Augmented Reality can also be used to enhance collaborative tasks. A good example of this is the StudierStube project of Schmalsteig, et al [Schmalsteig 96]. They use see-through head mounted displays to allow users to collaboratively view 3D models of scientific data superimposed on the real world (figure 3). They report users finding the interface very intuitive and conducive to real world collaboration, because the groupware support can be mostly left to social protocols. The AR2 Hockey work of Ohshima, et al, [Ohshima 98] is very similar. In this case two users wear see-through head mounted displays to play an AR version of the classic game of air hockey. As they move a real mallet over a real table, they send a virtual puck towards each other's goals.