Text 5: Virtual Reality and Applications

1.Virtual Reality

Virtual Reality (VR) is a computer technology that creates three dimensional real illusions in an artificial world. Virtual Reality is used in many real life applications, from business planning to manufacturing and entertainment.

1) History of Virtual Reality

Virtual Reality has a significant history that is both interesting and complex. A little over thirty years ago, a young cinematographer named Morton Heilig wanted to utilize the other seventy-two percent of the spectator's viewing field and create an ultimate full-view experience for the spectator.

Unable to obtain any financial support, Heilig was unable to create his dream; however, he created a unit called the “Sensorama Simulator”, released in the early 1960's. A photo of the creation is shown in Figure 9. This virtual Workstation utilized 3D video, obtained with three 35 mm cameras mounted on the cameraman. The setup included stereo sound, integrated with the full 3D camera views. The viewer could ride a motorcycle while sensing the wind, simulated by a fan, and even potholes in the road. The machine was crude, but it opened the door for a multitude of ideas.

In 1966, Ivan Sutherland, a graduate student at the University of Utah, picked up where Heilig had left of. He started the idea of the graphics accelerator, an integral part in modern virtual simulation. The military quickly recognized the potential of this idea in flight simulation, and spent most of the seventies designing helmets that could simulate a view of night. Also, National Aeronautics and Space Administration (NASA) began research on using the technology for space flight, and later, moon landings. Heilig's invention changed the world of computing, as well as the evolution of the computer itself.

The pivotal convergence of technologies that have made Virtual Reality possible has come about in the last ten years. The last ten years have seen advancements in areas that are absolutely crucial to the VR paradigm. These include the LCD and CRT display devices, high performance image generation systems, and tracking systems. As the world of the integrated circuits progressed into the MIPS era, high speed, high performance systems became affordable. As a result, non-military research was possible, and research migrated to other countries as well, Japan, France, and Germany in particular. Evolution of specific technologies included the display technology, as mentioned above, the human interface, and imaging. The evolution of display technology has played a vital role in the advancement of the Virtual Reality paradigm.

Virtual Reality can be divided into:

• The simulation of real environments such as the interior of a building or a spaceship often with the purpose of training or education.

• The development of an imagined environment, typically for a game or educational adventure.

Popular products for creating virtual reality effects on personal computers include Bryce, Extreme 3D, Ray Dream Studio, TrueSpace, 3D Studio MAX, and Visual Reality. The Virtual Reality Modeling Language (VRML) allows the creator to specify images and the rules for their display and interaction using textual language statements.

2) VRML

VRML (Virtual Reality Modeling Language) is an open, extensible, industry-standard scene description language for 3D scenes, or worlds, on the Internet. With VRML and Netscape's Live3D, users can author and view distributed interactive 3D worlds that are rich with text, images, animation, sound, music, and even video.

• Embed VRML into HTML document

Once VRML world is created, it can be embed within an HTML document by using the<EMBED>tag. Using the <EMBED>tag to place a VRML world in an HTML document is similar to using the<IMG>tag to place a 2D image in an HTML document. The following example embeds a VRML file called example.wrl into an HTML document:

    <EMBED SRC="example.wrl" WIDTH=128 HEIGHT=128 BORDED=0 ALIGN=middle>

• Performance

Even the most enthusiastic user has limited patience for a slow Web page. This is a key concern for VRML authors, since VRML is based on computation-intensive 3D graphics and may incorporate other resource-intensive media. As with HTML documents, download time is an important factor in VRML world creation. A VRML world may require greater client system resources once downloaded. A fast browser will offset this to some extent, but it is important to construct VRML worlds efficiently. How to use the following elements will affect Web page's performance.

• Polygons

Shapes in a VRML world are made of polygons. The more complex a shape, the more polygons are required. A cube, for example, is typically comprised of just twelve polygons, since each side is made of two triangles. In contrast, a seemingly simple sphere requires more than 200 triangular polygons. As more objects are added to a world, the polygon count for that world increases. Each time a user's viewpoint changes in the VRML world, the browser has to redraw the scene. The more polygons the world contains, the longer the redraws take. Therefore, low polygon counts are one way to increase the user's navigation speed.

• Textures

VRML allows the textures to be mapped onto shapes. Textures used in a VRML world may increase its size considerably. This will affect both download and redraw times. Therefore, if textures are used, small textures are desirable as one way to keep download times low and navigation speed high. Also, textures used in VRML worlds will require fewer client resources if they use fewer colors.

