Overview of graphics
system
Chapter 2
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Computer Grpahic Notes, Exams of Computer Graphics and Animation
Overview of Computer graphics Lectute notes
Typology: Exams
2018/2019
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Overview of graphics
system
Chapter 2
Basic Graphics System
Refresh Cathode-Ray Tube
o Focusing system
o Electrostatic focusing
o Positively charged metal cylinder
o Deflection of electron beam
o Persistence
o How long phosphors continue to emit light
o Low persistence is useful for animation
o Resolution
o Number of points per centimeter can be
plotted horizontally and vertically
Refresh Cathode-Ray Tube
o Intensity distribution of a phosphor spot
o Adjacent spots appear distinct: 60%
o Spot size also depends on intensity
o Deflection of electron beam
o Resolution of a CRT depends
o Type of phosphor
o Intensity to be displayed
o Focusing and deflection system
o Aspect ratio
o The ratio of vertical points to horizontal points
necessary to produce equal-length lines
Raster-Scan Display The electron beam is swept across the screen, one row at a time from top to bottom
Raster-Scan Display
o Frame buffer (refresh buffer)
Picture definition is stored in the memory area
o Pixel Picture each screen point is referred as pixel or pel
o Scan line
o Pixmap (bitmap) Picture for black-and-white system
with one bit per pixel, the frame buffer is called a bitmap. For systems with multiple bits per pixel the frame buffer is called a pixmap
o Refreshing (60 - 80 frames/sec)
o Horizontal retrace
o Vertical retrace
o Interlacing each frame is displayed in two pass
o Scan conversion
Random-Scan Display A CRT has the electron beam directed only to the parts of the screen where the picture is to be drawn draw a picture one line.
Random-Scan Display
o Random-scan (vector, stroke-writing,
calligraphic) displays
o (^) Draw a picture one line at a time
o Refresh rate
o (^) Depends on the number of lines to be displayed
o Picture definition
o (^) A set of line-drawing commands o (^) Refresh display file
o Designed for line drawing applications
o (^) Can not display realistic shaded scenes
Color CRT Monitors
o Shadow-mask method
o (^) Three phosphor color dots at each pixel position o (^) Three electron guns o (^) Color variations: Varying the intensity levels of the three electron beams o (^) Full-color (true-color) system: 24 bits of storage per pixel
Flat-Panel Displays
o Video devices have reduced
o volume,
o weight, and
o power requirements
o compared to a CRT.
o A significant feature - thinner than
CRT
o Classified into two categories:
o Emissive displays
o Nonemissive displays
Three-Dimensional Viewing Devices
o Three-dimensional display system
o (^) Reflects a CRT image from a vibrating, varifocal mirror. o (^) The mirror changes focal length to match the depth of points in a scene.
o Genisco SpaceGraph System
o (^) Project objects into a 25X25 X25 cm^3 volume o (^) Applications o (^) Medical o (^) Geological o (^) Molecules