VKD3D-Proton Working On Variable Rate Shading
Variable Rate Shading allows for changing the quality of the rendering based upon the region of the frame (screen). This variable rate shading is about allowing for greater performance when not needing consistent rendering quality across the entire frame -- such as for racing games if opting for lower quality rendering outside of the main area/focus of the frame.
Basically, game developers can also use Variable Rate Shading to reduce the shading rate in areas of the frame where the visual quality doesn't matter all that much. Variable Rate Shading has become increasingly popular with Windows titles for helping with performance.
DXVK / VKD3D-Proton developer Joshua Ashton has been working on implementing "TIER_1" variable rate shading support into VKD3D-Proton for allowing D3D12 VRS games work with Vulkan and its similar functionality.
Tier 1 Variable Rate Shading is for adjusting the per-draw shading rate. It's the Tier 2 functionality that allows for adjusting the shading rate within a draw, which isn't yet implemented by VKD3D-Proton. The Tier 1 VRS support for VKD3D-Proton can be found currently via this pull request.