• Instancing

If a user defines objects, the objects may be reused in a VRML world. This technique can help to keep a world file size small. This technique is called instancing. Though there are some limitations to instancing, its use can make VRML code easier to be written and maintained and the VRML worlds easier to be downloaded.

• Level of Detail

In the real world, as users get closer to an object, more details become visible. Level of Detail (LOD) makes this possible in VRML worlds. The LOD node determines which objects will be visible within defined ranges of coordinates within the VRML scene. This permits both special effects and realistic simulations.

• Inlines

Other world files may be “pulled into” a world to help create a VRML scene. When this technique is used, these files are called inlines. The WWWInline node is used to refer to a world file to be included and, optionally, to display a bounding box to show the user where the object, or objects, will be positioned before they are rendered.

• Compression

The larger the VRML world file, the longer it takes to be downloaded. World files may be compressed by using utilities such as GZIP. If a VRML browser recognizes the file type, it can automatically parse the compressed file to display the VRML world.

2.Virtual Reality Applications

Virtual reality may be described as a very special interaction between a human being and a computer. In VR, the person wears a “Head-Mounted Display (HMD)”—glasses, goggles, or a helmet with a tiny screen positioned in front of each eye (See Figure 10). Armed with a tracking system that links the HMD with the computer and some kind of navigational tool such as a 3D mouse, wand, or high-tech glove, the person is ready for a truly engaging computer adventure.

Once in the virtual world, the person sees the computer graphics in front, above, beside, below, and behind (See Figure 11). The traveler has a very convincing visual sense of being inside the computer's graphics.

The sort of systems common today had their beginnings in the 1960s. One of the first practical uses of virtual reality was the military's development of the heads-up display used by pilots.

While researchers agree it has a long way to go before it reaches its potential, VR is in practical use today in various occupations in the military, entertainment, education, and business. In education, gigantic growth in virtual reality is expected. Universities such as the University of Washington and the University of North Carolina devote resources to the study of virtual reality, its physical impact, and its application to the real world.

The next Step in education is to apply it to improve the learning process and to create new learning systems. The excitement and motivation that virtual reality creates ignites the imagination of far-sighted educators who perceive VR as the next logical step in computer-based instruction.

In business applications, using high-speed dedicated computer, multi-million-dollar flight simulators built by Singer, RediFusion, and others have led the way in commercial application of VR. Pilots of F-16s, Boeing 777s, and Rockwell space shuttles have made many dry runs before doing the real thing. At the California Maritime Academy and other merchant marine officer training schools, computer-controlled simulators teach the intricate loading and unloading of oil tankers and container ships. Virtual worlds and business intersect in the Virtual Worlds Consortium sponsored through the University of Washington. If current indicators pointing to virtual reality as a powerful learning tool are correct, future training in business and industry will take advantage of this ultimate visual learning method.

New Words and Expressions

manufacturing n. 制造业

cinematographer n. 电影摄影技师，放映技师

utilize v. 利用

spectator n. 观众

simulator n. 模拟器，假装者

workstation n. 工作站

accelerator n. 加速者，加速器

NASA abbr. National Aeronautics and Space Administration美国国家航空和航天局

Pivotal adj． 枢轴的，关键的

convergence n. 集中，收敛

paradigm n. 范例

interior n. 内部

adventure n. 冒险，冒险的经历

polygon n. 多角形，多边形

texture n. 纹理

compression n. 浓缩，压缩

shuttle n. 往返汽车（列车、飞机），航天飞机，梭子，穿梭

marine adj. 海的，海产的，航海的，船舶的，海运的

Exercises to the Text

1.Translate the following words and phrases into English.

（1）虚拟现实（2）三维图像（3）虚拟模拟（4）纹理（5）压缩

2.Translate the following words and phrases into Chinese.

(1) virtual reality modeling language (2) polygon (3) inlines (4) heads-up display (5) simulator

3.Translate the following paragraphs into Chinese.

(1) The pivotal convergence of technologies that have made Virtual Reality possible has come about in the last ten years. The last ten years have seen advancements in areas that are absolutely crucial to the VR paradigm. These include the Liquid LCD and CRT display devices, high performance image generation systems, and tracking systems (to compute display areas into calculated machine coordinates).

(2) VRML (Virtual Reality Modeling Language) is an open, extensible, industry-standard scene description language for 3D scenes, or worlds, on the Internet. With VRML and Netscape's Live3D, users can author and view distributed interactive 3D worlds that are rich with text, images, animation, sound, music, and even video.

(3) The larger the VRML world file, the longer it takes to be downloaded. World files may be compressed by using utilities such as GZIP. If a VRML browser recognizes the file type, it can automatically parse the compressed file to display the VRML world.