Shader programs are written and executed either at pixel or sample rate (aka super sampling). Multi-sampling anti-aliasing (MSAA) seeks the healthy balance between the two and shades pixels once per primitive. As the depth-stencil tests and Ouput Merger (OM) operations are done at the sample rate, the resolve pass needs to filter the color by taking some weighted combination of samples. Often it is desirable to evaluate slowing changing colors of a screen space (e.g., ambient occlusion) at a lower rate than rapidly changing colors (e.g., diffuse or specular highlights) of the screen space.
USPTO Backgrounds
USPTO Backgrounds