{ RCSid $Id: LaFortune1.cal,v 1.2 2019/06/10 13:56:52 greg Exp $ }
{ LaFortune reflectance model with one lobe }

	{ Sample parameters (change these) }
rho_d : 0.136465483630983;
rho_s : 0.144594472775860;
Cx : -0.605122636448704;
Cy : -0.664960041454502;
Cz : 0.586571000768196;
n : 29.629194300125050;

			{ Useful functions }
abs(x) : if(x, x, -x);
noneg(x) : if(x, x, 0);

	{ Normalization factor based on parameters }
snf : (n+2)/(2*PI*max(abs(Cx),abs(Cy),abs(Cz))^n);

{ Note that we assume i and o vectors are normalized, both pointing away }

lafortune(ix,iy,iz,ox,oy,oz) : if( -iz*oz, 0,
		rho_d/PI + rho_s*snf*noneg(Cx*ix*ox + Cy*iy*oy + Cz*iz*oz)^n );