Data Bases • Custom Term Papers • Free Term Papers • Free Research Papers • Free Essays • Free Book Reports • Plagiarism? Links • Top 100 Term Paper Sites • Top 25 Essay Sites • Top 50 Essay Sites • Search 97,000 Papers @ DirectEssays.com • Search 101,000 Papers @ ExampleEssays.com • Search 90,000 Papers @ MegaEssays.com Free Essays • Term Paper Sites • Chuck III's Free Essays • Free College Essays • TermPaperSites.com • My Term Papers • Get Free Essays • Essay World • Planet Papers	Search Lots of Essays Back to Subjects - Computers Virtual Reality Virtual Reality The term Virtual Reality (VR) is used by many different people with many meanings. There are some people to whom VR is a specific collection of technologies, that is a Head Mounted Display, Glove Input Device and Audio. Some other people stretch the term to include conventional books, movies or pure fantasy and imagination. However, for purposes of this research, we restrict VR to computer mediated systems. We would define Virtual Reality as a way for humans to visualize, manipulate and interact with computers and extremely complex data. The visualization part refers to the computer generating visual, auditory or other sensual outputs to the user of a world within the computer. This world may be a CAD model, a scientific simulation, or a view into a database. The user can interact with the world and directly manipulate objects within the world. Some worlds are animated by other processes, perhaps physical simulations, or simple animation scripts. Interaction with the virtual world, at least with near real time control of the viewpoint, is a critical test for a 'virtual reality'. Some people object to the term "Virtual Reality", saying it is an oxymoron. Other terms that have been used are Synthetic Environments, Cyberspace, Artificial Reality, Simulator Technology, etc. VR is the most common and sexiest. It has caught the attention of the media. A major distinction of VR systems is the mode with which they interface to the user. We would describe some of the common modes used in VR systems. Some systems use a conventional computer monitor to display the visual world. This sometimes called Desktop VR or a Window on a World (WoW). This concept traces its lineage back through the entire history of computer graphics. In 1965, Ivan Sutherland laid out a research program for computer graphics in a paper called "The Ultimate Display" that has driven the field for the past nearly thirty years. "One must look at a display screen," he said, "as a window through which one beholds a virtual world. The challenge to computer graphics is to make the picture in the window look real, sound real and the objects act real." A variation of the WoW approach merges a video input of the user's silhouette with a 2D-computer graphic. The user watches a monitor that shows his body's interaction with the world. Myron Kruger has been a champion of this form of VR since the late 60's. He has published two books on the subject: "Artificial Reality" and "Artificial Reality II". At least one commercial system uses this approach, the Mandala system. This system is based on a Commodore Amiga with some added hardware and software. A version of the Mandala is used by the cable TV channel Nickelodeon for a game show (Nick Arcade) to put the contestants into what appears to be a large video game. The ultimate VR systems completely immerse the user's personal viewpoint inside the virtual world. These "immersive" VR systems are often equipped with a Head Mounted Display (HMD). This is a helmet or a facemask that holds the visual and auditory displays. The helmet may be free ranging, tethered, or it might be attached to some sort of a boom armature. A nice variation of the immerse systems uses multiple large projection displays to create a 'Cave' or room in which the viewer(s) stand. An early implementation was called "The Closet Cathedral" for the ability to create the impression of an immerse environment within a small physical space. The Holodeck used in the television series "Star Trek: The Next Generation" is afar term extrapolation of this technology. Tele-presence is a variation on visualizing complete computer generated worlds. This technology links remote sensors in the real world with the senses of a human operator. The remote sensors might be located on a robot, or they might be on the ends of WALDO like tools. Fire fighters use remotely operated vehicles to handle some dangerous conditions. Surgeons are using very small instruments on cables to do surgery without cutting a major hole in their patients. The instruments have a small video camera at the business end. Robots equipped with tele-presence systems have already changed the way deep sea and volcanic exploration is done. NASA plans to use tele-robotics for space exploration. There is currently a joint US/Russian project researching tele-presence for space rover exploration. Merging the Tele-presence and Virtual Reality systems gives the Mixed Reality or Seamless Simulation systems. Here the computer-generated inputs are merged with tele-presence inputs and/or the user view of the real world. A surgeon's view of a brain surgery is overlaid with images from earlier CAT scans