RTX Direct Illumination Shows Games will soon feature up to millions of dynamic lights

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If you’re a regular Wccftech reader, chances are you’ve come across our story about ReSTIR, an in-depth learning algorithm devised by NVIDIA engineers to display millions of dynamic lights in real time.

At the time, almost a year ago, ReSTIR (Reservoir-based Spatio-Temporal Importance Resampling) wasn’t quite ready for game development purposes as the rendering cost was around 50ms for 3.4 million dynamic lights. That’s far too much to be of any use to game developers, as programmers need to get their full display budget back in 16.6ms if they target 60 frames per second.

But fast forward to this week, and everything has changed as NVIDIA unveils game developer ready RTX direct lighting technology at GTC 2021. The RTXDI SDK combines ray tracing with a significantly higher performing version of the ReSTIR algorithm in conjunction with another deep learning algorithm, ReGIR (Reservoir-based Grid Importance Resampling), which acts as a first sample generator for ReSTIR and can be applied to secondary surfaces, while ReSTIR is reserved for primary surfaces.

RTX Direct Illumination promises to forgo the so-called ‘hero lights’ phenomenon in games, where only a few selected light sources actually cast shadows. This will allow for much more realistic scenes. But what about the performance? Good, according to RTX UE4 Game Engine Evangelist Richard Cowgill, with RTXDI it shouldn’t really matter if you need tens, hundreds, thousands or millions of lamps; the costs are expected to be about the same. As a result, the performance should be essentially flattened and more consistent, especially with NVIDIA DLSS enabled.

Perhaps even more exciting is that RTX Direct Illumination offers tangible benefits to artists and gamers alike. The former has RTXDI which tells the game’s graphics renderer where to send the beams without requiring manual input. The latter will finally interact with all the lights in a scene as they are dynamic which can potentially improve gameplay as players will cleverly find benefits by turning off or shooting one of the lights to cover a stealth approach , for instance.

As expected, NVIDIA has made sure that RTX Direct Illumination can be easily integrated with the existing RTX Global Illumination (RTXGI) SDK. By mixing the two, scalable global illumination should be possible based on many, many light sources.

Best of all, all this promising graphics technology isn’t just reserved for GeForce RTX users. Richard Cowgill even confirmed that RTXDI and RTXGI are both completely architecture agnostic and will therefore not only work on AMD’s Radeon RX 6000 series GPUs, but also on consoles that support ray tracing, such as PlayStation 5 and Xbox Series S | X. Supported graphics APIs include DirectX Raytracing and Vulkan Ray Tracing.

Game developers interested in implementing RTX Direct Illumination will of course need a noise suppressor. While NVIDIA recommends their Real-Time Denoiser, which comes with the ReLAX algorithm specially designed for noise reduction of ray-traced specular and diffuse signals generated by RTX Direct Illumination, developers can use any other noise suppressor of their choice.

RTXDI has been made available as part of the NvRTX affiliate from Unreal Engine 4.26.1. There is no estimated time of arrival yet for integration into the mainline Unreal Engine 4 branch.

During GTC 2021, NVIDIA also released an ‘RTX Technology Showcase’ tool to easily demonstrate the capabilities of RTX Direct Illumination, RTX Global Illumination, Deep Learning Super-Sampling and NVIDIA Real-Time Denoiser in an Unreal Engine environment. You can download the executable file here and the project files here

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