Graphics processing systems

A tile-based graphics processing pipeline comprising:

• rendering circuitry for rendering graphics fragments to generate rendered fragment data, each graphics fragment having associated with it a set of one or more sampling positions to be rendered;
• a tile buffer configured to store rendered fragment data for sampling positions locally to the graphics processing pipeline prior to the rendered fragment data being written out to memory;
• write out circuitry configured to write a compressed representation of the rendered fragment data for a tile in the tile buffer to memory;
• and
• processing circuitry operable to:
• identify, based on the writing of rendered fragment data to the tile buffer for a tile, a block comprising a plurality of sampling positions within the tile having the same data value associated with each of the plurality of sampling positions in the block;
• and
• trigger the write out circuitry, when a block of sampling positions within a tile each having the same data value is identified, to write a compressed representation of the block of same data value sampling positions to the memory.

A non-transient computer readable storage medium storing computer software code which when executing on a graphics processing system performs a method of operating a tile-based graphics processing pipeline that comprises:

• a tile buffer configured to store rendered fragment data for sampling positions locally to the graphics processing pipeline prior to the rendered fragment data being written out to memory;
• the method comprising:
• rendering graphics fragments to generate rendered fragment data, each graphics fragment having associated with it a set of one or more sampling positions to be rendered in a tile;
• writing the rendered fragment data for sampling positions in the tile to the tile buffer;
• identifying, based on the writing of rendered fragment data to the tile buffer for a tile, a block comprising a plurality of sampling positions within the tile having the same data value associated with each of the plurality of sampling positions in the block;
• and
• when a block of sampling positions within a tile each having the same data value is identified, writing a compressed representation of the block of same data value sampling positions to the memory.