function [face, u, v] = h3d_coords_s2_to_cube(s)
	% function [face, u, v] = h3d_coords_s2_to_cube(s)
	%
	%	s:  3D vector on the sphere
	%	
	%	face: between 1 and 6
	%	u, v: both between -1 and 1
	
	s = s / norm(s);
	
	sa = abs(s);
	
	if (sa(1) >= sa(2)) && (sa(1) >= sa(3))
	
		if sign(s(1)) > 0
			face = 1;
		else
			face = 4;
		end
		
		u = s(2) / s(1);
		v = s(3) / s(1);
		return
	end

	if (sa(2) >= sa(1)) && (sa(2) >= sa(3))
	
		if sign(s(2)) > 0
			face = 2;
		else
			face = 5;
		end
		
		u = s(1) / s(2);
		v = s(3) / s(2);
		return
	end
	

	if (sa(3) >= sa(2)) && (sa(3) >= sa(1))
	
		if sign(s(3)) > 0
			face = 3;
		else
			face = 6;
		end
		
		u = s(1) / s(3);
		v = s(2) / s(3);
		return
	end
	
	error(sprintf('bug: s = %f %f %f\n',s(1),s(2),s(3)));