Virtual Reality

Virtual Reality

By: Tyler

E-mail: Stix36000@aol.com

Virtual Reality - What it is and How it Works Imagine being able to point into the sky and fly. Or perhaps walk through space and connect molecules together. These are some of the dreams that have come with the invention of virtual reality. With the introduction of computers, numerous applications have been enhanced or created. The newest technology that is being tapped is that of artificial reality, or "virtual reality" (VR). When Morton Heilig first got a patent for his "Sensorama Simulator" in 1962, he had no idea that 30 years later people would still be trying to simulate reality and that they would be doing it so effectively. Jaron Lanier first coined the phrase "virtual reality" around 1989, and it has stuck ever since. Unfortunately, this catchy name has caused people to dream up incredible uses for this technology including using it as a sort of drug. This became evident when, among other people, Timothy Leary became interested in VR. This has also worried some of the researchers who are trying to create very real applications for medical, space, physical, chemical, and entertainment uses among other things. In order to create this alternate reality, however, you need to find ways to create the illusion of reality with a piece of machinery known as the computer. This is done with several computer-user interfaces used to simulate the senses. Among these, are stereoscopic glasses to make the simulated world look real, a 3D auditory display to give depth to sound, sensor lined gloves to simulate tactile feedback, and head-trackers to follow the orientation of the head. Since the technology is fairly young, these interfaces have not been perfected, making for a somewhat cartoonish simulated reality. Stereoscopic vision is probably the most important feature of VR because in real life, people rely mainly on vision to get places and do things. The eyes are approximately 6.5 centimeters apart, and allow you to have a full-colour, three-dimensional view of the world. Stereoscopy, in itself, is not a very new idea, but the new twist is trying to generate completely new images in real- time. In 1933, Sir Charles Wheatstone invented the first stereoscope with the same basic principle being used in today's head-mounted displays. Presenting different views to each eye gives the illusion of three dimensions. The glasses that are used today work by using what is called an "electronic shutter". The lenses of the glasses interleave the left-eye and right-eye views every thirtieth of a second. The shutters selectively block and admit views of the screen in sync with the interleaving, allowing the proper views to go into each eye. The problem with this method though is that you have to wear special glasses. Most VR researchers use complicated headsets, but it is possible to create stereoscopic three-dimensional images without them. One such way is through the use of lenticular lenses. These lenses, known since Herman Ives experimented with them in 1930, allow one to take two images, cut them into thin vertical slices and interleave them in precise order (also called multiplexing) and put cylinder shaped lenses in front of them so that when you look into them directly, the images correspond with each eye. This illusion of depth is based on what is called binocular parallax. Another problem that is solved is that which occurs when one turns their head. Nearby objects appear to move more than distant objects. This is called motion parallax. Lenticular screens can show users the proper stereo images when moving their heads well when a head- motion sensor is used to adjust the effect. Sound is another important part of daily life, and thus must be simulated well in order to create artificial reality. Many scientists including Dr. Elizabeth Wenzel, a researcher at NASA, are convinced the 3D audio will be useful for scientific visualization and space applications in the ways the 3D video is somewhat limited. She has come up with an interesting use for virtual sound that would allow an astronaut to hear the state of their oxygen, or have an acoustical beacon that directs one to a trouble spot on a satellite. The "Convolvotron" is one such device that simulates the location of up to four audio channels with a sort of imaginary sphere surrounding the listener. This device takes into account that each person has specialized auditory signal processing, and personalizes what each person hears. Using a position sensor from Polhemus, another VR research company, it is possible to move the position of sound by simply moving a small cube around in your hand. The key to the Convolvotron is something called the "Head- Related Transfer Function (HRTF)", which is a set of mathematically modelable responses that our ears impose on the signals they get from the air. In order to develop the HRTF, researchers had to sit people in an anechoic room surrounded with 144 different speakers to measure the effects of hearing precise sounds from every direction by using tiny microphone probes placed near the eardrums of the listener. The way in which those microphones distorted the sound from all directions was a specific model of the way that person's ears impose a complex signal on incoming sound waves in order to encode it in their spatial environment. The map of the results is then converted to numbers and a computer performs about 300 million operations per second (MIPS) to create a numerical model based on the HRTF which makes it possible to reconfigure any sound source so that it appears to be coming from any number of different points within the acoustic sphere. This portion of a VR system can really enhance the visual and tactile responses. Imagine hearing the sound of footsteps behind you in a dark alley late at night. That is how important 3D sound really is. The third important sense that we use in everyday life is that of touch. There is no way of avoiding the feeling of touch, and thus this is one of the technologies that is being researched upon most feverishly. The two main types of feedback that are being researched are that of force- reflection feedback and tactile feedback. Force feedback devices exert a force against the user when they try to push something in a virtual world that is 'heavy'. Tactile feedback is the sensation of feeling an object such as the texture of sandpaper. Both are equally important in the development of VR. Currently, the most successful development in force- reflective feedback is that of the Argonne Remote Manipulator (ARM). It consists of a group of articulated joints, coiled by long bunches of electrical cables. The ARM allows for six degrees of movement (position and orientation) to give a true feel of movement.