System and method for efficiently determining a fog blend value in

Abstract

A system for generating blend values for three-dimensional graphic rendering includes a first register, a second register, third register, an index creation unit, a blend value generation unit and a blending unit. The first register receives and stores color pixel data, and the second register receives and stores a depth perspective component; and the third register receives and stores fog color data. The output of the second register is coupled to the index creation unit which uses the received depth perspective component to generate a two-part index. The two-part index is output by the index creation unit to produce a blend value. The first portion of the index is used to address a table in the blend generation unit, and the second portion of the index is used to produce an increment value added to output of the table resulting in the creation of a blend value. The blend value, the color pixel data and the fog color data are then blended by the blending unit and output by the system. The invention also includes a method for generating a blend value and producing a blended color output. The method includes the steps of: producing an index having a first portion and a second portion from a distance value; determining a base value using the first portion of the index, determining a delta between the base value and the next entry in the table using the first portion of the index, determining a blend increment using the delta and the second portion of the index; and producing a blend value by adding the base value to the blend increment; and blending the blend value with input pixel data.