Multi-resolution shading

Multi-resolution shading or multi-res shading is a VR technology introduced by Nvidia's Gameworks VR. In multi-res shading, the rendering accounts for the distortion caused by the lenses of the HMD. It will not render the parts of the image that the user will not see due to the distortion. Multi-res shading improves performance without sacrificing image quality.

Normally, an image on a screen, rendered by GPU, is flat. When the lenses in the HMD distorts the flat image, there is an extra process to "de-distort" the image before it is passed through the lenses and onto your eyes. Because of this, a significant percent of the flat image never makes to your eyes. Multi-res shading does not render the entire flat image. Instead it renders the distorted image directly, saving the processor from rendering a significant number of pixels.

Multi-res shading performs this function by diving the image into a grid with 9 viewpoints. Only the center viewpoint is rendered in full resolution. It renders the outer viewpoints at lower resolution because they merge and shrink during the distortion process. Multi-res shading improves the performance of the VR app by rendering fewer pixels.

According to Nvidia engineer Tom Peterson, multi-res shading can save about 50% of the pixel load.