《計(jì)算機(jī)專業(yè)英語(yǔ)》謝希仁第二版-第13章講義

1、1. Concept of virtual reality 2. Applications of VRML3. Describe the features of VRML4. 了解了解廣告文體廣告文體的特點(diǎn)的特點(diǎn)New Words & Expressions:Virtual reality 虛擬現(xiàn)實(shí)虛擬現(xiàn)實(shí)jerky 顛簸的，急動(dòng)的，此處指圖像抖動(dòng)顛簸的，急動(dòng)的，此處指圖像抖動(dòng)abuse 吸毒，濫用吸毒，濫用prevent from 阻止，妨礙阻止，妨礙in front of 在在前面前面relay vt. vi. 中繼，轉(zhuǎn)播中繼，轉(zhuǎn)播haptic a. 觸覺(jué)的觸覺(jué)的stylus n.

2、 指示筆，觸針指示筆，觸針dystrophy n. 營(yíng)養(yǎng)失調(diào)營(yíng)養(yǎng)失調(diào)teleconference n.（遠(yuǎn)程）電信會(huì)議（遠(yuǎn)程）電信會(huì)議13.1 Virtual RealityAbbreviations:LCD (Liquid-Crystal Display) 液晶顯示液晶顯示HMD (Head-Mounted Display) 頭部安裝的顯示器頭部安裝的顯示器 13.1 Virtual RealityVirtual reality is a system that enables one or more users to move and react in a computer-simulat

3、ed environment. Various types of devices allow users to sense and manipulate virtual objects much as they would real objects1. This natural style of interaction gives participants the feeling of being immersed in the simulated world. Virtual worlds are created by mathematical models and computer pro

4、grams.虛擬現(xiàn)實(shí)是一個(gè)能讓一個(gè)或多個(gè)用戶在計(jì)算機(jī)模擬環(huán)境下移虛擬現(xiàn)實(shí)是一個(gè)能讓一個(gè)或多個(gè)用戶在計(jì)算機(jī)模擬環(huán)境下移動(dòng)和做出反應(yīng)的系統(tǒng)。各種設(shè)備讓用戶去感覺(jué)和操作虛擬物動(dòng)和做出反應(yīng)的系統(tǒng)。各種設(shè)備讓用戶去感覺(jué)和操作虛擬物體，就像他們是真實(shí)物體一樣。這種自然的交互風(fēng)格讓參與體，就像他們是真實(shí)物體一樣。這種自然的交互風(fēng)格讓參與者感到融入到模擬世界。虛擬世界是由數(shù)學(xué)模型和計(jì)算機(jī)程者感到融入到模擬世界。虛擬世界是由數(shù)學(xué)模型和計(jì)算機(jī)程序創(chuàng)造的。序創(chuàng)造的。13.1 Virtual RealityVirtual reality simulations differ from other computer s

5、imulations in that they require special interface devices that transmit the sights, sounds, and sensations of the simulated world to the user2. These devices also record and send the speech and movements of the participants to the simulation program.虛擬現(xiàn)實(shí)模擬不同于其他要求特殊界面設(shè)備的計(jì)算機(jī)模擬，虛擬現(xiàn)實(shí)模擬不同于其他要求特殊界面設(shè)備的計(jì)算機(jī)模

6、擬，這些設(shè)備向用戶傳送模擬世界的視覺(jué)、聲音和感覺(jué)。這些設(shè)這些設(shè)備向用戶傳送模擬世界的視覺(jué)、聲音和感覺(jué)。這些設(shè)備還向模擬程序記錄和發(fā)送語(yǔ)音和參與者的運(yùn)動(dòng)。備還向模擬程序記錄和發(fā)送語(yǔ)音和參與者的運(yùn)動(dòng)。 13.1 Virtual RealityTo see in the virtual world, the user wears a head-mounted display (HMD) with screens directed at each eye. The HMD also contains a position tracker to monitor the location of the u

7、sers head and the direction in which the user is looking. Using this information, a computer recalculates images of the virtual world a slightly different view for each eye to match the direction in which the user is looking, and displays these images on the (HMD) .要觀看虛擬世界，用戶戴上一個(gè)頭部安裝的顯示器要觀看虛擬世界，用戶戴上

