Rearchitecting spatiotemporal resampling for production

Recent work by Bitterli et al. [BWP * 20] introduced a real-time, many-light algorithm for rendering dynamic direct illumination from millions of lights by iteratively applying resampled importance sampling using weighted reservoir sampling. While enabling new levels of lighting complexity in real-time, the total cost remained beyond the budgets of even the most computationally demanding games. We introduce key algorithmic improvements developed while productizing this method that collectively reduce lighting costs by up to 7X, dramatically improve memory coherence, shrink the required ray budget, increase rendering quality, and expose parameters that enable trading quality for performance.