function angle = h3d_rotation_error(R, Rest)
	% returns rotation error in degrees
	D = Rest'*R;
	
	angle = max([...
		angle_between_vectors(D*[1;0;0], [1;0;0]) ...
		angle_between_vectors(D*[0;1;0], [0;1;0]) ...
		angle_between_vectors(D*[0;0;1], [0;0;1]) ]);
		
	angle = rad2deg(angle);


	[v,theta] = rot_matrix_to_axis_angle(R*Rest');
	angle = rad2deg(abs(theta));