8、一個(gè)頭部安裝的顯示器(HMD)，HMD上有在每只眼睛前表演的屏幕。上有在每只眼睛前表演的屏幕。HMD還包括一個(gè)監(jiān)視還包括一個(gè)監(jiān)視用戶頭部位置和觀看方向的跟蹤器。用這個(gè)信息，計(jì)算機(jī)重用戶頭部位置和觀看方向的跟蹤器。用這個(gè)信息，計(jì)算機(jī)重新計(jì)算每只眼睛稍微視覺(jué)差異的虛擬世界圖像，使它與用戶新計(jì)算每只眼睛稍微視覺(jué)差異的虛擬世界圖像，使它與用戶的觀察方向一致，同時(shí)在的觀察方向一致，同時(shí)在HMD上顯示這些圖像。上顯示這些圖像。13.1 Virtual RealityThe computer must generate these new views at least ten times a second

9、in order to prevent the users view from appearing halting and jerky and from lagging behind the users movements. Virtual-world scenes must be kept relatively simple so that the computer can update the visual imagery quickly enough. Because of these simplifications and other shortcomings of current v

10、isual displays and computer graphics, VR participants can easily distinguish a simulation from physical reality.為了防止用戶視覺(jué)出現(xiàn)停止和抖動(dòng)以及滯后于用戶的運(yùn)動(dòng)，為了防止用戶視覺(jué)出現(xiàn)停止和抖動(dòng)以及滯后于用戶的運(yùn)動(dòng)，計(jì)算機(jī)必須以每秒至少十次的速度生成這些新圖像。虛擬世計(jì)算機(jī)必須以每秒至少十次的速度生成這些新圖像。虛擬世界的場(chǎng)景必須保持相對(duì)簡(jiǎn)單，這樣計(jì)算機(jī)就能夠快的更新視界的場(chǎng)景必須保持相對(duì)簡(jiǎn)單，這樣計(jì)算機(jī)就能夠快的更新視覺(jué)圖像。由于這些簡(jiǎn)單化及當(dāng)前視覺(jué)現(xiàn)實(shí)和計(jì)算機(jī)圖形的缺覺(jué)圖像。由于

11、這些簡(jiǎn)單化及當(dāng)前視覺(jué)現(xiàn)實(shí)和計(jì)算機(jī)圖形的缺點(diǎn)，虛擬現(xiàn)實(shí)參與者能很容易從物理現(xiàn)實(shí)中區(qū)分出模擬事物。點(diǎn)，虛擬現(xiàn)實(shí)參與者能很容易從物理現(xiàn)實(shí)中區(qū)分出模擬事物。13.1 Virtual RealityUsers hear sounds in the virtual world through earphones in the HMD, the information reported by the position tracker on the HMD can also be used to update audio signals. When a sound source in virtual spac

12、e is not directly in front of or behind the user, the computer transmits sounds to arrive at one ear a little earlier or later than at the other and to be a little louder or softer and slightly different in pitch. However, as with visual imagery, there are currently scientific and engineering challe

13、nges that must be overcome in order to simulate accurately all the sounds heard in the physical world.在虛擬世界中，用戶通過(guò)在虛擬世界中，用戶通過(guò)HMD中的耳機(jī)聽(tīng)到聲音，中的耳機(jī)聽(tīng)到聲音，HMD中的位置跟蹤器中的位置跟蹤器報(bào)告的信息也能用來(lái)更換音頻信號(hào)。當(dāng)虛擬空間的聲源不直接在用戶的前報(bào)告的信息也能用來(lái)更換音頻信號(hào)。當(dāng)虛擬空間的聲源不直接在用戶的前方或后方，計(jì)算機(jī)傳達(dá)到某只耳朵的聲音比到另一只稍微早些或晚些。然方或后方，計(jì)算機(jī)傳達(dá)到某只耳朵的聲音比到另一只稍微早些或晚些。然而，正如視覺(jué)圖像，為

14、了準(zhǔn)確模擬物理世界聽(tīng)到的聲音，當(dāng)前科學(xué)和工程而，正如視覺(jué)圖像，為了準(zhǔn)確模擬物理世界聽(tīng)到的聲音，當(dāng)前科學(xué)和工程面臨必須克服的挑戰(zhàn)。面臨必須克服的挑戰(zhàn)。13.1 Virtual RealityThe haptic interface, which relays, the sense of touch and other physical sensations in the virtual world, is the least developed and perhaps the most challenging to create. Currently, with the use of a glo

15、ve and position tracker, the computer locates the users hand and measures finger movements. The user can reach into the virtual world and handle objects but cannot actually feel them. 中繼虛擬世界中觸覺(jué)和其他物理感覺(jué)的觸覺(jué)界面最不發(fā)達(dá)、中繼虛擬世界中觸覺(jué)和其他物理感覺(jué)的觸覺(jué)界面最不發(fā)達(dá)、而且大概要引起最大挑戰(zhàn)。當(dāng)前，由于使用了手套和位置跟而且大概要引起最大挑戰(zhàn)。當(dāng)前，由于使用了手套和位置跟蹤器，計(jì)算機(jī)使用戶的手定

