NVIDIA has recently shared its SIGGRAPH 2020 paper studying how to render dynamic direct lighting and shadows from millions of area lights in real-time.
Previously, the game studios used baked solutions and added a few dynamic emitters. Then, RTX games allowed developers to use dynamic area lights with physically correct shadows, but the budget is currently limited at a certain number of lights.
A denoised rendering using ReSTIR, the algorithm from the SIGGRAPH 2020 paper, capable of ray tracing scenes with millions of lights in real-time.”
The NVIDIA research division teamed up with the Visual Computing Lab at Dartmouth College to study how to direct lighting from millions of moving lights with today’s ray budgets. There's no complex light structure, no baking, and no global scene parameterization. The team promises results up to 65x faster than the current state.
The model was described in the paper “Spatiotemporal Reservoir Resampling for Real-Time Ray Tracing with Dynamic Direct Lighting” which gives theoretical and implementation details for the reservoir-based spatiotemporal importance resampling (ReSTIR) technique.
“Our key insight was to reuse information from spatially and temporally adjacent pixels to inform which rays to trace,” said Benedikt Bitterli, one of the model’s developers. “This idea resembles modern post-process denoising and antialiasing, but while denoising filters the pixel colors directly, we filter probabilities to help guide rays to reduce future noise.”
You can learn more here.