and real-time ultrasound. A fighter pilot sees computer generated maps and data displays inside his fancy helmet visor or on cockpit displays. The phrase "fish tank virtual reality" was used to describe a Canadian VR system that combines a stereoscopic monitor display using LCD Shutter glasses with a mechanical head tracker. The resulting system is superior to simple stereo-WoW systems due to the motion parallax effects introduced by the head tracker. There are a number of specialized types of hardware devices that have been developed or used for Virtual Reality applications. One of the most time consuming tasks in a VR system is the generation of the images. Fast computer graphics opens a very large range of applications aside from VR, so there has been a market demand for hardware acceleration for a long while. There are currently a number of vendors selling image generator cards for PC level machines; many of these are based on the Intel i860 processor. These cards range in price from about $2000 up to $6 or $10,000. Silicon Graphics Inc. has made a very profitable business of producing graphics workstations. SGI boxes are some of the most common processors found in VR laboratories and high-end systems. SGI boxes range in price from under $10,000 to over $100,000. The simulator market has produced several companies that build special purpose computers designed expressly for real time image generation. These computers often cost several hundreds of thousands of dollars. One essential element for interaction with a virtual world, is a means of tracking the position of a real world object, such as a head or hand. There are numerous methods for position tracking and control. Ideally a technology should provide three measures for position (X, Y, Z) and three measures of orientation (roll, pitch, yaw). One of the biggest problems for position tracking is latency, or the time required to make the measurements and preprocess them before input to the simulation engine. The simplest control hardware is a conventional mouse, trackball or joystick. While these are two-dimensional devices, creative programming can use them for 6D controls. There are a number of three and six dimensional mice/trackball/joystick devices being introduced to the market at this time. These add some extra buttons and wheels that are used to control not just the XY translation of a cursor, but its Z dimension and rotations in all three directions. The Global Devices 6D Controller is one such 6D joystick. It looks like a racket ball mounted on a short stick. You can pull and twist the ball in addition to the left/right & forward/back of a normal joystick. Other 3D and 6D mice, joystick and force balls are available from Logitech, Mouse System Corp. among others. One common VR device is the instrumented glove. A basic patent in the USA covers the use of a glove to manipulate objects in a computer. Such a glove is outfitted with sensors on the fingers as well as an overall position/orientation tracker. There are a number of different types of sensors that can be used. VPL (holders of the patent) made several datagloves, mostly using fiber optic sensors for finger bends and magnetic trackers for overall position. Mattel manufactured the PowerGlove for use with the Nintendo game system, for a short time. This device is easily adapted to interface to a personal computer. It provides some limited hand location and finger position data using strain gauges for finger bends and ultrasonic position sensors. The gloves are getting rare, but some can still be found at Toys R' Us and other discount stores. Anthony Clifton recently posted this suggestion for a" very good resource for PowerGloves etc.: small children. A friend's son had gotten a glove a couple years ago and almost NEVER used it, so I bought it from the kid. Remember children like money more than toys they never use." The concept of an instrumented glove has been extended to other body parts. Full body suits with position and bend sensors have been used for capturing motion for character animation, control of music synthesizers, etc. in addition to VR applications. Mechanical armatures can be used to provide fast and very accurate tracking. Such armatures may look like a desk lamp (for basic position/orientation) or they may be highly complex exoskeletons (for more detailed positions). The drawbacks of mechanical sensors are the encumbrance of the device and its restrictions on motion. Exos Systems builds one such exoskeleton for hand control. It also provides force feedback. Shooting Star system makes a low cost armature system for head tracking. Fake Space Labs and LEEP Systems make much more expensive and elaborate armature systems for use with their display systems. Ultrasonic sensors can be used to track position and orientation. A set of emitters and receivers are used with a known relationship between the emitters and between the receivers. The emitters are pulsed in sequence and the time lag to each receiver is measured. Triangulation gives the position. Drawbacks to ultrasonic are low resolution, long lag times and interference from echoes and other noises in the environment. Logitech and Transition State are two companies that provide