Extending the graphics pipeline with adaptive, multi-rate shading

Due to complex shaders and high-resolution displays (particularly on mobile graphics platforms), fragment shading often dominates the cost of rendering in games. To improve the efficiency of shading on GPUs, we extend the graphics pipeline to natively support techniques that adaptively sample components of the shading function more sparsely than per-pixel rates. We perform an extensive study of the challenges of integrating adaptive, multi-rate shading into the graphics pipeline, and evaluate two- and three-rate implementations that we believe are practical evolutions of modern GPU designs. We design new shading language abstractions that simplify development of shaders for this system, and design adaptive techniques that use these mechanisms to reduce the number of instructions performed during shading by more than a factor of three while maintaining high image quality.