AMD has filed a patent for Variable Rate Shading, or VRS, that looks as if it could be utilised in its next-gen Navi GPU architecture. Navi will power not only the next generation of AMD Radeon graphics cards but also the upcoming PlayStation 5 and Xbox Scarlett consoles.
VRS is a method for identifying which parts of any given image need rendering priority, diverting more resources to the areas that players will be looking at, or areas that are consistently changing. It tracks colour coherence and spatial movement from frame to frame, learning which pixels don’t need re-rendering.
In a nutshell, Variable Rate Shading can help decide which parts of the screen to render at lower resolutions in order to increase overall performance. How this would be best used in going to vary on a case by case basis, but the centre of the screen, for example, would be a priority as it’s the point of focus. The outer edges could, therefore, be rendered at a lower resolution, improving performance while minimising the visual impact.
In terms of visualising how this works, let's use the example below, handily provided by Nvidia:
Here you can see the colour coded areas of rendering priority in Forza Horizon 3. The car and the immediate track in front is given the greatest priority and rendered at the highest resolution. Green is high priority, yellow is mid, and purple is low priority. The red areas are given the least priority as they're in the corners and disappearing off-screen fast. Finally, the top part of the image is the background and is relatively static, so renders as normal.
The obvious benefit to this is playing a game at 4K. Rather than rendering the entire game at 4K, and pushing four times the number of pixels as 1080p, VRS can render an image at a variety of resolutions that can still approximate the quality of a 4K render.
If all of this sounds a little familiar, that’s because it’s fundamentally the same Adaptive Shading tech that Nvidia unveiled last November. This innovation is exclusive to Nvidia’s Turing GPUs but can already be seen in action in Wolfenstein II: The New Colossus. It’s nice to see AMD hit feature parity here, and the more widespread the availability of the tech, the more it’ll ultimately be used.
AMD is yet to confirm which Radeon graphics cards will actually support VRS, although it seems safe to assume that Navi could stand to benefit a great deal from this tech. VRS could be used to push high resolutions while maintaining steady frame rates on consoles, for example.
What do you reckon then, can tech like VRS work or do you think rendering parts of the image at lower resolution will significantly damage image quality? Let us know your thoughts below!