Introduction to Computer Graphics                        Pradondet Nilagupta                   Dept. of Computer Engineeri...
Lecture Outline        Course Information: Format, Resources        Overview            Topics covered            What...
Course Info and Administrative     Instructor: Pradondet Nilagupta         E-mail: pom@ku.ac.th         Phone: 9428555 ...
Course Overview (1/2)        Graphics Systems and         Techniques            2-D, 3-D models: surfaces,             v...
Course Overview (2/2)        Mathematical Review            Review of mathematical foundations of CG:             analyt...
Relevant Disciplines                                         Rendering Hardware                 CAD                       ...
What is Computer Graphics?204481 Foundation of Computer Graphics   March 7, 2013   7
This is not Computer Graphics                    1%                     8             9%                                  ...
What is Computer Graphics ?        Computer graphics is commonly         understood to mean the creation, st         orag...
Computer Graphics        Computer Graphics            Synthesis of graphical images            Visualization :         ...
Image Processing        Image Processing            the transformation of an existing image into a             more desi...
Image Analysis        Image Analysis (Computer Vision)             extracting symbolic information from the             ...
What is Interactive Computer Graphics?        User controls contents, structure, and         appearance of objects and th...
Why Computer Graphics? (1/5)        Humans communicate well with images            1/3 of your brain is devoted to visua...
Why Computer Graphics? (2/5)        Developing Computational Capability            Rendering: synthesizing realistic-loo...
Why Computer Graphics? (3/5)        Better Understanding of Data, Objects,         Processes through Visualization       ...
Why Computer Graphics? (4/5)        Time is Right            Recent progress in algorithms and theory            Rapidl...
Why Computer Graphics? (5/5)        advances in the last decade due mostly to the         microchip        software adva...
Image Synthesis Pipeline  Graphics  Database   Editing                                    Front-End    Graphics    Databas...
A Brief History         teletype printouts were first graphical output devices          lightpens were an early input dev...
History of Computer Graphics (1/5)      1950 MIT’s Whirlwind       computer had computer       generated CRTs mid 19     ...
History of Computer Graphics (2/5)        1960s GM (general Motor)            developed CAD (Computer Aided Design) and ...
History of Computer Graphics (3/5)          Mid 1970s engineering workstations and           personal computers emerged s...
History of Computer Graphics (4/5)     At first - progress was slow because      cost of equipment was high (specially   ...
History of Computer Graphics (5/5)     Now - previous use      cost of equipment is low.      Most computer have necessa...
Some of Historical Picture (1/2)                            First truly interactive graphics                             ...
Some of Historical Picture (2/2)                                    http://www.man.ac.uk/Science_Engineering/CHSTM/nahc.ht...
Applications of Computer Graphics     Applications of Computer Graphics      divided in 4 majors area         Display of...
Display of Information        Geographic         information system         (GIS)        Computerized         Tomography...
Design        Computer-Aided Design (CAD)          Architecture          Design of Mechanical part          VLSI      ...
Simulation        Graphical flight simulator            reduce training process        Robotic simulation              ...
User Interfaces        Window system          Window 2003          X window          MAC OS        Graphical Network ...
Areas of research in Graphics (1/2)        mathematical modeling:            interpolation, curve and surface fitting   ...
Areas of research in Graphics (2/2)        Software technology            standardized graphics languages and libraries ...
Graphics Applications        Entertainment: Cinema                       Pixar: Geri’s Game                              ...
Graphics Applications (1/4)         Entertainment: Games                                                                 ...
Graphics Applications (2/4)          Medical Visualization                                                               ...
Graphics Applications (3/4)        Computer Aided Design (CAD)204481 Foundation ofComputer Graphics        March 7, 2013 ...
Graphics Applications (4/4)        Scientific Visualization204481 Foundation ofComputer Graphics            March 7, 2013...
Hypermedia User Interfaces (1/2)                                                  NCSA D2K:                               ...
Hypermedia User Interfaces (2/2)        Virtual Environments            Immersion: interactive             training, tut...
