1. Lecture 01: Introduction Dr. Manal Helal – Fall 2014
Computer Graphics CC416
Lecture 01: Introduction
Dr. Manal Helal – Fall 2014

2. Course Description
Introduction - History and survey of graphics applications - Overview of graphics systems and output devices - Output primitives including points, lines, circles, splines, area filling, and character generation - Attributes of output primitives - Two dimensional transformations - Windowing and clipping - Interactive input methods – Three dimensional graphics.

3. Course Topics
Introduction, history and Survey of Computer Graphics Applications
Overview of Graphics Systems : Raster and Random scan displays
Color diplay – Color models (RGB, CMY, ..)
Output Primitives : Bresenham line and Mid-point Circle / Ellipse drawing algorithms
Drawing free curves : Bezier and Spline techniques
Two – Dimensional Transformations
Viewing transformation
Line and Polygon clipping algorithms
Filling algorithms
Animation
Three – Dimensional Concepts Viewing and Representation
Three – Dimensional Transformations

4. Grading Scheme Week 7 Week 12 Final Exam 40% Quizzes 5%
Lab Submissions 2.5%
Assignments 2.5%
Midterm 1 20%
Week 12
Midterm 2 10%
Project 10%
Final Exam 40%

5. Course Rules
Website:
Signup using First and Last Names exactly as your records in AASTMT, and your student ID as your student ID in AASTMT. Otherwise, your grades will not be transferred to your academy records.
Login often to follow up with assignment deadlines and announcements. Its your responsibility to keep up with the course. Failure to receive s or notifications is no excuse. Everything is announced in class and then published in moodle.
Academic Honesty:
Please confirm with the AASTMT policies regarding plagiarism and cheating. A zero grade for the violating submission will be given the first time, then reported to the department for further action.
Please ask questions in the online forum to allow everyone to join and benefit from the discussions, and avoid private s to the lecturers and TAs. Contact the teachers privately only about your personal grades or circumstances, not about the course content.

6. How to score A+ in this course?
Please do all practicals and assignments and study regularly. In case of problems, please ask questions. Accumulating problems will make things worse as the semester goes by.

7. Office Hours Dr. Manal Helal – Room 308 Eng. Nour – to be announced
Sun and Monday 2:00-04:00 p.m. or by appointment
Eng. Nour – to be announced
Eng. Hossam – to be announced
Fall 2014
CC 215 Data Structures

8. Computer Graphics Applications
Computer Aided Design (CAD)
Presentation Graphics
Computer Art
Entertainment
Education and Training
Visualization
Image Processing
Graphical User Interface

9. Computer Aided Design (CAD)

10. Presentation Graphics
Architectural presentation

11. Visualization
Protein Structure
aerodynamics flow

12. Computer Art
Fractals

13. Entertainment

14. Education and Training

15. Image Processing
Feature detection
Enhancement

16. Graphical User Interface

17. Graphics Systems Video Display Devices Raster- Scan Systems
Random Scan Systems
Input Devices
Hard Copy Devices
Graphics Software

18. Video Display Devices
Cathode Ray Tube (CRT) & Raster scan display

19. Raster Scan Display

20. Flat panel Display Plasma panels
The cells are sandwiched between x- and y-axis panel
Each pixel is made up of three cells full of ionized gas
When charged, the gas emits ultraviolet light that causes the phosphors to emit their color
The amount of charge determines the intensity

21. Light Emitting Diode (LED) display
A matrix of diodes are arranged to form the pixel position in the display
Image definition is stored in a buffer

22. Liquid Crystal Display (LCD)
A polarized light is generated
The polarized light is passed through a liquid crystal material
The liquid crystal material can be aligned to block or bypass the light

23. 3 Dimensional Viewing Devices
3D devices reflect a CRT image from a vibrating flexible mirror.
The vibration changes the focal length such that each point is reflected from the mirror into a spatial position corresponding to the distance of the point from a specified viewing location.

24. Virtual Reality

25. Video Controller
Frame buffer is a part of memory for graphics and has the intensity value for all the screen coordinates. 
According to the photo info an application program updates frame buffer.
Then, the display controller converts the binary values to pixel information which is later displayed in to a Cathode Ray Tube.
Frame buffer can be used as a part of computer memory using a common bus or it can be used separately by using host system bus and graphics system bus.

26. Coordinating system There are 3 defined coordinate systems:
World Coordinate System
Normalized Device Coordinate
Device Coordinate System

27. World Coordinate System:
It is a write-hand coordinate system
It allows the user to set any conversion dimension regardless of any output device.
Normalized Device Coordinate:
Before final conversion to device specific coordinates we convert our graphics primitives to normalized device coordinates.
It makes graphics system visible enough to match with any output graphical devices.
Normalized Coordinate of X and Y (point coordinate) are each assigned values to the interval from 0 to 1.

28. Device Coordinate System :
The normalized coordinates are transformed into device
coordinates within the range from (0,0) to (Xmax , Ymax), where this is the coordinates of specific device.

