Microsoft Patent Describes How Xbox Series X Does Variable Rate Shading

Microsoft has a patent that provides an insight into how variable rate shading (VRS) will help Xbox Series X achieve stable frame rates in games at higher resolutions without compromising the final image quality.

The patented system describes a method where a graphical processing unit can “vary the rate at which fragment shading is performed” while rendering an image. Here, different shading rates can be applied for different regions to be displayed. In summary, the graphical processing unit of Xbox Series X can change shading rates on the fly while inside of a fix parameter.

In particular, the described aspects allow different shading rates to be used for different regions of a primitive based on a new, interpolated shading rate parameter. In other words, the described aspects enable the GPU to change shading rates on-the-fly between different fragments of each primitive.

In addition, the patented system can help Xbox Series X determine the shading samples according to position. Hence, in the case of color, the same sample can be shared across two or more pixels on the display instead of processing each color for each pixel.

The GPU utilizes each respective shading rate parameter to determine how many sample positions to consider to be covered by the computed shaded output, e.g., the fragment color, thereby allowing the color sample to be shared across two or more pixels.

Another way to understand what variable rate shading is by imagining yourself driving a car in a game. You’re likely to be focusing on the road head. Hence, developers can utilize special tools to save crucial graphical resources by dialing back on certain segments on the left and right side of the screen, and completely on the back. Hence, improving performance while not compromising on the final image quality. Xbox Series X will allow developers to incorporate this technology into every game.

Earlier today, Phil Spencer, head of the Xbox brand, revealed new details about what to expect from Xbox Series X. The next-generation console will indeed be four times more powerful than the normal Xbox One and grant developers up to “12TFLOPS” of graphical performance. Spencer also noted how Xbox Series X will employ variable rate shading technology to utilize the full power of the graphical processing unit on “specific game characters or important environmental objects.” This is one of the most important features of the console and Microsoft will be talking more about variable rate shading during its press conference at E3 2020.