ultrasonic tracking systems. Magnetic trackers use sets of coils that are pulsed to produce magnetic fields. The magnetic sensors determine the strength and angles of the fields. Limitations of these trackers are a high latency for the measurement and processing, range limitations, and interference from ferrous materials within the fields. However, magnetic trackers seem to be one of the preferred methods. The two primary companies selling magnetic trackers are Polhemus and Ascension. Optical position tracking systems have been developed. One method uses a ceiling grid LEDs and a head mounted camera. The LEDs are pulsed in sequence and the camera's image is processed to detect the flashes. Two problems with this method are limited space (grid size) and lack of full motion (rotations). Another optical method uses a number of video cameras to capture simultaneous images that are correlated by high-speed computers to track objects. Processing time (and cost of fast computers) is a major limiting factor here. One company selling an optical tracker is Origin Instruments. Inertial trackers have been developed that are small and accurate enough for VR use. However, these devices generally only provide rotational measurements. They are also not accurate for slow position changes. Stereo vision is often included in a VR system. This is accomplished by creating two different images of the world, one for each eye. The images are computed with the viewpoints offset by the equivalent distance between the eyes. There are a large number of technologies for presenting these two images. The images can be placed side-by-side and the viewer asked (or assisted) to cross their eyes. The images can be projected through differently polarized filters, with corresponding filters placed in front of the eyes. Anaglyph images user red/blue glasses to provide a crude (no color) stereovision. The two images can be displayed sequentially on a conventional monitor or projection display. Liquid Crystal shutter glasses are then used to shut off alternate eyes in synchronization with the display. When the brain receives the images in rapid enough succession, it fuses the images into a single scene and perceives depth. A high display-swapping rate (min. 60hz) is required to avoid perceived flicker. A number of companies made low cost LC shutter glasses for use with TVs (Sega, Nintendo, Toshiba, etc.). There are circuits and code for hooking these up to a computer available on many of the On-line systems, BBSs and Internet FTP sites mentioned later. However, locating the glasses themselves is getting difficult as none are still being made or sold for their original use. Stereographics sells a very nice commercial LC shutter system called CrystalEyes. Another alternative method for creating stereo imagery on a computer is to use one of several split screen methods. These divide the monitor into two parts and display left and right images at the same time. One method places the images side by side and conventionally oriented. It may not use the full screen or may otherwise alter the normal display aspect ratio. A special hood viewer is placed against the monitor that helps the position the eyes correctly and may contain a divider so each eye e sees only its own image. Most of these hoods, such as the one for the V5 of Rend386, use Fresnel lenses to enhance the viewing. An alternative split screen method orients the images so the top of each points out the side of the monitor. A special hood containing mirrors is used to correctly orient the images. A very nice low cost (under $200) unit of this type is the Cyberscope available from Simsalabim. One hardware device closely associated with VR is the Head Mounted Device (HMD). These use some sort of helmet or goggles to place small video displays in front of each eye, with special optics to focus and stretch the perceived field of view. Most HMDs use two displays and can provide stereoscopic imaging. Others use a single larger display to provide higher resolution, but without the stereoscopic vision. Most lower cost HMDs ($3000-10,000 range) use LCD displays, while others use small CRTs, such as those found in camcorders. The more expensive HMDs use special CRTs mounted along side the head or optical fibers to pipe the images from non-head mounted displays, ($60,000 and up). A HMD requires a position tracker in addition to the helmet. Alternatively, the display can be mounted on an armature for support and tracking (a Boom display). Health Hazards from Stereoscopic Displays There was an article supplement with CyberEdge Journal issue #17 entitled "What's Wrong with your Head Mounted Display". It is a summary report on the findings of a study done by the Edinburgh Virtual Environment Lab, Dept. of Psychology, Univ. of Edinburgh on the eye strain effects of stereoscopic Head Mounted Displays. There have been a number of anecdotal reports of stress with HMDs and other stereoscopic displays, but few, if any, good clinical studies. This study was done very carefully and the results are a cause for some concern. The basic test was to put 20 young adults on a stationary bicycle and let them cycle around a virtual rural road setting using a HMD (VPL LX EyePhone