The alias-free shadow maps technique is the first shadow map-based algorithm that computes shadows at floating-point accuracy and handles transparent surfaces elegantly. However, its major disadvantage is that it is a specialized software rendering technique, because shadow computations are performed by using irregular sampling point locations. We present a new algorithm that inherits the strengths of alias-free shadow maps and has an efficient hardware-accelerated implementation. With our method, the sampling points are transformed into multiple layers of regular pixel boundaries with a point sprite rendering technique, and the rasterized geometry is modified to include the necessary information for computing accurate shadow terms. We also present novel acceleration techniques and propose a few hardware modifications to enable real-time implementations.
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