Curve and Surface Modeling          1            http://www.geocities.com/SiliconValley/Lakes/2057/nurbs.html             ...
Photorealistic Illumination Models                                http://www.pixar.com http://www.ktx.com/3dsmaxr3/       ...
Fractal Systems204481 Foundation of                   http://sprott.physics.wisc.edu/fractals.htmComputer Graphics        ...
Information Visualization204481 Foundation of          Visible Decisions SeeIT        (http://www.vdi.com)Computer Graphic...
Interesting Industrial Applications                                                 6500 news stories                     ...
Overview of Programmer’s Model (1/2)        Pixel - smallest addressable unit of display        Hardware (I/O)         ...
Overview of Programmer’s Model (2/2)     Software      application data      application program      graphics interfac...
Graphical System And Standard         (1/5)        Graphical Systems            High level language interface to graphic...
Graphical System And Standard         (2/5)        Requirements of Graphical Systems            Portability             ...
Graphical System And Standard         (3/5)        Graphical Kernel System (GKS)          Workstation                GK...
Graphical System And Standard       (4/5)           Output Functions                              Line-Drawing Primitive...
Graphical System And Standard       (5/5)           Input Modes                            Request mode: waits for a req...
Professional Societies     ACM SIGGRAPH     - Association for Computing       Machinery Special Interest G       roup in G...
Software Portability and graphics       standards     STANDARD       ORGANIZATION      ANSI = American National       Sta...
History: graphics libraries        initially, low-level device-dependent         packages were the norm        movement ...
Official Standards        1977 and 1979 - 3D SIGGRAPH CORE (ACM         SIGGRAPH)        3D Core Graphics System ("Core"...
Emerging Standards in APIs        OpenGL (developed by Silicon Graphics)            open standard            available ...
Some Notable Systems        Tektronix commands in BASIC (mid-1970s)        HP commands (Hewlett Packard)        Microso...
Good graphics requires ? (1/3)        ability to control every dot (pixel) of display        ability to control primitiv...
Good Graphics requires ? (2/3)        mathematical transformations and         representations        transmission of pi...
Good Graphics requires ? (3/3)      understanding and manipulation of       data structures      good software engineeri...
Lecture Topics      Introduction            Visible Surface      Mathematical            Determination       Foundation...
Mathematical foundation        Mathematical appears throughout 3D graphics     Example:        Object surfaces can be re...
Geometric transformation      Goal: specify object’s position and       orientations in a 3D world      Use Linear trans...
Viewing      Goal: map the visible part of a 3D       world to a 2 D image      Use camera-like parameters to define    ...
OpenGL        OpenGL is strictly defined as “a software         interface to graphics hardware”.        It is a 3D graph...
Clipping        Goal: cut off the part of objects outside         the view volume to avoid rendering         them204481 F...
Scan Conversion      Goal: convert a project, clipped object       into pixels on raster lines.      Use efficient incre...
Antialiasing      Raster displays produce blocky       aliasing artifacts      Antialiasing techniques reduces the      ...
Color      Various color spaces provide ways to       specify colors in term of components:      red, green, blue      ...
Hidden Surface Removal         When several overlapping polygons are          drawn on the screen, which one is on       ...
Z-buffering        A fast hardware solution is   This pixel is                                       drawn on         the...
Lighting Models and Shading     For visual realism, lighting             Ambient lighting:      models have been develope...
Ray Tracing                                               Light Source                                               Shado...
Radiosity        Diffuse illumination         results from the         absorption and reflection         of diffuse light...
Texture Mapping        For realism, photographic textures are         “mapped” onto the surfaces of objects        Examp...
Example of Shading         Wireframe               Flat Shaded        Smooth Shaded             Shadows204481 Foundation o...
