Virtual reality technology through more than 20 years of research and exploration, in the late 80s out of the laboratory, began to enter the practical stage. At present, a few developed countries in the world in the economy, art and even the military and other fields, has begun to widely apply this high-tech, and has achieved significant comprehensive benefits. According to foreign magazine reports, the U.S. Army in 1994, "Louisiana 94" combat exercises, is the use of virtual reality technology. The exercise not only test demonstrated the U.S. Army formulated orders, tactics and troop formations, so that it is more in line with the requirements of the 21st century operations, but also to save nearly 2 billion U.S. dollars in exercise funds.
So, what is virtual reality technology? Simply put, it is a new technology in which people use computers to generate a realistic three-dimensional virtual environment with which they interact through natural skills using sensing devices. It is completely different from the traditional simulation technology, is the simulation environment, vision system and simulation system into three, and the use of helmet displays, graphic glasses, data suits, stereo headphones, data gloves and foot pedals and other sensing devices. The operator is connected to a computer-generated three-dimensional virtual environment. The operator interacts with the virtual environment through sensor devices, can obtain visual, auditory, tactile and other perceptions, and in accordance with their own wishes to change the "not with the heart" of the virtual environment. For example, the computer virtual environment is a building, with a variety of equipment, items, the operator will be as if they were there, through a variety of sensing devices in the house walking to see, open and close the door, move the items; the design of the house is not satisfied with the place, but also can be changed at will. Obviously, the use of this virtual reality technology for construction, machinery, weapons and other design modifications, the implementation of technical operations training and military exercises to be much easier and much cheaper.
Virtual reality technology, once applied, shows people an attractive prospect, and thus favored by the military community of various countries. From the early 1990s, the United States took the lead in the use of virtual reality technology in the military field, mainly used in the following four aspects: First, the virtual battlefield environment. That is, through the corresponding three-dimensional battlefield environment graphic image library, including combat background, battlefield scenes, various weapons and equipment and combatants, etc., for the user to create a kind of treacherous, nearly real three-dimensional battlefield environment. In order to enhance their sense of presence, improve the quality of training. The second is to carry out single soldier simulation training. Let soldiers wear data clothing, wearing a helmet display and data gloves, through the operation of sensing devices to choose a different background of the battlefield, enter a different disposal program, the taste of different combat effects, and then like participating in the actual battle, exercise and improve the level of technical skills, rapid response capabilities and psychological endurance. Such as the U.S. Air Force with virtual reality technology developed flight training simulator, can produce visual control, can handle three-dimensional real-time interactive graphics, and there are graphics outside the sound and sense of touch, not only can be maneuvered in a normal way and control the aircraft, but also deal with virtual reality outside the aircraft in a variety of situations, such as the threat of the balloon, the trajectory of the launch of missiles and so on. Third, the implementation of joint exercises of all military branches, the establishment of a "virtual battlefield", so that the two sides in the same place, according to the virtual environment of the various situations and their changes, "deployment of troops", "fight wisdom and courage! ", the implementation of the "real" confrontation exercises. Fourth, conductor training. The use of virtual reality technology, based on reconnaissance intelligence information synthesized a panoramic map of the battlefield, so that trained commanders through the sensing device to observe the deployment of enemy forces and the battlefield, in order to determine the enemy situation, set the correct determination. The U.S. Navy developed the "virtual ship combat command center" can be realistically simulated with the real ship combat command center is almost completely similar to the environment, vivid visual, auditory and tactile effects, so that trained officers immersed in the "real" battlefield.
Of course, virtual reality is still a young science and technology, there are still a lot of problems to be solved. For example, in the computer-generated virtual environment, each time the operator turns his head, the computer must update the three-dimensional image, due to the update of the data is too large, so that the computer has not been able to complete the real-time computing. This results in system lag. Then again, there are also discrepancies between the visual motion signals generated by the U.S. Air Force's virtual reality simulators and the human senses, which can easily cause headaches and vertigo.
But no matter what, virtual reality technology has opened up a new field of development potential, it will be perfected over time, in the military field of application will become more and more extensive, play a role will be more and more.
Just like other emerging science and technology, virtual reality technology is also many related disciplines cross, the integration of the product.