16、位，而且測(cè)量手指的運(yùn)動(dòng)。用戶蹤器，計(jì)算機(jī)使用戶的手定位，而且測(cè)量手指的運(yùn)動(dòng)。用戶能達(dá)到虛擬世界而且觸摸物體，但不能實(shí)際感覺(jué)到他們。能達(dá)到虛擬世界而且觸摸物體，但不能實(shí)際感覺(jué)到他們。13.1 Virtual RealityIt is particularly difficult to generate the sensations that are felt when a person taps a hard surface, picks up an object, or runs a finger across a textured surface. To simulate these sen

17、sations, a set of computer-controlled motors faster and more accurate than any presently available would have to generate force feedback by physically pushing against the user. Another problem is determining how a user would wear these motors and the wiring needed to control them. 當(dāng)某人輕敲一個(gè)硬的表面，撿起一個(gè)物體

18、、或手指拂過(guò)有織當(dāng)某人輕敲一個(gè)硬的表面，撿起一個(gè)物體、或手指拂過(guò)有織紋的表面時(shí)，特殊難產(chǎn)生出感覺(jué)到的感覺(jué)。要模擬這些感覺(jué)，紋的表面時(shí)，特殊難產(chǎn)生出感覺(jué)到的感覺(jué)。要模擬這些感覺(jué)，一套比目前能得到的任何電機(jī)都快和精確的計(jì)算機(jī)控制的電一套比目前能得到的任何電機(jī)都快和精確的計(jì)算機(jī)控制的電機(jī)將必須由多用戶的實(shí)際推力產(chǎn)生反饋力。另一個(gè)問(wèn)題是決機(jī)將必須由多用戶的實(shí)際推力產(chǎn)生反饋力。另一個(gè)問(wèn)題是決定用戶如何穿戴這些電機(jī)和用于控制他們的電線。定用戶如何穿戴這些電機(jī)和用于控制他們的電線。13.1 Virtual RealityTouch sensations would also have to be synch

19、ronized with the sights and sounds users experienced in their HMDs. A current solution to the haptic challenge is the use of desktop devices that can apply small forces, through a mechanical linkage, to a stylus held in the users hand. Users can feel when the point of the stylus encounters a virtual

20、 object, and they can drag the stylus across the surface to feel its texture and surface geometry. 觸覺(jué)還必須與用戶在他們觸覺(jué)還必須與用戶在他們HMD中經(jīng)歷的視覺(jué)和聲音同步。對(duì)中經(jīng)歷的視覺(jué)和聲音同步。對(duì)觸覺(jué)挑戰(zhàn)的當(dāng)前解決辦法是使用可以施加小力的，通過(guò)一個(gè)觸覺(jué)挑戰(zhàn)的當(dāng)前解決辦法是使用可以施加小力的，通過(guò)一個(gè)機(jī)械連趕到用戶手中握著的觸針的臺(tái)式設(shè)備。當(dāng)觸針的針尖機(jī)械連趕到用戶手中握著的觸針的臺(tái)式設(shè)備。當(dāng)觸針的針尖碰到一個(gè)虛擬物體，用戶能感覺(jué)到，而且他們能在表面上拖碰到一個(gè)虛擬物體，用戶能感覺(jué)到，而且他們

21、能在表面上拖過(guò)觸針來(lái)感覺(jué)它的織紋和表面幾何形狀。過(guò)觸針來(lái)感覺(jué)它的織紋和表面幾何形狀。13.1 Virtual RealityIn recent years, virtual-reality devices have improved dramatically as the result of various technological advances. Computers now are more powerful, have a higher memory capacity, are smaller, and cost less than in past. These developmen

22、ts, along with the advent of small liquid-crystal displays (LCDs) that can be used in HMDs, have made it possible for scientists to develop virtual-reality simulation.最近幾年，由于各種技術(shù)進(jìn)步的結(jié)果，虛擬現(xiàn)實(shí)設(shè)備已顯著最近幾年，由于各種技術(shù)進(jìn)步的結(jié)果，虛擬現(xiàn)實(shí)設(shè)備已顯著改進(jìn)。現(xiàn)在計(jì)算機(jī)功能更強(qiáng)大，存儲(chǔ)容量更高，比過(guò)去更小，改進(jìn)?，F(xiàn)在計(jì)算機(jī)功能更強(qiáng)大，存儲(chǔ)容量更高，比過(guò)去更小，價(jià)格更低。伴隨著可以用在價(jià)格更低。伴隨著可以用在HMD

