Method for determining tiles in a computer display that are covered by a graphics primitive

Abstract

A geometry tiler identifies tiles on a computer's screen that are covered by a graphics primitive by use of edges of the graphics primitive. Precise identification of tiles of various types (such as edge tiles covered by a segment) eliminates identification of one or more tiles that are merely located adjacent to the graphics primitive, but are not touched by the graphics primitive. For example, the geometry tiler can identify each of three types of tiles: vertex tiles, edge tiles and interior tiles. In one implementation, the geometry tiler identifies all tiles that are covered by a graphics primitive in the form of a convex polygon by: (a) determining attributes of at least one segment in the convex polygon, (b) determining iteration descriptors for each segment by using the attributes, (c) for each segment in the convex polygon, scanning the segment and identifying each edge tile that is covered by the segment, and (d) for each column of tiles in the screen, going from one edge tile in the column to another edge tile in the column and identifying each interior tile that is located within an area enclosed by the segments of the primitive. In one specific implementation, the geometry tiler simultaneously identifies edge tiles that are covered by two segments of the convex polygon that are located opposite to each other (such as a top segment and a bottom segment).