1. A computing device configured to shade graphics primitives using hybrid antialiasing, the computing device comprising: a rasterizer including a hybrid antialias control unit configured to: receive the graphics primitives; determine a number of supersample clusters that are used to antialias each pixel that intersects the graphics primitives; determine a number of multisamples that are used to process the graphics primitives for each one of the supersample clusters; and rasterize the graphics primitives to output a fragment for each pixel that intersects a graphics primitive; and a fragment processing unit coupled to the rasterizer and configured to shade the fragments using multiple passes through the fragment processing unit, wherein the fragment processing unit comprises a hardware parallel processing engine, and the number of multiple passes used to produce each hybrid-antialiased pixel that intersects the graphics primitives is less than or equal to the number of supersample clusters, and geometry computations performed when rasterizing the graphics primitive are not repeated for each pass through the fragment processing unit.