Circuit and method for deferring the binding of render states to primitives in a graphics system

Abstract

A method performed in a graphics processor postpones the processing of one or more changes in render state until after one or more tiles that are affected by a primitive are identified (e.g. by use of a bounding box around the primitive to identify tiles within the bounding box, or by visiting an area enclosed by vertex tiles and edge tiles of the primitive to identify tiles covered by the primitive). The method may be performed by: storing value(s) of render state(s) on receipt, receiving one or more primitives affected by the render state(s), identifying from among a number of render state(s) whose values are being stored one or more render state(s) whose values have changed since last update to a tile covered by a received primitive, and associating with the covered tile the changed render states. Such a deliberate delay in association of changed render states eliminates the need to process render state(s) for tiles that are not identified as being covered by a received primitive, and render states that have not changed for such tiles, thus saving processing power and memory bandwidth. Identification of a render state that has changed since the last update to a tile can be accomplished in any manner, e.g. (1) by storage of a sequence signal (such as a time stamp) that indicates the order in which render states (and optionally primitives) are received, and are updated to a tile, or (2) by comparison of render state values that were previously updated to a tile, with the most current render state values, or (3) by some combination of (1) and (2).