Efficient redundant coverage discard mechanism to reduce pixel shader work in a tile-based graphics rendering pipeline

Abstract

A computer-implemented redundant-coverage discard method and apparatus for reducing pixel shader work in a tile-based graphics rendering pipeline is disclosed. A coverage block information (CBI) FIFO buffer is disposed within an early coverage discard (ECD) logic section. The FIFO buffer receives and buffers coverage blocks in FIFO order. At least one coverage block that matches the block position within the TCPM is updated. The TCPM stores per-pixel primitive coverage information. The FIFO buffer buffers a moving window of the coverage blocks. Incoming primitive information associated with the coverage blocks is compared with the per-pixel primitive coverage information stored in the tile coverage-primitive map (TCPM) table at the corresponding positions for the live coverages only. Any preceding overlapping coverage within the moving window of the coverage blocks is rejected. An alternate embodiment uses a doubly linked-list rather than a FIFO buffer.