What do the output vectors in optical flow technique of live motion detection indicate?

There are two vectors one is a real vector and the other is imaginary. In this page http://www.mathworks.in/help/imaq/examples/live-motion-detection-using-optical-flow.html what do the vectors V and H denote and how can I use them. Is is related to the vertical and horizontal motion of the object pixels?

Answer 1

[Anand]

V and H are the vertical and horizontal components of optic flow. They represent the horizontal and vertical components of motion predicted by the optic flow algorithm at that pixel.

How you use them depends on what you want out of them.

[Tanmay]

Thanks Anand, I wanted to know whether any object is approaching the camera or going away from it. Any idea of how can it be done ??

[Anand]

Here's a simplistic approach: Once you've delineated the 'object' as a connected component, use regionprops to see if the area of the object increases significantly. That means it moved closer.

Obviously there are a lot of assumptions here. For example, the object could have just gotten bigger and not moved closer at all.