Fast Soft Shadow Mapping by Backprojection

The recent soft shadow mapping technique allows the rendering in real-time of convincing soft shadows on complex and dynamic scenes using a single shadow map.While attractive,this method becomes extremely expensive when dealing with large penumbrae.This paper proposes a new edge data structure to remove these limitations and hence providing an efficient and practical technique for soft shadow generation,which is an algorithm with three passes.First,we generate the depth map from the light view point.It is then followed by the second pass to extract the silhouette edge using our new area light edge operator.In the rendering pass,for each fragment we query all edge points in kernel area,find its corresponding silhouette edge,and back-project them onto the 2D light source domain,in which the occluded area is radially integrated.Finally,we use the visibility of the fragment to generate realistic soft shadow.Experimental results show that the algorithm can be used to achieve good results with the current graphics hardware.