CS-460/560, Wk1a
Spring, 2000
R. Eckert

An Introduction to Computer Graphics

Computer Graphics--
    Using a computer to generate visual images

    Human visual channel highly developed
    Visual channel very efficient for communicating complex ideas

Definition of Computer Graphics:
    Creation, storage, manipulation, and display of models of
    objects (real or imagined) using the computer.

Interactive Computer Graphics:
    User dynamically controls displayed image attributes by means
    of interactive input devices.

Image Processing--
    Related to computer graphics
    Reconstruction of objects from their images

Computer Graphics--Synthesis of images (Objects ---> Images)

Image Processing--analysis of images (Images ---> Objects)

Image Processing subfields--
    image enhancement
    computer vision
    pattern recognition
    (AI important)

Two Phases of Computer Graphics--

    1. Modeling
         Mathematical representations of objects/scenes

    2. Rendering
         Production of an image from a model

Features of computer graphics models-
    Output primitives: building blocks
    Data structures: how primitives relate to each other

Levels of Complexity of Computer Graphics--

  Depends on objects/scenes to be modeled and rendered

    a. 2-D Line Drawings (charts, graphs); drawing programs
         Need algorithms to efficiently draw lines, circles, text, etc.

    b. 2-D colored images (colored objects); painting programs
         Need efficient area fill algorithms


    c. 3-D line drawings (wire frames)
         Need efficient algorithms to project from 3-D to 2-D


    d. 3-D line drawings with hidden lines removed
         Need efficient hidden line removal algorithms


Note: all hidden lines in each object have been removed,
but lines in objects hidden by other object have not been removed.

    e. 3-D colored images
         Need algorithms for hidden surface removal, color, shading


Also all hidden surfaces have removed.
All surfaces have been "flat shaded."

Plane surfaces have been flat shaded.
Cylinders & condes have been "Gouroud smooth shaded."
The sphere has been "Phong smooth shaded"--note specular highlight.

    f. 3-D photorealistic images
         Need models that take into account materials properties,
         lighting, reflection, transparency, shadows;
         The physical interaction of light with material (physics)
         Modeling techniques for complex (natural) objects (e.g., fractals)


A ray traced scene with transparency, reflection, & texture mapping.

A scene with fractal mountains & L-system generated plants.

    g. Animation at all levels
         Make things move realistically

The above image is one frame in a robot runner animation.
Each frame was generated with a ray tracing program.


  Data Presentation (statistics, business, scientific, demographics...)


  Painting/Drawing systems

  TV commercials

    Video Games


  Computer Art

  Motion Picture Industry (animation, special effects, etc.)

  Desktop publishing

  Architectural Design

  Simulation of Reality
    Flight simulators
    Ground vehicle simulators
    Arcade games
    Virtual reality devices

  Scientific Simulation/Visualization
    Use graphics to make sense of vast amounts of scientific data

    Integration of broadcasting, computing, publishing


  Process Control


  Image Processing/Enhancement

    Computed Tomography
      X-ray, ultrasound, NMR, PET:
         --> 3-D images of human anatomy


  World Wide Web Development

  New Stuff--can't even be imagined

Computer Graphics--

    A huge, fast-moving, exciting field that integrates the best of art
    and science

    Needs new Renaissance men & women
        Bright and analytic enough to understand the science & math
        Sensitive and creative enough to do the art

    Both left and right sides of the brain required!


  Early 50s--MIT Whirlwind Computer
             First computer-driven CRT

  Middle 50s--SAGE Air Defense System
              Selection of targets with light pen
              First interactive graphics

  Early 60s--Ivan Sutherland (father of computer graphics)
             Ph.D. Thesis: SKETCHPAD
             Proposed 1st complete model for interactive graphics
             Identified basic data structures
             Discovered important algorithms
             Many of his ideas still in use

  Middle 60s--GM's Digigraphic Design System
              Beginning of CAD

Costly hardware, Hard-to-write programs, Non-portable software

  Late 60s--Tektronix Direct View Storage Tube
            First inexpensive graphics display device

  Early 70s--First microprocessors --> first microcomputers
                                       primitive graphics capability

  Late 70s--First graphics software standard (CORE--1977)
            First attempt at portable graphic software

  1980s--Proliferation of micros with extensive graphics capabilities
         Introduction of first Work Stations (graphics engines)
         Appearance of graphics standards with increased capabilities
             GKS (1984), GKS-3D (1988), PHIGS (1988)
         Microcomputer GUIs (Macintosh, Windows)

  1990s--Graphics engines (algorithms implemented in hardware)
         Fast, powerful, cheap
         Multimedia systems
         Windows-95, Windows-NT, X Windows, PEX
         GL, OpenGL industry standard graphics libraries
         Microsoft Direct-X