Second-Order Occlusion-Aware Volumetric Radiance Caching

TL;DR

This paper introduces a second-order gradient-based radiance caching method for volumetric light transport that adaptively samples and interpolates radiance, accounting for occlusion changes, with improved accuracy and efficiency.

Contribution

It develops a second-order Hessian-based error metric for adaptive sampling in volumetric radiance caching, enhancing accuracy and reducing computation time.

Findings

Outperforms previous radiance caching algorithms in accuracy.

Reduces computation time by up to 30%.

Provides a validated 2D model for light transport analysis.

Abstract

We present a second-order gradient analysis of light transport in participating media and use this to develop an improved radiance caching algorithm for volumetric light transport. We adaptively sample and interpolate radiance from sparse points in the medium using a second-order Hessian-based error metric to determine when interpolation is appropriate. We derive our metric from each point's incoming light field, computed by using a proxy triangulation-based representation of the radiance reflected by the surrounding medium and geometry. We use this representation to efficiently compute the first- and second-order derivatives of the radiance at the cache points while accounting for occlusion changes. We also propose a self-contained two-dimensional model for light transport in media and use it to validate and analyze our approach, demonstrating that our method outperforms previous radiance caching algorithms both in terms of accurate derivative estimates and final radiance extrapolation. We generalize these findings to practical three-dimensional scenarios, where we show improved results while reducing computation time by up to 30\% compared to previous work.