function ip = cv_3d_2d(pts, R,T)
%
[num_pts,dummy] = size(pts);
ip = pts(:,1:2);
for p = 1:num_pts
   ip(p,1) = R(1,:)*pts(p,:)' + T(1);
   ip(p,1) = ip(p,1)/(R(3,:)*pts(p,:)' + T(3));
   ip(p,2) = R(2,:)*pts(p,:)' + T(2);
   ip(p,2) = ip(p,2)/(R(3,:)*pts(p,:)' + T(3));
end
