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Computer Graphicschapter 1

Dr. Jehad Q. O. Alnihoud

Email: jehad@aabu.edu.jo

Phone: 3354

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Books

•F.S. Hill, Computer Graphics Using OpenGL, Prentice-Hall (2001).

•Mason Woo, OpenGL Programming Guide, Addison Wesley (2000).

•Hearn and Baker, Computer Graphics, Prentice-Hall (1997).

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Books (Supplementary reference)

Foley, V. Dam, Feiner, Hughes, Computer Graphics Principles and Practice, 2/e, Addison Wesley, 1997.

Edward Angel, Interactive Computer Graphics, Addison Wesley, 1997.

Zhigang Xiang, Schaum’s Outlines: Computer Graphics, McGrawHill, 2001.

Shreiner D, OpenGL Reference Manual, Addison-Wesley, 2000.

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Course Assessment

Coursework 50% First Exam 15% Second Exam 15% Group Project 10% Lab 10%

Final Exam 50%

Attendance in both lecture and lab sessions is compulsory.

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Graphics Applications

Art and Entertainment Animations Movies Commercials Special Effects

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Graphics Applications

Image Processing Analysis, Reconstruction Medical Imaging Movies

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Graphics Applications

Simulation Modeling and Analysis Virtual Environments

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Graphics Applications

Scientific Visualization Data Representation and Plotting 3D Views

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Graphics Applications

CAD/CAM Industrial Design Structural Design Surface Modeling

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Graphics Software Packages

Early graphics libraries:

GKS (Graphical Kernel System)

PHIGS

OpenGL (Silicon Graphics)

Java2D (Sun Microsystems)

Java3D (Sun Microsystems)

VRML (Silicon Graphics)

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Graphics: Main Components

Theory

Analytical Geometry

Vectors and Matrices

Algorithms

Eg: Line drawing, Filling etc.

Implementation

Programming (OpenGL)

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Graphics Hardware

Line Drawing Devices: Eg. Pen Plotters Advantages: Perfect lines, Sharp Diagrams Disadvantages: Not suitable for filled regions.

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Graphics Hardware

Raster Devices: Create pictures by displaying dots Eg: Video monitor, dot-matrix printer,

laser printer, ink-jet printer, film recorder Advantages: Filled, shaded regions are

easily displayed Disadvantages: Jaggies

Pixel

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Pixel Depth Pixel depth refers to the number of bits used

to represent a pixel value.

1 bit/pixel: 0

1

2 Levels(Bi-level image)

2 bits/pixel: 0

0

4 Levels0

1

1 0

1 1

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Pixel Depth

1 bit per pixel produce 2 levels (bi-level image).

2 bits per pixel produce 4 levels.8 bits per pixel produce 256 levels.

In general, if the pixel depth is n, then it is possible to have 2n levels.

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Raster Display

Most display used for computer graphics nowadays are raster displays.

Image presented in display surface that contains certain number of pixels. Eg. 480 x 640 (r x c).

Frame buffer is a region of memory sufficiently large to hold all the pixel values for display.

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Frame Buffer

System with 64 color (3 DACs): Each DAC uses 2 bits/pixel. Total color: 4 x 4 x 4 = 64 If the display surface is 1024 x 1280, then the

memory required for frame buffer is 0.9375 MB Monochrome Video display:

Only one DAC required. 6 planes of memory in frame buffer gives 26 = 64 level of gray.

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Frame Buffer

System with 24 bit color (3 DACs): Each DAC uses 8 bits/pixel. (Total 24 bits/pixel) Total color: 28 x 28 x 28 = 224 If the display surface is 1024 x 1280, then the memory

required for frame buffer is 3.75MB

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Basis colors: R, G, B

R: Red=[1, 0, 0]

G: Green=[0, 1, 0]

B: Blue=[0, 0, 1]

C: Cyan=[0, 1, 1]

M: Magenta=[1, 0, 1]

Y:Yellow=[1, 1, 0]

W:White=[1,1,1]

K: Black=[0,0,0]

Color Models: RGB Diagram• RGB Model is used for colored light sources• RGB Model is additive

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Complementary Colors: Two colors that combine to form White. Eg. Red, Cyan.

Gray Values: Every point on the primary diagonal has equal values for all the components.

Color Models: RGB Cube

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Basis colors: C, M, Y

C: Cyan=[1, 0, 0]

M: Magenta=[0, 1, 0]

Y: Yellow=[0, 0, 1]

R: Red=[0, 1, 1]

G: Green=[1, 0, 1]

B: Blue=[1, 1, 0]

W:White=[0,0,0]

K: Black=[1,1,1]

Color Models: CMY Diagram• CMY Model is used for colored pigments• CMY Model is subtractive

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Color Models: RGB <-> CMY

(r, g, b)RGB = (1,1,1) (c, m, y)CMY

Light

A red colored surfaceabsorbs cyan from awhite light

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Color Models: HSV HexCone

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H (Hue): 0 to 360 degrees 0: Red, 60: Yellow ….

S (Saturation): 0 to 1 0: Axis, 1: Boundary

V (Value): 0 to 1 0: Vertex, 1: Base

Examples:

Eg. Yellow: [60, 1.0, 1.0]

Black: [ -, -, 0.0]

White: [-, 0.0, 1.0]

Color Models: HSV

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RGB Color Definition (OpenGL)

Set a particular color: glColor3f(r,g,b);

Set a background color: glClearColor(r,g,b,1);

Clear the window to background color:

glClear(GL_COLOR_BUFFER_BIT);