In this paper, we present an algorithm that renders anti-aliased, soft edged shadows using a modified shadow-mapping approach. Our algorithm adds the silhouette information to the shadow map, thus allowing rendering precise and continuous shadow boundaries. Soft shadows for small spherical light sources are rendered using a variation of the percentage closer filtering algorithm [Reeves 1987]. The critical improvement of our algorithm over previous approaches is that it runs completely on the GPU using only two passes. This includes the silhouette detection step which is done completely in the vertex and pixel shaders using specially generated version of the mesh.
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