AI-accelerated ray tracing: Nvidia's real-time neural radiance caching for path tracing could soon debut in Cyberpunk 2077

Nvidia’s Tensor cores that act as a small-scale neural network are seeing quite a few use cases these days with the advent of generative AI. Besides offering decent performance for local implementations of text-to-image and, more recently, text-to-video solutions, Tensor cores have proven their proficiency with real-time high-quality image upscale models like DLSS and frame generation. But there are other ways to utilize Tensor cores in games. One such use case was demonstrated two years ago by Nvidia in a research paper detailing a real-time neural radiance caching for path tracing (NRC), which essentially provides a less taxing and more precise way of showing ray traced reflections in games. According to CapFrameX, the NRC method is rumored to soon be implemented for Cyberpunk 2077 with the upcoming Phantom Liberty DLC releasing this June.

Cyberpunk 2077 already supports path tracing with the latest update. However, this feature drastically reduces performance on any of the RTX 30 or 40 cards. Thankfully, DLSS can help regain some of the lost fps. CD Project Red seems to be turning Cyberpunk 2077 into an Nvidia tech showcase, as the company now allegedly plans to improve the path tracing quality even further with the introduction of the neural radiance caching method.

In the 2021 research paper, Nvidia explains that NRC is optimized for fully dynamic scenes, yet it does not rely on pre-training and inference techniques to generalize surface light bounce. Instead, NRC is achieving generalization via adaptation, training the model in real-time as the rendering occurs. This self-training technique is similar to the older radiosity algorithms. While this can efficiently boost fps counts and visual fidelity, as well as free up VRAM, there is a slight downside, nonetheless. Each frame would see a 2.6 ms render time increase for FHD resolution, possibly more than 3 ms for 4K. Presumably this can still be combined with frame generation.

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