Graphics processing

A method of storing information representative of a micromap for use by a graphics processor that is operable to render a scene represented by primitives by tracing rays through the scene and controlling interactions between rays and sub-regions of primitives using property values defined by one or more micromaps;

• the method comprising:
• providing a micromap that defines property values for a set of sub-regions of a primitive;
• and
• generating and storing information representative of the micromap by:
• for one or more larger sub-regions of the primitive:
• determining whether the micromap defines the same or different property values for sub-regions of the set of sub-regions that are encompassed by the respective larger sub-region;
• and
• generating and storing first information indicating whether the micromap defines the same or different property values for sub-regions of the set of sub-regions that are encompassed by the respective larger sub-region;
• and
• when it is determined that the micromap defines different property values for sub-regions of the set of sub-regions that are encompassed by the respective larger sub-region:
• generating and storing further information representing the different property values.

A graphics processing system that is operable to render a scene represented by primitives by tracing rays through the scene and controlling interactions between rays and sub-regions of primitives using property values defined by one or more micromaps;

• the system comprising:
• a generating circuit configured to generate and store information representative of a micromap, wherein the micromap defines property values for a set of sub-regions of a primitive;
• and
• a processing circuit configured to:
• use information generated and stored by the generating circuit to determine a property value defined by a micromap for a sub-region of a set of sub-regions of a primitive;
• and
• use the determined property value to control an interaction between a ray and the sub-region of the primitive;
• wherein:
• the generating circuit is configured to generate and store information representative of a micromap that comprises first information that can be used by the processing circuit to determine whether further information should be used to determine a property value defined by the micromap;
• and
• the processing circuit is configured to use information generated and stored by the generating circuit to determine a property value defined by a micromap for a sub-region of a set of sub-regions of a primitive by:
• using first information to determine whether further information should be used to determine the property value for the sub-region;
• and
• when it is determined that further information should be used to determine the property value for the sub-region:
• fetching further information;
• and
• using the further information to determine the property value for the sub-region.

A graphics processor that is operable to render a scene represented by primitives by tracing rays through the scene and controlling interactions between rays and sub-regions of primitives using property values defined by one or more micromaps;

• the processor comprising:
• a fetching circuit configured to fetch information representative of a micromap, wherein the micromap defines property values for a set of sub-regions of a primitive;
• and
• a processing circuit configured to:
• use information fetched by the fetching circuit to determine a property value defined by a micromap for a sub-region of a set of sub-regions of a primitive;
• and
• use the determined property value to control an interaction between a ray and the sub-region of the primitive;
• wherein the processing circuit is configured to use information fetched by the fetching circuit to determine a property value defined by a micromap for a sub-region of a set of sub-regions of a primitive by:
• using first information to determine whether further information should be used to determine the property value for the sub-region;
• and
• when it is determined that further information should be used to determine the property value for the sub-region:
• causing the fetching circuit to fetch further information;
• and
• using the further information to determine the property value for the sub-region.