In all of the applications we have seen so far,
a user is indirectly aware of the actions of another through telepointers,
encoding of users by colours,
audio feedback,
and other features.
Clearboard [],
designed for two-user collaboration,
shows that it is possible for a user to be directly aware of the actions
of a remote use.
It appears to each user that other user is behind a transparent whiteboard,
and the drawings made by the two users are shared rather than
overlaid.
Thus, one
user can,
for instance,
erase a drawing made by another user or refine it.
.
Mirrors, projectors, and a multiuser shared whiteboard application are used to create this illusion of face-to-face awareness. The displays of the users are tilted 45 degrees, and the image of a user is is reflected by a mirror, captured by an overhead camera, and transmitted to a rear projector at the other site which overlays the image on the screen. The shared whiteboard application ensures that users share changes to the objects drawn on the whiteboard.