Patent ID: 8477134

Claim:
In a raster stage of a graphics processor, a method for using low precision evaluation and high precision evaluation to determine polygon status, comprising: receiving a graphics primitive for rasterization in a raster stage of a graphics processor; rasterizing the graphics primitive to generate a plurality of tiles of pixels related to the graphics primitive; rasterizing the tiles at a first level precision to generate a plurality of sub-tiles related to the graphics primitive, wherein the sub-tiles are evaluated against the graphics primitive at each of their respective corners; discarding each of the sub-tiles not related to the graphics primitive; rasterizing the sub-tiles related to the graphics primitive at a second level precision; determining whether a partially covered sub-tile exists upon the rasterizing at the first level precision; and if a partially covered sub-tile exists rasterizing the partially covered sub-tile at the second level precision to identify pixels of the sub-tile that are covered and pixels of the sub-tile that are not covered wherein a sub-tile rasterized at the second level of precision comprises pixels that are a part of a tile rasterized at said first level of precision; wherein the first level precision is a low precision edge evaluation level and the second level precision is a high precision edge evaluation level and wherein the low level precision is truncated to ensure a conservative evaluation of the sub-tiles with respect to coverage by the graphics primitive; wherein the low precision edge evaluation level utilizes less than half the number of bits of the high level precision edge evaluation level.