Patent ID: 7088361

Claim:
A method of rendering a digital image using raytracing in a three-dimensional (3-D) space, a 3-D digital differential analyser (DDA) numerator vector holding the progress within a cell and a 3-D DDA denominator vector describing a size condition for stepping to a next cell, said method comprising the steps of: setting up a denominator vector for a first sample of a first horizontal line of samples; (a) casting a ray into said 3-D space for a current sample of said horizontal line of samples dependent upon said denominator vector; (b) generating an updated value of said denominator vector for a next sample of said horizontal line of samples; (c) incrementally computing first and second order differential vectors for said sample in said horizontal line of samples using only additions; and (d) repeatedly carrying out steps (a) to (c) until raycasting for said entire horizontal line of samples is completed; (e) generating another updated value of said denominator vector for a next line of samples; (f) incrementally computing first and second order differential vectors for said vertical axis using only additions; and (g) repeatedly carrying out steps (a) to (f) until raycasting for said entire vertical axis is completed.