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Introduction to Computer Graphics

Computer Graphics is related to the generation of graphics using computer. It involves the creation, storage and manipulation of images of objects which come from diverse fields such as physical, mathematical, engineering, abstract structures ,architectural and natural phenomenon. Computer graphics today is largely interactive , the user controls the contents, structure, and appearance of images of the objects by using input devices, like mouse, keyboard, or touch-sensitive panel on the screen.

In 1980's computer graphics was a small, specialized field because the hardware was expensive. Then personal computers, built-in raster graphics displays-such as the Xerox Star, Apple Macintosh and the IBM PC- popularized use of bitmap graphics for user computer interaction. A bitmap is a ones and zeros representation of the rectangular array points on screen. Each point is called a pixel, "Picture Elements”. Once bitmap graphics became cheap, and explosion of easy-to-use and inexpensive graphics-based applications. Graphics-based user interfaces allowed huge of new users to control simple, low-cost application programs, such as spreadsheets, word-processors, and drawing programs.

Nowadays, almost all interactive application programs use graphics extensively in the user interface and for manipulating and visualizing the application specific objects.

Computer graphics is an integral part of all computer user interfaces, and is indispensable for visualizing 2D, 3D objects in most of all areas such as education, engineering, medicine, commerce, science, the military, advertising, and entertainment. Theme is that learning how to program and use computers now includes learning to use 2D graphics.

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Advantages of Computer Graphics

Computer graphics has a broad area in computer science, incorporating elements of:

  1. graphic design
  2. ray tracing and rendering
  3. graphics hardware, libraries, and window systems API's
  4. user interfaces and graphical input

Areas of Applications

  1. User interfaces
    Computer graphics allows most applications to have user interfaces that rely on desktop windows systems to perform multiple simultaneous activities , and on point and click facilities that allow users to select menu items, objects and icons on the screen. E.g., spreadsheet, Word processing, and desktop-publishing programs uses user-interface techniques.
  1. Plotting
    Plotting 2D and 3D graphs of physical, mathematical, and economic functions use computer graphics extensively. The bar, histograms, and pie charts; the task- scheduling charts are the most commonly used plotting.
  1. Office automation and electronic publishing
    Computer graphics helps in the office automation and electronic publishing which is also commonly known as desktop publishing, giving more power to organizations to print the meaningful materials . Office automation and electronic publishing produce both Hardcopy documents and softcopy documents that contain text, , tables, graphs, and other forms of drawn or scanned-in graphics.
  1. Computer Aided Drafting and Design
    Computer graphics allows to design components and systems of electrical, mechanical, electrochemical, and electronic devices, and structures such as automobile bodies, buildings, airplane and ship hulls, optical systems, very large scale integrated (VLSI) chips, and telephone and computer networks5. Scientific and business Visualization
  1. Simulation and modeling
    The simulation is the imitation of the conditions , which is encountered in real life. It thus helps to learn or feel the conditions that one might have to face in future without being in danger at the beginning of course. Simulators are used to optimize the system, for example the vehicle, observing the reactions of driver during the operation of the simulator.
  1. Entertainment
    The best example of the application of computer graphics in the field of entertainment such as Disney movies such as Lion Kings and The Beauty of Beast, and other scientific movies like Jurassic Park, iron man, etc . Computer games such as FIFA, farcry , creed are few to name where graphics is used extensively.
  1. Art and commerce
    computer graphics is used to produce pictures that gives a message and attract attention. These pictures are frequently seen at supermarkets , transportation terminals , hotels etc. The slide production for , scientific, commercial or educational presentations is another cost effective use of graphics. One of such graphics packages is a PowerPoint.
  1. Cartography
    Cartography deals with the making of maps and charts which are accurate and schematic representations of geographical and natural phenomena. Examples include geographic maps , weather maps, oceanographic charts, contour maps and population-density maps. Surfer is extensively used for cartography.

Hardware Concepts - Input Devices

  1. Tablet
    In general, a digitizer is a digitizer which is used to scan over an object, and to input set of discrete coordinate positions. These positions can be joined with straight line segments to approximate shape of the original object. A tablet is a flat surface whose size varies from about 6/6 inches up to 48/72 inches or more. There are mainly three types of tablets.
    • Electrical tablet
    • Sonic tablet
    • Resistive tablet

  2. Touch Panel
    The touch panel allows users to point at the screen directly with a finger to move a cursor around the screen and to select the icons. Mostly used touch panels are:
    • Optical touch panel
    • Sonic panel
    • Electrical touch panel

  3. Light Pen
    Light pen is a pencil-shaped device that determines the coordinates of a point on the screen where it is initiated such as pressing a button. By reading saved values, the graphics package is able to determine the coordinates of position seen by the light pen.
    Because of the following drawbacks the light pens are not popular now:
    • Light pen obscures screen image as it is pointed to required spot
    • Prolong use of light pen can cause arm fatigue
    • It can’t report the coordinates of a point which is completely black.
    • It gives sometimes wrong reading due to background lighting in the room

  4. Keyboard
    Keyboard creates code like ASCII uniquely corresponding to pressed key. It usually consists of alphanumeric keys, cursor control keys, function keys, and separate numeric pad. It is used to move the cursor, select menu item, predefined functions. In computer graphics it is mainly used for entering screen coordinates and text, for invoking certain functions.

  5. Mouse
    A mouse is small hand held device used to position cursor on the screen. Mice are relative devices, i.e, they can be picked up, moved in space, and put down gain without any change in reported position. For this, the computer maintains current mouse position, which is incremented/decremented by the it’s movements. Following are the mice, which are mostly used in computer graphics.
    • Mechanical Mouse
      When roller in the base is moved, a pair of orthogonally arranged toothed wheels, each placed in between LED and photo detector, interrupts the light path. The number of interrupts generated are used to report a mouse movements to that computer.
    • Optical Mouse
      It is used on special pad having a grid of alternating light and dark lines. A LED on the bottom of the mouse directs a beam of light down onto the pad, reflected and sensed by the detectors on the bottom of mouse. As the mouse is moved, reflected light beam is broken each time a dark line is crossed. The number of pulses generated, which is equal to number of lines crossed, are used to report mouse movements to particular computer.

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