Depth buffer priority processing for real time computer image generating

Abstract

A method for determining color information in a computer image generated display in which the display is divided into a plurality of spans and each span comprises a matrix of pixels, each of the pixels being further divided into a matrix of subpixels, which method and apparatus allows overlapping and inner penetrating faces appearing in an image to be resolved without conflict. Faces of objects appearing in an image are resolved by a range ordering process for each span in an image. The faces are reordered into range separable groups in which a range separable group is defined as faces in which the maximum range to the most distant face in a group does not overlap the minimum range of the nearest face in another group. Each range separable group of faces is then processed on a per pixel basis for determining the color contribution of that face or group of faces to each subpixel within a pixel. In one form, the process of identifying the colors contributing to a pixel may be terminated at the end of processing of one group of faces when at least a minimum number of subpixels within a pixel have been identified as covered by faces in the processed group. Where groups of faces cannot be divided into range separable groups, forced separation of groups can be implemented by establishing a predetermined maximum number of faces in a group or by inserting a pseudo-face within a group and breaking the groups at the pseudo-face.