Rendering antialiased shadows with depth maps

@inproceedings{Reeves1987RenderingAS,
  title={Rendering antialiased shadows with depth maps},
  author={William T. Reeves and D. Salesin and Robert L. Cook},
  booktitle={SIGGRAPH '87},
  year={1987}
}
We present a solution to the aliasing problem for shadow algorithms that use depth maps. The solution is based on a new filtering technique called percentage closer filtering. In addition to antialiasing, the improved algorithm provides soft shadow boundaries that resemble penumbrae. We describe the new algorithm in detail, demonstrate the effects of its parameters, and analyze its performance. 
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