[email protected] VR Hardware. [email protected] Project Create your own virtual world...
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Transcript of [email protected] VR Hardware. [email protected] Project Create your own virtual world...
Project
Create your own virtual world VRML Marks are based on :
Creativity Navigation Human Computer Interface (HCI)
HARDWARE
Desktop VR is very popular because it can be used at little additional cost to a typical personal computer.
Desktop VR is delivered through computer graphics and multimedia.
As long as our senses are distracted by events outside of the computer simulation, our minds are quick to remember a virtual place is not reality.
Specialized types of hardware devices for VR applications :
1. Image generators2. Manipulation & control devices3. Stereo vision4. Head mounted display (HMD)
1. Image generator
Most time consuming in VR system : generation of images
Market demand Sell – image generator cards for PC
level Expensive Eg : Silicon Graphics
2. Manipulation & control devices
Key elemen of interaction with virtual world
Tracking position of real world object Head, hands, etc
Many methods for position tracking & control
Basically – 3 measures for position (x, y, z) 3 measures for orientation (roll, pitch, yaw)
Yaw, rotation about the Y axis Pitch, rotation about the X axis Roll, rotation about the Z axis
Y
Z
X
Problem for position tracking : latency The time required to make the
measurements & preprocess them b4 input to the simulation engine
Simplest control hardware : Mouse Trackball Joystick
B4 : 2D (x & y) Add extra buttons & wheels, can control
not only xy but also z dimension Common VR device : instrumented glove Use : manipulate objects in a computer The glove is outfitted with sensors on the
fingers & overall position/orientation tracker
Many different types of sensors can be used
DataGloves (by VPL) : use fiber optic sensors for finger bends & magnetic trackers for overall position
PowerGlove (by Mattel) : use for Nintendo game system Easily adapted to interface to a PC Limited edition of hand location & finger
position data using strain gauges for finger bends & ultrasonic position sensors
Concept of an instrumented glove has been extended to other body parts
Full body suits with position & bend sensors Capturing motion for character animation Control of music synthesizers VR applications
Mechanical sensors can be used to provide fast & accurate tracking Basic position/orientation
Desk lamp Detailed position
Complex skeleton Drawbacks : restriction on motions
Ultrasonic sensors to track position & orientation
A set of emitters & receivers are used The emitters are pulsed in sequence &
the the time lag to each receiver is measured
Drawback : Low resolution Long lag times Interference from echoes & other noise
Magnetic trackers : use sets of coils that are pulsed to produce magnetic fields
Limitation : High latency Interference
3. Stereo vision
Often included in VR system Create 2 different images of the
world, one for each eye The images are computed with the
viewpoints offset by the equivalent distance between the eyes
The images can be Placed side by side & the viewer
asked to crossed their eyes Projected through differently
polarized filters Some use red/blue glasses to
provide a crude (no color) stereovision
Health hazards from stereoscopic displays
Study by : Edinburgh Virtual Environemt Lab, Dept. of Psychology, Univ. of Edinburgh“eye strains effects of stereoscopic Head Mounted Displays”
A number of report of stress with HMDs & other stereoscopic displays
Test : 20 young adults on a stationary bicycle & let them cycle around a virtual rural road using a HMD
After 10 minutes, the subjects were tested : Over half the subjects reported
symptoms of stress & blurred vision
4. HMD
Use : sort of helmets or goggles to lace small video displays in front of each eye, with special optics to focus & stretch the perceived field of view
Most HMDs use 2 displays & can provide stereoscopic imaging
Some use a single larger display to provide higher resolution, but without the stereoscopic vision
CRT : Cathode Ray TubeLCD : Liquid Crystal Display
Most lower cost HMDs use LCD display, some use small CRT (like in camcorder)
The most expensive HMDs use special CRTs mounted along side the head or optical fibers to pipe the images from non-head mounted displays
A HMD requires a position tracker in addition to the helmet
LEVELS OF VR H/W SYSTEMS
Entry VR (EVR) Basic VR (BVR) Advanced VR (AVR) Immersion VR (IVR) SIMNET, Defense Simulation
Internet
1. Entry VR
Takes a stock PC or workstation Based on an IBM clone machine or
Apple Macintosh Whatever the base computer it
includes a graphic display, a 2D input device (mouse, trackball or joystick), the keyboard, hard disk & memory
2. Basic VR
The next stage up from EVR system adds some basic interaction & display enhancements
Such enhancements would include stereographic viewer (LCD shutter
glasses) a I/O control device such as Mattel
PowerGlove a multidimensional (3D or 6D) mouse
or joystick
3. Advanced VR
Add rendering accelerator Simplest enhancement is faster display card For PC, there are a number of new fast VGA
& SVGA accelerator cards These makes dramatic improvement in the
rendering performance of a desktop VR An AVR system also add sound card to
provide mono, stereo or true 3D audio output
Some soundcard provide voice recognition
4. Immersion VR
Add some type of immersive display system : a HMD, or multiple large projection type displays (Cave)
A common variation on VR is to use a Cockpit or Cab compartment to enclose the user
A virtual world is viewed through some sort of view screen & usually projected to a conventional monitor
The cockpit simulation usually known as aircraft simulator
It is mounted on a motion platform that can give the illusion of a much larger range of motion
Cabs are also used in driving simulators for ships, trucks, tanks & ‘battle mechs’
‘battle mechs’ are walking robotic devices Eg : in Star Wars films
5. SIMNET
One of the biggest VR projects is Defense Simulation Internet
Pushed by USA Defense Department to enable diverse simulators to be interconnected into a vast network
SIMNET is a collection of tank simulators (Cab type) that are networked together
Simulators in Germany can operate the same virtual world as simulators in USA
Sensory displays : VISUAL AUDITORY KINESTHETIC
1. Visual
One of the basic goals of a virtual reality system is to supply your senses with information from the computer-generated reality in much the same way as you experience the real world.