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  • Many hidden surface removal algorithms have been developed
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    1. 1. Introduction to Computer Graphics Pradondet Nilagupta Dept. of Computer Engineering Kasetsart University204481 Foundation of Computer Graphics March 7, 2013 1
    2. 2. Lecture Outline  Course Information: Format, Resources  Overview  Topics covered  What is computer graphics?  Applications204481 Foundation ofComputer Graphics March 7, 2013 2
    3. 3. Course Info and Administrative  Instructor: Pradondet Nilagupta  E-mail: pom@ku.ac.th  Phone: 9428555 ext. 1415 (office)  Office hours: after class; 1-2pm Monday or by appointment  Web Page  Course Homepage: http://www.cpe.ku.ac.th/~pom/courses/204481/ 204481.html  Course Syllabus: http://www.cpe.ku.ac.th/~pom/courses/204481/syllabus.html204481 Foundation ofComputer Graphics March 7, 2013 3
    4. 4. Course Overview (1/2)  Graphics Systems and Techniques  2-D, 3-D models: surfaces, visible surface identification, illumination  Photorealistic rendering : shading models, ray tracing, radiosity  Operations  Surface modeling, mapping  Pipelines for display, transformation, illumination204481 Foundation ofComputer Graphics March 7, 2013 4
    5. 5. Course Overview (2/2)  Mathematical Review  Review of mathematical foundations of CG: analytic geometry, linear algebra  Line and polygon rendering  Matrix transformations204481 Foundation ofComputer Graphics March 7, 2013 5
    6. 6. Relevant Disciplines Rendering Hardware CAD Immersive Training VR Systems CAE / CASE  Analytic Geometry Portable/Embedded CG CAM Tutoring Interfaces  Art and Graphic Design  Cognitive Science Color/Optical Models CG/Vision Duality  Computer Engineering Interface Design  Engineering Design Layout CG Design  Education Visualization  Film Parametric Equations  Human Factors Conics Computer Polygon Rendering  Linear Algebra Graphics  Numerical Analysis (CG) Surface Modeling Physically-Based Modeling Stat/Info Visualization Transformations Change of Coordinate Systems User Modeling Animation204481 Foundation of Ergonomic Interfaces, I/O Large-Scale CGComputer Graphics March 7, 2013 6
    7. 7. What is Computer Graphics?204481 Foundation of Computer Graphics March 7, 2013 7
    8. 8. This is not Computer Graphics 1% 8 9% 1 2 3 4 4% 6 2% 7  [ 29:akin@sgi.com ] Re: Future development of PEX/PHIGS]  [ 9:bthompso@reed] What is a good book for Digital Image Processing]  [ 15:csp48@seq1.ke] Help! ASCII picture needed…  [ 14:rcj2@cbnewsd.] Re: 3D igitizers… again  [240:raj@ms.uky.ed] Call For Papers -- ACM Multimedia 93204481 Foundation ofComputer Graphics March 7, 2013 8
    9. 9. What is Computer Graphics ?  Computer graphics is commonly understood to mean the creation, st orage and manipulation of models a nd images. (Andries van Dam)  Computer graphic is concerned with  all aspects of producing pictures or images using a computer.  the pictorial synthesis or real or imaginary objects from their computer based model204481 Foundation ofComputer Graphics March 7, 2013 9
    10. 10. Computer Graphics  Computer Graphics  Synthesis of graphical images  Visualization :  creating an image from an abstract, symbolic description.  Generation of Synthesis Image  using graphical primitives  data from real world phenomena204481 Foundation ofComputer Graphics March 7, 2013 10
    11. 11. Image Processing  Image Processing  the transformation of an existing image into a more desirable or useful image.  image enhancement, pattern detection The following images represent how noise affects images204481 Foundation ofComputer Graphics March 7, 2013 11
    12. 12. Image Analysis  Image Analysis (Computer Vision)  extracting symbolic information from the image. Computer Graphics Data => Picture Image Processing Picture => Picture204481Image Analysis of Foundation Picture => DataComputer Graphics March 7, 2013 12