23、的小型液晶顯示器的到來(lái)，的小型液晶顯示器的到來(lái)，這些發(fā)展已經(jīng)使科學(xué)家開(kāi)發(fā)虛擬現(xiàn)實(shí)模擬成為可能。這些發(fā)展已經(jīng)使科學(xué)家開(kāi)發(fā)虛擬現(xiàn)實(shí)模擬成為可能。13.1 Virtual RealityVirtual-reality is currently used to explore and manipulate experimental data in ways that were not possible before. Therapists use VR to treat sufferers of child abuse and people who are afraid of heights. Mus

24、cular dystrophy patients can learn to use a wheelchair through virtual reality.虛擬現(xiàn)實(shí)當(dāng)前用于探索和操縱實(shí)驗(yàn)數(shù)據(jù)，以前這種方式是不虛擬現(xiàn)實(shí)當(dāng)前用于探索和操縱實(shí)驗(yàn)數(shù)據(jù)，以前這種方式是不可能的。精神治療家用可能的。精神治療家用VR去治療兒童虐待的受害者和恐高癥去治療兒童虐待的受害者和恐高癥患者。肌肉萎縮患者可以通過(guò)虛擬現(xiàn)實(shí)學(xué)習(xí)使用輪椅。患者。肌肉萎縮患者可以通過(guò)虛擬現(xiàn)實(shí)學(xué)習(xí)使用輪椅。13.1 Virtual RealityIn the future, surgeons may use VR to plan and pr

25、actice an operation on a virtual patient rather than a real person. Architects could take clients on a virtual tour of a new house before it was built. VR could be used to train the operators of aircraft and other complicated machinery. Network VR simulations could enable people in many different lo

26、cations to participate together in teleconferences, virtual surgical operations, or simulated military training exercises. 將來(lái)，外科醫(yī)生可以用將來(lái)，外科醫(yī)生可以用VR在虛擬病人身上計(jì)劃和實(shí)習(xí)手術(shù)，在虛擬病人身上計(jì)劃和實(shí)習(xí)手術(shù)，而不是在真人身上。在房子建設(shè)前，建筑師可以帶領(lǐng)客戶在而不是在真人身上。在房子建設(shè)前，建筑師可以帶領(lǐng)客戶在新房中作虛擬旅行。新房中作虛擬旅行。VR可以用來(lái)訓(xùn)練戰(zhàn)斗機(jī)和其它復(fù)雜機(jī)械可以用來(lái)訓(xùn)練戰(zhàn)斗機(jī)和其它復(fù)雜機(jī)械的操作者。網(wǎng)絡(luò)的操作者。網(wǎng)絡(luò)VR模擬能讓在

27、許多不同地方的人一起參加電模擬能讓在許多不同地方的人一起參加電信會(huì)議、虛擬外科手術(shù)或模擬軍事演習(xí)。信會(huì)議、虛擬外科手術(shù)或模擬軍事演習(xí)。 13.2 Real Work in Virtual RealityIn the future, your office may be less like a cubicle and more like the Holodeck on “Star Trek”. Computer scientists are already experimenting with the technology, called tele-immersion, that will al

28、low us to peer into the offices of colleagues hundreds of miles away and make us feel as if we are sharing the same physical space. 將來(lái)你的辦公室也許不像個(gè)小臥室而更像星際旅行的全息駕將來(lái)你的辦公室也許不像個(gè)小臥室而更像星際旅行的全息駕駛艙。計(jì)算機(jī)科學(xué)家已經(jīng)用叫做遠(yuǎn)程參與的技術(shù)進(jìn)行試驗(yàn)，駛艙。計(jì)算機(jī)科學(xué)家已經(jīng)用叫做遠(yuǎn)程參與的技術(shù)進(jìn)行試驗(yàn)，這將我們窺見(jiàn)數(shù)百英里以外同事的辦公室，使我們感到就像這將我們窺見(jiàn)數(shù)百英里以外同事的辦公室，使我們感到就像我們?cè)诜窒硗晃锢砜臻g。

29、我們?cè)诜窒硗晃锢砜臻g。13.2 Real Work in Virtual RealityComputer scientists at several universities working on a project called the National Tele-Immersion Initiative have demonstrated a prototype system that enables a scientist working at his desk in Chapel Hill to see his distant colleagues on two screens mo

