Graphics processing systems

A tile-based graphics processing pipeline comprising:

• a plurality of processing stages, including at least a rasteriser that rasterises input primitives to generate graphics fragments to be processed, each graphics fragment having one or more sampling points associated with it, and a renderer that processes fragments generated by the rasteriser to generate rendered fragment data;
• a tile buffer configured to store rendered fragment data locally to the graphics processing pipeline prior to that data being written out to an external memory, the tile buffer storing data values for an array of sample positions, with respective sets of the sample positions corresponding to and being associated with respective pixels of an output data array that the rendered fragment data relates to;
• a write out stage configured to write data stored in the tile buffer to an external memory;
• and
• a programmable processing stage operable to, in response to one or more graphics program instructions, read rendered uncompressed tile texture data that is stored in the tile buffer, perform a compression operation on the read texture data, and write out the result of the compression operation to the tile buffer or to an external memory, thereby to provide a compressed version of the texture;
• wherein:
• the reading of the uncompressed texture data from the tile buffer to generate the output, compressed texture data comprises reading texture data samples stored in the tile buffer associated with plural different pixels in the tile buffer.

A tile based graphics processing pipeline comprising:

• a plurality of processing stages, including at least a rasteriser that rasterises input primitives to generate graphics fragments to be processed, and a renderer that processes fragments generated by the rasteriser to generate rendered fragment data;
• a tile buffer configured to store rendered fragment data locally to the graphics processing pipeline prior to that data being written out to an external memory;
• a write out stage configured to write data stored in the tile buffer to an external memory;
• and
• a programmable processing stage operable under the control of graphics program instructions to read data stored in the tile buffer, and perform a processing operation using the read data to generate metadata.

A method of operating a tile-based graphics processing pipeline that comprises:

• a plurality of processing stages, including at least a rasteriser that rasterises input primitives to generate graphics fragments to be processed, each graphics fragment having one or more sampling points associated with it, and a renderer that processes fragments generated by the rasteriser to generate rendered fragment data;
• a tile buffer configured to store rendered fragment data locally to the graphics processing pipeline prior to that data being written out to an external memory, the tile buffer storing data values for an array of sample positions, with respective sets of the sample positions corresponding to and being associated with respective pixels of an output data array that the rendered fragment data relates to;
• a write out stage configured to write data stored in the tile buffer to an external memory;
• and
• a programmable processing stage operable to, in response to one or more graphics program instructions, read fragment data stored in the at least one tile buffer, perform a processing operation using the read fragment data, and write the result of the processing operation into the tile buffer or to an external memory;
• the method comprising:
• issuing graphics program instructions to the programmable processing stage to cause the programmable processing stage to, for respective pixel positions that data stored in the tile buffer represents, read data stored in the tile buffer for one or more sampling positions that are not associated with the pixel position in question, perform a processing operation using the read sampling position data and write the result of the processing operation into the tile buffer or to an external memory;
• and
• the programmable processing stage in response to the graphics program instructions, for respective pixel positions that data stored in the tile buffer represents, reading data stored in the tile buffer for one or more sampling positions that are not associated with the pixel position in question, performing a processing operation using the read sampling position data and writing the result of the processing operation into the tile buffer or to an external memory.

A method of generating compressed texture data for a render-to-texture output using a tile-based graphics processing pipeline that comprises:

• a plurality of processing stages, including at least a rasteriser that rasterises input primitives to generate graphics fragments to be processed, each graphics fragment having one or more sampling points associated with it, and a renderer that processes fragments generated by the rasteriser to generate rendered fragment data;
• a tile buffer configured to store rendered fragment data locally to the graphics processing pipeline prior to that data being written out to an external memory, the tile buffer storing data values for an array of sample positions, with respective sets of the sample positions corresponding to and being associated with respective pixels of an output data array that the rendered fragment data relates to;
• a write out stage configured to write data stored in the tile buffer to an external memory;
• and
• a programmable processing stage operable to, in response to one or more graphics program instructions, read fragment data stored in the at least one tile buffer, perform a processing operation using the read fragment data, and write the result of the processing operation into the tile buffer or to an external memory;
• the method comprising:
• rendering a tile of the texture to be output in an uncompressed form using the graphics processing pipeline and storing the rendered uncompressed tile texture data in the tile buffer;
• the programmable processing stage reading the stored texture data and performing a compression operation on the read texture data, and writing out the result of the compression operation to the tile buffer or to an external memory, thereby to provide a compressed version of the texture;
• wherein:
• the reading of the uncompressed texture data from the tile buffer to generate the output, compressed texture data comprises reading texture data samples stored in the tile buffer associated with plural different pixels in the tile buffer.

A method of generating metadata using a tile based graphics processing pipeline that comprises:

• a plurality of processing stages, including at least a rasteriser that rasterises input primitives to generate graphics fragments to be processed, and a renderer that processes fragments generated by the rasteriser to generate rendered fragment data;
• a tile buffer configured to store rendered fragment data locally to the graphics processing pipeline prior to that data being written out to an external memory;
• a write out stage configured to write data stored in the tile buffer to an external memory;
• and
• a programmable processing stage operable under the control of graphics program instructions to read data stored in the tile buffer, and perform a processing operation using the read data to generate metadata;
• the method comprising:
• issuing graphics program instructions to the programmable processing stage to cause the programmable processing stage to read data stored in the tile buffer, and perform a processing operation using the read data to generate metadata;
• and
• the programmable processing stage in response to the graphics program instructions, reading data stored in the tile buffer, and performing a processing operation using the read data to generate metadata.

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

• a plurality of processing stages, including at least a rasteriser that rasterises input primitives to generate graphics fragments to be processed, each graphics fragment having one or more sampling points associated with it, and a renderer that processes fragments generated by the rasteriser to generate rendered fragment data;
• a tile buffer configured to store rendered fragment data locally to the graphics processing pipeline prior to that data being written out to an external memory, the tile buffer storing data values for an array of sample positions, with respective sets of the sample positions corresponding to and being associated with respective pixels of an output data array that the rendered fragment data relates to;
• a write out stage configured to write data stored in the tile buffer to an external memory;
• and
• a programmable processing stage operable to, in response to one or more graphics program instructions, read fragment data stored in the at least one tile buffer, perform a processing operation using the read fragment data, and write the result of the processing operation into the tile buffer or to an external memory;
• the method comprising:
• issuing graphics program instructions to the programmable processing stage to cause the programmable processing stage to, for respective pixel positions that data stored in the tile buffer represents, read data stored in the tile buffer for one or more sampling positions that are not associated with the pixel position in question, perform a processing operation using the read sampling position data and write the result of the processing operation into the tile buffer or to an external memory;
• and
• the programmable processing stage in response to the graphics program instructions, for respective pixel positions that data stored in the tile buffer represents, reading data stored in the tile buffer for one or more sampling positions that are not associated with the pixel position in question, performing a processing operation using the read sampling position data and writing the result of the processing operation into the tile buffer or to an external memory.