| "Virtual
Reality: A computer system used to create an artificial
world in which the user has the impression of
being in that world and with the ability to navigate
through the world and manipulate objects in the
world."
- C. Manetta and R. Blade in "Glossary of
Virtual Reality Terminology" in the International
Journal of Virtual Reality, Vol.1 Nr.2 1995.
"Virtual Reality allows you to explore a
computer generated world by actually being in
it"
- B. Sherman and P. Judkins (1992) "Glimpses
of Heaven, Visions of Hell: Virtual Reality and
its implications" (Hodder and Stoughton:
London).
Please see, VR, A
Short Introduction for a continued definition
of VR.
Real-time Versus Pre-Rendered Graphics
| Conceptually,
virtual reality (VR) is used by artists
to explore an alternate reality while the
military, automobile manufacturers, architects,
and medical doctors use VR to display real
world scenarios and data. Planners need
to capitalize on data visualization techniques
and utilize the VR platform for exploring
alternative "What If" scenarios
about the built environment. VR also provides
the opportunity to explore conceptual visualization
about environmental data.
Real time graphics are rendered (or drawn)
in real time as you interact with them while
pre-rendered computer graphics are static
or in the case of cinematography, a series
of rendered images. Real time has
many advantages over pre-rendered graphics.
The user within a real time display has
free range of movement. The user can walk,
fly, or examine any object within the scene
by moving closer to the object and walking
around it. Preselected viewpoints allow
the user to travel easily from one place
to another. Within a simulation, the user
can manipulate buildings by moving and scaling
them. If it has been programmed, the user
can also swap out buildings to judge the
appropriateness of building types. Real
time simulations are dynamic. Cars, doors,
lights, and sound can be manipulated and
immediately address the client's concerns.
|
Real-time Graphics In Depth
Real-time graphics is part of
a computer graphics system. The five major elements
are as follows:
1. Processor
2. Memory
3. Frame Buffer
4. Output Devices
5. Input Devices
A raster image is produced and
comprised of pixels. Collectively, the pixels
are stored in a part of memory called the frame
buffer. In high-end systems, the frame buffer
is implemented with special types of memory chips—video
random-access memory (VRAM) or dynamic random-access
memory (DRAM)—that enable fast redisplay
of the contents of the frame buffer. The depth
of the frame buffer, defined as the number of
bits that are used for each pixel, determines
properties such as how many colors can be represented
on a given system. For example, a 8-bit deep frame
buffer allows 256 colors. The resolution (the
number of pixels in the fame buffer) determines
the detail that you can see in the image.
In a raster system, the graphics
system takes pixels from the frame buffer and
displays them as points on the surface of the
display. The entire contents of the frame buffer
are displayed at a rate high enough to avoid flicker.
This rate is called the refresh rate.
A low refresh rate is important
to avoid. When creating content for the CAVE,
you must monitor both your polygon count and texture
map file size to avoid a slow refresh rate.
Most graphics systems provide
a keyboard and at least one other input device.
In the CAVE, a 3D mouse called a wand is used.
It has three buttons and a joystick. The buttons’
uses are determined by the program developer,
meaning you.
|