Its research involves artificial intelligence, computer science, electronics, sensors, computer graphics, intelligent control, psychology and so on. We must soberly realize that although the technical potential of this field is huge, the application prospect is also very broad, but there are still many unresolved theoretical issues and technical obstacles that have not yet been overcome. Objectively speaking, at present, the achievements of virtual reality technology, the vast majority of them are still limited to the expansion of the computer's interface capability, only just started to involve the human perception system and muscle system and the computer's combination of the role of the problem, has not been involved in the practice of human sensory information is how to be stored in the human brain and processing processing to become a human being on the objective world's understanding of this important process. The important process of "how sensory information obtained in practice is stored and processed in the human brain to become a person's understanding of the objective world. Only when it really starts to involve and find a way to realize the technology of these problems, the gap between human and information processing system can be completely overcome. We look forward to the day when the virtual reality system becomes a powerful system for multidimensional information processing, an assistant for human thinking and creativity, and a powerful tool for deepening people's existing concepts and acquiring new ones.
Just as the movie "The Matrix" described, in the future we can live in a virtual world controlled by computers. In this world, we have the same senses, the same relatives and friends, the same jobs, and all the "reality" of the real world. It's just that it's all virtual.
Human beings have many dreams, some of which have become reality, while some of which may never be realized. However, there is a technology that can make all dreams come true, and that is Virtual Reality (VR).
Virtual Reality is a cross-discipline developed on the basis of computer graphics, computer simulation technology, human-computer interface technology, multimedia technology, and sensing technology, and the research on this technology began in the 1960s. It was not until the early 1990s that virtual reality technology began to receive great attention as a more complete system.
Basic Concepts
In a nutshell, virtual reality is a brand-new way for people to visualize and interact with complex data through computers, and compared with traditional human-computer interfaces and the popular Windows operation, virtual reality has made a qualitative leap in technological thinking.
Virtual reality in the "reality" is a general reference to the physical or functional sense of the existence of any thing in the world or the environment, it can be practically achievable, can also be practically difficult to achieve or simply can not be realized. The term "virtual" means computer-generated. Therefore, virtual reality refers to a special computer-generated environment, people can use a variety of special devices to "project" themselves into this environment, and operate, control the environment, to achieve special purposes, that is, people are the master of this environment.
In essence, virtual reality is an advanced computer user interface, which maximizes user convenience by providing users with various intuitive and natural means of real-time perception and interaction, such as visual, auditory, and tactile senses. According to the virtual reality technology is applied to different objects, its role can be expressed in different forms, such as a certain conceptual design or idea visualization and operability, to achieve realistic remote control site effects, to achieve any complex environment under the cheap simulation training purposes. The main features of the technology are as follows:
Multi-perception (Multi-Sensory) - the so-called multi-sensory means that in addition to the visual perception of general computer technology, there is also auditory perception, force perception, tactile perception, motion perception, and even include taste perception, olfactory perception and so on. The ideal virtual reality technology should have the following features. The ideal virtual reality technology should have all the perceptual functions that people have. Due to the relevant technology, especially the limitation of sensing technology, the current virtual reality technology has the perception function is limited to visual, auditory, force perception, tactile, motion and so on.
Immersion - also known as the sense of presence, refers to the degree of realism that the user feels as the protagonist exists in the simulated environment. Ideal simulation environment should make it difficult for users to distinguish the real from the fake, so that the user is fully engaged in the computer-created three-dimensional virtual environment, the environment looks real, sounds real, moving is real, and even smell, taste, and so on, all the feelings are real, as in the real world feeling the same.
Interactivity - the degree to which a user can manipulate objects within a simulated environment and the degree of naturalness (including real-time) with which they receive feedback from the environment. For example, a user can use their hand to directly grasp a virtual object in the simulation, which feels like they are holding something and can feel the weight of the object, and the object being grasped in the field of view can immediately move with the movement of their hand.
Conceptualization (Imagination) - emphasizes that virtual reality technology should have a broad imaginable space, can broaden the scope of human cognition, not only can reproduce the real existence of the environment, but also can be arbitrary conceptualization of the objective does not exist, or even impossible to happen the environment.
Generally speaking, a complete virtual reality system consists of a virtual environment, a high-performance computer as the core of the virtual environment processor, a helmet display as the core of the visual system, a speech recognition, sound synthesis and sound positioning as the core of the auditory system, an orientation tracker, data gloves, and data clothing as the main body of the body orientation tracking equipment, as well as the taste, smell, touch, and force feedback system and other functional units.
