Abstract: In an apparatus and method for performing perspective interpolation of texture coordinates in computer graphics, an incremental interpolation technique is used to calculate the pixel values along a display line from the associated texture map. The incremental technique is based on Bresenham's algorithm adapted for use with hyperbolae. On the basis of the parameters of the start and end pixels of a span along a display line, a set of interpolation test parameters is set and the texel coordinates for the current pixel are tested against these parameters to determine whether they are still valid for the next pixel. If they are not valid, the test parameters are updated and the texel coordinates are incremented and retested. This process is repeated until the correct texel is identified.

Abstract: In an image-data processing apparatus, halftoning or dither values are generated by performing operations on initial "seed" values. In one example, this is done within the registers in the central processing unit, thereby avoiding the need for repetitive, and time consuming, access to a memory external to the central processing unit.