CS-460/560, Wk1a
Spring, 2000
R. Eckert
An Introduction to Computer Graphics
Computer Graphics--
Using a computer to generate visual images
Motivation--
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.
Example:
b. 2-D colored images (colored objects); painting programs
Need efficient area fill algorithms
Example:
c. 3-D line drawings (wire frames)
Need efficient algorithms to project from 3-D to 2-D
Example:
d. 3-D line drawings with hidden lines removed
Need efficient hidden line removal algorithms
Example:
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
Examples:
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)
Examples:
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.
SOME APPLICATIONS OF COMPUTER GRAPHICS:
Data Presentation (statistics, business, scientific, demographics...)
CAD, CAM, CIM
Painting/Drawing systems
TV commercials
Entertainment
Video Games
Cartography
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
Hypermedia
Integration of broadcasting, computing, publishing
Education
Process Control
CASE
Image Processing/Enhancement
Medicine
Computed Tomography
X-ray, ultrasound, NMR, PET:
--> 3-D images of human anatomy
GUIs
World Wide Web Development
VRML
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!
BRIEF HISTORY OF COMPUTER GRAPHICS
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
inexpensive
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