Here, the virtual environment processor is the heart of the VR system, accomplishing the virtual world generation and processing functions. The input device provides input from the user to the VR system and allows the user to change his/her position, sight direction and field of view in the virtual environment, as well as to change the position and direction of virtual objects in the virtual environment. And the output devices are used by the VR system to output all kinds of sensory information produced by the virtual environment synthesized to the user, so that the user can produce a sense of immersive realism. Its main research content includes the following aspects:
Dynamic environment modeling - the establishment of the virtual environment is the core content of the VR system, the purpose of the dynamic environment modeling technology is to obtain the actual environment of the three-dimensional data, and according to the needs of the application of the establishment of the corresponding virtual environment model. Three-dimensional data acquisition can use CAD technology, more often need to use non-contact visual technology, the two organic combination can effectively improve the efficiency of data acquisition.
Real-time 3D graphics generation technology - 3D graphics generation technology has been more mature, the key here is how to realize the "real-time" generation. In order to achieve the purpose of real-time, at least to ensure that the graphics refresh frequency is not less than 15 frames / second, preferably higher than 30 frames / second.
Without reducing the quality and complexity of the graphics, how to increase the refresh rate is the main focus of the technology.
Stereoscopic display and sensor technology - The interactive capability of virtual reality depends on the development of stereoscopic display and sensor technology, and existing equipment is far from being able to meet the needs, for example, helmet-mounted 3D stereoscopic displays have the following drawbacks: excessive weight (1.5 kg to 2 kg), low resolution (poor image quality), high latency (low refresh frequency), mobility (wired), low tracking accuracy, insufficiently wide field of view, easy eye fatigue, etc. Therefore, it is necessary to develop new 3D display technologies. Similarly, data gloves, data clothes, etc. have the disadvantages of high latency, low resolution, small range of action, and inconvenience of use. In addition, the research of force and tactile sensing devices needs to be further deepened, and the tracking accuracy and tracking range of virtual reality devices also need to be improved.
Application system development tools - the key to the application of virtual reality is to find the right occasion and object, that is, how to play imagination and creativity. Selecting the appropriate application object can significantly improve productivity, reduce labor intensity, and improve product quality. In order to achieve this purpose, it is necessary to study the development tools of virtual reality, such as VR system development platform, distributed virtual reality technology.
System integration technology - because the VR system includes a large amount of perceptual information and models, so the system integration technology plays a vital role. Integration technology includes synchronization technology of information, calibration technology of model, data conversion technology, data management model, recognition and synthesis technology and so on.
Key technologies
Virtual reality is the synthesis of a variety of technologies, including real-time three-dimensional computer graphics technology, wide-angle (wide field of view) stereoscopic display technology, tracking technology for the observer's head, eyes and hands, as well as haptic/force feedback, stereo sound, voice input and output technology. These technologies are described below.
Real-time 3D computer graphics
In comparison, using computer models to generate graphic images is not too difficult. With a sufficiently accurate model and enough time, we can generate accurate images of various objects under different lighting conditions, but the key here is real time. For example, in a flight simulation system, image refresh is quite important, and the demand for image quality is also very high, and coupled with a very complex virtual environment, the problem becomes quite difficult.
Wide-angle (wide field of view) stereoscopic displays
When a person looks at the world around him, he gets slightly different images due to the different positions of the two eyes, which are fused together in his head to form an overall view of the world around him, a view that includes information about distance and proximity. Of course, distance information can also be obtained by other methods, such as the focal length of the eyes, the comparison of the size of objects, and so on.
In VR systems, binocular stereo vision plays a big role. Different images seen by the user's two eyes are generated separately and displayed on different monitors. Some systems use a single monitor, but when the user puts on special glasses, one eye can only see odd frames and the other eye can only see even frames, and the difference between the odd and even frames, or parallax, creates a sense of three-dimensionality.
User (head, eye) tracking: In an artificial environment, each object has a position and attitude relative to the system's coordinate system, and so does the user. The view the user sees is determined by the user's position and head (eye) orientation.
Virtual reality headgear that tracks head movements: In traditional computer graphics technology, the change of field of view is realized by mouse or keyboard, and the user's visual system and motion perception system are separated, whereas by using head tracking to change the viewing angle of an image, the user's visual system and motion perception system can be linked to each other, and the feeling is more realistic. Another advantage is that the user can not only recognize the environment through binocular stereo vision, but also observe the environment through head movements.