    13. 13. What is Interactive Computer Graphics?  User controls contents, structure, and appearance of objects and their displayed images via rapid visual feedback  Basic components of an interactive graphics system  input (e.g., mouse, tablet and stylus, force feedback device,scanner…)  processing (and storage)  display/output (e.g., screen, paper-based printer, video recorder…)204481 Foundation ofComputer Graphics March 7, 2013 13
    14. 14. Why Computer Graphics? (1/5)  Humans communicate well with images  1/3 of your brain is devoted to visual processing  A picture is worth a few hundred megabytes204481 Foundation ofComputer Graphics March 7, 2013 14
    15. 15. Why Computer Graphics? (2/5)  Developing Computational Capability  Rendering: synthesizing realistic-looking, useful, or interesting images  Animation: creating visual impression of motion  Image processing: analyzing, transforming, displaying images efficiently204481 Foundation ofComputer Graphics March 7, 2013 15
    16. 16. Why Computer Graphics? (3/5)  Better Understanding of Data, Objects, Processes through Visualization  Visual summarization, description, manipulation  Virtual environments (VR), visual monitoring, interactivity  Human-computer intelligent interaction (HCII): training, tutoring, analysis, control systems204481 Foundation ofComputer Graphics March 7, 2013 16
    17. 17. Why Computer Graphics? (4/5)  Time is Right  Recent progress in algorithms and theory  Rapidly emergence of new I/O (display and data acquisition) technologies  Available computational power, improving price- performance-ratio of hardware  Growth and interest of graphics industries (e.g., information visualization, entertainment CAD)204481 Foundation ofComputer Graphics March 7, 2013 17
    18. 18. Why Computer Graphics? (5/5)  advances in the last decade due mostly to the microchip  software advances, especially in object-oriented programming and real-time rendering algorithms  Hardware advances continue to benefit graphics:  faster inexpensive microprocessors and dedicated graphics chips  screen technology: High-definition television (HDTV), colour LCD  virtual reality interfaces (corneal implants?)204481 Foundation ofComputer Graphics March 7, 2013 18
    19. 19. Image Synthesis Pipeline Graphics Database Editing Front-End Graphics Database (Geometry Processing) Back-End Display Traversal Modeling Transformation Viewing Operation  (Rasterization) • Visible-Surface Determination • Scan Conversion Image • Shading / Illumination204481 Foundation ofComputer Graphics March 7, 2013 19
    20. 20. A Brief History  teletype printouts were first graphical output devices lightpens were an early input device CAD applications beg an in the 1960s plotters also a 60s development: high-res olution, but slow main bottlenecks of computer graphics ba ck then  cost of graphics hardware  expense of computer resources batch systems werent suitable for interactive graphics non-portability of hardware and software a new field: technology was 204481 primitive Foundation ofComputer Graphics March 7, 2013 20
    21. 21. History of Computer Graphics (1/5)  1950 MIT’s Whirlwind computer had computer generated CRTs mid 19 50s SAGE command an d control  1960s Ivan Sutherland’s thesis - Sketchpad  introduced data structures and interactive techniques http://www.computer.org/history/development/1951.htm204481 Foundation ofComputer Graphics March 7, 2013 21
    22. 22. History of Computer Graphics (2/5)  1960s GM (general Motor)  developed CAD (Computer Aided Design) and CAM  1968 Tektronix storage tubes  1970s Boeing CAD CAM204481 Foundation ofComputer Graphics March 7, 2013 22
    23. 23. History of Computer Graphics (3/5)  Mid 1970s engineering workstations and personal computers emerged separately  1980s new algorithms and techniques  new standards  ever more powerful system  transition from specialized field  1990s widespread use low cost, but powerful personal workstations   networks  essential part of systems  now part of multimedia204481 Foundation ofComputer Graphics March 7, 2013 23
