Below are video demonstrations of an interactive software piece still in an early stage of development. The program uses frame differencing to detect the presence of motion in a certain region of incoming video (in this case, a live webcam feed).
When a certain amount of motion is detected, the physics engine is invoked and rigid physical bodies are placed at the location of detected movement. This allows the 3D models which are dropped periodically to collide with the rigid bodies.
3D models can of course be swapped out to meet a variety of applications such as product showcases and public game installations.