The 3DMark Sampler Feedback feature test uses sampler feedback to generate information about which texels require shading.
The test shows how game engines can improve performance by using sampler feedback as part of texture space shading to more efficiently shade texture regions based on whether they’re sampled in the final output or not.
The test scene is a broken robot in a repair shop and runs in two passes. As the camera moves around the scene, texture space shading is used to optimize the shading of the scene.
The test uses a pre-generated set of maps that defines the required information for shading each texel of the shading map in texture space.
In the first pass, we shade using texture space shading without sampler feedback, using a software solution developed in-house to determine the sampled texels along with a matching software sampler in the screen space sampling pass.
The second passes uses the sampler feedback feature to determine the MIP levels and MIP regions that will be sampled for each frame, shading only them in texture space and sampling the shading map in screen space to produce the final image.
The frame rates of running the test in each mode are recorded, and the result is the relative difference between performing texture space shading with and without the sampler feedback feature.