    24. 24. History of Computer Graphics (4/5) At first - progress was slow because  cost of equipment was high (specially memory)  significant computing resources needed  difficulty in writing software ( harder than it looks)  lack of standard and thus portability  lack of software tools204481 Foundation ofComputer Graphics March 7, 2013 24
    25. 25. History of Computer Graphics (5/5) Now - previous use  cost of equipment is low.  Most computer have necessary computing resources for graphics  established standards, implementations and tools  still difficulty in writing software ( still harder than it looks)204481 Foundation ofComputer Graphics March 7, 2013 25
    26. 26. Some of Historical Picture (1/2)  First truly interactive graphics system, Sketchpad, pioneered at MIT by Ivan Sutherland for h is 1963 Ph.D. thesis. Sketchpad , A Man-Machine Graphical Comm unication System:  Sketchpad in 1963. Note the use of a CRT monitor, light pe n and function-key panel.204481 Foundation ofComputer Graphics March 7, 2013 26
    27. 27. Some of Historical Picture (2/2) http://www.man.ac.uk/Science_Engineering/CHSTM/nahc.htm John VonNeuman http://ei.cs.vt.edu/~history/VonNeumann.html Mark I204481 Foundation ofComputer Graphics March 7, 2013 27
    28. 28. Applications of Computer Graphics Applications of Computer Graphics  divided in 4 majors area  Display of Information  Design  Simulation  User Interface204481 Foundation ofComputer Graphics March 7, 2013 28
    29. 29. Display of Information  Geographic information system (GIS)  Computerized Tomography (CT)  Magnetic resonance http://www.soest.hawaii.edu/soest/about.ftp.html imaging (MRI)  Ultrasound  positron-emission tomography (PET)204481 Foundation of http://www.queens.org/qmc/services/imaging/ct.htmComputer Graphics March 7, 2013 29
    30. 30. Design  Computer-Aided Design (CAD)  Architecture  Design of Mechanical part  VLSI  etc... http://www.memagazine.org/contents/current/features/push/push.html204481 Foundation ofComputer Graphics March 7, 2013 30
    31. 31. Simulation  Graphical flight simulator  reduce training process  Robotic simulation The Concorde Panel.  TV, Movie, advertising industries  generate photo realistic images  Virtual Reality (VR)  reduce risk of training  surgery  astronaut204481 Foundation of http://www.motionshop.com/pr/festocosimirlg.shtmlComputer Graphics March 7, 2013 31
    32. 32. User Interfaces  Window system  Window 2003  X window  MAC OS  Graphical Network browsers  Netscape  Internet Explorer204481 Foundation ofComputer Graphics March 7, 2013 32
    33. 33. Areas of research in Graphics (1/2)  mathematical modeling:  interpolation, curve and surface fitting  computational geometry: algorithmic applications in geometry  study of light and optical phenomenon: colour, texture, shades  modelling the characteristics of physical objects (bouncing Jello)204481 Foundation ofComputer Graphics March 7, 2013 33
    34. 34. Areas of research in Graphics (2/2)  Software technology  standardized graphics languages and libraries  graphics tools and interfaces  algorithm design  Hardware  specialized graphics chips, monitors, interface devices204481 Foundation ofComputer Graphics March 7, 2013 34
    35. 35. Graphics Applications  Entertainment: Cinema Pixar: Geri’s Game Universal: Jurassic Park Antz204481 Foundation of A bug’s LifeComputer Graphics March 7, 2013 35
    36. 36. Graphics Applications (1/4)  Entertainment: Games Aki Ross : Final Fantasy Star Wars Jedi Outcast: Jedi Knight II204481 Foundation of Quake IIIComputer Graphics March 7, 2013 36
    37. 37. Graphics Applications (2/4)  Medical Visualization The Visible Human Project204481 Foundation of http://www.ercim.org/publication/Ercim_News/enw44/koenig.htmlComputer Graphics March 7, 2013 37
    38. 38. Graphics Applications (3/4)  Computer Aided Design (CAD)204481 Foundation ofComputer Graphics March 7, 2013 38
    39. 39. Graphics Applications (4/4)  Scientific Visualization204481 Foundation ofComputer Graphics March 7, 2013 39
