I am trying to derive the inverse depth equation used in monocular SLAM algorithms. Specifically the equation 8 of the ORB SLAM paper
I am very close, except I do not understand where the (u_j-c) term comes form. I get the same formulae with only the c (principal point) component.
I am thinking it is because u_j in this case is indexed from the start of the epipolar line instead of the image (0,0). Is this correct?