Overview of Computer Graphics

In short description, i present some useful topics in Computer Graphics.

1. Computer Graphics Department of Computer Science & Engineering Hamdard University Bangladesh Prepared By

2. The definition of  computer graphics  is the technology that deals with designs and pictures on computers. C omputer graphics 2

3. • Recognize how a visual image can be an effective means of communication • Distinguish and interpret various types of typography. • Utilize a broad range of type styles in combination with visual images. • Use a computer to create and manipulate images and text for use in various print and digital mediums . Goals of Computer Graphics 3

4. Applications of Computer Graphics Computational biology Computational physics Computer-aided design Digital art Education Graphic design Information visualization Scientific visualization Special Effects for cinema Video Games Web design Design 4

5. Overview of Graphics Systems Images Hardware Input Systems Output Systems Software OpenGL 5

6. Two Dimensional Images Images (at least the ones in this class) are two dimensional shapes. The two axes we will label as X (horizontal), and Y (vertical). X Axis Y Axis (0,0) +X +Y 6

7. Three Dimensional Images The three axis: X (horizontal ), Y (vertical ) and Z (middle). 7

8. Color Model RGB Color cube (what we use in computer graphics) Other color spaces include HSV, CMY, and YIQ 8

9. Hardware Pipeline Input Output Computation We want to draw a rectangle, how do we describe it to a computer? Model (n) - object description that a computer understands. 9

10. Record every position Bitmap - a rectangular array of bits mapped one-to-one with pixels. 10

11. Position relative Vector display system - graphical output system that was based on strokes (as opposed to pixels). Also known as: random, calligraphic, or stroke displays. 11

12. Representing Objects Most common method is the VERTEX method. Define the object as a set of points with connectivity information. Why is connectivity important? Connectivity - information that defines which vertices are connected to which other vertices via edges. Edge - connects two vertices 12

13. Input Devices Locator Devices Keyboard Scanner Images Laser Cameras 13

14. Locator Devices When queried, locator devices return a position and/or orientation. Tablet Joystick Virtual Reality Trackers Data Gloves Digitizers 14

15. Keyboard Text input List boxes, GUI CAD Modeling Hard coded Vertex locations are inserted into code 15

16. Computation Stage Now that we have a model of what we want to draw, what goes on inside the computer to generate the output? Input Output Computation Computation Transformations Rasterization 16

17. Computation Stage Computation Transformations Rasterization Model Transformed Model Output 17

18. Store process in memory We would like to allocate memory to hold the results of the computation stage. 18

19. Frame buffer Frame buffer – The picture definition is stored in a memory is called refresh or frame buffer. Pixel - one element of the framebuffer 19

20. Basic architecture of raster graphics of frame buffer 20

21. Frame buffer in Memory If we want a frame buffer of 640 pixels by 480 pixels, we should allocate: Frame buffer = 640*480 bits =307200 bits =38400 bytes =38.4 kilobytes 21

22. Output Hardcopy Display Vector or random scan Raster Scan Input Output Computation 22

23. Image Quality Issues Screen resolution Color Blank space between the pixels Intentional image degradation Brightness Contrast Refresh rate Sensitivity of display to viewing angle 23

24. Pixels Pixel - The  pixel  (a word invented from "picture element") is the basic unit of programmable color on a computer display or in a computer image.  CRT - Color triad (RGB phosphor dots) LCD - Single color element Screen Resolution - measure of number of pixels on a screen (m by n) m - Horizontal screen resolution n - Vertical screen resolution 24

25. Raster Displays Cathode Ray Tubes (CRTs), most “tube” monitors. Very common, but big. Liquid Crystal Displays (LCDs), there are two types transmissive (laptops, new flat panel monitors) and reflective (wrist watches). 25

26. Cathode Ray Tube 26

27. CRT color monitor Beam Penetration Method (Red & Green) Shadow Mask Method (RGB) 27

28. CRTs Strong electrical fields and high voltage Very good resolution Heavy, not flat 28

29. Liquid Crystal Displays (LCDs) Also divided into pixels, but without an electron gun firing at a screen, LCDs have cells that either allow light to flow through, or block it. 29

30. Advantages of LCDs Flat Lightweight Low power consumption 30

31. Projection Displays Use bright CRT or LCD screens to generate an image which is sent through an optical system to focus on a (usually) large screen. 31

32. Basic Projector Designs                                                                                                                                                   Reflective Projection System Transmittive Projection System 32

33. Graphics Software Special purpose software Excel AutoCAD Medical Visualization Programming API 33

34. Computer animation  is a general term for a kind of visual digital display technology that simulates moving objects on-screen. Computer animation 34

35. Displaying animation sequences Movies work by fooling our eyes A sequence of static images presented in a quick succession appears as continuous flow 35

36. Displaying animation sequences To achieve smooth animation, a sequence of images (frames) have to be presented on a screen with the speed of at least 30 per second Animations frames can be pre-computed in advance and pre-loaded in memory computed in real time (e.g. movement of the cursor) 36