    40. 40. Hypermedia User Interfaces (1/2) NCSA D2K: http://chili.ncsa.uiuc.edu Visual programming system for high-performance knowledge discovery in databases (KDD)  Hypermedia  Database format (similar to hypertext) that provides display-based access to (internetworked) multimedia (text, image, audio, video, etc.) documents  Chimera: http://www.ics.uci.edu/pub/chimera/204481 Foundation ofComputer Graphics March 7, 2013 40
    41. 41. Hypermedia User Interfaces (2/2)  Virtual Environments  Immersion: interactive training, tutoring systems  Entertainment hypermedia  Visualization and Computer- Aided Design and Engineering (CAD/CAE)  Visualization: scientific, data/information, statistics  User interfaces for CAD/CAE/CAM/CASE: http://www.isii.com http://www.psl.cs.columbia.edu/chime/204481 Foundation ofComputer Graphics March 7, 2013 41
    42. 42. Curve and Surface Modeling 1 http://www.geocities.com/SiliconValley/Lakes/2057/nurbs.html 2 3 4 5 8 7 6204481 Foundation ofComputer Graphics March 7, 2013 42
    43. 43. Photorealistic Illumination Models http://www.pixar.com http://www.ktx.com/3dsmaxr3/ http://www.aliaswavefront.com204481 Foundation ofComputer Graphics March 7, 2013 43
    44. 44. Fractal Systems204481 Foundation of http://sprott.physics.wisc.edu/fractals.htmComputer Graphics March 7, 2013 44
    45. 45. Information Visualization204481 Foundation of Visible Decisions SeeIT (http://www.vdi.com)Computer Graphics March 7, 2013 45
    46. 46. Interesting Industrial Applications 6500 news stories from the WWW in 1997 Cartia ThemeScapes – http://www.cartia.com Hypermedia and Statistical Visualization Destroyed Normal Extinguished Ignited Fire Alarm Engulfed Flooding Virtual Environments for204481 Foundation of DC-ARM – http://www-kbs.ai.uiuc.edu Immersive TrainingComputer Graphics March 7, 2013 46
    47. 47. Overview of Programmer’s Model (1/2)  Pixel - smallest addressable unit of display  Hardware (I/O)  output display device (normally raster scan)  on the order of a million pixels displayed  image stored in memory by pixel (how much memory?)  video controller  scans the memory periodically (30-72 times a second) produces video signal to drive a video monitor (or flat screen di splay)  input devices - keyboard, mouse (track ball), tablet, voice etc.204481 Foundation ofComputer Graphics March 7, 2013 47
    48. 48. Overview of Programmer’s Model (2/2) Software  application data  application program  graphics interface  operating system204481 Foundation ofComputer Graphics March 7, 2013 48
    49. 49. Graphical System And Standard (1/5)  Graphical Systems  High level language interface to graphical devices.  Intended for development of portable code.  Standard graphical systems include CORE,   Graphical Kernel System (GKS), GKS+  Programmers Hierarchical Interactive Graphics System (PHIGS), PHIGS+  OpenGL, DirectX, Quickdraw 3D, VRML, Open Inventor, X-Windows.204481 Foundation ofComputer Graphics March 7, 2013 49
    50. 50. Graphical System And Standard (2/5)  Requirements of Graphical Systems  Portability  Device Independence Concept of a logical device.  Language Independence Language Bindings for graphical systems.  Computer Independence Trade-off between standard hardware and high performance hardware.  Programmer Independence  Flexibility - In conflict with portability.204481 Foundation ofComputer Graphics March 7, 2013 50
    51. 51. Graphical System And Standard (3/5)  Graphical Kernel System (GKS)  Workstation  GKS has concept of a workstation.  Device Normalisation  World Coordinates, Window in World Coordinates  Clipping to the window  Normalised Device Coordinates [0,1]x[0,1]  Normalisation Transformation  Viewports in normalised device coordinates204481 Foundation ofComputer Graphics March 7, 2013 51
    52. 52. Graphical System And Standard (4/5)  Output Functions  Line-Drawing Primitives  Area-filling primitives  Text Output  Input Functions  Logical input types : Locator, Valuator, Choice, String, Pick, Stroke.204481 Foundation ofComputer Graphics March 7, 2013 52
