Interactive voxelized epipolar shadow volumes

Abstract

Current algorithms for rendering shadows inside participating media hit a bottleneck when computing light visibility throughout the media. These algorithms rely either on sampling along viewing rays, often thrashing memory caches, or slower analytic solutions using object-space computations, such as shadow volumes. We present a new cache-coherent sampling technique that computes volumetric light visibility that requires as little as one texture lookup per pixel. We efficiently voxelize shadow volumes in epipolar-space using standard parallel scan operations. The only step dependent on geometric complexity is an image-space voxelization [Eisemann and Décoret 2006] that often takes under a millisecond. This allows us to render shadows in participating media at up to 300 frames per second.