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1、计算机图形学西安电子科技大学 计算机学院 计算机外部设备研究所 王义峰 135720446241教材和参考书o教材计算机图形学导论James D.Foley，董 士海等译，机械工业出版社。o主要参考书：l孙家广，计算机图形学（第三版），清华 大学出版社，1999。l唐泽圣，计算机图形学基础清华大学出版 社 2001。 lHill,F.S. “Computer Graphics Using Open GL”,Prentice Hall, 2001. 2教学要求o理解交互式计算机图形学o掌握2D图形学经典算法 o具备一定的图形应用系统开发能力 3第一章 计算机图形学概述 1.1 计算机图形学的应
2、用1.2 计算机图形学的基本概念1.3 计算机图形学的发展历史1.4 当前计算机图形学的研究热点41.1 计算机图形学应用1 ) Graphical User Interface (GUI) W.I.M.P - Windows, icons, menu, pointers Apple iPhoneTM52）GIS地理信息系统 o建立在地理图形之上的 关于各种资源的综合信 息管理系统o数字地球，地形数据作 为载体，全球信息化.o军事，政府决策，旅游 ，资源调查。 1.1 计算机图形学应用63) 建模（image, model creation）n坐标系统n数据生成n几何-观察变换 n裁剪-消隐n
3、颜色纹理 n光照阴影n绘制1.1 计算机图形学应用71.1 计算机图形学应用81.1 计算机图形学应用Frame from animation by William Latham, shown at SIGGRAPH 1992. Latham uses rules that govern patterns of natural forms to create his artwork.9CAD/CAM104）科学计算可视化(Scientific Visualization)n必要性：直接分析大量的测量数据或统计数 据有困难n目标：用图形表现抽象的数据n应用领域：医学图象重建，遥感，流场、气 象、
4、核爆模拟，有限元分析。1.1 计算机图形学应用111.1 计算机图形学应用12医学可视化13科学可视化145）多媒体系统在计算机控制下，对多种媒体信息进行生成、操作、 表现、存储、通信、或集成的信息系统。n计算机处理的常见媒体：文本、图形、图像、语 音、音频、视频、动画n特点：媒体多样性、操作交互性、系统集成性nCAI， 教学娱乐。1.1 计算机图形学应用156）数字娱乐o电脑动画、电脑游戏n实时性n逼真性n蕴含了先进的图形处理技术o电影特技，电视广告，节目片头、FLASH 采用的动画工具：MAYA, 3D-MAX, SOFTIMAGE1.1 计算机图形学应用16数字娱乐：电影17CG游戏与电
5、影Pixar: Monsters Inc. Square: Final Fantasy18CG 游戏197）计算机艺术o工具： Coreldraw, Photoshop等 o相片真实感模拟 与自然媒体仿真 技术 o分形艺术o乐谱，舞谱1.1 计算机图形学应用208）Virtual Reality是用计算机技术来生 成一个逼真的三维视、 听、触等感觉世界，让 用户可以从自己的视点 出发，利用自然的技能 和某些设备对这一生成 的虚拟世界客体进行浏 览和交互考察，如战斗 机驾驶模拟系统等 1.1 计算机图形学应用Mars data visualizationElumens VisionStation
6、21o计算机图形学定义o计算机图形学的研究内容1.2 图形学基本概念22What is Computer Graphics? (1/2)oComputer graphics generally means creation, storage and manipulation of models and imagesoSuch models come from diverse and expanding set of fields including physical, mathematical, artistic, biological, and even conceptual (abstra
7、ct) structureso计算机图形学(Computer Graphics，简称CG)是一种使用数学算法将二 维或三维图形转化为计算机显示器的栅格形式的科学。 随着以计算机 为主要工具进行视觉设计和生产的一系列相关产业的形成,国际上习惯 将利用计算机技术进行视觉设计和生产的领域通称为CG。 23oWilliam Fetter coined term “computer graphics” in 1960 to describe new design methods he was pursuing at BoeingoCreated a series of widely reproduced
8、 images on pen plotter exploring cockpit design, using 3D model of human body. “Perhaps the best way to define computer graphics is to find out what it is not. It is not a machine. It is not a computer, nor a group of computer programs. It is not the know-how of a graphic designer, a programmer, a w
9、riter, a motion picture specialist, or a reproduction specialist.Computer graphics is all these a consciously managed and documented technology directed toward communicating information accurately and descriptively.”Computer Graphics, by William A. Fetter, 1966What is Computer Graphics? (2/2)24图形的输入
10、 如何开发利用图形输入设备及软件将图形输入 到计算机中去，以便作各种处理。 图形的处理 包括对图形进行变换(几何变换，投影变换)和 运算（集合运算）,着色，形变等 图形的输出如何将图形格式转换、并在显示屏或打印机等 输出设备上输出。计算机图形学的研究内容25图形与图像图像生成（计算机图形学）模型（特征）提取 （计算机视觉，模式识别）模型变换 （计算几何）数 字 图 像数 据 模 型图像变换 （图像处理）发展特点: 交叉、界线模糊、相互渗透采样 量化 滤波 增强26基于采样的图形（光栅，点阵)oImages are made up of grid of discrete pixels, for
11、2D “picture elements”Mathematical pixel gridLCD displayCRT beam illumination patternNB: Cant resolve adjacent pixels on CRT1 pixellight intensity27采样oLets do some sampling of CIT buildingoA color value is measured at every grid point and used to color corresponding grid squareoNote: this poor sampli
12、ng and image reconstruction method creates blocky image3D scene0 = white, 5 = gray, 10 = black28oOnce image is defined in terms of colors at (x, y) locations on grid, can change image easily by altering location or color valuesoE.g., if we reverse our mapping above and make 10 = white and 0 = black,
13、 the image would look like this:oPixel information from one image can be copied and pasted into another, replacing or combining with previously stored pixelsWhats the Advantage?29Whats the Disadvantage?oWYSIAYG (What You See Is All You Get): No additional informationnno depth informationncant examin
14、e scene from different point of viewnat most can play with the individual pixels or groups of pixels to change colors, enhance contrast, find edges, etc.oBut recently, strong interest in image-based rendering to fake 3D scenes and arbitrary camera positions. New images constructed by interpolation,
15、composition, warping and other operations.Photo Tourism: Exploring photo collections in 3D (Siggraph 2006)30Examples of 2D Image Manipulation (1/3)The news: digitally “enhanced” images are more and more common. Usually just sharpening, color balancing, but sometimes much more. To “Photoshop somethin
16、g in”: Reuters doctored Beirut bombing photo (below right; note cloned smoke) else31Examples of 2D Image Manipulation (2/3)oPeople can now mutate into other people or objects through morphing, and can carry on conversations in different times and placesnInteractive Digital Photomontage, Siggraph 2004眼见为实？32Examples of 2D Image Manipulation (3/3)oIn artwork the processes and techniqu
