{ SCCSid "$SunId$ LBL" }

{
	Interpolate triangle-mesh values using barycentric coordinates.

	A1 through A12	= Transformation matrix for barycentric system
and:
	A13 through A21	= Surface normal perturbation matrix
or:
	A13 through A18	= Lookup in 2-dimensional pattern or texture
}
					{ Compute barycentric coordinates }
a = Px*arg( 1) + Py*arg( 2) + Pz*arg( 3) + arg( 4);
b = Px*arg( 5) + Py*arg( 6) + Pz*arg( 7) + arg( 8);
c = Px*arg( 9) + Py*arg(10) + Pz*arg(11) + arg(12);
					{ Compute variables }
v1 = a*arg(13) + b*arg(14) + c*arg(15);
v2 = a*arg(16) + b*arg(17) + c*arg(18);
v3 = a*arg(19) + b*arg(20) + c*arg(21);
					{ 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;