1. Introduction to Computer Graphics CS 445 / 645
David Brogan

2. Administrivia Syllabus Instructor/TA coordinates Prereqs Texts
Assignments
Grading & Honor Code
Topic list

3. Impact of Computers Moore’s Law
Power of a CPU doubles every 18 months / 2 years

4. Impact of Video Games (Nvidia)
Number of transistors on GPU doubles each 6 mos.
Three times Moore’s Law
Good article on Jen-Hsun Huang, Nvidia CEO:
Lee Majors
Col. Steve Austin
Worldwide
revenues
Retro flashback???
$7 Billion Man
$5.6 Billion Man

5. Impact of Video Games But…
Video game sales is roughly same as Hollywood boxoffice
Americans bought $3.2 in VCRs and DVDs last yr
Total revenues to movie studios is 5 times total video game revenues

6. Future of Consoles 33 million PS2s 3.9 million Xboxes
MSFT still losing $89 per console
Predicted 200 million PDA/Cell game players in 2005
Do you believe it?

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

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

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

10. Graphics Applications
Scientific Visualization

11. Graphics Applications
Computer Aided Design (CAD)

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

13. 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

14. Why Study Computer Graphics?
Graphics is cool
I like to see what I’m doing
I like to show people what I’m doing
Graphics is interesting
Involves simulation, AI, algorithms, architecture…
I’ll never get an Oscar for my acting
But maybe I’ll get one for my CG special effects
Graphics is fun

15. Can we learn from history?
Among the studies of natural causes and laws, it is light that most delights its students. Among all the great branches of mathematics, the certainty of its demonstrations pre-eminently elevates the minds of its investigators. Perspective, therefore, should be preferred above all man’s discourses and disciplines. In this subject the visual rays are elucidated by means and demonstrations which derive their glory nor only from mathematics but also from physics; the one is adorned equally with the flowers of the other.
Leonardo da Vinci (1400’s) quoting John Pecham (1200’s)

16. Perspective

17. Machines

18. Leonardo Again
There are some who look at the things produced by nature through glass, or other surfaces or transparent veils. They trace outlines on the surface of the transparent medium… But such an invention is to be condemned in those who do not know how to portray things without it, no how to reason about nature with their minds… They are always poor and mean in every invention and in the composition of narratives, which is the final aim of this science

19. Perspective
Lorenzetti
Birth of the Virgin
1342

20. Leonardo
The Last Supper
1498

21. Shape

22. We Labor On… Light Stage – 2002 USC, Institute for
Creative Technologies
Note: Paul Debevec will visit UVa in October to talk about this and other cool things

23. 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

24. Electron Gun
Contains a filament that, when heated, emits a stream of electrons
Electrons are focused with an electromagnet into a sharp beam and directed to a specific point of the face of the picture tube
The front surface of the picture tube is coated with small phospher dots
When the beam hits a phospher dot it glows with a brightness proportional to the strength of the beam and how often it is excited by the beam

25. Display Technologies: CRTs
Vector Displays
Anybody remember Battlezone? Tempest?

26. 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

27. 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

28. Display Technologies: CRTs
Raster Displays
Black and white 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.

29. Display Technologies: CRTs
Phosphers
Flourescence: Light emitted while the phospher is being struck by electrons
Phospherescence: Light emitted once the electron beam is removed
Persistence: The time from the removal of the excitation to the moment when phospherescence has decayed to 10% of the initial light output

30. Display Technologies: CRTs
Raster Displays
Frame must be “refreshed” to draw new images
As new pixels are struck by electron beam, others are decaying
Electron beam must hit all pixels frequently to eliminate flicker
Critical fusion frequency
Typically 60 times/sec
Varies with intensity, individuals, phospher persistence, lighting...

31. Display Technologies: CRTs
Raster Displays
Interlaced Scanning
Assume can only scan 30 times / second
To reduce flicker, divide frame into two “fields” of odd and even lines
1/30 Sec
1/60 Sec
Field 1
Field 2
Frame

32. Display Technologies: CRTs
Raster Displays
Scanning (left to right, top to bottom)
Vertical Sync Pulse: Signals the start of the next field
Vertical Retrace: Time needed to get from the bottom of the current field to the top of the next field
Horizontal Sync Pulse: Signals the start of the new scan line
Horizontal Retrace: The time needed to get from the end of the current scan line to the start of the next scan line

33. Display Technology: Color CRTs
Color CRTs are much more complicated
Requires manufacturing very precise geometry
Uses a pattern of color phosphors on the screen:
Why red, green, and blue phosphors?
Delta electron gun arrangement
In-line electron gun arrangement

34. Display Technology: Color CRTs
Color CRTs have
Three electron guns
A metal shadow mask to differentiate the beams

35. Display Technology: Raster
Raster CRT pros:
Allows solids, not just wireframes
Leverages low-cost CRT technology (i.e., TVs)
Bright! Display emits light
Cons:
Requires screen-size memory array
Discreet sampling (pixels)
Practical limit on size (call it 40 inches)
Bulky
Finicky (convergence, warp, etc)