A sort-based deferred shading architecture for decoupled sampling

Stochastic sampling in time and over the lens is essential to produce photo-realistic images, and it has the potential to revolutionize real-time graphics. In this paper, we take an architectural view of the problem and propose a novel hardware architecture for efficient shading in the context of stochastic rendering. We replace previous caching mechanisms by a sorting step to extract coherence, thereby ensuring that only non-occluded samples are shaded. The memory bandwidth is kept at a minimum by operating on tiles and using new buffer compression methods. Our architecture has several unique benefits not traditionally associated with deferred shading. First, shading is performed in primitive order, which enables late shading of vertex attributes and avoids the need to generate a G-buffer of pre-interpolated vertex attributes. Second, we support state changes, e.g., change of shaders and resources in the deferred shading pass, avoiding the need for a single über-shader. We perform an extensive architectural simulation to quantify the benefits of our algorithm on real workloads.