graphics system
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Graphics System
2012, 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 512Size 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
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 » http://www.rambus.com/kr/technolo
gy/applications/display/index.html
Plasma Display Panels
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
LED vs. PDP vs. LCD (1/2)
LED LCD vs. plasma vs. LCD
Light output (brightness)Winner: LED LCD, Loser: Plasma, Runner-Up: CCFL LCD
Black levelWinner: Plasma, Loser: CCFL LCD, Runner-up: LED LCD
Contrast ratio : the ratio between the darkest part of the image and the brightestWinner: Plasma, Loser: CCFL LCD, Runner-up: LED LCD
Viewing angleWinner: Plasma, Loser: CCFL LCD/LED LCD
LED vs. PDP vs. LCD (2/2)
Energy consumptionWinner: LED LCD, Loser: Plasma, Runner-up: CCFL LCD
PriceWinner: CCFL LCD, Loser: LED LCD, Runner-up: Plasma
LifespanTie
Burn-in : 고정된 화면을 장시간 켜놓거나 동일한 이미지가 반복될 경우 해당 이미지가 사라지지 않고 화면상에 남아 있는 현상Tie
Uniformity : a consistent brightness to the imageWinner: Plasma, Loser: CCFL LCD/LED LCD
Viewing Systems
Large-screen stereoscopic view Wide screen view
Multi-panel displayCurved 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 position
• Graphics tablet
• 3D digitizer
Desktop tablet
Artistic Digitizer System3D digitizing system
Input Device
Image Scanners
Hand-held scanner
flatbed 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
Desktop pen plotter
Roll-free 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,
graphs
• 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 Standard)
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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