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Introduction to Computer Graphics. COMP 3003. Recommended Reading. Computer Graphics – Principles and Practice Foley, Van Dam, Feiner, Huges Computer Graphics D. Hearn, M. P. Baker 3D Computer Graphics Alan Watt Computer Graphics F.S. Hill, JR. Fundamentals of Digital Image Processing

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recommended reading
Recommended Reading
  • Computer Graphics – Principles and Practice
    • Foley, Van Dam, Feiner, Huges
  • Computer Graphics
    • D. Hearn, M. P. Baker
  • 3D Computer Graphics
    • Alan Watt
  • Computer Graphics
    • F.S. Hill, JR.
  • Fundamentals of Digital Image Processing
    • Anil K. Jain
course overview
Course Overview
  • Hardware, Input & Output - Display Technology
  • The Eye and image perception
  • Colours & Colour Models
  • Object Modelling
  • 2D Viewing - Windows and Viewports
  • Transformations - Matrix Representation
  • Bezier Curves
  • Clipping
  • 3D Graphics
  • Image Compression - JPEG, MPEG, GIF etc.
  • VRML and the WEB
contact details
Contact Details
  • Michela Bertolotto
  • Room B2.21
  • Email :
  • Web pages (see
    • Lecture Notes & Handouts
hardware issues input technology
Hardware Issues (Input Technology)
  • Pieces of hardware by which a user enters information into a computer system
    • mouse, trackball, joystick, voice systems, touch screens etc.
hardware issues digital camera input
Hardware Issues (Digital Camera Input)
  • Cameras
    • The image is focused onto a photosensitive surface (such asa charge coupled device (CCD)) line by line to accumulate entire image
  • The CCD produces current (or simply digital output in newer systems) which is proportional to light intensity (filtered for each of three colour bands)
  • Different quality/functionality cameras are used:Monochrome, Colour, Smart ( Designed for machine vision applications )
virtual reality and voice recognition
Virtual Reality and Voice Recognition
  • Virtual reality has generated a completely new set of input devices
    • Dataglove
    • Pressure pads
    • Digitizing arm
    • Various other tactile and gesture input device
  • Much research is currently in progress to devise better ways of interacting with the machine
  • Voice recognition and natural language comprehension are also currently the focus of much research
hardware issues input technology12
Hardware Issues (Input Technology)
  • A major goal in designing graphics packages is device-independence
    • enhances portability of the application
  • To provide a level of abstraction for graphics input, most graphics systems support logical input devices
  • These shield the application from the details of the physical devices available
logical input devices
Logical Input Devices
  • Locator
    • to indicate a position or orientation
  • Pick
    • selects from a displayed entity
  • Valuator
    • to input a single real number (Volume Control Dial)
  • Keyboard
    • to input a character string
  • Choice
    • to select from a set of possible actions or choices (Function Keys)
logical input devices14
Logical Input Devices
  • Locator:
    • Inputs a position (x,y) typically via pointer (mouse/joystick)
  • Pick:
    • Identifies a displayed object NOT just an (x,y).
      • Selects a whole object that is normally associated with a segment via e.g. a lightpen
  • Choice:
    • Selects from a set of alternatives:
      • i.e. integer value from buttons on a box or via a menu selection with lightpen or digitiser, most common is function keys
  • Valuator:
    • Inputs a value (real or integer) perhaps from a dial (can be bounded – radio tuner or unbounded – provides relative info.)
locator input devices
Locator Input Devices
  • Absolute or Relative
    • Absolute: report position with regard to an origin
      • e.g. data tablet, touch screen
    • Relative: report position w.r.t. their former position
      • e.g. mouse, joystick
  • Direct or Indirect
    • Direct: user points directly at screen
      • e.g. light-pen or finger on touch screen
    • Indirect: user moves cursor on screen with device not on screen
      • e.g. mouse or joystick
locator input devices cont
Locator Input Devices (cont)
  • Discrete or Continuous
    • Continuous: smooth hand motion
      • e.g. mouse, trackball
    • Discrete: define action
      • e.g. cursor-control keys
hardware issues display technology
Hardware Issues (Display Technology)
  • Different outputdevices may be used - monitors, printers, plotters
  • Most common is the Cathode Ray Tube (CRT) monitor
    • Horizontal and vertical deflectors focus an electron beam emitted by an electron gun on any spot on a phosphor coated screen
    • The maximum number of points, or pixels that can be displayed without overlap is called the resolution, e.g. 1024x768, 800x600 etc.
    • Colour systems have groups of 3 different phosphors, for red, green and blue (the primary colours)
    • The CRT uses a combination of these phosphors to emit different coloured light
  • Once struck by the electron beam most phosphors relax back to the ground state by emitting a photon of light
  • This light is called fluorescence, which normally decays in under a millisecond
  • Some molecules may be further excited, and emit a light call phosphorescence, which decays slower, but still rapidly (15-20 milliseconds)
  • Therefore, the screen must be refreshed by redrawing the image
  • So phosphors may be characterised by their persistence
    • (time to decay of emitted light)
  • High persistence cheap and good for text, bad for animation (original IBM PC monitor)
  • Low persistence, good for animation, but needs a high refresh rate or flicker can be observed
  • 50-60 Hz is usually sufficient to avoid flicker