The Soft Shadow Occlusion Camera

Abstract

A fundamental challenge for existing shadow map based algorithms is dealing with partially illuminated surfaces. A conventional shadow map built with a pinhole camera only determines a binary light visibility at each point, and this all-or-nothing approach to visibility does not capture penumbral regions. We present an interactive soft shadow algorithm based on a variant of the depth discontinuity occlusion camera, a non-pinhole camera with rays that reach around blockers to sample normally hidden surfaces. Our soft shadow occlusion camera (SSOC) classifies a fragment on a continuum from fully visible to fully hidden, as seen from the light. The SSOC is used directly in fragment illumination computation without building an explicit "soft shadow map." This method renders plausible soft shadows at interactive speeds under fully dynamic conditions.