30、unted at right angles to his desk. It gives him the illusion of looking through windows into offices on the other side. And unlike videoconferencing, tele-immersion provides life-size 3-D images. 致力于國(guó)家遠(yuǎn)程參與主動(dòng)性項(xiàng)目的幾所大學(xué)計(jì)算機(jī)科學(xué)家已致力于國(guó)家遠(yuǎn)程參與主動(dòng)性項(xiàng)目的幾所大學(xué)計(jì)算機(jī)科學(xué)家已展示了一個(gè)原始系統(tǒng)，讓在他的展示了一個(gè)原始系統(tǒng)，讓在他的Chapel Hall辦公室桌上工作辦公室桌上工

31、作的科學(xué)家能在他桌上直角安裝的兩個(gè)屏幕上看到他的遠(yuǎn)方同的科學(xué)家能在他桌上直角安裝的兩個(gè)屏幕上看到他的遠(yuǎn)方同事。這給他一個(gè)錯(cuò)覺(jué)就像是從窗戶看到另一面的辦公室。與事。這給他一個(gè)錯(cuò)覺(jué)就像是從窗戶看到另一面的辦公室。與視頻會(huì)議不同，遠(yuǎn)程參與提供真實(shí)的立體圖像。視頻會(huì)議不同，遠(yuǎn)程參與提供真實(shí)的立體圖像。13.2 Real Work in Virtual RealityIn the prototype system, each researcher is surrounded by a bank of digital cameras that monitor his movements from a va

32、riety of angles. The researchers also wear head-mounted tracking gear and polarized glasses similar to those used to view 3-D movies. When a researcher moves his head, his view of his co-workers shifts accordingly. If he leans forward, for example, his colleagues appear closer, even though they are

33、hundreds of miles away. 在原始系統(tǒng)中，每位研究人員被一群從不同角度監(jiān)視他的攝在原始系統(tǒng)中，每位研究人員被一群從不同角度監(jiān)視他的攝像機(jī)所包圍。研究人員還帶著頭部安裝的跟蹤裝置和類似那像機(jī)所包圍。研究人員還帶著頭部安裝的跟蹤裝置和類似那些用于觀看立體電影的偏振眼睛。當(dāng)研究人員移動(dòng)他的腦袋些用于觀看立體電影的偏振眼睛。當(dāng)研究人員移動(dòng)他的腦袋時(shí)，他的同事的圖像也相應(yīng)變動(dòng)。例如，如果它向前傾，他時(shí)，他的同事的圖像也相應(yīng)變動(dòng)。例如，如果它向前傾，他的同事就靠近，雖然他們相距數(shù)百英里。的同事就靠近，雖然他們相距數(shù)百英里。13.2 Real Work in Virtual Realit

34、yTo make the system work, powerful computers must convert digital images of each participant into data that is transmitted via the Internet, then reconstructed into images projected on the screens. So far, the movement is jerky because todays computers cannot transmit data fast enough. 要使系統(tǒng)工作，強(qiáng)大的計(jì)算機(jī)

35、必須把每個(gè)參與者圖像轉(zhuǎn)換通要使系統(tǒng)工作，強(qiáng)大的計(jì)算機(jī)必須把每個(gè)參與者圖像轉(zhuǎn)換通過(guò)因特網(wǎng)傳輸?shù)臄?shù)據(jù)，然后重新還原或投射在屏幕上的圖像。過(guò)因特網(wǎng)傳輸?shù)臄?shù)據(jù)，然后重新還原或投射在屏幕上的圖像。到目前為止，因?yàn)楝F(xiàn)在的計(jì)算機(jī)不能足夠快地傳送數(shù)據(jù)，運(yùn)到目前為止，因?yàn)楝F(xiàn)在的計(jì)算機(jī)不能足夠快地傳送數(shù)據(jù)，運(yùn)動(dòng)還是抖動(dòng)的。動(dòng)還是抖動(dòng)的。13.2 Real Work in Virtual RealityThe scientists hope that tele-immersion will open up a host of other applications: For example, patients in

36、rural areas could “visit” medical specialists in faraway cities. 科學(xué)家們希望遠(yuǎn)程參與將通向許多其它的應(yīng)用，例如，農(nóng)村科學(xué)家們希望遠(yuǎn)程參與將通向許多其它的應(yīng)用，例如，農(nóng)村的患者可以的患者可以“瞧瞧”遠(yuǎn)在城市的醫(yī)學(xué)專家。遠(yuǎn)在城市的醫(yī)學(xué)專家。New Words & Expressions:interactive 交互的交互的intranet n.企業(yè)內(nèi)部互聯(lián)網(wǎng)企業(yè)內(nèi)部互聯(lián)網(wǎng)integrate 使成整體，結(jié)合使成整體，結(jié)合visualization n.可視化可視化presentation n.演示演示virtual adj.虛

