Gradient – More formal
•Suppose we move D in direction q.
•Motion: v=(Dcosq, Dsinq)
•Intensity change: <v, I>
•Recall <v,w> = ||v|| ||w||
cos a.
•So <v, I> is maximized when v is in
the direction of I.
•In that direction, rate of image
change is: || I||.
