To deal of umbra overestimation in some current soft shadow algorithms considering only the outer penumbra effects extended from traditional shadow mapping

a real-time approximating algorithm for plausible soft shadows based on depth peeling is proposed. The algorithm extracts the scene silhouette edges in geometry shader and generates the inner and outer penumbra primitives respectively through the silhouette edges. In the final rendering pass

the shading of each pixel is decided by referring to the shadow map and penumbra map

and plausible soft shadow effect which is more realistic than the results of previous methods is finally simulated. This algorithm runs entirely on GPU. Several experimental results show that

this algorithm generates more plausible soft shadows for relatively uncomplicated scenes than other methods and has real-time rendering speed.