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Graphics System


									Graphics System

    2011, Fall
Overview of Graphics System

 Graphics Hardware
   Video Display Devices
     • CRT Basic
     • Type of CRT
         – Random-Scan Displays
         – Raster-Scan-Displays
     • Flat-Panel Displays
   Others
 Graphics Software
Video Display Devices

 Cathode-Ray Tube(CRT)

                          (cathode ray)
CRT Basic (1/2)

   Phosphor(형광체)
     • Emit a small spot of light contacted by the electron beam
   refresh CRT
     • To maintain image, refresh electron beam repeatedly
     • refresh rate : frequency at which a picture is redrawn
   Persistence
     • how long the phosphor continue to emit light after the election
       beam is removed.
     • defined as the time to takes 1/10 of its original intensity
     • general purpose graphic monitors : from 10 to 60 ms
CRT Basic (2/2)

    Resolution
        • the maximum number of points that can be displayed without
          overlap on a CRT
        • simply the total number of points in horizontally and vertically
    Aspect Ratio.
        • ratio of vertical points to horizontal points necessary to produce
          equal-length line in both direction
        • ex) 4/3 : length of 4 points on horizontal line = length of 3points
                    on vertical line

 Spot Intensity (Gaussian distribution)   Overlap position (distinguishable  60%)
Type of Display Device

 Type of CRT
    Random-Scan Displays
    Raster-Scan-Displays
 Flat-Panel Displays
    Emissive displays
    Nonemissive displays
Random-Scan Display

   Vector Display (calligraphic display)
   stored as a set of line-drawing commands in an area of
    memory (refresh display file, display list, display program)
   draw a picture one line at a time
Raster-Scan Displays (1/3)

   Point plotting device : pixel or pel (Picture Element)
   picture info. for all the screen points is stored in separate
    Memory called Frame buffer (Refresh Buffer)
   one row at a time (scan line) from top to bottom
Raster-Scan Displays (2/3)

 Frame buffer
    Depth of the buffer area, Number of bit planes
    Bitmap: one bit per pixel
    Pixmap: multiple bits per pixel
 Refresh rate
    Above about 24 frame per second
    Unit of refresh rates  Hz
       • Ex) 60 frames per second (60Hz)
Raster-Scan Displays (3/3)

 Retrace
    Horizontal retrace/Vertical retrace
 Interlaced refresh procedure
    used with slower refreshing rates
       • avoid flicker
       • provide adjacent scan lines
Vector vs Raster Displays

 Rendering performance
    VD: Sensitive to scene and object complexity
    RD: Insensitive to scene and object complexity
 Memory and processing requirement
    VD: variable (depends on scene and object complexity)
    RD: Large but constant
 Screen space aliasing
    VG: None
    RG: Frequent
 Rendering of interior
    VG: No (boundary only)
    RG: Yes (Colored, Shaded and Textured surface)
Raster Displays (Bitmap)

 Intensity for each pixel depends on the size of
  frame buffer
    ex) Black & White system
              one bit per pixel is needed
              the frame buffer is commonly called Bitmap
Raster Displays (Pixmap)

   With multiple bits per pixel, we can display gray-scale or
    color pictures
           the frame buffer is commonly called pixmap

  Ex) Size of Frame Buffer when N=3, with 512 X 512
      Size of Frame buffer = 3 X 512 X 512 = 3 X 256k = 768k
Color CRT Display

 Random-scan monitor
   Beam-penetration
     • Two layers of phosphor(red, green)
 Raster-scan monitor
   Shadow Mask method
   System has 3 electron guns (R, G, B)
   Each Gun is controlled by Frame buffer
True Color System
Raster Graphics System Architecture
Flat-Panel Displays (1/2)

 Flat-Panel Displays
    Video devices that have reduced
     volume, weight, and power requirement
     compared to a CRT
    emissive displays
      • convert electrical energy into light
          – Plasma Display Panels (PDP)
               » Less efficient than CRTs (Not as     Plasma Display Panels
                 bright, More power)
               » Large Pixels(~1mm compared to
                 0.2mm for CRT)
          – Field Emission Devices (FED)
               » Limited in size
          – Light-Emitting Diode (LED)
               » LED-backlight LCD television
                                                      Field Emission Display
Flat-Panel Displays (2/2)

  nonemissive displays
    • convert other source (heat, electromagnetic force,..) into light
    • Liquid-Crystal Displays (LCD)
        –   Liquid Crystal
        –   The LCD's transition between crystalline and liquid states
        –   less energy on average than their plasma counterparts
        –   a limited viewing angle relative to CRT and plasma displays
Viewing Systems

Large-screen stereoscopic view    Wide screen view

        Multi-panel display
                                 Curved viewing screen
3D Display

 3D Display
   360° Light Field Display

   Philips 3DTV

   Hologram TV
Input Device

 Input Device
   Keyboard, Mouse

   Button Boxes, Dials
Input Device

   Trackballs
     • A ball device that can be rotated
       with fingers
   Spaceballs
     • Provide six degrees of freedom
   Joysticks
   Data grove
Input Device

 Digitizer
    • Device for drawing, painting,
      or interactively selecting
                                      Desktop tablet
    • Graphics tablet
    • 3D digitizer

         3D digitizing system           Artistic Digitizer System
Input Device

   Image Scanners

                           flatbed scanner

      Hand-held scanner

                          Wide-format scanner
Input Device

   Plasma panels with touch screens   Resistive touch screen overlays

              Light pen                        Voice system
Hard-Copy Devices

 Picture generated on a dot-matrix printer

                                             Roll-free pen plotter

            Desktop pen plotter
Graphics Software (1/2)

 Two general classifications
    general programming package
      • provides a library of graphics functions that can be used in a
        programming language such as C, C++, Java, or Fortran
      • CG API
          – Computer-graphics application programming interface
      • Ex) GL, OpenGL, VRML, Java2D, Java3D, Direct3D
    Special purpose package
      • design for nonprogrammers who want to generate picture,
      • ex) 3D MAXstudio, Autocad, MAYA, WAVEFRONT, ALIAS,
        SOFTIMAGE for Workstations
Graphics Software (2/2)

   Software standard
     • GKS (Graphical Kernel System) 1984
          2-D oriented package
     • PHIGS (Programmer’s Hierarchical Interactive Graphics
          extension of GKS
          Increased Capabilities for modeling, rendering
     • OpenGL
         – GL (Graphics Library)  Hardware Independent
         – OpenGL Architecture Review Board

   Script Language
     • Render Man, Radiance, PovRay

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