Variable Rate Shading

Microsoft today introduced a new graphics rendering feature called the ”Variable Rate Shading” within the DirectX 12, that uses a new API and said to provide 14% faster rendering on the same hardware. Microsoft announces the new feature via its official blog post, which also notes that the new graphics feature will be available only on DirectX 12. Microsoft also shared a picture comparing the differences between rendering quality on the same hardware.

What is Variable Rate Shading?

Well, if you are not sure what this new Variable Rate Shading is, then below is how Microsoft explains it.

In a nutshell, it’s a powerful new API that gives the developers the ability to use GPUs more intelligently.

Let’s explain.

For each pixel in a screen, shaders are called to calculate the color this pixel should be. Shading rate refers to the resolution at which these shaders are called (which is different from the overall screen resolution). A higher shading rate means more visual fidelity, but more GPU cost; a lower shading rate means the opposite: lower visual fidelity that comes at a lower GPU cost.

The new Variable Rate Shading API allows developers to selectively reduce the shading rate as well as boost the rendering performance of a game. Doing this will provide extra performance in the game, even on with lower-spec hardware and the game will run much better with a higher framerates.

The new Variable Rate Shading API lets developers set the shading rate in 3 different ways:

  • Per draw
  • Within a draw by using a screenspace image
  • Or within a draw, per primitive

More details on the new Variable Rate Shading API feature can be found here.