Soft Planar Shadows Using Plateaus

This paper presents an algorithm for rapidly creating and rendering soft shadows on a plane. It has the advantages of rapid generation on current hardware, as well as high quality and a realistic feel on a perceptual level. The algorithm renders the soft shadow to a texture. It begins with a hard drop shadow, then uses the object’s silhouette edges to generate penumbrae in a single pass. Though the shadows generated are physically inaccurate, this technique yields penumbrae that are smooth and perceptually convincing.