Variable Rate Shading (VRS) is a rendering technique used by graphics cards to improve performance and quality by varying the shading rate for different regions of the frame. The shading rate refers to the number of times per pixel that the GPU runs the pixel shader, which dictates the visual characteristics of each pixel. VRS allows developers to allocate rendering performance and power at rates that vary across the rendered image, meaning that the shading rate can be reduced in some areas with little or no reduction in perceptible output quality, leading to a performance improvement thats essentially free of charge.
VRS is available on NVIDIA graphics cards based on the Turing and Ampere architectures, and AMD has a similar alternative called FidelityFX Variable Shading. The shading rate can be adjusted dynamically across the image, and every 16 pixel x 16 pixel region of the screen can have a different shading rate. The developer can specify the shading rate spatially via a texture, and a single triangle can be shaded using multiple rates, providing the developer with fine-grained control.
VRS breaks the screen into blocks and weights those blocks by importance, with the importance dictating how many pixels will be shaded. The shading rate is set based on the largest luminance delta between the pairs of pixels in 2x2 blocks within the tile. VRS allows players to enjoy high picture quality and high frames in a large field of view, making it a game changer for the next generation of mobile gamers and devices.
