Interactive volumetric shadows in participating media with single-scattering

Abstract

Scattering effects arising from participating media, such as smoke, haze, and fog, dramatically add to perceived realism in renderings. As shadows affect illumination throughout an environment, they significantly diminish scattering effects in umbral regions. Unlike surface shadowing, accurate volumetric shadows require simultaneously integrating illumination, scattering, and attenuation throughout the volume, which proves challenging for interactive applications. We propose a method for rendering volumetric shadows in homogeneous single scattering media that combines ray marching and shadow volume techniques, eliminating performance deficiencies inherent in both. We extend this approach to interactively render shadows from textured lights and show results under two scattering models. Our prototype uses graphics hardware to accelerate shadow volume and ray marching computations. However since our hybrid selects sample points more intelligently than brute force techniques, it could also be applied to traditional ray tracing.