1. Introduction to Computer Graphics

2. Personal information
Prof. Ludovit Niepel Computer Science Department, office 26B web page: Phone - extension: 5321

3. Textbook:
Course Textbook: F.S.Hill,Jr. Computer Graphics - using Open GL. Prentice-Hall 2-nd or 3-rd ed
Recommended Textbook: OpenGL programming Guide. (Red book) Addison-Wesley Pub (exists on-line version)

4. Office hours:
Sun: Mon:11-12 Tue: 9-11 Wed: on demand Thu: subject to change

5. Course Details
Course evaluation: Homework and quizzes 20% Project 10% Midterm 30% Final 40% Dates: Homework to be announced when assigned Project to be announced when assigned Midterm NOV :15 Final JAN-03 14:00- 16:00

6. Introduction
CS 455

7. What is Computer Graphics?
Different meanings – simplest definition: “pictures that ere generated by computers”.
Tools to create pictures generated by computer.

8. Basic notions
Computer graphics – process of producing a picture or image using the computer
Computer interfaces popular on personal computers
Desktop publishing
Realistic images generated using mathematical and physical methods

9. Graphics Applications
Entertainment: Games
GT Racer 3
Polyphony Digital: Gran Turismo 3, A Spec

10. Graphics Applications
Entertainment: Cinema
Square: Final Fantasy
Pixar: Monster’s Inc.

11. Areas of Applications Entertainment Movies Games
Technical and business applications

12. Graphics Applications
Computer Aided Design (CAD)

13. Computer-Aided Design; Training
Electronic blueprints
Architectural CAD
Mechanical CAD
Electronic CAD
Visual simulation and Training
Apollo spacecraft
Flight simulators
Ship
Automobile and driving simulators
Surgical simulation

14. Digital Media Technologies
Traditional media (analog to digital transition)
-Desktop publishing and printing
-Digital photography
-Digital video and HDTV
“New” media experiences
-Multimedia personal computer
-Networked graphics and the www
-Photo (flickr) and video sharing (youTube)

15. Visualization Interdisciplinary: Theory & Practice
Mathematics, science, engineering, medicine, …
Education
Interdisciplinary: Theory & Practice
Science
Physics of light, color and appearance
Geometry and perspective
Mathematics of curves and surfaces
Engineering
Hardware: Graphics/media processors
Software: Graphics libraries, window systems
Art and Perception
Color: harmony and perception
Composition, lighting, ...

16. Graphics Applications
Medical Visualization
The Visible Human Project
MIT: Image-Guided Surgery Project

17. Graphics Applications
Scientific Visualization

18. Graphics Applications
Everyday Use
Microsoft’s Whistler OS will use graphics seriously
Graphics visualizations and debuggers
Visualize complex software systems

19. The Basics
Computer graphics: generating 2D images of a 3D world represented in a computer.
Main tasks:
modeling: (shape) creating and representing the geometry of objects in the 3D world
rendering: (light, perspective) generating 2D images of the objects
animation: (movement) describing how objects change in time

20. Steps for creating a picture
Creating a model
Perform necessary transformation
Lighting and rendering the object
The goal is the creation of an image by writing a program instead of taking a picture with a camera
There exists an analogy between writing graphical programs and taking pictures by a camera

21. Graphical User Interfaces
Desktop metaphor
Input: Lightpen, mouse, keyboard
Output: CRT, printer
Immersive interfaces
Virtual reality
Input: 3D tracking, gloves
Output: HMD, projection display

22. Display Technologies Cathode Ray Tubes (CRTs)
Most common display device today
Evacuated glass bottle
Extremely high voltage
Heating element (filament)
Electrons pulled towards anode focusing cylinder
Vertical and horizontal deflection plates
Beam strikes phosphor coating on front of tube

23. Display Technologies: CRTs
Vector Displays
Early computer displays: basically an oscilloscope
Control X,Y with vertical/horizontal plate voltage
Often used intensity as Z
Name two disadvantages
Just does wireframe
Complex scenes  visible flicker

24. Display Technologies: CRTs
Raster Displays
Raster: A rectangular array of points or dots
Pixel: One dot or picture element of the raster
Scan line: A row of pixels

25. Display Technologies: CRTs
Raster Displays
Color television: an oscilloscope with a fixed scan pattern: left to right, top to bottom
To paint the screen, computer needs to synchronize with the scanning pattern of raster
Solution: special memory to buffer image with scan-out synchronous to the raster. We call this the framebuffer.

26. Pixels
Pixel or “Picture element” is the simplest element in computer graphics
Single location on the computer screen or printout
Value of each pixel is the range from white to black or range of intensities of red, green, blue (RGB) colors.

27. Frame buffers
The pixels of an image are organized into two dimensional grid – frame buffer
Multiple frame buffers can be stored in computer memory
Double buffering – first image is drawn into frame buffer and sent to display. While the user is looking on the display, the next picture is drawing to the second buffer.

28. Windows Image don’t fill the entire screen but is drawn into a window
Pixels are adressed within the window based on their location
Relative position of each pixel enables moving the window and change its size

29. Realistic images
Calculating pixel values to create impression of a realistic picture
Simulation of objects from the real word
Approximation of physical properties of objects
Limitations given by computing time and memory space

30. The Graphics Pipeline
Modeling – creates an internal representation of the objects in the scene
Rendering – converts the screen description into image
Display – shows the image on the output device

31. The Graphics Pipeline Model Transformation Object Specification
Scene Description
Scene Description
Clipping and Hidden
Surface Removal
Model
Transformation
View and Light Specification
Shading
Image

32. The Graphics Pipeline cont.
Image
Display Transformation
Output

33. Output primitives Points Lines Polylines Text Filled regions
Raster images

34. Object modeling
Model contains - shape of the object - material and physical properties - color, transparency, shiness - texture
Different levels of complexity of modeling - polytopes with planar faces - curved lines and surfaces

35. Rendering
The rendering process simulates the flow of light through the sceneas it interacts with the objects
The presence of light lets to see objects in the world
An illumination model approximates the way how light interacts with the object.

36. Camera model
Model used in computer graphics to project 3D-objects to 2D-display
Geometrical transformations simulate the role of camera
Projection is represented by multiplications of transformation matrices

37. Coordinate systems World coordinate system View coordinate system
Window coordinate system
Object coordinate system
Different kind of coordinates: -affine coordinates -homogenous coordinates - integer/real coordinates

38. Color models
RGB model (red, green, blue ) for displays, additive model
CMY model (cyan, magenta, yellow) for printers, subtractive model
blue
magenta
cyan
red
black
green
yellow