaries to subdivide an area light source into a small number of triangles that can be integrated efficiently using low degree numerical cubatures.