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 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/technology

/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

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