1. A graphics system configured to retain a primitive pixel in a rasterized bounds primitive when coverage data stored in a shape buffer indicates that a mask pixel corresponding to the primitive pixel is a covered pixel and to discard the primitive pixel when the coverage data indicates that the mask pixel corresponding to the primitive pixel is an uncovered pixel, the corresponding mask pixel being a covered pixel when a shape bounded by the bounds primitive covers the mask pixel such that one or more coverage criteria is satisfied and being an uncovered pixel when the shape does not cover the mask pixel such that the one or more coverage criteria are satisfied.