Real-Time Geometric Patterns on the Stage

Can we create patterns like these in real time? Patterns that are pushed away by the actors' shadows or that---on the contrary---live inside those shadows?

A basic technique would be to illuminate the projection surface with infrared light and then apply image processing on the image of a camera that is only sensitive to infrared, for instance a slightly modified webcam. Here are two examples of this technique: 1 2

This could be accomplished with graphical programming languages such as

Max/MSP Jitter
EyesWeb
Pure Data
vvvv

I, however, find OpenCV much easier to use (see the example) and much more versatile.

The "living" patterns could for instance be created by reaction-diffusion processes or by physics (or non-physics, so to speak), see the examples.