Well first off, I think funny hats are in order.

If you require funny hats, then tracking someones head becomes trivial.

A simple down looking camera could track the top of the persons head from below the projector.

I'm thinking a couple super simple QR codes could give roll/pitch/yaw.

Add 6 QR codes and you could track arms and wrists.

Strobe some colored LED's on the fingers of some gloves, and use two cameras.  Now you have Minority Report.