Method and apparatus for generating an output surface from one or more input surfaces in data processing systems

An apparatus for generating an output surface from one or more input surfaces in a data processing system, the apparatus comprising:

• memory that stores one or more input surfaces to be used to generate an output surface;
• and
• processing circuitry configured to generate an output surface as a plurality of respective regions that together form the output surface, each respective region of the output surface being generated from a respective region or regions of one or more of the input surfaces;
• wherein:
• the processing circuitry is further configured to, when a new version of the output surface is to be generated:
• for at least one region of the output surface, determine which region or regions of the input surface or surfaces contribute to the region of the output surface;
• check whether the contributing region or regions of the input surface or surfaces have changed since the previous version of the output surface region was generated;
• and
• if there has been a change in the contributing region or regions of the input surface or surfaces since the previous version of the region in the output surface was generated, regenerate the region of the output surface.

A computer readable storage medium storing computer software code which, when executed on a processor, performs a method of generating an output surface from one or more input surfaces in a data processing system, the method comprising:

• generating the output surface as a plurality of respective regions that together form the output surface, each respective region of the output surface being generated from a respective region or regions of one or more input surfaces;
• and
• when a new version of the output surface is to be generated, for at least one region of the output surface:
• (i) determining which region or regions of the input surface or surfaces contribute to the region of the output surface;
• (ii) checking whether the contributing region or regions of the input surface or surfaces have changed since the previous version of the output surface region was generated;
• and
• (iii) if there has been a change in the contributing region or regions of the input surface or surfaces since the previous version of the region in the output surface was generated, regenerating the region of the output surface.