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Overview of Graphics System
Graphics Hardware Video Display Devices
• CRT Basic
• Type of CRT– Random-Scan Displays– Raster-Scan-Displays– Direct-View Storage Tubes(DVST)– Flat-Panel Displays
Others
Graphics Software
Video Display Devices
Cathode-Ray Tube(CRT)
CRT Basic (1/2)
Phosphor refresh CRT
• To maintain image, refresh electron beam repeatedly
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
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) 3/4 : length of 3points on vertical line = length of 4 points on horizontal line
Type of CRT
Ramdon-Scan Displays
Raster-Scan Displays
Direct-View Storage Tubes (DVST)
Flat-Panel 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, frame buffer) draw a picture one line at a time
Raster-Scan Displays (1/2)
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 (2/2)
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 Bit map
Raster Displays (Pixmap)
With multiple bits per pixel, we can display gray-scale or color pictures
the frame buffer is commonly called pixmap
Size of Frame Buffer when N=3, with 512 X 512
Size of Frame buffer = 3 X 29 X 29 = 3 X 218 = 768k
LUT (Look - Up - Table)
N bits per pixel = only 2N intensities are
possible
To get more intensity use LUT
The LUT must contain 2N entries.
if the LUT consists ofbits then total
2 intensities are available
but only 2N intensities are available at a
time
Advantage of LUT
• 1. Save Memory
• 2. Speed of color change
Color CRT Display
Random-scan monitor Beam-penetration
• Two layers of phosphor (red, green) Raster-scan monitor
Called 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
DVST & Flat-Panel Displays
DVST Direct-view storage tube maintaining a screen image
• store the picture information inside the CRT instead of refreshing the screen (Refresh CRT)
Flat-Panel Displays emissive displays
• convert electrical energy into light
nonemissive displays• convert other source into light
• LCD(Liquid-Crystal Displays)
Graphics Software (1/2)
Two general classifications general programming package
• provides an extensive set of graphics functions used by high level prog. lang (Fortran, C)
• GKS (Graphical Kernel System) 2-D oriented package
• PHIGS (Programmer’s Hierarchical Interactive Graphics Standard)
extension of GKS Increased Capabilities for modeling, rendering
• PEX (PHIGS Extension to X) good for network environments
Graphics Software (2/2)
• CGI (Computer Graphics Interface) device interface methods
• CGM (Computer Graphics Metafice) standards for archiving and transporting pictures
• Open GL & DirectX– Graphics Library
Special purpose package
• design for nonprogrammer
• ex) 3D MAXstudio, Topas, Autocad for PC
• MAYA, WAVEFRONT, ALIAS, SOFTIMAGE for Workstations
Script Language
• Render Man, Radiance, PovRay