Real-Time Approximate Soft Shadow Rendering on GPU

This paper presents a real-time approximate soft shadow rendering algorithm which runs entirely on GPU by extending the shadow mapping algorithm.This is an algorithm with three passes.In the first pass the depth map is generated from the light view point.It is then followed with the second pass to extract the silhouette edge using geometry shader and to generate penumbra map by extending the silhouette vertex along the normal.The new generated primitive is automatically interpolated by GPU.For the part of the penumbra map which is occluded,it is diminated using the depth map generated in the first pass in fragment shader.For the overlapped part,a fake depth value is set for each of the fragments so that they will be blended automatically by hardware through depth comparison.In the rendering pass,for each fragment we first lookup the depth map to decide whether the fragment is in shadow.For those not in shadow,we lookup the penumbra map to get the penumbra value.