A Hybrid Approach

One more shadow algorithm which deserves mention is McCool's clever idea shadow volume reconstruction from depth maps [McCool 2000]. This algorithm is a hybrid of the shadow map and shadow volume algorithms and does not require a polygonal representation of the scene.  Instead of finding the silhouette edges via a dot product per model edge (shadow volumes), a depth map of the scene from the light's point of view is acquired (shadow map) from which the silhouette edges are extracted using computer vision techniques. From these edges the shadow volumes are constructed (silhouette edges are extruded) Creating soft shadows