Team : i3d
Section: Scientific Foundations
Keywords : CAVE, flat or cylindrical wall, workbench, HMD, immersion.
Virtual Reality Configurations and Workbench
Much of the research work and especially of the developments of the i3D group are dictated by the Workbench installed at the end of 1999. This paragraph briefly describes this configuration and positions it within the set of other configurations of the same class.
Virtual reality has been identified for a while with head mounted displays. In this class, one finds HMD (Head Mounted Display) which isolate the user from his/her real environment and require the use of avatars. One finds also see-through HMD which have the advantage of allowing to see the real world but whose characteristics in term of resolution, field of view etc... are often too weak for the majority of the industrial applications.
Currently, projection-based virtual environments often take the place of HMDs. More recent, less invasive and offering better characteristics, these configurations take several forms. In this class, one finds the CAVETM, the flat or cylindrical walls and the Workbenchs. See  for a more detailed introduction of this class of configurations.
The CAVETM(CAVE is a trademark of the university of Illinois) is probably the best known of these configurations. It is also the most expensive and the most complex to install and maintain. It appears as a room of approximatively 3 meters on each side with the virtual world retro-projected on 4 (three walls and the ground) to 6 (for some recent configurations) of the faces of the room. This configuration provides a good feeling of immersion thanks to the screens which "surround" the person, to stereoscopic visualization and to head tracking. This configuration is very well adapted to navigation inside large spaces (for example, a visit to a virtual scene such as architecture, a amusement park, or a driving simulation).
The wall is a large flat or cylindrical screen on which the virtual world is visualized generally with the assistance of 3 video projectors. The fact that people sit in front of the screen, without head tracking, makes this configuration more passive. It is a nice configuration for presenting projects to a group of approximatively 20 persons, like projects reviews for example.
The Workbench (or Responsive WorkbenchTM("Reponsive Workbench" is a tademark of GMD), by reference to the first developed system ) is the "lightest" configuration (see Figures 1, 3, 4). Often less known than the CAVETM, this configuration is, from many points of view, far from being less attractive. With a horizontal screen (plus, possibly, a second vertical one providing a wider field of view) which represents a tabletop, the Workbench makes it possible to visualize a virtual scene within the range of hands, in front of the observer. A video projector, after reflexion on one or more mirrors, retro-projects the image on the screen representing the surface of the table. 3D effects are provided thanks to stereoscopic visualization with shutter glasses. As with the CAVETM, head-tracking is provided.
The form of the Workbench predestines it with manual manipulations on a table. This configuration is also characterized by strong potential for interaction. Its head tracking feature allows a superposition of the visualization and the manipulation spaces (virtual and real spaces) and opens the way to simpler and more intuitive interactions. In addition, whereas a maximum immersion of the person into the virtual world was preached a long time, in particular with the HMDs, this configuration introduces the opposite approach, which is more comfortable: the immersion of the application into the user's (real) environment. This configuration is thus integrated into the users' real world, providing him with very pleasant feelings, close to what he/she is used to when manipulating objects on a table in the real world. It is thus quite naturally that the applications of this configuration are those where the user observes and handles data or numerical mockups which rest in front of him, within the range of hands.