3d graphics rendering with selective read suspend

Abstract

A system and method for increasing rendering efficiency in pipelined graphics systems. In the disclosed embodiments, reads of pixel information during the rendering of a primitive are suspend if the pixel information has not been updated by a previous primitive. In some embodiments, reads of pixel information are also suspended periodically when a table tracking the information becomes full. In some embodiments a Read Monitor Unitcontrolled by the graphics system's Memory Controlleris used to track pixels which have been affected by rendered primitives. In some embodiments, a history list is used to avoid suspension of reads for antialiased lines. In a particular embodiment, the table used to track affected pixels is two-bits, the first bit tracking whether the pixel has been touched by a primitive since the last SuspendReads command was invoked and the second bit tracking whether the pixel has been touched by the current primitive. Both bits are reset when a power on or SuspendReads command occurs. The second bit is also reset at the start of rendering for each primitive. In a separate embodiment, a unique number is assigned to each primitive to be rendered. The number is recorded for each active pixel touched by the primitive. If an earlier primitive has touched this pixel, suspension of reads can be invoked and the table reset (i.e., every entry is marked invalid).