1. 求关于虚拟世界(virtual world)的英语资料，急
Virtual Reality
Virtual reality (VR) is a technology that allows you to enter and interact with a world that is generated by a computer. Special graphics, video images and stereo sound make this pretend world seem real.
The uses for virtual reality are wide ranging and cover everything from games where you can drive a car, fly a plane, ski down a mountain or track a dinosaur - to helping train doctors in the art of surgery or teaching pilots to fly aircraft safety. These computer generated worlds can be any size - as vast as the universe or as microscopically small as atoms and molecules.
Uses Of Virtual Reality
The uses for virtual reality are infinite. It can be used for air traffic control, medicine, entertainment, office work and instrial design. However, along with the good comes the bad. Virtual reality could also be used for destructive purposes, such as war and crime.
The idea of virtual reality emerged in the 1930s when scientists created the first fight simulator for the training of pilots. They wanted to put the pilote in a real situation before letting him fly.
In 1965, an American, called Ivan Sutherland, hit on a new idea and published his findings in a document called 'The Ultimate Display'. His idea was to create a portable, or personal, virtual world using two tiny television sets, one for each eye. In order to realise this, he also designed a head mounted display. Although his invention worked, and he did create a sort of a virtual world, the images were very crude and basic. Another problem was the helmet - it was extremely heavy and cumbersome and needed to be supported from the ceiling. It was also very expensive. In the following years, scientists continued to work on Sutherland's initial idea and great improvements were made. Then in 1985, Michael McGreevey of NASA/AMES developed a much cheaper and lighter version of the helmet. He used a motorcycle helmet and fitted it with mini display screens, and special sensors which were designed to track movement and were linked to powerful, but sensitive computers.
The final piece of equipment for a complete virtual reality kit was a glove. One had been designed in the early 1980s, but modern virtual reality was born in 1986 when a computer games programmer, called Jaron Lanier, designed a new glove. This brought the VR helmet and glove kit into existence for the first time. It was Lanier who gave this new technology the name Virtual Reality.
Types of Virtual Realities
There are three main forms of virtual reality:
The first is perhaps the most familiar. It consists of a helmet which has small TV screens and earphones fitted into it, and a glove (some systems use a joystick or wand instead of a glove). The helmet and glove are linked to computers which are programmed with special sounds and graphics.
The second form of virtual reality uses video cameras to track the image of the user in a virtual world where you can also pick up or move objects. Both these VR systems allow more than one person to take part at the same time.
The final type of VR is where three- dimensional images are played on a large, curved screen. The shape of the screen helps to give you a greater sense of being in the virtual world. By wearing special 3-D glasses, this effect can be greatly improved.
Advantages Of Virtual Reality
VR has a lot of positive benefits. It gives disabled people the opportunity to join in activities not usually available to them. In virtual worlds, people in wheelchairs, for example, can have a freedom of movement that they do not have in the real world. At the moment very few people can afford to buy a VR system. But as the technology advances, lightweight helmets and more powerful computers will take VR into ordinary homes.
Virtual reality has very important uses in all types of architecture and instrial design. Computer Aided Design, or CAD, has been an important design tool since the mid 1970s, because it allows the user to draw three- dimensional images on a computer screen. However, unless you have a VR helmet and glove to project the images on to, you will not be immersed in your virtual world.
Building aircraft
Virtual reality has been a huge boost in the aviation business as it avoids the need to build several different prototypes (models built to the correct size). Every time an engineer designs a new aircraft or helicopter, a prototype has to be built to ensure that it works, whether it will fly fast enough and whether it is safe for the crew and the passengers. If the prototype is wrong, the designers have to go back to the drawing board, make the changes and then build another one. This is a very expensive and time-consuming business.
By using VR, designers can design, build and test their aircraft in a virtual environment without having to build a real aircraft. It also allows the designers to try out different ideas - all the ideas can be looked at in detail and they can then select the best one. NASA has used virtual reality to design a helicopter and Boeing have used it to design their latest aircraft.
Using virtual reality, doctors have already been 'inside' a body. At the University of North Carolina, USA, virtual reality allowed doctors to enter a cancer patient's thorax (part of the chest) to make sure that radiation beams needed to treat the cancer were in the right place. Doctors will soon be able to look at and study tumours at first hand and in 3-D rather than from scans and x-rays.
A virtual body
In the USA, a murderer who was executed on the electric chair donated his body to science. His corpse was sliced into very thin sections from top to bottom and used to create an entire virtual body for medical research. Soon all medical students will be able to train using virtual bodies instead of real patients.
On a microscopic level, virtual reality is being used in drug research. Scientists at the University of North Carolina are able to create the molecules and then visualize and 'feel' how they react with each other. Before the use of virtual reality, this process was very slow and complicated. Therefore, it is likely that virtual reality will have a strong impact on the speed with which new drugs and remedies are developed and become available in the future.
Virtual reality is also important because it can visualize the unknown or the unpredictable. This might lead to virtual reality operators carrying out repairs in space, with the help of a robot. In a technique called virtual puppetry a robot is controlled by a skilled operator and mimics all the operator's movements.
The possibilities for virtual reality are enormous. Future residents of new towns will be able to walk around virtual streets, shops, houses and parks before a single brick has beer laid. There are already plans to redesign the whole of the city of Berlin, the capital of Germany, using virtual reality.
Disavantages of virtual reality
Limited field of view with same lenses, except newest pro models.
requires matching of film type to lighting ad use of color correction (cc) filters.Narrow latitude for transparency film (5 stops). Consumer level (less expensive) cameras have narrower latitudes similar to transparency films.Requires scanning for post proction.Consumer cameras often require long delays (10-30 seconds) between shots while previous image(s) are being saved.Limited resolution compared to film, except for high end (expensive) digital cameras. Consumer cameras are generally limited to full page or less reproction.Scanning slows down post proction speed & adds cost.Digital systems can lose value quickly (up to 50% or more each year). Requires 8-12 photos (or more) for each panorama, more for multi-row (cubic) panos. Cubic viewing requires that viewers have a recent version of QuickTime installed, although this is already standard on most computers.Same disadvantages as film, but digital capture generally requires more source images per panorama in order to yield same field of view as with film.Requires annual license fee for software use. Need special fisheye lenses to shoot, limited maximum resolution compared to QTVR, users must have IPIX™ plug-in or IPIX viewer installed (free), authoring software available only from IPIX.Same disadvantages as film, but with lower maximum resolution (except for extremely high end/expensive digital systems).Expensive, difficult to use when supplemental lighting is required, film-based models not usually capable of fisheye or 360°° coverage.Same disadvantages as film, although digital models are significantly more expensive than film models. Current digital models also require that a portable or laptop computer be tethered to the camera when in use.Low resolution, requires proprietary software for dewarping, hard to visualize resulting image when looking through viewfinder, not capable of 360°x360° views, limited exposure control while shooting. Some also require royalty payment or "processing service" fee for every image created.Same disadvantages as film, but maximum resolution even further limited.