Reducing redundant rendering in a graphics system

Abstract

A method and system for performing a render using a graphics processing unit that implements a tile-based graphics pipeline where a rendering space is sub-divided into tiles. Geometry data for the render is received, the geometry data including primitives associated with one or more vertex shader programs. The geometry data is processed using the vertex shader programs to generate processed primitives, and it is determined in which tile each of the processed primitives are located. For at least one selected tile there is stored i) a representation of per-tile vertex shader data identifying the one or more vertex shader programs used to generate the processed primitives in that tile, and ii) a representation of per-tile render data that can be used when rendering the processed primitives in that tile in subsequent stages of the graphics pipeline. It is determined whether the output of a previous render for the selected tile(s) can be used as an output for the render by comparing the per-tile vertex shader data of that tile with that of the previous render before comparing the per-tile render data of that tile with that of the previous render.