A Gentle Introduction to ReSTIR Path Reuse in Real-Time
Chris Wyman, Markus Kettunen, Daqi Lin, Benedikt Bitterli, Cem Yuksel, Wojciech Jarosz, Pawel M. Kozlowski
Abstract
In recent years, reservoir-based spatiotemporal importance resampling (ReSTIR) algorithms appeared out of nowhere to take parts of the realtime rendering community by storm, with sample reuse speeding direct lighting from millions of dynamic lights [1], diffuse multi-bounce lighting [2], participating media [3], and even complex global illumination paths [4]. Highly optimized variants (e.g. [5]) can give 100x efficiency improvement over traditional ray- and path-tracing methods; this is key to achieve 30 or 60 Hz framerates. In production engines, tracing even one ray or path per pixel may only be feasible on the highest-end systems, so maximizing image quality per sample is vital.