05计算机图形学双语课程is computer graphics

1、Chapter 1 Graphics Systems and Models(What is Computer Graphics?)原著Ed AngelProfessor of Computer Science, Electrical and Computer Engineering, and Media ArtsUniversity of New Mexico编辑 武汉大学计算机学院图形学课程组ObjectivesIn this lecture, we explore what computer graphics is about 1.1 A survey of some applicatio

2、n areas1.2 Graphics system and hardware1.3 A brief introduction to history of computer graphicsComputer GraphicsComputer graphics deals with all aspects of creating images with a computerHardwareSoftwareApplicationsExampleWhere did this image come from?What hardware/software did we need to produce i

3、t?Preliminary Answer(a top-down answer)Application: The object is an artists rendition 表演 of the sun for an animation to be shown in a domed 有穹顶的 environment (planetarium 天文馆)Software: Maya for modeling and rendering but Maya is built on top of OpenGLHardware: PC with graphics card for modeling and

4、rendering1.1 Application areas of graphics1.1.1 Display of information1.1.2 Design1.1.3 Simulation and animation1.1.4 User interfaces1.1.1 Display of information (Graphs and charts)Graphs and chartsEarly application of computer graphic: data plotting 绘图Typical examplesLine graphs, bar charts, pie ch

5、arts, surface graphsApplication areasSummarize data for research reportsManagerial summariesConsumer information医学CT、MRI、PET1.1.1 Display of information (Printed Media)Computer Graphics plays a major role inpublishing with page layout, paint, and image processing programs1.1.2 Design (Computer Aided

6、 Design, CAD)Computer graphics has had a dramatic impact on the design and engineering processMechanical designElectronic designArchitectural designProduct designIf you can imagine it, it can be done with computer graphicsHollywood big screen mega-productions, music videos1.1.3 Simulation and animat

7、ion（ Graphics is Entertainment ! ）1.1.3 Simulation and animation （Animated Features）Toy Story IIPixar (2000)ShrekPDI (2001)Monsters, Inc.Pixar (2001)1.1.3 Simulation and animation （Graphics got Game!）Like it or not: Computer games drive todays interactive graphics technology$10 billion industry - la

8、rger than TV and moviesGame characters have e celebrities 名人, often with their own moviesThe lines between games and entertainment (movies) continue to be blurred 模糊 (M-G, G-M)1.1.3 Simulation and animation （Graphics got Game!）How the games industry impacts computer graphics:Games drive graphics har

9、dware developmentFocus on interactivityCost-effective solutions and tricks 窍门Entertainment / art medium of the 21st century1.1.3 Simulation and animation (Education and training)Various special hardware setting for simulation1.1.3 Simulation and animation (Virtual Reality Environment)Virtual reality

10、 environmentInteract with the objects in a three-dimensional environmentsAnimations in virtual reality environments helps in analyzing interactive effectse.g. Train heavy-equipment operators1.1.3 Simulation and animation (Virtual and Augmented Reality)Virtual Reality (VR) immerses the viewer into a

11、synthetic 合成的 worldWe distinguish between immersive 沉浸 virtual reality and augmented 增强 realityIvan Sutherland, the creator of the first computer graphics system, worked in the 1960s on “the ultimate display”, a head-mounted set of tiny screens1.1.3 Simulation and animation (Virtual and Augmented Re

12、ality)Virtual Reality虚拟现实（VR），也称灵境技术或人工环境。利用电脑模拟产生一个三维空间的虚拟世界，提供使用者关于视觉、听觉、触觉等感官的模拟，让使用者如同身临其境一般，可以及时、没有限制地观察三度空间内的事物。Augmented Reality增强现实（AR），也称之为混合现实。它通过电脑技术，将虚拟的信息应用到真实世界，真实的环境和虚拟的物体实时地叠加到了同一个画面或空间同时存在。增强现实不仅展现了真实世界的信息，而且将虚拟的信息同时显示出来，两种信息相互补充、叠加。1.1.4 User interfaces(Graphical User Interface, GU

13、I) Graphical user interface (GUI)Major components: display windows, screen cursor, selection menus and iconsExampleGUI showing multiple display windows微软亚洲研究院1.1.4 User interfaces (Interaction)Computer graphics is an integral part of every day computingUse graphics in order to present output to user

14、s1.2 Graphics System and hardware 1. Input devices5. Output device4. Frame Buffer, FBFig 1.1 A graphics system2. processor3. MemoryGraphics HardwareGraphics LibraryApplicationdisplaysimagedisplay devicetalks totalks toModern Graphics System1.2.1 Pixel and the Frame Buffer (Raster 光栅 Graphics)Image p

15、roduced as an array (the raster) of picture elements (pixels) in the frame bufferFig 1.2 Pixel (a) Image of the cat. (b) Detail of area around one eye showing individual pixels.Frame buffersIntensity of the raster scan beam is modulated调整 according to the contents of a framebufferEach element of the

