Web cam interaction

Basically what I am trying to do is to make the webcam interact with the person in front of it.
I have this object called ball that once it makes contact with the image of the person standing in front of the camera it bounces or changes direction. A different interaction will also be if the person intersects the ball in X or Y axis the object changes direction again.
Can someone please tell me which patch would I be using to achieve this interaction.

Thanks in advance.