Friday March 01, 2019

Patent Suggests Future AMD GPUs Could Support Variable Rate Shading

Twitter user 0x22h spotted a patent suggesting that AMD could introduce Variable Rate Shading in their future GPUs. Nvidia's Turing architecture already supports VRS, which AMD's patent succinctly describes as "a technique for performing rasterization and pixel shading with decoupled resolution..." In other words, different parts of a scene could natively be rendered at different resolutions. Such a technique would be particularly useful with high resolution, high density displays, where rendering the whole scene at 4K might not be necessary, and it could give future consoles a higher-quality alternative to rendering games at non-native resolutions. Theoretically, it could also provide an easier way for developers to support foveated rendering in traditional displays and VR headsets that support eye tracking, and PCGamesN mentions that Nvidia already intends to use VRS for motion adaptive shading.

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Nvidia's Turing GPUs, found in both the high-end RTX 2080 Ti and the lower-caste GTX 1660 Ti, uses two key algorithms to take advantage of VRS - motion adaptive shading and content adaptive shading. The use of motion adaptive shading is most obvious when applied to something like a racing game, or something like Grand Theft Auto, where there is a huge amount of motion. Things in the middle of the screen, such as the car or character, which aren't be subject to a lot of relative motion will be rendered in full. Everything else that is moving rapidly can then be rendered at a lower rate as they don't need the same level of detail. Our eyes can't perceive the pixel quality difference when they're flying past at speed anyway.