Circle disturb with a force with kinect or webcam movement

Hi, I need to make a circle and disturb it with a force (wind, deform, for example) when a person shows in the camera. I don’t want the person to show on the screen, just use the movement to alter the circle and then the circle goes back to its original form. Can anyone help me? please

Can you please describe in more detail how your input data look like (vectors, textures etc.)?

Thanks for taking the time to read my request. I would like to use this http://barradeau.com/blog/?p=621 but move it with the webcam.