Abstract: Among various soft shadow mapping techniques, the back-projection one can generate highquality soft shadows effects efficiently.The shadow map is adopted to represent the geometries of the scene discretely.The method evaluates the visibility factor of each pixel by back-projecting occluder contour edges extracted from the shadow map to the area light.However it suffers from shadow over estimation and light leaking artifacts for the scenes with complex depth and geometry distributions.In this paper we propose a mask based occluder contour edge back-projecting soft shadow method.By computing the depth complexity function of every sample-mask on the area light, we can successfully remove the shadow over estimation artifact.By incorporating it into multi-layered shadow mapping, we can then overcome the light leaking artifact.The experimental results show that the proposed method can generate more realistic and accurate soft shadows with high efficiency.