Predictable and Targeted Softening of the Shadow Terminator

Abstract

A well known artifact in production rendering from the use of shading normals is the shadow terminator problem: the abrupt interruption of the light’s smooth cosine falloff at geometric horizons. Recent publications introduced several ad-hoc techniques, based loosely on microfacet theory to deal with these issues. We show that these techniques can themselves introduce artifacts and suggest a new technique that is an improvement in many situations. More importantly we introduce a framework for analyzing these different techniques so artists and researchers can choose appropriate solutions and more reliably predict and understand expected results.