and a second HMD LEEP optic equipped system). After 10 minutes of light exercise, the subjects were tested... "The results were alarming: measures of distance vision, binocular fusion and convergence displayed clear signs of binocular stress in a significant number of the subjects. Over half the subjects also reported symptoms of such stress, such as blurred vision." The article goes on to describe the primary reason for the stress - the difference between the image focal depth and the disparity. Normally, the when your eyes look at a close object they focus (accommodate) close and rotate inward (converge). When they accommodate on a far object, the eyes also diverge. However, a stereoscopic display does not change the either the effective focal plane (set by the optics) and the disparity depth. The eyes strain to decouple the signals. The article discusses some potential solutions, but notes that most of them (dynamic focal/disparity) are difficult to implement. It mentions monoscopic HMDs only to say that while they would seem to avoid the problems, they were not tested. The article does not discuss non-HMD stereoscopic devices at all, but I would extrapolate that they should show some similar problems. The full article is available from CyberEdge Journal for a small fee. There has been a fair bit of discussion ongoing in the sci.virtual-worlds newsgroup (check the Sept./Oct. 93 archives) about this and some other studies. One contributor, Dipl.-Ing. Olaf H. Kelle, University of Wuppertal, Germany reported only 10% of his users showing eyestrain. His system is setup with a focal depth of 3m, which seems to be a better, more comfortable viewing distance. Others have noted that long duration monitor use often leads to the user staring or not blinking. It is common for VDT users to be cautioned to look away from the screen occasionally to adjust their focal depth and to blink. Another contributor, John Nagle provided the following list of other potential problems with HMDs: electrical safety, Falling/tripping over real world objects, simulator sickness (disorientation due to conflicting motion signals from eyes and inner ear), Eye Strain, Induced post-HMD accidents ("some flight simulators some flight simulators, usually those for military fighter aircraft, it's been found necessary to forbid simulator users to fly or drive for a period of time after flying the simulator"). The following defines a number of levels of VR hardware systems. These are not hard levels, especially towards the more advanced systems. The 'Entry Level' VR system takes a stock personal computer or workstation and implements a WoW system. The system may be based on an IBM clone (MS-DOS/Windows) machine, an Apple Macintosh, or perhaps a Commodore Amiga. The DOS type machines (IBM PC clones) are the most prevalent. There are Mac based systems, but few very fast rendering ones. Whatever the base computer it includes a graphic display, a 2D input device like a mouse, trackball or joystick, the keyboard, hard disk & memory. The next step up from an EVR system adds some basic interaction and display enhancements. Such enhancements would include a stereographic viewer (LCD Shutter glasses) and an input/control device such as the Mattel PowerGlove and/or a multidimensional (3D or 6D) mouse or joystick. The next step up the VR technology ladder is to add a rendering accelerator and/or frame buffer and possibly other parallel processors for input handling, etc. The simplest enhancement in this area is a faster display card. For the PC class machines, there are a number of new fast VGA and SVGA accelerator cards. These can make a dramatic improvement in the rendering performance of a desktop VR system. Other more sophisticated image processors based on the Texas Instruments TI34020 or Intel i860 processor can make improvements that are even more dramatic in rendering capabilities. The i860 in particular is in many of the high-end professional systems. The Silicon Graphics Reality Engine uses a number of i860 processors in addition to the usual SGI workstation hardware to achieve stunning levels of realism in real time animation. An AVR system might also add a sound card to provide mono, stereo or true 3D audio output. Some sound cards also provide voice recognition. This would be an excellent additional input device for VR applications. An Immersion VR system adds some type of immersive display system: a HMD, a Boom, or multiple large projection type displays (Cave). An IVR system might also add some form of tactile and touch feedback interaction mechanisms. The area of Touch or Force Feedback (known collectively as Haptics) is a very new research arena. A common variation on VR is to use a Cockpit or Cab compartment to enclose the user. The virtual world is viewed through some sort of view screen and is usually either projected imagery or a conventional monitor. The cockpit simulation is very well known in aircraft simulators, with a history dating back to the early Link Flight Trainers (1929?). The cockpit is often 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 and tanks. The latter are fictional walking robotic devices (i.e. the Star Wars films). The BattleTech location based entertainment (LBE) centers use this type of system. One of the biggest VR projects is the Defense Simulation Internet. This project is standardization being pushed by the USA Defense Department to enable diverse simulators to be interconnected into a vast network. It is an outgrowth of the Defense Advanced Research Projects Administration (DARPA) SIMNET project of the later 1980s. SIMNET was/is a collection of tank simulators (Cab type) that are networked together to allow unit tactical training. Simulators in Germany can operate in the same virtual world as simulators in the USA, partaking of the same battle exercise. The applications being developed for VR run a wide spectrum, from games to architectural and business planning. Many applications are worlds that are very similar to our own, like CAD or architectural modeling. Some applications provide ways of viewing from an advantageous perspective not possible with the real world, like scientific simulators and tele-presence systems or air traffic control systems. Other applications are much different from anything we have ever directly experienced before. These latter applications may be the hardest and most interesting systems. Visualizing the ebb and flow of the world's financial markets. Navigating a large corporate information base, etc. Virtual Reality in Education: The Virtual Chemistry Lab Building a chemistry lab in a high school is often cost-prohibitive. First, there is the cost of the chemistry professor, a recurring cost of say $35,000 per year. Next, the cost of the lab and lab equipment is very expensive. Finally, finding the space in the school, installing the proper chemical and fire safety systems, and having the lab inspected and approved for use. Moreover, let us not forget the liability insurance costs. Enter the Virtual Chemistry Lab. Visually it’s a podium with a VR headset and glove. A student puts on the VR equipment, logs in with their student ID and begins their lab session. Immediately they are immersed in a virtual high school chem. lab. Looking around they see beakers, flasks, scales, Bunsen burners and many chemicals. Following the instructions of the virtual teacher, they perform their required chemistry experiments. They mix chemicals, apply heat, observe and log the results, and, occasionally cause an explosion. If the class period ends in the middle of an experiment, they can "save" the experiment in midstream, and continue the following day exactly where they left off, chemicals under heat and all. VR in Business: Stock Market Analysis The June 1992 issue of Forbes magazine discusses data visualization used in the stock market. Streams of market data create a 3-D landscape covered with groups of shapes. These shapes represent stocks, which change in shape and color as prices fluctuate. Stock analysts can “fly” over the landscape and easily grasp the meaning of the normally complex data. It is a step beyond picture telephones and video conferencing: Two or more people can interact in a virtual business conference, observing the voice and body movements of each other. VR in Business: Aircraft Inspection The KC135 Aircraft is a Boeing 707 modified for the United States Armed Services. The pictures below depict the work being performed by an inspector when the aircraft is brought in for overhaul. The inspector is wearing a personal computer and a head mounted display with integrated speaker and microphone. All of the inspection for the exterior sheet metal components is performed using this application. There is no mouse or keyboard attached to this personal computer (although the capability is present) because the inspector talks through the inspection from login through form generation and transmission. The application the Air Force Technical orders in combination with the Current Air Force Inspection Process for the refueling fleet of the KC135s. The application displays a series of graphics of the airplane that the inspector can navigate through via voice commands to mark a region of the airplane that is in need of service. Once identified, the application tags the area for transmission to the maintenance database and initiates the proper form for the inspector to fill out. The form is completed and then transmitted to the same maintenance database. When the inspector has identified all of the problems with a particular region, voice navigation is used to continue to other areas of the aircraft. The inspector is not required to take any information about the aircraft, previous defect records, clipboards, paper, etc. with them, everything required to perform the inspection is on-line and displayed in a manageable fashion in real time during the inspection. When the inspector completes the inspection, no further input is required. The inspector is not required to take notes and then pass them off to someone else to decipher and input to the system. The information is already in the maintenance database and ready for verification, planning, and scheduling. The timesaving realized from start to finish of that inspection is 30-50% depending on the inspector and the aircraft. Bibliography: Various internet posted information Word Count: 4240
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