Since most people have two eyes, a natural way to see the world requires not one computer display, but two.
A common way to produce a realistic 3D view of a virtual world is to place a small computer monitor in front of each eye.
Each monitor displays the perspective that the corresponding eye would see in an actual environment.
Such a system is called a binocular head-mounted display (HMD).
There are many safety concerns with HMDs that have yet to be resolved.
Consideration for the safety of individuals must be considered.
Other alternatives of getting a sense of partial immersion are with the use of shutter glasses or 3D projection systems.
Companies are working continually to give consumers a sense of immersion in their Virtual Environments.
The choice of shutter glasses or 3D projection depends upon the platform of use, the resolution desired, and personal preferences.
2. Auditory
Most people also have two ears. This is the main reason for the appeal
of stereophonic sound. Just as two visual perspectives make
a 3D view, two audio perspectives can make a 3D soundscape.
However, with free-standing stereo speakers the left and right sounds are mixed: both ears hear sound from both speakers.
By using headphones and presenting the correct acoustical perspectives to each ear, many of the spatial aspects of sounds can be preserved.
HMDs often have headphones built into them.
3. Kinesthetic
Additional displays can be used to engage other senses in VR.
There are some companies that offer force-feedback devices where you can actually "feel" different sensations.
Since there is not much of a demand for such things as smell or taste generators, you generally have be creative and figure out your own way of catering to more senses than just vision and hearing.
Tracking Systems
The tracking system measures position and orientation.
From the position and orientation of your head, the computer can determine how to display the virtual world so that it seems your are in it as opposed to watching it on television.
When you turn your head the head tracker senses the change in position, and adjusts the displays accordingly.
The head tracker needs to be capable of taking a measurement of position and orientation at least 20 times every second.
There also must be no more than a 1/20th of a second delay between when the measurements are taken, and when the visual display is updated.
Any slower than this, and the eyes and inner-ear give your brain conflicting information about which direction your head is pointing.
This is similar to what happens on a small boat in rough waters: It can make you seasick, or in VR terms, simulator-sick.
Other Input Devices
You use input devices to communicate your intentions and actions to the virtual world.
Since it is often difficult to touch-type or use a mouse while standing up and wearing a head-mounted display, other types of input systems are used instead of or in addition to keyboards and mice.
A wand is basically a hand-held joystick with a number of buttons on it.
Wands often include a tracker which then allows you to pick up and rotate objects in the virtual world.
You can use a wand in VR in much the same way you use a mouse on a computer desktop.
Moving the wand in space moves a 3D pointer in the virtual environment.
You can also click and drag virtual objects, but instead of just moving them vertically and horizontally, you can also move them in depth and rotate them about all three axes.
This is why wands which can move objects in the X, Y, and Z directions and also rotate them about the X, Y, and Z axes are sometimes called six-dimensional or 6D controllers.
Since distances can be large in a virtual environment (and trackers have a limited range) it is not usually practical to travel through VR on foot.
Some of the wand buttons are often used for "flying": you pointing your wand or your head in the direction you wish to travel, and then press the "fly" button.
In VR, there is no speed limit.
VR gloves are like wands, only more complex.
They consist of a tracker to sense the position and orientation of your hand, and some kind of flex sensors to measure the bend of your fingers.
Gloves tend to be expensive and tricky to use partially because the computer must be able to recognize intricate hand signals instead of simple button presses.
Body suits are also used to sense the users body positions and also to provide some tactile feedback to the user.
