1. In an image generating system of the type for converting digital data into a sequence of display frames of image data suitable for display on a video image system, the image system forming a display by individually illuminating each of a plurality of color pixels, each of the frames of image data defining a plurality of faces and each of the frames being divided into a plurality of spans, a method for determining the faces to be displayed in each of the spans comprising the steps of: (a) identifying data for one of the frames of display, the data defining face locations, each of the faces associated with at least one span and being arranged in a descending order of priority; (b) determining the highest priority face for each span; (c) determining an area within each span covered by the highest priority face; (d) computing pixel image data representative of the pixels within each span covered by the highest priority face of the span; (e) repeating step (b) through step (d) for each span by replacing the highest priority face of each span with the next highest priority face not having been processed until the last face of each span is processed into pixel image data or until all areas of each span are fully covered by faces and the corresponding pixel image data have been computer; and (f) transferring the pixel image data to the video image system; wherein he step of determining an edge further comprises the steps of: identifying data representative of an edge of a face, each edge having a beginning and ending vertex and a slope; searching along the edges of a face in a predetermined direction, starting with a beginning vertex of an edge of the face, for each span that the edge passes through; storing each span intersected by the edge; calculating a perpendicular distance from each corner of each intersected span to the edge; determining a next span intersected by an edge; repeating the steps of searching, storing, calculating and determining a next edge until the last edge of the face is processed; and repeating the steps of searching, storing, calculating, determining a next edge and repeating using the next face, until all the faces are processed.