{ RCSid $Id: WGMDaniso.cal,v 1.1 2014/03/24 20:51:16 greg Exp $ }
{ Ward-Geisler-Moroder-Duer anisotropic BRDF model }

			{ Parameters (change these) }
rho_d : 0.095;
rho_s : 0.05;
ax : 0.02;
ay : 0.08;

exfunc(hx,hy,hz) : exp(-(hx*hx/(ax*ax) + hy*hy/(ay*ay))/(hz*hz)) *
			(hx*hx + hy*hy + hz*hz) /
			(PI*ax*ay*hz*hz*hz*hz);

{ Note that we assume i and o vectors are normalized }

wgmdaniso(ix,iy,iz,ox,oy,oz) : if( -iz*oz, 0,
			rho_d/PI + rho_s*exfunc(ix+ox,iy+oy,iz+oz) );