Removal of Light Bleeding in Variance Shadow Maps

Variance shadow maps algorithm adopts a probability method to estimate the up-bound of the probability of a pixel falling in shadow,it effectively reduces the aliasing in traditional shadow maps algorithm by filtering the shadow maps themselves.However,this method may cause light bleeding in scenes of high depth complexity,i.e.areas with umbra may receive some light.In this paper,we propose an algorithm of integrating min-max shadow maps with variance shadow maps to remove light bleeding.We construct min-max shadow maps when we filter variance shadow maps.During the rendering process,the min-max shadow maps are used to determine whether a fragment is in shadow or not.While our new approach generates more realistic and accurate shadows,it can be easily integrated into the fragment shader of variance shadow maps,and lay no influence on soft edges of shadows and fps.