Patent ID: 6246416
Filing Date: 2001-06-12
Classification: G06T

Abstract:
A method for performing computer graphic simulation of an anisotropic surface reflecting light towards a viewer, the method comprising the steps of:(a) obtaining data necessary to calculate the amount of light reflected from each point of the anisotropic surface toward the viewer, said data comprising the direction from which the incident light strikes the surface, the direction of the light reflected towards the viewer, the refractive index of the surface, the wavelength of the incident light, and a statistical description of the roughness of the surface;(b) sending said data to a renderer;(c) calculating the amount of light reflected from each point of the anisotropic surface toward the viewer, using the formula ##EQU37##wherein F=F(.theta..sub.1, n.sub..lambda.), the Fresnel coefficient;n.sub..lambda. is the refractive index of the surface;.theta..sub.1 is the angle between the incident light and the surface's normal vector;.theta..sub.2 is the angle between the direction of the light reflected towards the viewer and the surface's normal vector;w=-cos.theta..sub.1 -cos.theta..sub.2 ;k.sub.1 is a unit vector pointing from a reflection point on the surface towards a light source;k.sub.2 is a unit vector pointing from a reflection point towards the viewer;k=2.pi./.lambda.;.lambda. is the wavelength of the incident light; ##EQU38##u=-cos.phi..sub.1 sin.theta..sub.1 -cos.phi..sub.2 sin.theta..sub.2 ;v=sin.phi..sub.1 sin.theta..sub.1 -sin.phi..sub.2 sin.theta..sub.2 ;.phi..sub.1 is a first spherical coordinate of the direction of the incident light;.phi..sub.2 is a first spherical coordinate of the direction of the light reflected towards the viewer;C.sub.p (x,y) is a correlation function of a function p(x,y);.sigma..sub.p is the standard deviation of the function p(x,y):p(x,y)=e.sup.(ikwh(x,y)) ;h(x,y) is the height of the surface at a point (x,y);.mu..sub.p =X.sub.1 (kw);X.sub.1 is a characteristic function of the function p(x,y); and.delta..sub.2 is a 2-dimensional delta function, wherein.delta..sub.2 (u,v)=1 is u=v=0, .theta..sub.1 =.theta..sub.2, .theta..sub.2 =.pi.-.theta..sub.1 =0 elsewhere; and(d) creating an image based on the results of step (c).