Shadow Silhouette Maps

Pradeep Sen, Mike Cammarano, Pat Hanrahan
Computer Science Department
Stanford University

Submitted to Siggraph 03


The most widely used techniques for interactive rendering of hard shadows are shadow maps and shadow volumes. We observe that shadow map algorithms often suffice to determine shadowing for most areas of a rendered image. However, objectionable aliasing artifacts can arise in neighborhoods near the shadow silhouettes. In contrast, shadow volumes generate precise silhouettes, but perform significant amounts of extra work even for pixels far from shadow edges. In this paper, we propose the method of silhouette maps, in which a shadow depth map is augmented by storing the locations of representative points on the geometric silhouette. A piece-wise linear approximation to the true silhouette can then be found by applying dual-contouring techniques. The proposed method allows each silhouette map texel to represent a polygonal approximation to the actual shadowing geometry, in contrast to the jagged approximation provided by a conventional shadow map. We demonstrate an implementation of our approach running on programmable graphics hardware at interactive rates.

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Pradeep Sen
This page created by Mike Cammarano, Mon 27 Jan 2003
Last modified: Mon 27 Jan 2003