Introducing variable rate shading

Variable rate shading (VRS) is a technique that allows developers to control the rate at which fragments are shaded. When this feature is disabled, all fragments are shaded using a 1x1 rate, meaning that the fragment shader will run for all fragments in the image.

With the introduction of virtual reality (VR) headsets, developers have started to investigate ways to reduce the amount of time it takes to render a frame. This is crucial, not only because VR requires rendering two frames (one for the right eye and one for the left) but also because VR is quite sensitive to frame latency, and higher frame rates are required to avoid users experiencing motion sickness.

One technique that was developed is called foveated rendering: the idea is to render the center of the image at full rate while lowering the quality outside the center. Developers have noticed that users are focused primarily on the central region of the image and don’t notice...