Virtual reality systems consist of four main components: 1. A computer and software known as the reality engine 2. Input sensors like head-mounted displays, gloves, and audio units 3. Output sensors like head-mounted displays and audio units 4. The user, who directs the environment and reacts to it

1. 1. List different components of virtual reality system ?
Essentially, virtual reality systems consist of the computer and software—known as the
reality engine—input sensors, and output sensors. The input sensors are the equipment to
computer enthusiasts, and include the keyboard, mouse, knobs, and joysticks. Output
devices include the printer and the video display monitor. In addition, virtual reality input
and output devices include the head- and ear-mounted equipment mentioned above, and
gloves for controlling the virtual world. Finally, the fourth sensory component is the user,
who both directs and reacts to the chosen environment.
Virtual reality is an artificial environment that is created and maintained by a computer
and that is at least partly shaped and determined by the user. A virtual reality system
allows the user to "leave" the real world and step into a world whose sensory inputs
(sights, sounds, smells, etc.) are provided not by natural objects but by computer-created
means. The things that happen in that virtual world can then be manipulated to a large
extent by the user.
Components
In its most basic form, virtual reality systems consist of a computer and software—known
as the reality engine—and input and output sensors. A sensor is a device that responds to
some physical stimulus. A human eye, for example, is a sensor that responds to light rays.
In standard computer technology, input devices are the familiar keyboard, mouse, knobs,
and joysticks; output devices include the printer and video display. Virtual reality
input/output devices include head- and earmounted equipment for hearing and seeing and
gloves for controlling the virtual world. The fourth "component" is the user, who directs
the chosen environment and reacts to it.
The reality engine. The reality engine employs both computer hardware and software to
create the virtual world. Reality engines are based largely on the same components that
make up a personal computer (PC), although much more computing power is required for
the reality engine than is available in a standard PC.
One key to virtual reality is creating a world that appears real. The images created by the
computer and software are extremely complex compared to the relatively simple line-
based graphics associated with computer games. Virtual reality images are made with
tiny dotlike segments of a picture known as pixels, or picture elements. Each pixel itself
is made up of hundreds of thousands of dots. The more pixels there are per inch, the
better or more realistic the image will be.

2. Words to Know
Cathode-ray tube (CRT): A form of vacuum tube in which a beam of electrons is
projected onto a screen covered with a fluorescent material in order to produce a visible
picture.
Ergonomics: The study of the way humans and objects interact with each other.
Haptic: Relating to the sense of touch.
Light-emitting diode (LED): A device made of semiconducting materials that emits
light when an electric current is applied to it.
Liquid crystal display (LCD): A way of displaying visual information by using liquid
crystals that emit light when exposed to electric current.
Pixel: One of the small individual elements of which a visual image consists.
Reality engine: The hardware and software used in virtual reality systems.
Virtual: Something that is representative or the essence of a thing but not the actual
thing.
Creating realistic images that can be manipulated is known as realization. These images
can be either opaque, in which all the viewer sees is the virtual world, or see-through, in
which the virtual image is projected or superimposed onto the outer world.
Sound enriches the virtual world. The experience of soaring through the air in a simulated
cockpit is more realistic if the user hears the roar of the engines. Sound also enhances
participation in the virtual world by providing the user with audio cues. For example, the
user may be directed to look for the virtual airplane flying overhead.
To incorporate the total experience, the reality engine also may use haptic enhancement.
Haptic experiences are those that involve the participant's senses of touch and pressure.
Haptic cues, however, are complex and expensive and have been used primarily for
military and research applications.
Headsets. Head-mounted display (HMD) units use a small screen or screens (one for
each eye) that are worn in a helmet or a pair glasses. Unlike a movie, where the director
controls what the viewer sees, the HMD allows viewers to look at an image from various
angles or change their field of view by simply moving their heads.
HMD units usually employ cathode-ray tube (CRT) or liquid crystal display (LCD)
technology. CRTs incorporate optic systems that reflect an image onto the viewer's eye.
Although more bulky and heavy than LCD displays, CRT systems create images that
have extremely high resolutions, making a scene seem that much more realistic. In