37、擬的虛擬的criteria 準(zhǔn)則準(zhǔn)則authorability n. 創(chuàng)作性創(chuàng)作性compose 組成，寫作，排字組成，寫作，排字re-usability n. 可重用性可重用性extensibility 可擴(kuò)展性可擴(kuò)展性explicitly 明白地，明確地明白地，明確地platform 平臺(tái)平臺(tái) arbitrarily 武斷地，任意地武斷地，任意地static 靜態(tài)的靜態(tài)的animated 動(dòng)畫的，活生生的動(dòng)畫的，活生生的dynamic 動(dòng)態(tài)的動(dòng)態(tài)的hyperlink 超級(jí)聯(lián)接超級(jí)聯(lián)接author v. 制作制作available 可利用的可利用的registration 注冊(cè)，登記注冊(cè)，登

38、記community 團(tuán)體，公用團(tuán)體，公用interoperable 能共同使用的能共同使用的extension n. 延長(zhǎng)，范圍延長(zhǎng)，范圍scope 范圍范圍specification 規(guī)范，說(shuō)明書規(guī)范，說(shuō)明書13.3 About VRML New Words & Expressions:conceptually 概念地概念地aural 聽(tīng)覺(jué)的聽(tīng)覺(jué)的modify 更改，修改更改，修改mechanisms 機(jī)制機(jī)制primary 原始的原始的composition 合成法，排版合成法，排版encapsulation 封裝封裝semantic 語(yǔ)義語(yǔ)義resolution 分辨率分辨率l

39、atitude 緯度，范圍，地區(qū)緯度，范圍，地區(qū)interpretation 解釋，闡明解釋，闡明mouse 鼠標(biāo)鼠標(biāo)implicitly 含蓄地，暗中地含蓄地，暗中地coordinate 坐標(biāo)坐標(biāo)recursively 遞歸地，回歸地遞歸地，回歸地sphere 球體球體 reference 提及，參考書目提及，參考書目enclose 放入，封閉，包裝放入，封閉，包裝hierarchical 分層的，層次的分層的，層次的spatial adj. 空間的空間的accumulation 積聚，積累積聚，積累dissipate v. 使消失，失去使消失，失去intractable 難處理的難處理的c

40、ompact 緊湊的，簡(jiǎn)潔的緊湊的，簡(jiǎn)潔的syntax n. 語(yǔ)法語(yǔ)法13.3 About VRML 13.3 About VRML Abbreviations :VRML (The Virtual Reality Modeling Language) 虛擬現(xiàn)實(shí)建模語(yǔ)言虛擬現(xiàn)實(shí)建模語(yǔ)言API (application programmer interface) 應(yīng)用程序界面應(yīng)用程序界面The Virtual Reality Modeling Language (VRML) is a file format for describing interactive 3D objects and wo

41、rlds. VRML is designed to be used on the Internet, intranets, and local client systems. VRML is also intended to be a universal interchange format for integrated 3D graphics and multimedia. VRML may be used in a variety of application areas such as engineering and scientific visualization, multimedi

42、a presentations, entertainment and educational titles, web pages, and shared virtual worlds. 虛擬現(xiàn)實(shí)建模語(yǔ)言虛擬現(xiàn)實(shí)建模語(yǔ)言(VRML)是一種描述交互式三維對(duì)象及客觀是一種描述交互式三維對(duì)象及客觀世界的文件格式。世界的文件格式。VRML用于用于Internet、Intranet和局域客戶和局域客戶系統(tǒng)。系統(tǒng)。VRML也是組合三維圖形和多媒體的通用轉(zhuǎn)換格式。也是組合三維圖形和多媒體的通用轉(zhuǎn)換格式。VRML的應(yīng)用領(lǐng)域很廣，包括工程、科學(xué)可視化、多媒體演的應(yīng)用領(lǐng)域很廣，包括工程、科學(xué)可視化、多媒體演示、娛樂(lè)

43、教育、示、娛樂(lè)教育、Web頁(yè)面和共享虛擬世界等方面。頁(yè)面和共享虛擬世界等方面。13.3 About VRML 13.3.1 Design CriteriaVRML has been designed to fulfill the following requirements:l Authorability Enable the development of computer programs capable of creating, editing, and maintaining VRML files, as well asautomatic translation programs for

