Primitive fragment processing in the rasterization phase of a graphics processing system

A system for processing primitive fragments in a rasterization phase of a graphics processing system wherein a rendering space is subdivided into a plurality of tiles, the system comprising:

• a priority queue for storing primitive fragments;
• a non-priority queue for storing primitive fragments;
• logic configured to:
• receive a plurality of primitive fragments, each primitive fragment corresponding to a pixel sample in a tile,
• determine whether a depth buffer read is to be performed for hidden surface removal processing of one or more of the primitive fragments, and
• sort the primitive fragments into the priority queue and the non-priority queue based on the depth buffer read determinations;
• and
• hidden surface removal logic configured to perform hidden surface removal processing on the primitive fragments in the priority and non-priority queues wherein priority is given to the primitive fragments in the priority queue.