The keyboard and mouse are by far the most commonly used tools in user interaction with computers, but they are not well suited for three-dimensional space. In three dimensions because of the six degrees of freedom, it is difficult to figure out a more intuitive way to map the planar motion of the mouse to arbitrary motion in three dimensions. Nowadays, there are devices that provide six degrees of freedom, such as the 3Space digitizer and the SpaceBall space ball. Some other devices that perform better are the Data Glove and Data Suit.
Stereo sound
Humans are very good at determining the direction of a sound source. In the horizontal direction, we rely on the phase difference of the sound and the difference in intensity to determine the direction of the sound, because the time or distance it takes for the sound to reach each ear is different. The common stereo effect is achieved by the left and right ears hearing different sounds recorded at different locations, so there is a sense of direction. In real life, when the head is turned, the direction of the sound heard changes. But currently in VR systems, the direction of the sound is independent of the movement of the user's head.
Haptic and force feedback
In a VR system, the user is presented with a virtual cup. You can try to grab it, but your hand doesn't really feel like it's touching the cup, and it's possible to pass through the "surface" of the virtual cup in a way that's not possible in real life. A common device to solve this problem is to install some vibrating contacts in the inner layer of the glove to simulate the sense of touch.
Voice input and output
Voice input and output are also important in VR systems. This requires a virtual environment that understands human language and can interact with people in real time. It is very difficult for computers to recognize human speech, because speech signals and natural language signals have their own "multiplicity" and complexity. For example, there is no obvious pause between words in continuous speech, and the pronunciation of the same word is affected by the words before and after the word, and not only different people say the same word differently, but also the same person's pronunciation will be affected by the psychological, physiological and environmental influences and different.
There are two problems with using human natural language as computer input. First, there is the problem of efficiency, as the input speech may be quite verbose for the computer to understand. The second is the problem of correctness; computers understand speech by comparison matching, without human intelligence.
Representative Devices
There are many interesting and specialized devices with different functions in a VR system, and a selection of representative devices are described below.
BOOM removable display: it is a kind of semi-input visual display device. When in use, the user can put the display conveniently in front of the eyes, when not in use can be quickly removed. BOOM uses a small cathode ray tube, the number of pixels produced is much smaller than the LCD screen, the image is softer, the resolution of 1280 × 1024 pixels, color images.
Data Glove: The Data Glove is an input device that converts human hand movements into input signals for a computer. It consists of a very lightweight elastic material. The elastic material fits snugly on the hand while many position and orientation sensors and fiber optic wires are attached to detect hand movement. The fiber optics measure the flexion and extension of each finger, and through photoelectric conversion, the finger movement information can be recognized by the computer.
TELETACT Glove: It is a device for tactile and force feedback that utilizes small air pockets to provide tactile and force stimulation to the hand. These small air pockets can be rapidly pressurized and depressurized. When the virtual hand touches a virtual object, the force pattern stored in the computer for that object is recalled, and the compressor rapidly inflates or deflates the air pockets, giving the hand a very precise sense of touch.
A data suit is an input device designed to allow a VR system to recognize full-body motion. The data suit takes measurements of about 50 different joints in the body, including the knees, arms, torso, and feet. Through photoelectric conversion, the body movement information is recognized by the computer. The data suit is interacted with virtual reality via a BOOM display and data gloves.
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Virtual reality is essentially a human-computer communication technology that can support virtually any human activity and is applicable to any field.
An earlier virtual reality product was the graphical simulator, the concept of which was introduced in the 1960s and gradually emerged in the 1980s, with products introduced in the 1990s. 1992 saw the world's first virtual reality development tool, 1993 saw the emergence of numerous virtual reality applications, and 1996 saw the use of inertial sensors and omni-directional steppers by NPS to integrate human motion gestures into the virtual environment. By 1999, virtual reality technology was more widely used in various fields such as aerospace, military, communications, medical, education, entertainment, graphics, architecture, and business. Experts predict that with the development of computer software and hardware technology and the decline in prices, virtual reality technology is expected to enter the home in this century.
VR technology is also making a big difference in the medical field. The technology can be used for teaching anatomy, planning complex surgical procedures, providing operational and informational assistance during surgery, and predicting surgical outcomes. In addition, in telemedicine, virtual reality technology also has great potential. For example, in remote mountainous areas, through the telemedicine virtual reality system, patients are able to receive treatment from famous doctors without going into the city. For critical patients, remote surgery can also be implemented. A doctor operates on a patient model and his movements are transmitted via satellite to a distant surgical robot. The actual image of the surgery is transmitted back to the doctor's helmet stereo display through the camera on the robot and superimposed on the virtual patient model to provide the doctor with useful information. The Stanford International Research Institute in the United States has successfully developed a tele-surgical medical system.
