Is the relationship between the optical flow in an image plane and the velocities of objects in the 3-D world space necessarily obvious? Justify your answer How are the derivatives of intensity...

Is the relationship between the optical flow in an image plane and the velocities of objects in the 3-D world space necessarily obvious? Justify your answer

How are the derivatives of intensity function and the Laplacian of flow components estimated in the Horn and Schunck method?