Second-Order Occlusion-Aware Volumetric Radiance Caching

Abstract

Accurate simulation of light transport in participating media is expensive, due to the many scattering events. However, the band-limiting effect of scattering in media makes this kind of light transport very suitable for adaptive sampling and reconstruction techniques. In this work we present a novel algorithm that adaptively samples radiance from sparse points in the medium using up-to second-order occlusion-aware derivatives to determine when interpolation is appropriate. We derive our metric from each point's incoming light field. We use a proxy triangulation-based representation of the radiance reflected by the surrounding medium and geometry to efficiently compute the first- and second-order derivatives of the radiance at the cache points while accounting for occlusion changes. We validate the quality of our approach on a self-contained two-dimensional model for light transport in media. Then we show how our results generalize to practical three-dimensional scenarios, where we show much better results while reducing computation time up to a 30% compared to previous work.