Reducing redundant rendering in a graphics system

A graphics processing system configured to implement a tile-based graphics pipeline in which a rendering space is sub-divided into a plurality of tiles, comprising:

• geometry processing logic configured to:
• receive geometry data for a render, the geometry data comprising a plurality of primitives each associated with one or more vertex shader programs;
• and process the geometry data using the one or more vertex shader programs to generate one or more processed primitives;
• a tiling unit configured to determine which of the processed primitives are located within each tile;
• a data characterisation unit configured to, for at least one selected tile of the plurality of tiles, store in a memory i) a representation of per-tile vertex shader data identifying the one or more vertex shader programs used to generate the processed primitives located within that tile, and ii) a representation of per-tile render data that can be used to render the processed primitives within that tile in subsequent stages of the graphics pipeline;
• and
• a testing unit configured to determine, for the at least one selected tile, whether the output of a previous render for that tile 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.

A non-transitory computer readable storage medium having stored thereon an integrated circuit definition dataset that, when processed in an integrated circuit manufacturing system, configures the integrated circuit manufacturing system to manufacture a graphics processing system configured to implement a tile-based graphics pipeline in which a rendering space is sub-divided into a plurality of tiles, the graphics processing system comprising:

• geometry processing logic configured to:
• receive geometry data for a render, the geometry data comprising a plurality of primitives each associated with one or more vertex shader programs;
• and process the geometry data using the one or more vertex shader programs to generate one or more processed primitives;
• a tiling unit configured to determine which of the processed primitives are located within each tile;
• a data characterisation unit configured to, for at least one selected tile of the plurality of tiles, store in a memory i) a representation of per-tile vertex shader data identifying the one or more vertex shader programs used to generate the processed primitives located within that tile, and ii) a representation of per-tile render data that can be used to render the processed primitives within that tile in subsequent stages of the graphics pipeline;
• and
• a testing unit configured to determine, for the at least one selected tile, whether the output of a previous render for that tile 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.