Patent ID: 6317126
Filing Date: 2001-11-13
Classification: G06T

Abstract:
In a computer graphics system, a method for associating a pixel on a surface with one of a plurality of concentric regions defined on the surface, with a cutoff angle .phi. and a transition angle .DELTA. defining the plurality of concentric regions on the surface, the concentric regions having a center point that is aligned with a source point disposed above the center point wherein the source point and the center point form a first axis, the source point and the pixel defining a second axis therebetween, the method comprising the operations of:determining a difference angle (.phi.-.DELTA.);converting the difference angle into cosine space by determining cos(.phi.-.DELTA.);converting the difference angle in the cosine space into a log space;evaluating a pixel angle .theta. between the first axis and the second axis in the log and cosine spaces; anddetermining in which region the pixel belongs by comparing the difference angle and the pixel angle in one or both of the log space and the cosine space.