Graphics processing

A graphics processor, the graphics processor comprising:

• a rasteriser that is operable to test regions of a render output being generated against edges defined for a primitive to be rendered to determine whether the primitive covers any part of the regions of the render output;
• and
• a processing circuit configured to, when the graphics processor is generating a render output in which primitives to be rendered are to be clipped against a user-defined clip plane defined for the render output, such that when at least part of a primitive to be rendered falls behind a user-defined clip plane, the at least part of the primitive to be rendered that falls behind the user-defined clip plane should be clipped to the user-defined clip plane:
• determine for a primitive to be rendered for a render output that is intersected by a user-defined clip plane defined for the render output, an edge representing the intersection of the primitive with the user-defined clip plane;
• wherein the rasteriser is configured to, when rasterising a primitive for which an edge representing the intersection of the primitive with a user-defined clip plane has been determined:
• test one or more regions of a render output being generated against the determined edge representing the intersection of the primitive with a user-defined clip plane to determine whether the region or regions should not be rendered for the primitive on the basis of the user-defined clip plane.

A non-transitory computer readable storage medium storing computer software code which when executed on one or more processors performs a method of operating a graphics processor that includes a rasteriser that is operable to test a region of a render output being generated against edges defined for a primitive to be rendered to determine whether the primitive covers any part of the region of the render output, the method comprising:

• when generating a render output in which primitives to be rendered are to be clipped against a user-defined clip plane defined for the render output, such that when at least part of a primitive to be rendered falls behind the user-defined clip plane, the at least part of the primitive to be rendered that falls behind the user-defined clip plane should be clipped to the user-defined clip plane;
• for a primitive to be rendered for the render output that is intersected by the user-defined clip plane defined for the render output:
• determining an edge representing the intersection of the primitive with the user-defined clip plane;
• and
• the rasteriser, when rasterising the primitive:
• testing one or more regions of the render output being generated against the determined edge representing the intersection of the primitive with the user-defined clip plane to determine whether the region or regions should not be rendered for the primitive on the basis of the user-defined clip plane.