Using Pfinder's estimates of the user's head, hands, and feet position it is possible to create convincing shared virtual spaces. The ALIVE system, for instance, places the user at a particular place in the virtual room populated by virtual occupants by compositing real-time 3-D computer graphics with live video. To make a convincing 3-D world, the video must be placed correctly in the 3-D environment, that is, video of the person must be able to occlude, or be occluded by, the graphics.
The high level description of the user is also suitable for very-low bandwidth telepresence applications. On the remote end information about the user's head, hand, and feet position is used to drive an video avatar that represents the user in the scene. One such avatar is illustrated in Fig. 3(d). It is important to note that the avatars need not be an accurate representation of the user, or be human at all.