16、 framebuffer is associated with a single pixel on the screenThe brightness of a pixel is controlled by the voltage 电压 coming from the DAC (digital-analog converter 数模转换)PixelFramebufferDisplayDACsRaster Graphics Raster-Scan Display PrinciplesSample of Raster-Scan displays principlesRaster-Scan syste

17、msOrganization of raster systemFixed area of system memory reserved for framebuffer which can be directly accessed by video controllerCPUSystemMemoryVideoControllerMonitorSystem BusI/O DevicesRaster-Scan systemsVideo ControllerRefresh operations 刷新操作X, Y register used to indicate pixel positionFix Y

18、 register and increment X register to generate scan lineDouble bufferingPixel value can be loaded in buffer while Provide a fast mechanism for real-time animation generationRaster-Scan SystemsRaster-Scan Display ProcessorFree the CPU from the graphics chores 杂事Provide separate display-processor memo

19、ryFig. Architecture of raster-scan display system withdisplay processorCPUSystemMemoryVideoControllerSystem BusI/O DevicesDisplay Processormemory(Frame Buffer)DisplayProcessorMonitorDisplay ProcessorRather than have the host computer try to refresh display, use a special purpose computer called a di

20、splay processor (DPU)Graphics stored in display list (display file) on display processorHost compiles display list and sends to DPU291.2.2 Output DevicesCan be used either asA line-drawing device (calligraphic 线画模式) orTo display contents of frame buffer (raster mode 光栅模式)CRTFig 1.3 The cathode-ray t

21、ube (CRT)Scan controllerDigital-to-Analog ConvertersColor CRT MonitorsColor CRT MonitorsColor CRT Monitors: Raster DisplaysRaster Displays: 通过 Video Controller, Frame Buffer, Shadow Mask 等实现。Color CRT Monitors : True-Color SystemsThe term true-color is sometimes used to refer to systems which the fr

22、amebuffer directly stores the values of each channel.Even true-color systems often use color tables. In this case, there is a separate color table for each 8 bit channel.(28*2*8*28 = 224), 24 bit true-colorColor CRT Monitors : Raster Displays : Refresh 刷新, Flicker 闪烁, Scan Line 扫描线Color CRT Monitors

23、: shadow mask CRT Operation of delta-delta, shadow mask CRTRequires manufacturing very precise geometryAligned metal shadow mask (荫罩/荫栅)Summary of raster graphics hardwarePixel 象素Picture elementRaster 光栅Array of pixelsFrame Buffer 帧缓存Memory where pixels storedDepth 深度 of Frame Buffer Number of bits

24、that are used for each pixel (ex. 8-bit-depth 28(=256) colors, 24 or more bits per pixel RGB-color)Summary of raster graphics hardwareResolution 分辨率Number of pixels in frame bufferRasterization 光栅化 (Scan Conversion扫描转换)Converting of geometric entities (such as lines, circles, and polygons) to pixel

25、assignment in frame buffer Refresh Rate 刷新率Rate of retracing （折回） on displaysAs refresh rate slows below 60Hz, flicker developsGraphic vs. Image （图形和图像间的关系）Flat-Panel DisplaysA class of video devices that have reduced volume, weight and power requirement compared with CRTTwo main categoriesEmissive

26、发光 DisplaysConvert electrical energy to light energye.g. Plasma 等离子 panelsNon-emissive DisplaysUse optical effects to convert light from other sources into graphics patternse.g. LCD 液晶显示器 monitorsLiquid Crystal Displays (LCD)Liquid-crystal material: long crystalline moleculesThe molecules arrange in

27、 a spiral fashion (twisted nematic cell)Light change to polarized light, vertical or horizontalLight rotate 90 degree through the twisted nematic cellLiquid Crystal Displays (LCD)Add an electric fieldthe molecules arrange in same directionLight dont change the polarization, light remains verticallyV

28、ertical light can not pass through the horizontal polarizer: the light is absorbed, and the viewer sees a dark spot on the displayLCD显示器的基本指标可视角度视线与屏幕中心法向成一定角度时，人们就不能清晰地看到屏幕图像，而那个能看到清晰图像的最大角度被我们称为可视角度。一般所说的可视角度是指左右两边的最大角度相加。工业上有CR10（Contrast Ratio）、CR5两种标准来判断液晶显示器的可视角度。较小尺寸的15英寸或15英寸以下的LCD显示器，120度的可

29、视角度便足以显示完整的画面；对于17英寸及以上的大尺寸LCD显示器，140至160度的可视角度是基本指标。41LCD显示器的基本指标点距与分辨率液晶屏幕的点距就是两个液晶颗粒（光点）之间的距离，一般0.280.32mm就能得到较好的显示效果通常所说的液晶显示器的分辨率是指其真实分辨率，表示水平方向的像素点数与垂直方向的像素点数的乘积刷新频率液晶低于CRT原因：液晶原理是分子的扭曲；CRT原理是电子流的发射存在某些需要高刷新频率的应用，如时分法立体影视高速液晶面板已出现，如索尼的240Hz无残影运动补偿技术42Plasma Panels Array of tiny neon bulbs (gla