3. addition, CRT images can be semireflective, allowing the viewer to see the outside world
as well. Such units have practical applications since the user can operate a machine or
other device while viewing the virtual world.
Although LCD technology has lagged behind CRT in picture quality, LCD systems are
slimmer, lighter, and less expensive, making them better suited for home use. These units
use liquid crystal monitors to display two slightly different images that the brain
processes into a single three-dimensional view. Initial efforts to market this technology to
home users failed because of poor LCD image quality. But rapid advances in LCD
technology have improved the images, and higher quality LCD-based units have become
available for home use.
Audio units. Sound effects in virtual reality rely on a prerecorded sound set that is
difficult to alter once the reality engine begins to generate audio. The audio portion of
virtual reality is transmitted through small speakers placed over each ear. Audio cues may
include voices, singing, the sound of bubbling water, thudlike noises of colliding objects
—in short, any sound that can be recorded.
Three-dimensional (or omnidirectional) sound further enhances the virtual reality
experience. Sounds that seem to come from above, below, or either side provide audio
cues that mimic how sounds are heard in the real world. Three-dimensional sound is
achieved through the use of highly complex filtering devices. This technology must take
into account factors like interaural time difference (which ear hears the sound first) and
interaural amplitude difference (which ear hears the sound louder). The most complex
human hearing dynamic is called head-related transfer functions (HRTF). HRTF accounts
for how the eardrum and inner ear process sound waves, taking into consideration the
various frequencies at which these waves travel as well as how waves are absorbed and
reflected by other objects. HRTF audio processing enables the listener not only to locate
a sound source but also to focus in on a specific sound out of a multitude of sounds, like
distinguishing the call of a hot dog vendor out of a noisy crowd at a baseball game.
Gloves. Gloves in virtual reality allow the user to interact with the virtual world. For
example, the user may pick up a virtual block, turn it over in a virtual hand, and set it on
a virtual table. Wired with thin fiberoptic cables, some gloves use light-emitting diodes
(LEDs) to detect the amount of light passing through the cable in relation to the
movement of the hand or joint. The computer then analyzes the corresponding
information and projects this moving hand into the virtual reality. Magnetic tracking
systems also are used to determine where the hand is in space in relation to the virtual
scene.
Some gloves use haptic enhancement to provide a sense of touch and feel. In haptic
enhancement, the reality engine outputs the tactile experience, which may include force,
heat, and texture. Tactile experiences are created by remeasuring a pattern of forces,
which is programmed into the reality engine and then relayed back to the user when the
appropriate object is touched. Virtual reality gloves may use either air pressure (such as
strategically placed inflated air pockets in the glove) or vibrating transducers placed next

4. to the skin (such as a voice coil from a stereo speaker or alloys that change shape through
the conduction of electrical currents) to simulate tactile experience.
Tools under development. Many other virtual reality tools are in the phases of research
and development. Remote control robotic or manipulator haptic devices are being tested
for industry and medicine. Special wands with sensors, joysticks, and finger sensors such
as picks and rings will eventually be as common to virtual reality technology as
microwaves are to cooking. The technology to control the virtual world through voice
commands also is rapidly advancing.
Perhaps the most impressive technology under development is the whole body suit. These
suits would function similarly to the gloves, creating a virtual body that could take a stroll
through a virtual world and feel a virtual windstorm.
Read more: Virtual Reality - humans, body, used, water, process, form, system, air,
effects, waves, basic, change, Components, Applications
http://www.scienceclarified.com/Ti-Vi/Virtual-Reality.html#ixzz18UVukCZI
3. What is Graphics Tablets? What is advantage of using them
as input device?
Ans. A graphics tablet (or digitizer, digitizing tablet, graphics pad, drawing tablet) is
a computer input device that allows one to hand-draw images and graphics, similar to the
way one draws images with a pencil and paper. These tablets may also be used to capture
data or handwritten signatures. It can also be used to trace an image from a piece of paper
which is taped or otherwise secured to the surface. Capturing data in this way, either by
tracing or entering the corners of linear poly-lines or shapes is called digitizing.
A graphics tablet (also called pen pad or digitizer) consists of a flat surface upon which
the user may "draw" or trace an image using an attached stylus, a pen-like drawing
apparatus. The image generally does not appear on the tablet itself but, rather, is
displayed on the computer monitor. Some tablets, however, come as a functioning
secondary computer screen that you can interact with images directly by using the stylus.
A graphics tablet is an input device used by artists which allows one to draw a picture
onto a computer screen without having to utilize a mouse or keyboard. A graphics tablet
consists of a flat tablet and some sort of drawing device, usually either a pen or stylus. A
graphics tablet may also be referred to as a drawing tablet or drawing pad. While the
graphics tablet is most suited for artists and those who want the natural feel of a pen-like
object to manipulate the cursor on their screen, non-artists may find them useful as well.
The smooth flow of a graphics tablet can be refreshing for those who find the mouse to

5. be a jerky input device, and repetitive stress injuries such as carpal tunnel syndrome are
less likely when using a graphics tablet.
4. Explain different area filling techniques.
In an all-points-addressable (APA) graphics display, a hardware area fill technique for
clipped graphics objects is described which allows graphics objects to be area filled by
simple hardware at high speed, even when part of the object is clipped off by a screen or
viewport boundary. Hardware registers defining X and Y coordinates of screen pels
(picture elements) include additional bits to define off-screen space. Logic is provided to
prevent drawing in off-screen space and automatically to complete the boundaries before
filling. An APA graphics system normally consists of a number of memory arrays (bit
planes), each having one addressable location per screen pixel. Most of these planes are
usually used to define the colour of the pixels, but often one is reserved for use when
drawing area-filled (Image Omitted) objects.
5. What is homogenous co-ordinate system? How does it differ
from Cartesian system?
homogeneous coordinates, are a system of coordinates used in projective geometry
much as Cartesian coordinates are used in Euclidean geometry. They have the advantage
that the coordinates of a point, even those at infinity, can be represented using finite
coordinates. Often formulas involving homogeneous coordinates are simpler and more
symmetric than their Cartesian counterparts. Homogeneous coordinates have a range of
applications, including computer graphics and 3D computer vision, where they allow
affine transformations and, in general, projective transformations to be easily represented
by a matrix.
If the homogeneous coordinates of a point are multiplied by a non-zero scalar then the
resulting coordinates represent the same point. An additional condition must be added on
the coordinates to ensure that only one set of coordinates corresponds to a given point, so
the number of coordinates required is, in general, one more than the dimension of the
projective space being considered. For example, two homogeneous coordinates are
required to specify a point on the projective line and three homogeneous coordinates are
required to specify a point on the projective plane.