Rendering many lights with grid-based reservoirs

Abstract

Efficient rendering of scenes with many lights is a longstanding problem in graphics. Sampling a light to shade from the pool of all lights, e.g., using next event estimation, is a nontrivial task. Sampling must be computationally efficient, must select lights contributing significantly to the shaded point, and must produce low noise while introducing little or no bias. Typically, the light pool is preprocessed to create a data structure that accelerates sampling queries; this may be complex to implement, build, and update. This chapter builds a new sampling algorithm, ReGIR, based on a simple uniform grid structure and the recent screen-space resampling algorithm ReSTIR, which we extend to sample secondary rays in world space.