Variable Rate Shading, first introduced to the market with the GeForce RTX line of graphics cards, received its own API thanks to Microsoft's efforts as revealed at the latest Game Developers Conference.
Variable rate shading is a technique that allows game developers to selectively reduce the shading rate in certain areas of the frame where there isn't much going on, thus improving the performance. Additionally, developers also have the option to do the opposite, to increase the shading rate in the areas that matter the most, thus improving visual quality there.
The first game to support this feature was Wolfenstein II: The New Colossus, which got it via patch last November. The new Wolfenstein: Youngblood game, due for release next week, also includes variable rate shading (as well as real-time ray tracing).
Today, 3DMark revealed that the popular suite of benchmarks is also getting a dedicated VRS feature test on August 26th. Hopefully, this is just the start of a larger adoption among developers.
3DMark feature tests are special tests designed to highlight specific techniques, functions or capabilities. The 3DMark VRS feature test is designed to help you compare differences in performance and image quality when using variable-rate shading. The test also offers an interactive mode for experimenting with different VRS settings and exporting frames for comparison.
The test features a forest scene with floating lanterns. VRS is disabled on the first pass of the test to provide a baseline for comparison.
3DMark VRS feature test screenshot with VRS turned off
Variable-rate shading is enabled for the second pass of the test. Click on the images to download and compare the full-size originals.
3DMark VRS feature test screenshot with VRS on
With VRS, a single pixel shader operation can be applied to a block of pixels, for example shading a 4x4 block of pixels with one operation rather than 16 separate operations.
In the 3DMark VRS feature test, the shading rate varies with camera distance when VRS is enabled: 4×4 for the furthest objects, (the blue areas in the image below), 2×2 for the middle-distance geometry (green areas), and 1×1 (red areas) for the closest foreground objects.
3DMark VRS feature test screenshot showing where the different shading rates are used