30、ss sheet with holes) between two addressing grids of wires. The hysteresis 磁滞 in discharge tube physics allows matrix addressing to be used to turn bulbs on and off high voltage initiates, lower voltage maintains. Can be changed one row at a time. Does not need to be refreshed. Expensive.1.2.3 Input

31、 DevicesKeyboardsMouse DevicesData GlovesTrackball and SpaceballJoysticksDigitizersImage ScannerOther input devicesStandard Input Devices Keyboard- For alphanumeric 文本 input. Mouse/Trackball- A two degrees of freedom device controlled by rolling a ball.- Provides relative movement information.2D Inp

32、ut Devices Joystick- Controlled by potentiometers 电位计- Provides relative movement information. Digitizer/Tablet- Controlled by electro - magnetic or sonar sensing.- Provides absolute position information. Touch Screen- A screen that can sense pressure on its surface. Light Pen- Synchronized with the

33、 CRT scan, it can locate a position on screen.3D Input DevicesWired Glove / Data GloveProvides six degrees of freedom (three rotation/translation) Head Mounted DisplayMeasures position and orientation like the Wired Glove Space BallSix degrees of freedom sphere (three rotation/translation)Haptic 触觉

34、DevicesSix degrees of freedom with Force Feedback1.3 A History of Computer Graphics1950-19601970-19801980-19902000-2010Computer Graphics: 1950-1960Computer graphics goes back to the earliest days of computingStrip chartsPen plottersSimple displays using A/D converters to go from computer to calligra

35、phic CRTCost of refresh for CRT too high Computers slow, expensive, unreliableCRT Display MIT: 1950The Whirlwind Computer 旋风计算机 had computer-driven Cathode Ray Tube (CRT) displays for output. Using CRT displayIt is possible to drawing computer graphicsWhirlwind IComputer Graphics: 1960-1970Wireframe

36、 graphicsDraw only linesSketchpadDisplay ProcessorsStorage tube 存储管wireframe representationof sun objectSutherland and SketchpadIvan Sutherlands PhD thesis at MITRecognized the potential of man-machine interaction Sketchpad allowed interactive design on a vector graphics display monitor with a light

37、 pen input device.LoopDisplay somethingUser moves light penComputer generates new displaySutherland also created many of the now common algorithms for computer graphics图灵奖得主The Origins of Computer GraphicsIn 1963 Ivan Sutherland presented his paper “Sketchpad: A man-machine graphical communication s

38、ystem” at the Summer Joint Computer Conference. The Origins of Computer GraphicsMost people mark Sutherland and Sketchpad as the origins of CAD & computer graphics (1963)DAC-1 CAD System by IBM for GM (1959)first CAD system (IBM 1959)The Origins of Computer Graphics1964年美国人道格拉斯恩格尔巴特（Douglas Englebar

39、t）在斯坦福研究所制作了第一只鼠标器只有一个按键，外壳用木头雕刻而成，底部有金属滚轮，但当时并不被重视。直到1979年12月，施乐PRAC研究中心的科学家拉瑞泰斯勒（L.Tesler）演示了窗口、图标、菜单，还有随着”鼠标器“移动的光标，鼠标的重大历史意义在这一刻才真正得到显示。Display ProcessorRather than have the host computer try to refresh display use a special purpose computer called a display processor (DPU)Graphics stored in dis

40、play list (display file) on display processorHost compiles display list and sends to DPUDirect View Storage Tube 存储管Created by TektronixDid not require constant refreshStandard interface to computersAllowed for standard softwarePlot3D in FortranRelatively inexpensiveOpened door to use of computer gr

41、aphics for CAD communityComputer Graphics: 1970-1980Raster GraphicsBeginning of graphics standardsIFIPSGKS: European effort es ISO 2D standardCore: North American effort 3D but fails to e ISO standardWorkstations and PCsRaster GraphicsImage produced as an array (the raster) of picture elements (pixe

42、ls) in the frame bufferRaster GraphicsAllows us to go from lines and wire frame images to filled polygonsPCs and WorkstationsAlthough we no longer make the distinction between workstations and PCs, historically they evolved from different rootsEarly workstations characterized byNetworked connection: client-server modelHigh-level of interactivityEarly PCs included frame buffer as part of user memoryEasy to change contents and create imagesGraphical User Interface70年代施乐公司在Alto计算机上首次开发了位映像图形显示技术，为开发可重叠窗口、弹出式菜单、菜单条等提供了可能。这些工作奠定了图形用户界面的基础，形成了以窗口（Windows