Forward area light map projection

Abstract

We present a new method for soft shadow visualization. This two-stage approach generates high-quality soft shadow images by projecting sampled surface points, which are kept in a "layered area light map", onto the viewing screen. The layered area light map is created in the preprocessing stage, and is multi-layered in the sense that each map cell keeps the visibility ratio of the area light source with respect to multiple surface points at varying depth. In the forward projection stage, we project the sampled surface points in the layered area light map onto the screen buffer to attenuate a shadowless reference image in order to quickly generate the final image. Dynamic splatting and object surface-based convolution are used in the process to fill "holes" and to smooth out minor artifacts that are caused by insufficient sampling. When a series of images for a given scene are to be produced this forward projection rendering technique is much faster than ray tracing and still results in soft shadows with comparable quality.