In the space field, VR technology is also very important. For example, weightlessness is a difficulty that must be overcome in spaceflight because it is difficult to predict the movement of objects in weightlessness. In order to perform precise maneuvers in space, astronauts need to be trained in weightlessness simulation for long periods of time. In order to realistically simulate the situation in space, the U.S. space agency NASA in the "Hubble Space Telescope Repair and Maintenance" program uses VR simulation training technology.
During the training, astronauts sit in a simulated chair with sensors that function as a "manned maneuvering vehicle". The chair has a displacement controller for linear motion in virtual space and a rotary controller for adjusting the astronaut's orientation around his center of gravity. The astronaut wears a stereoscopic helmet display that shows models of the telescope, shuttle, and space, and uses a data glove as a means of interacting with the system. During training, the astronauts were able to maneuver around the telescope and touch the joystick with their virtual hands to grab the module changer that needed to be replaced. Once the module changer is grasped, the astronaut can use the seat's controls to fly through space.
An example of the use of VR technology in object visualization is the simulation of a wind tunnel. A simulated wind tunnel allows the user to see a simulated air flow field, making him feel as if he were actually standing in the wind tunnel. The purpose of virtual wind tunnels is to allow engineers to analyze the complex three-dimensionality and effects of multiple vortices, air circulation areas, turbulence where vortices are destroyed, and so on. For example, data from a CAD model of a space shuttle can be pulled into a simulated wind tunnel for performance analysis. To analyze the pattern of the airflow, a trajectory tracker can be injected into the air stream that will drift with the airflow and display the motion to the user. The tracker can be surrendered to any specified location via a data glove, and the user can observe its trajectory from any viewpoint.
One example of the use of VR technology in the military is the Connected Military Training System. In this system, troops are placed in the same location as actual vehicles and command centers, and they can see a simulated battlefield with mountains, trees, clouds, smoke, roads, buildings, and vehicles operated by other troops. These vehicles, operated by actual personnel, can shoot at each other, and the system utilizes radio communications and sound to enhance realism. Each user of the system can observe the actions of others through an environmental viewpoint. The display of artillery fire is extremely realistic, and users can see what is being blown up by the attacking force. Scenes seen from helicopters are also very realistic. The simulation can be used to train tanks, helicopters and conduct military exercises, as well as train troops to work together.
Of course, the application of virtual reality technology is much more than these. With the further development of computer technology, virtual reality and our lives will be increasingly close.
VRML
VRML (Virtual Reality Modeling Language) is a multimedia communication (Multimedia Communication), the Internet (Internet), virtual reality (Virtual Reality, VR) and so on. VRML (Virtual Reality Modeling Language) is a new technology closely related to the fields of Multimedia Communication, Internet and Virtual Reality (VR), and its basic goal is to establish interactive three-dimensional multimedia on the Internet.VRML was formally approved as an international standard in January 1998 (ISO/IEC 14772-1:1997, commonly known as VRML97), creating an ISO/IEC record of standardization, and it was the first international standard published in HTML. It is also the first international standard published in HTML.
VRML is a 3D interchange format that defines most of the common concepts used in today's 3D applications, such as transformation levels, light sources, viewpoints, geometry, animation, fog, material properties, and texture mapping, etc. The basic goal of VRML is to ensure that it can be a valid format for exchanging 3D files.
VRML is a 3D model of HTML. It brings interactive 3D capabilities to the World Wide Web, i.e. VRML is a cross-platform language that can publish 3D web pages. Indeed, 3D provides a more natural way of experiencing things such as games, engineering and scientific visualization, education and architecture. Typical projects such as these are not enough to rely on web-based text and images, but require enhanced interactivity, a sense of continuity in dynamic effects, and user participation in exploration, which is the goal of VRML.
VRML provides the technology to integrate 3D, 2D, text, and multimedia into a unified whole. When these media types are combined with a scripting language and the power of the Internet, a whole new kind of interactive application is possible, and VRML supports the classic two-dimensional desktop model while extending it to a wider spatial and temporal context.
VRML is the foundation of cyberspace. The concept of cyberspace was developed by science fiction writer William Gibson. Although VRML does not define the necessary network and database protocols for true user simulation, it should be seen as rapidly evolving. As a standard, it must maintain simplicity and realizability, and within that context encourage cutting-edge experimentation and extensions.