Page 347 - Concise Encyclopedia of Robotics

Virtual Reality
VIRTUAL REALITY
Virtual reality (VR) is the ultimate simulator. The user can see and hear
in an artificial realm called a virtual universe or VR universe. In the most
sophisticated VR systems, other senses are replicated as well. Hardware
and software developers in several countries, particularly the United
States and Japan, are actively involved in VR technology.
Forms of VR
There are three degrees, or types, of VR. They are categorized according
to the extent to which the operator participates in the experience. The
first two forms are sometimes called virtual virtual reality (VVR).
Passive VR is, in effect, a movie with enhanced graphics and sound.
You can watch, listen, and feel the show, but you have no control over
what happens, nor on the general contents of the show. An example of
passive VR is a ride in a virtual submarine, a small room with windows
through which you can look at a rendition of the undersea world.
Exploratory VR is like a movie over which you have some control of
the contents. You can choose scenes to see, hear, and feel, but you cannot
participate fully in the experience.An example of exploratory VR is a ride
in a tour bus on an alien planet, in which you get to choose the planet.
Interactive VR is what most people imagine when they think of true
VR.You have nearly as much control over the virtual environment as you
would have if you were really there.Your surroundings react directly to your
actions. If you reach out and push a virtual object, it moves. If you speak
to virtual people, they respond.
Programming
The program,or set of programs,containing all the particulars for each VR
session is called the simulation manager. The complexity of the simulation
manager depends on the level of VR.
One dimension: In passive VR,the simulation manager consists of a large
number of frames, one representing each moment in time. The frames
blend together into a space-time experience path. This can be imagined,
in simplified form, as a set of points strung out along a straight line in one
geometric dimension (Fig. 1). Each point represents data for one instant
of time in the VR session. This is similar to the way frames exist in a
movie or a videotape.
Two dimensions: In exploratory VR, there are several different sets of
frames, from among which you can choose to construct the experience
path. Imagine each set of frames as lying along its own individual line,
as shown in Fig. 2. You choose the line through space-time along which

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