Looks like they track the position of shutter glasses in space, and have some way of positioning the image per user as it gets projected through the tabletop: <a href="https://newatlas.com/hologram-tables-euclideon/50868/#gallery" rel="nofollow">https://newatlas.com/hologram-tables-euclideon/50868/#galler...</a>
They must have a cap for the number of users because of the glasses tracking.