VRWorks - Variable Rate Shading (VRS)

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Variable Rate Shading

Turing introduces a new and more flexible technique to control the shading rate called Variable Rate Shading (VRS). With VRS, the shading rate can now be adjusted dynamically across the image - every 16 pixel x 16 pixel region of the screen can now have a different shading rate.

This fine level of control enables developers to deploy new algorithms that were not previously possible for optimizing shading rate and increasing image quality. In this section, we will describe the underlying hardware mechanisms of VRS, and a few of the ways developers can enable it.

Figure 1 – Turing VRS supported shading rates and example application to a game frame.

Without VRS, every pixel in the scene in Figure 1 would be shaded individually (the 1x1 blue grid case). With VRS, the pixel shading rate of triangles can vary. The developer has seven options to choose from for each 16x16 pixel region, including having one shading result be used to color four pixels (2x2), or 16 pixels (4x4), or non-square footprints like 1x2 or 2x4. The colored overlay on the right side of Figure 01 shows a possible application to a frame - the car, sky, and foliage have been shaded at full rate (i.e., blue region) to preserve fine details. The area next to the car has been shaded once per four pixels (green), and the road to the far left and right periphery has been shaded once per eight pixels (yellow).

Wwith Turing’s Variable Rate Shading technology, a scene can be shaded with a mixture of rates varying between once per visibility sample (super-sampling) and once per sixteen visibility samples. The developer can specify the shading rate spatially (via a texture). As a result, a single triangle can be shaded using multiple rates, providing the developer with fine-grained control.

Note that VRS allows the developer to control the shading rate without changing the visibility rate. The ability to decouple shading rate and visibility rate makes VRS more broadly applicable than techniques such as MRS and LMS, that lower total rendering resolution in specified regions. At the same time, VRS, MRS, and LMS can be used in combination since they are independent techniques enabled by separate hardware paths.

Get Started with VRS (VRWorks Graphics SDK)

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VRS Wrapper

VRS Wrapper consists of the following two interfaces and easy to use presets:

• VRS Helper controls the foveated rendering parameters
• Gaze Handler gathers and manages the eye-tracking data

Learn more about VRS Wrapper in our DevBlog Easy VRS Integration with Eye Tracking

Get Started with VRS Wrapper (VRWorks Graphics SDK)

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Variable Rate Supersampling (VRSS)

Figure 2 – Conceptual representation of VRSS. Background image of Boneworks courtesy of Stress Level Zero

The center mask region can be super-sampled up to 8x to optimize image quality. The maximum shading rate achieved is limited to the MSAA sample count per pixel, so 8x supersampling is enabled via 8x MSAA, 4x supersampling is enabled via 4x MSAA, and so forth.

VRSS can be applied to all VR games and applications that are DX11, Forward Rendered and have MSAA. The VRSS functionality resides in the NVIDIA Driver. Developers do not have to write any code to integrate VRSS; they simply submit their VR game or application to NVIDIA for testing. NVIDIA will test the VR game or application, and if it benefits from VRSS, then it will be whitelisted in the NVIDIA Driver. VRSS benefits both new and existing VR games and applications.

In order to leverage this technology, developers must submit their game or application to NVIDIA for validation and inclusion in the drivers.

Submit your application

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VRS in-action

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Additional Resources