44、 converting other commonly used 3D file formats into VRML files.13.2.1 設(shè)計(jì)標(biāo)準(zhǔn)設(shè)計(jì)標(biāo)準(zhǔn)VRML需要滿足如下要求：需要滿足如下要求：l 創(chuàng)作性創(chuàng)作性使得應(yīng)用程序能夠建立、編輯、保存使得應(yīng)用程序能夠建立、編輯、保存VRML文件，也是一個(gè)自文件，也是一個(gè)自動(dòng)翻譯程序，能夠?qū)⑼ǔＪ褂玫膭?dòng)翻譯程序，能夠?qū)⑼ǔＪ褂玫?D文件格式轉(zhuǎn)換成文件格式轉(zhuǎn)換成VRML文件。文件。13.3 About VRML l Composability Provide the ability to use and combine dynamic 3D obj

45、ects within a VRML world and thus allow re-usability. l Extensibility Provide the ability to add new object types not explicitly defined in VRML.l 重構(gòu)性重構(gòu)性能夠在能夠在VRML環(huán)境中使用和組合動(dòng)態(tài)環(huán)境中使用和組合動(dòng)態(tài)3D對(duì)象，并允許重用。對(duì)象，并允許重用。l 擴(kuò)展性擴(kuò)展性能夠加入在能夠加入在VRML中沒(méi)有明確定義的新的對(duì)象類型。中沒(méi)有明確定義的新的對(duì)象類型。13.3 About VRML l Implementability Capable of

46、 implementation on a wide range of systems. l Performance Emphasize scalable, interactive performance on a wide variety of computing platforms.l ScalabilityEnable arbitrarily large dynamic 3D worlds. l 適用性適用性能夠在各種系統(tǒng)中使用。能夠在各種系統(tǒng)中使用。l 性能性能在各種不同的計(jì)算機(jī)平臺(tái)上強(qiáng)調(diào)可擴(kuò)展的、交互的性能。在各種不同的計(jì)算機(jī)平臺(tái)上強(qiáng)調(diào)可擴(kuò)展的、交互的性能。l 可擴(kuò)展性可擴(kuò)展性適于任意

47、大的動(dòng)態(tài)三維世界。適于任意大的動(dòng)態(tài)三維世界。13.3 About VRML 13.3.2 Characteristics of VRMLVRML is capable of representing static and animated dynamic 3D and multimedia objects with hyperlinks to other media such as text, sounds, movies, and images 1. VRML browsers, as well as authoring tools for the creation of VRML file

48、s, are widely available for many different platforms.VRML的特性的特性VRML能表示靜態(tài)及動(dòng)態(tài)的三維和多媒體對(duì)象，并通過(guò)超鏈能表示靜態(tài)及動(dòng)態(tài)的三維和多媒體對(duì)象，并通過(guò)超鏈接連到諸如文本、聲音、電影及圖像等其它媒體。接連到諸如文本、聲音、電影及圖像等其它媒體。VRML瀏瀏覽器，同制作覽器，同制作VRML文件的制作工具一樣，廣泛應(yīng)用于許多文件的制作工具一樣，廣泛應(yīng)用于許多不同的平臺(tái)上。不同的平臺(tái)上。13.3 About VRML VRML supports an extensibility model that allows new dyna

49、mic 3D objects to be defined and a registration process that allows application communities to develop interoperable extensions to the base standard. There are mappings between VRML objects and commonly used 3D application programmer interface (API) features.VRML支持?jǐn)U展模式，即允許創(chuàng)建新的支持?jǐn)U展模式，即允許創(chuàng)建新的3維動(dòng)態(tài)對(duì)象，并允

50、維動(dòng)態(tài)對(duì)象，并允許應(yīng)用程序組開(kāi)發(fā)在基礎(chǔ)模式上加以擴(kuò)展的可共同操作的許應(yīng)用程序組開(kāi)發(fā)在基礎(chǔ)模式上加以擴(kuò)展的可共同操作的文件。在文件。在VRML對(duì)象和通常使用的應(yīng)用程序接口特性間有對(duì)象和通常使用的應(yīng)用程序接口特性間有相應(yīng)的映射。相應(yīng)的映射。13.3 About VRML 13.3.3 ScopeThe VRML specification defines a file format that integrates 3D graphics and multimedia. Conceptually, each VRML file is a 3D time-based space that contai

51、ns graphic and aural objects that can be dynamically modified through a variety of mechanisms. VRML defines a primary set of objects and mechanisms that encourage composition, encapsulation, and extension. VRML能表示靜態(tài)及動(dòng)態(tài)的三維和多媒體對(duì)象，并通過(guò)超鏈接能表示靜態(tài)及動(dòng)態(tài)的三維和多媒體對(duì)象，并通過(guò)超鏈接連到諸如文本、聲音、電影及圖像等其它媒體。連到諸如文本、聲音、電影及圖像等其它媒體。

