This video is a little old now, but if you’ve not seen it, it’s worth a look! Called Magic Projection, it’s an Augmented Reality Projection Tracking System developed by a guy called Marco Tempest and he filmed this trial run of the technology in December last year.
Essentially, it works like any other projection system, but because it’s based around Augmented Reality, it allows you to virtually interact with the projection in real time. Pretty dam cool, I can only imagine with this sort of thing will head over the next few years. (via Chris at Blogilvy)

