1. A method of determining a percentage of at least one pixel on a graphics system display screen that is covered by a primitive to be displayed on the display screen, the method comprising the steps of: (a) apportioning the at least one pixel into a plurality of sub-scan lines that define a plurality of subsample points for the at least one pixel, each of the plurality of subsample points being located on a corresponding one of the plurality of sub-scan lines; (b) stepping between the plurality of sub-scan lines of the at least one pixel; (c) determining, at each one of the plurality of sub-scan lines, whether the corresponding subsample point on the one of the plurality of sub-scan lines is covered by the primitive; and (d) approximating the percentage of the at least one pixel covered by the primitive based upon the number of the plurality of subsample points of the at least one pixel that are covered by the primitive.