    53. 53. Graphical System And Standard (5/5)  Input Modes  Request mode: waits for a request for an event.  Sample mode: continually samples value of input device.  Event mode: unsolicited input stored on a stack, made available for processing in FIFO order.  Mixed mode.204481 Foundation ofComputer Graphics March 7, 2013 53
    54. 54. Professional Societies ACM SIGGRAPH - Association for Computing Machinery Special Interest G roup in Graphics IEEE - The Institute of Electrical and Electronics Engineers, Technical Committee on Co mputer Graphics204481 Foundation ofComputer Graphics March 7, 2013 54
    55. 55. Software Portability and graphics standards STANDARD ORGANIZATION  ANSI = American National Standard Institute (private, non government)  ISO = International Standards Organization(voluntary, non treaty)  ANSI is a member of ISO204481 Foundation ofComputer Graphics March 7, 2013 55
    56. 56. History: graphics libraries  initially, low-level device-dependent packages were the norm  movement towards high-level device- independent packages, in order to promote application program portability  requires standardization:204481 Foundation ofComputer Graphics March 7, 2013 56
    57. 57. Official Standards  1977 and 1979 - 3D SIGGRAPH CORE (ACM SIGGRAPH)  3D Core Graphics System ("Core") devd in late 70s as unofficial std  GKS (Graphical Kernel System, 1985): official 2D standard built from Core  GKS-3D (1988): 3d objects ANSI X3.124-1985  PHIGS (Programmers Hierarchical Interactive Graphics System, 1988) 3D nested objects  PHIGS+ (1988): rendering enhancements204481 Foundation ofComputer Graphics March 7, 2013 57
    58. 58. Emerging Standards in APIs  OpenGL (developed by Silicon Graphics)  open standard  available on all platforms  intended for professional-level graphics like CAD  Direct3D  developed by Microsoft  Windows only  intended for games204481 Foundation ofComputer Graphics March 7, 2013 58
    59. 59. Some Notable Systems  Tektronix commands in BASIC (mid-1970s)  HP commands (Hewlett Packard)  Microsoft BASIC (for PCs) graphics commands (early 1980s)  QuickDraw (Apple Macintosh)  X (MIT)  OpenGL (Silicon Graphics)  SRGP (Simple Raster Graphics Package)  SPHIGS (Simple PHIGS)  MS Windows  Java AWT204481 Foundation ofComputer Graphics March 7, 2013 59
    60. 60. Good graphics requires ? (1/3)  ability to control every dot (pixel) of display  ability to control primitive shapes on the screen  models to deal with images as a whole  use of color, lighting, and shading  construction of "languages" or "packages" to extend languages  knowledge of hardware  systems work204481 Foundation ofComputer Graphics March 7, 2013 60
    61. 61. Good Graphics requires ? (2/3)  mathematical transformations and representations  transmission of pictures and commands to make pictures  ability to store lots of information  high performance computers  algorithms such as visible surface algorithms204481 Foundation ofComputer Graphics March 7, 2013 61
    62. 62. Good Graphics requires ? (3/3)  understanding and manipulation of data structures  good software engineering principles  human factors engineering  some feeling for artistic principles  lots of effort - harder than it looks204481 Foundation ofComputer Graphics March 7, 2013 62
    63. 63. Lecture Topics  Introduction Visible Surface  Mathematical Determination Foundation  Algorithm efficiency  Coordinate Systems  Z-buffer algorithm  Introduction to  Scan line algorithms Graphics in 2D  Visible-surface Ray Tracing  Windows and Clipping  Introduction to  Other algorithms Graphics in 3D  Color Models  Viewing in 3D  Illumination and Shading204481 Foundation ofComputer Graphics March 7, 2013 63
    64. 64. Mathematical foundation  Mathematical appears throughout 3D graphics Example:  Object surfaces can be represented as polygons whose vertex position are specified by vectors  Rendering requires testing whether vertices lie in front of or behind various planes.  The test involves a dot product with the plane’s normal vector.204481 Foundation ofComputer Graphics March 7, 2013 64