29. Screen Coordinates

30. Using Color in Computer Graphics
Aesthetic uses
Highlight
Code numeric quantities
Scientific visualization: fluids in computational fluid dynamics (streamlines)
Color legends

31. Careless use of color is dangerous
Color Selection
Visually appealing.
Convey a message.
Careless use of color is dangerous
in experiments, poor color choices reduced user performance by one-third
“Worst Website”:

33. Color Models What is the color?
Color is a sensation produced by the human eye and nervous system.
Photosensitive Receptors
Rods: 130,000,000 night vision + peripheral (scotopic)
Cones: 5-7,000,000, daylight vision + acuity (one point only)
L-cones
M-cones
S-cones

34. From left to right, the curves above show the sensitivity of the S, M, and L cones to various wavelengths of visible light

35. It is useful to represent a color by a set of exactly three numbers.
- In practice, the set of three numbers must be related to some actual color reproduction process. The numbers commonly specify portions of some set of primary colors such as:

36. A color model is an orderly system for creating a whole range of colors from a small set of primary colors.
Mixing of 3 primaries
Target colour
overlap
Adjust intensities to match the colour

37. Types of Color model
There are two types of color models, those that are subtractive and those that are additive.
Additive color models use light to display color while subtractive models use printing inks.
Colors perceived in additive models are the result of transmitted light.
Colors perceived in subtractive models are the result of reflected light.

38. Color Models for Raster Graphics
Hardware-oriented models: do not relate to concepts of hue, saturation, brightness
RGB, used with color CRT monitors
YIQ, broadcast TV color system
CMY (cyan, magenta, yellow) color printing
CMYK (cyan, magenta, yellow, black) color printing
IRODORI, six-primary-color projection system
User-oriented models
HSV (hue, saturation, value), corresponds to the way that the human describe and interpret color.
HLS (hue, lightness, saturation)
The Munsell system
CIE Lab

39. Problems

40. Solution

41. The CIE 1931 Standard Observer represents the color perception of a "normal" person. The curves show the intensity of X, Y, and Z values (akin to cone response) for a given wavelength

42. RGB Color Model Additive color model. For computer displays.
Uses light to display color.
Colors result from transmitted light.
Red + Green + Blue = White.

43. The individual contributions of each primary are added together to yield the result.
The RGB cube (Grays on dotted main diagonal)
Main diagonal => gray levels
black is (0, 0, 0)
white is (1, 1, 1)

44. Two CRTs with different phosphors will cover different gamuts.
The color gamut covered by the RGB model is defined by the chromaticities of a CRT’s phosphors.
Two CRTs with different phosphors will cover different gamuts.
Conversion between colors specified in the gamut of one CRT to the gamut of another CRT.
Convert one to XYZ, then convert from XYZ to another

45. Each transformation
Xr, Xg and Xb are the weights applied to the monitors’ RGB colors to find X and so on.
With M1 and M2 the matrices that convert from each of the two monitor’s gamuts to CIE, M2-1M1 converts from the RGB of monitor 1 to the RGB of monitor 2. ú û ù ê ë é = B G R Z Y X b g r

46. CMY Color Model
CMY stands for Cyan, Magenta, and Yellow, which are the complements of red, green and blue
Subtractive color model: Used as filters to subtract color from white light.
For printed material.
Uses ink to display color.
Colors result from reflected light: Colors are specified by what is removed or subtracted from white light, rather than by what is added to blackness.
Cyan + Magenta + Yellow = Black.

47. Relations between RGB and CMY
Magenta
Red
Yellow
Green
Cyan
Blue
Black
(minus green)
(minus blue)
(minus red) ú û ù ê ë é - = B G R Y M C 1
The unit column vector is the RGB representation for white and the CMY representation for black.

48. A knowledge of CMY is important when dealing with hardcopy devices that deposit colored pigments onto paper: electrostatic and ink-jet plotters.
When a surface is coated with cyan ink, no red light is reflected from the surface.
Cyan subtracts red from the reflected white light.
Cyan is white minus red, that is blue plus green.
Magenta absorbs green, so it is red plus blue.
Etc.
dye color
absorbs
reflects
cyan
red
blue and
magenta
green
blue and red
yellow
blue
red and green
black
all
none

49. Use RGB For Screen Displays and CMYK For Print
- It is important to choose the right color model for the job. If your images will be printed, then convert them to CMYK and manually bring them into gamut before printing. If your images are to be displayed on a computer, then make sure you use RGB color so the full gamut will be available for display. Because both models can be available at the same time while using an application, it is easy to make a mistake and choose the wrong palette or set of color swatches.

50. CMYK Color Model:
Most devices that deposit colored pigments on paper such as color printer require CMY data input.
Equal amounts of cyan, magenta, yellow will produce black.
But in practice we use black as a dominant color for printing so we add the black color to the model CMYK