52、VRML瀏覽器，瀏覽器，同制作同制作VRML文件的制作工具一樣，廣泛應(yīng)用于許多不同的平文件的制作工具一樣，廣泛應(yīng)用于許多不同的平臺(tái)上。臺(tái)上。 13.3 About VRML The semantics of VRML describe an abstract functional behavior of time-based, interactive 3D, multimedia worlds. VRML does not define physical devices or any other implementation-dependent concepts (e.g., screen r

53、esolution and input devices). VRML is intended for a wide variety of devices and applications, and provides wide latitude in interpretation and implementation of the functionality. For example, VRML does not assume the existence of a mouse or 2D display device. VRML的語(yǔ)義描述了一個(gè)抽象的時(shí)間依賴的、交互性的語(yǔ)義描述了一個(gè)抽象的時(shí)間依

54、賴的、交互性3維的功能維的功能行為。行為。VRML并不定義一個(gè)具體的設(shè)備或任何依賴它實(shí)現(xiàn)的概并不定義一個(gè)具體的設(shè)備或任何依賴它實(shí)現(xiàn)的概念（比如：屏幕分辨率和輸入設(shè)備）。念（比如：屏幕分辨率和輸入設(shè)備）。VRML適用于大量的設(shè)適用于大量的設(shè)備和應(yīng)用程序，并且提供了一個(gè)對(duì)功能加以解釋和實(shí)現(xiàn)的廣泛備和應(yīng)用程序，并且提供了一個(gè)對(duì)功能加以解釋和實(shí)現(xiàn)的廣泛空間。比如：空間。比如：VRML并不認(rèn)為有鼠標(biāo)或并不認(rèn)為有鼠標(biāo)或2維顯示設(shè)備的存在。維顯示設(shè)備的存在。 13.3 About VRML 13.3.4 Each VRML file:1. implicitly establishes a world coo

55、rdinate space for all objects defined in the file, as well as all objects recursively included by the file;2. explicitly defines and composes a set of 3D and multimedia objects;3. can specify hyperlinks to other files and applications;4. can define object behaviors. 1. 為文件中的所有對(duì)象建立了一個(gè)世界坐標(biāo)系，也包括在文件為文件中

56、的所有對(duì)象建立了一個(gè)世界坐標(biāo)系，也包括在文件中遞歸包含的所有對(duì)象。中遞歸包含的所有對(duì)象。2. 明確定義并構(gòu)成一個(gè)明確定義并構(gòu)成一個(gè)3D和多媒體對(duì)象的集合。和多媒體對(duì)象的集合。3. 可定義超鏈接與其它文件和應(yīng)用程序相連。可定義超鏈接與其它文件和應(yīng)用程序相連。4. 可定義對(duì)象的行為?？啥x對(duì)象的行為。 13.3 About VRML An important characteristic of VRML files is the ability to compose files together through inclusion and to relate files together thro

57、ugh hyperlinking. For example, consider the file earth.wrl which specifies a world that contains a sphere representing the earth. This file may also contain references to a variety of other VRML files representing cities on the earth (e.g., file paris.wrl). The enclosing file, earth.wrl, defines the

58、 coordinate system that all the cities reside in. Each city file defines the world coordinate system that the city resides in but that becomes a local coordinate system when contained by the earth file.VRML文件的一個(gè)重要特性是能夠通過(guò)包含和超鏈接將文件組合在一起。比文件的一個(gè)重要特性是能夠通過(guò)包含和超鏈接將文件組合在一起。比如：文件如：文件earth.wrl, 定義了一個(gè)表示地球的球體，定義

59、了一個(gè)表示地球的球體， 它也可以包含指向表示地它也可以包含指向表示地球上其它城市的文件的索引（如：文件球上其它城市的文件的索引（如：文件 paris.wrl）。外封文件：）。外封文件：earth.wrl定定義了所有城市所處的坐標(biāo)系。每一個(gè)城市文件定義了城市所在的世界坐標(biāo)系義了所有城市所處的坐標(biāo)系。每一個(gè)城市文件定義了城市所在的世界坐標(biāo)系系統(tǒng)，但是當(dāng)包含在文件系統(tǒng)，但是當(dāng)包含在文件earth.wrl中時(shí)，就變成了局部坐標(biāo)系統(tǒng)。中時(shí)，就變成了局部坐標(biāo)系統(tǒng)。13.3 About VRML Hierarchical file inclusion enables the creation of arbi

60、trarily large, dynamic worlds. Therefore, VRML ensures that each file is completely described by the objects and files contained within it and that the effects of each file are strictly scoped by the file and the spatial limits of the objects defined in the file. Otherwise, the accumulation of files into large