    65. 65. Geometric transformation  Goal: specify object’s position and orientations in a 3D world  Use Linear transformations that rotate and translate objects’ vertices.  Apply these transformations in matrix form204481 Foundation ofComputer Graphics March 7, 2013 65
    66. 66. Viewing  Goal: map the visible part of a 3D world to a 2 D image  Use camera-like parameters to define a 3D view volume  Project the view voulme onto a 2D image plane  Map viewport on the image plane to the screen204481 Foundation ofComputer Graphics March 7, 2013 66
    67. 67. OpenGL  OpenGL is strictly defined as “a software interface to graphics hardware”.  It is a 3D graphics and modeling library  variety purposes, CAD engineering, architectural applications, computer-genera ted dianosaurs in blockbuster movies  Developed by SGI204481 Foundation ofComputer Graphics March 7, 2013 67
    68. 68. Clipping  Goal: cut off the part of objects outside the view volume to avoid rendering them204481 Foundation ofComputer Graphics March 7, 2013 68
    69. 69. Scan Conversion  Goal: convert a project, clipped object into pixels on raster lines.  Use efficient incremental methods204481 Foundation ofComputer Graphics March 7, 2013 69
    70. 70. Antialiasing  Raster displays produce blocky aliasing artifacts  Antialiasing techniques reduces the problem by applying the theory of sam pling and signal processing204481 Foundation ofComputer Graphics March 7, 2013 70
    71. 71. Color  Various color spaces provide ways to specify colors in term of components:  red, green, blue  hue, saturation, value  Different output devices display different subsets of the perceptible col ors204481 Foundation ofComputer Graphics March 7, 2013 71
    72. 72. Hidden Surface Removal  When several overlapping polygons are drawn on the screen, which one is on top? Which is right?204481 Foundation ofComputer Graphics March 7, 2013 72
    73. 73. Z-buffering  A fast hardware solution is This pixel is drawn on the Z-buffer screen  The “depth” of each pixel relative to the screen is Screen calculated and saved in a Polygons buffer  The pixel with the smallest depth is the one that is displayed  The other pixels are on Z surfaces that are hidden204481 Foundation ofComputer Graphics March 7, 2013 73
    74. 74. Lighting Models and Shading  For visual realism, lighting Ambient lighting: models have been developed to illuminate the surfaces of solid models  These models incorporate incident reflected light  ambient lighting and illumination light  diffuse reflection of directional lighting  specular reflection of directional reflected light incident lighting light204481 Foundation ofComputer Graphics March 7, 2013 74
    75. 75. Ray Tracing Light Source Shadow Ray Eye Object Eye Ray Shadow Ray Object Light Source  Ray tracing traces a ray of light from the eye to a light source  Ray tracing realistically renders scenes with shiny and transparent204481 objects Foundation ofComputer Graphics March 7, 2013 75
    76. 76. Radiosity  Diffuse illumination results from the absorption and reflection of diffuse light from many objects in the scene  Radiosity uses thermal models of emission and reflection of radiation to Radiosity is very good at accurately calculate rendering architectural interiors diffuse lighting204481 Foundation ofComputer Graphics March 7, 2013 76
    77. 77. Texture Mapping  For realism, photographic textures are “mapped” onto the surfaces of objects  Example textures: texture mapping  woodgrain  concrete  grass reflections  marble shadows  Texture mapping is very computationally intensive204481 Foundation ofComputer Graphics March 7, 2013 77
    78. 78. Example of Shading Wireframe Flat Shaded Smooth Shaded Shadows204481 Foundation ofComputer Graphics March 7, 2013 78
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