Methods and graphics processing systems render primitives using a rendering space which is subdivided into a plurality of regions. Geometry processing logic performs a geometry processing phase which determines, for each of a plurality of primitives which are present in a region, whether the primitive totally covers the region; and stores data for the primitives which are present in the region, wherein the stored data comprises, for each of the primitives which are determined to totally cover the region, data to indicate total coverage of the region. Rendering logic performs a rendering phase for rendering primitives within the region. The rendering phase retrieves the stored data for the primitives which are present in the region; selectively processes the primitives which are present in the region based on the retrieved data to determine which sample points within the region are covered by the primitives, wherein if the retrieved data includes data which indicates total coverage of the region for a particular primitive then the processing determines which sample points within the region are covered by the particular primitive is skipped; and determines rendered values at the sample points within the region based on the primitives which cover the respective sample points.