Dawn M Wallner

US Patent:

51230852, Jun 16, 1992

Filed:

Mar 19, 1990

Appl. No.:

7/495338

Inventors:

Stuart C. Wells - Santa Clara CA
James V. Loo - Los Altos CA
Dawn M. Wallner - San Jose CA

Assignee:

Sun Microsystems, Inc. - Mountain View CA

International Classification:

G06F 1572
G06F 1562

US Classification:

395121

Abstract:

A scan conversion process is performed on a polygon using a single pass technique. The pixels which comprise the edges and vertices of the polygon are first determined from the vertices which define the polygon. The alpha channel comprises either a sub-pixel mask associated with each pixel which indicates the amount and sub-pixel regions of coverage or a single value indicative of the percentage of coverage of a pixel. Furthermore, a z value indicative of the depth of each pixel is maintained. The pixels between the edge pixels of the polygon are then turned on, thereby filling the polygon. The pixels which comprise the polygon are then composited with the background pixels on a per pixel basis. The depth value of each pixel of the polygon (the z value) is used to determine the compositing equations to be used to composite each pixel of the polygon to the background. The compositing equations update the color of the pixel, the z buffer value of the background pixel and the sub-pixel mask to reflect the addition of information from the compositing of the pixel of the polygon into the background pixel.