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Abstract

In this paper we propose a new method for rendering soft shadows at interactive
frame rates. Although the algorithm only uses information obtained from a
single light source sample, it is capable of producing subjectively realistic
penumbra regions. We do not claim that the proposed method is physically
correct but rather that it is aesthetically correct. Since the algorithm
operates on sampled representations of the scene, the shadow computation does
not directly depend on the scene complexity. Having only a single depth and
object ID map representing the pixels seen by the light source, we can
approximate penumbrae by searching the neighborhood of pixels warped from the
camera view for relevant blocker information.

We explain the basic technique in detail, showing how simple observations can
yield satisfying results. We also address sampling issues relevant to the
quality of the computed shadows, as well as speed-up techniques that are able
to bring the performance up to interactive frame rates.