{ SCCSid "$SunId$ LBL" }

{
	Interpolate triangle-mesh values using barycentric coordinates.

	A1		= Major axis (0==X, 1==Y, 2==Z)
	A2 through A7	= Transformation for barycentric system
and:
	A8 through A16	= Surface normal perturbation matrix
or:
	A8 through A13	= Lookup in 2-dimensional pattern or texture
}
					{ Compute barycentric coordinates }
bu = select(arg(1)+1, Py, Pz, Px);
bv = select(arg(1)+1, Pz, Px, Py);
a = bu*arg( 2) + bv*arg( 3) + arg( 4);
b = bu*arg( 5) + bv*arg( 6) + arg( 7);
c = 1 - a - b;
					{ Compute variables }
v1 = a*arg( 8) + b*arg( 9) + c*arg(10);
v2 = a*arg(11) + b*arg(12) + c*arg(13);
v3 = a*arg(14) + b*arg(15) + c*arg(16);
					{ Surface normal perturbation }
nf = 1/sqrt(v1*v1 + v2*v2 + v3*v3);
dx = v1*nf - Nx;
dy = v2*nf - Ny;
dz = v3*nf - Nz;
					{ Lookup table index }
u = v1;
v = v2;