Patent ID: 6697066
Filing Date: 2004-02-24
Classification: G06T

Abstract:
A method of determining shading values in a graphics processing system using an approximation of a Beckmann Distribution Function (BDF), the BDF being defined as: D=14&it;m2&it;cos4&it;Î²&it;&ee;-(tan&it;â€ƒ&it;Î²m)2where,m=Root mean square slope of microfacets &bgr;=Angle between {overscore (N)} and {overscore (H)}the method comprising the steps of:(a) reformulating the BDF in terms of the scalar product of the surface normal {overscore (N)} and the viewpoint-light half-vector {overscore (H)} ({overscore (N)}Â·{overscore (H)}) to produce a modified BDF; (b) dividing a portion of the BDF into a plurality of intervals, n, each interval defined by first and second control points at its boundaries; and, (c) approximating each interval using a cubic approximation to produce coefficients for use in determining the shading values.