overview of graphics system graphics hardware video display devices crt basic type of crt...

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