Unreal Engine 5 NvRTX Branch Has Been Updated with Experimental ReSTIR GI Support

NVIDIA has announced an update to the NvRTX branch of Epic's Unreal Engine 5. The major new feature is the addition of experimental support for ReSTIR Global Illumination, the ray tracing algorithm first discussed by NVIDIA researchers in the seminal paper Spatiotemporal Reservoir Resampling for Real-Time Ray Tracing with Dynamic Direct Lighting released at ACM SIGGRAPH 2020.

ReSTIR GI allows 'direct lighting from millions of moving lights' with ray budgets that are compatible with the demands of real-time rendering for games. The approach also doesn't require complex light structure, baking, or global scene parameterization, while still providing results up to 65x faster than prior techniques. All of the lights cast shadows, everything can move however necessary, and new emitters can be added dynamically.

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Since then, ReSTIR GI has been implemented in just two games: DESORDRE: A Puzzle Game Adventure and CD Projekt RED's Cyberpunk 2077 with Patch 2.1, which dropped last December. Modder Pascal Gilcher (also known as Marty McFly) showcased a work-in-progress path tracing ReShade mod featuring lighting based on the ReSTIR GI technique, though the mod is still far from done. Meanwhile, fellow modder NiceGuy also implemented a technique inspired by ReSTIR GI in his Complete RT shader (version 1.3).

The impact of this official addition is, of course, on another level entirely. Unreal Engine 5 is by far the most popular engine among PC and console developers and, as such, the potential adoption is immeasurably greater.

The implementation on the NvRTX branch was handled by NVIDIA's Jiayin Cao, who first joined NVIDIA in 2012 as a Developer Technology Engineer based in Shanghai, China. In 2016, he moved to Singapore to work at Ubisoft on Skull and Bones (which finally launched earlier this year after a very long development), where he filled the role of Senior Graphics