1. A method comprising: identifying a primitive to be processed for a tile of a graphics output being processed and then determining whether one or more already-calculated primitive-specific equations representing the geometry of the identified primitive that were calculated when processing another tile of the graphics output are stored in a memory; and in response to a determination that one or more already-calculated primitive-specific equations representing the geometry of the identified primitive that were calculated when processing another tile of the graphics output are stored in the memory, retrieving one or more of those already-calculated primitive-specific equations representing the geometry of the identified primitive and using those one or more retrieved primitive-specific equations to process the identified primitive; in response to a determination that one or more already-calculated primitive-specific equations representing the geometry of the identified primitive are not stored in the memory, calculating one or more primitive-specific equations representing the geometry of the identified primitive, using those one or more calculated primitive-specific equations to process the identified primitive, and storing, for use after the identified primitive has been processed, at least some of the one or more calculated primitive-specific equations.