A virtual environment (VE) is characterized by the display mode and the
visualized information. Monoscopic and stereoscopic rendering provide a virtual
depth perception to immerse the viewer in a virtual world. The degree of
immersion depends on the projection type and nature of the information which
is supposed to be visualized.
Head Mounted Displays (HMDs)
These single user display devices are mounted on a helmet-like structure. The field of view is
usually very limited. For multiple users, multiple units are needed. Since exact synchronization is
necessary, collaborative work environments usually don't employ HMDs.
Some displays are mounted on full helmets, which are too heavy for long time use.
HMDs are often used in Augmented Reality projects.
The specific HMD on the picture below was used at
Mississippi State University.
Immersive Workbench
Single-screen projection-based systems such as ImmersaDesk and
Responsive Workbench (RWB) consist of one screen, usually
several feet in diameter, which is mounted at a variable angle.
These Virtual Model Displays (VMDs) lack complete immersion, but guarantee
excellent object presence.
While the ImmersaDesk utilizes a near-vertical pitch of the
display surface, the RWB uses a tabletop metaphor, in which virtual objects appear
to lie on the table's surface. This ensures easy accessibility for interaction
with the data and allows intuitive interfaces to be shared by several users.
The field of vision is limited by the screen dimensions, since the displayed
data can be explored only by looking down and in a forward direction. No surrounding
view of the environment is possible, and only small or a reasonable number
of a very small set of large structures fit on the screen.
Therefore, navigation in the whole scene is not necessary, only navigation methods
for object manipulations must be available.
The picture below was taken at
CIPIC at UC Davis.
CAVE
The CAVE is a multiple-screen projection-based virtual reality system with four
to six screens that are arranged in a cube for total immersion. The most common
setup consists of three walls and a floor.
The major advantage of the CAVE is the fact that it enables collaborative
exploration of several large-scale objects through manipulation and navigation
within an immersive virtual world.
The viewer navigates the virtual scene by naturally moving around inside the
cube, while his field of vision is completely covered by the images.
Spatially Immersive Displays (SIDs) like the CAVE enable simultaneous
access to a greater amount of information than any other display devices and help
escaping the bias towards 2D computing by organizing objects more effectively in 3D.
Intensive work for the MolVis project was done in the COVE at the
NSF-Engineering Research Center at
Mississippi State University.
In a Virtual Environment the user should feel comfortable and unconstrained when interacting with the
environment and have access to traditional interaction tools, augmented by new virtual gadgets.
Wands
Wands are easy to use interaction devices for single handed input. Most wands support digital
and very often also analog input data. Object positioning is easy, but gesture recognition
for sophisticated interaction and object manipulation is, of course, not possible.
The custom wand in the picture below was taken from a Nintendo 64 system, features
four digital and two analog controls, and is used in the
COVE
at the NSF-Engineering Research Center at Mississippi State University.
Pinch Gloves
Gloves are used to emulate intuitive and unencumbered two-handed interaction in VEs.
Unfortunately, most glove models do not permit tracking of the exact finger
positions. Nevertheless, basic gesture recognition for navigation, interaction, and
modelling tasks is possible through adequate pinch combinations.
Pinch gloves were used as primary interaction devices in the
VirtualClay project at
CIPIC at
UC Davis.
Haptic Input
Haptic input and force feedback allow sophisticated interaction with data in
VR systems. The exact finger position is tracked and can be incorporated in the
application. Since not only the equipment itself but also the data transfer between
hardware and application is expensive, haptic devices usually only allow single-handed
input, which is also encumbered by the external skeleton structure.
A haptic device as shown in the picture below is available at the
Computer Graphics Group
at the University of Kaiserslautern.