Abstract: Methods and apparatus for rendering images of digital objects or for preparing digital objects for subsequent processing. The method includes sorting data representative of the positions of at least three vertices of at least one polygon of a digital object, then determining whether the orientation of the vertices of each polygon from a specific reference point differs from the actual, or original, orientation of the vertices. Such a determination may be made by generating an orientation decision variable based on the relative positions of the vertices and calculating a cross product term (CPT) after the vertex data has been sorted. The CPT may also be used in other operations involving the polygon, such as in imparting appearance characteristics to the polygon. The method may be embodied as a computer program (i.e., software or firmware) that controls the operation of a processor.

Abstract: A graphics processor capable of rendering three-dimensional polygons with color, shading; and other visual effects also corrects interpolation errors that occur as a result of mapping the polygon to a pixel grid display. The processor renders polygons using an Incremental Line-Drawing algorithm and features an error correction circuit capable of adjusting the initial and incremental gradient parameters for each pixel characteristic and then rendering each scan line with the proper orthogonal adjustment. The error correction circuit includes an ortho correction engine for correcting errors in the initial and incremental pixel parameters and an ortho adjust engine to accommodate overflows in the x-coordinate calculations. The processor is able to render the polygons with monotonic gradients in color, shading, depth, and other visual characteristics without interpolation error.