institute for visualization and perception research 1 © copyright 2000-2010 haim levkowitz graphics...

Institute for Visualization and Perception ResearchI VPR 1

© Copyright 2000-2010 Haim Levkowitz

Graphics Systems Overview

• Video display devices …

• Input devices …

• Hard-copy devices

• Graphics software ...



Video display devices …

• CRTs …

• Raster-scan displays …

• Vector displays …

• Graphics displays, monitors, workstations ...



CRTs …

• Magnetic deflection

• Accelerating anode

• Electrostatic deflection

• Phosphor persistence

• Intensity distribution

• Resolution

• Aspect ratio



Magnetic deflection



Accelerating anode



Electrostatic deflection



Phosphor persistence

Off OffOn

Brightness

Time

Visibility Threshold



Intensity distribution

Illuminated phosphor spot



Resolution

• Distinguishable

• Spearation > D s.t. I = 0.6 Max I



Aspect ratio

W

HW/H



Raster-scan displays ...

• Pixel

• Scan line

• Frame buffer

• Bitmap/pixmap

• Scan & retrace …

• Frame timing …



Scan & retrace

• Horizontal

• Vertical

• Interlace vs. non interlace …



Interlace vs. non interlace

• 2:1 vs. random



Frame timing …• Retrace: V: 1.3 mSec; H: 10 micro Sec.

• Sync pulse every: V: 1/60 Sec.; H: 63.5 micro Sec.

• 525 scan lines (RS 170 video standard)

• 1st 21: V blanked ==> 483 displayed

• 53 microSec./scan line

• 512 pixels ==> 100 nSec./pixel

• 512 x 1024 ==> 50 nSec./pixel

• 1024 x 1024 ==> 25 nSec./pixel



Frame buffer …

• Simple: Frame buffer is part of system memory ...

• Dedicated frame buffer …

• Video controller …

• Display processor …



Simple: Frame buffer is part of system memory

CPU System Memory

Video Controller

System Bus

Monitor



Dedicated frame buffer

CPUSystem Memory

Video Controller

System Bus

I/O Devices

MonitorFrame Buffer



Video controller



Display processor

• Scan conversion

• Characters: outline curves/pixel grids …



Characters: outline curves / pixel grids



Vector displays …

• Random-scan/stroke

• Line drawing

• Display list

• No shaded image

• Higher resolution

• Smooth lines (beam follows line)



Vector display example …



Graphics displays, monitors, workstations …

• Direct view storage tubes …

• Color CRT monitors …

• Flat-panel displays …

• Three-dimensional viewing devices

• Stereoscopic and virtual-reality systems



Direct view storage tubes• Store in CRT• 2 guns

• Primary: Store• Flood: Maintain

• Advantages• No refresh ==> High res’n, no flicker

• Disadvantages• No color/selective erase; slow



Color CRT monitors …

• Shadow mask

• Composite

• RGB

• 24 bits/pixel

• +16 Million colors

• Full-/true-color



Delta-delta



Flat-panel displays

• Emissive …

• Nonemissive ...



Emissive …

• Electricity --> light• Plasma …• Thin-film electroluminescent …• LED• Flat CRTs

• Electron beams accelerated parallel to screen



Plasma …• Gas-discharged

• “Sandwich”• 2 glass plates

• Vertical ribbons• Horizontal ribbons

• Mixture of gasses (neon)• High brightness• Monochrome



Thin-film electroluminescent …

• Similar to plasma

• Phosphor instead of gas

• Phosphor becomes conductor



Nonemissive

• Optical effects

• Sunlight / other source --> graphics pattern

• LCD ...



LCD …

• Nematic (threadlike) liquid-crystal

• Polarized light

• Internal source / surrounding

• Passive-matrix ...

• Active-matrix ...



Passive-matrix …

• Align to block/transmit• H + V rows of conductors• Pixel: intersection of 2

conductors• On: twist polarized light to pass• Off: don’t twist ==> block• Back lighting• Color: triads/dyes



Active-matrix …

• Transistor at each pixel

• Thin film transistor

• Control voltage at pixel location

• Prevent charge from leaking



Three-dimensional viewing devices

• Varifocal mirror

• Other



Stereoscopic and virtual-reality systems• Stereoscopic

• Eye separation

• Natural / mechanical aid

• Head-mounted displays

• Resolution

• “Legally blind”

• Affect on user



Input devices ...• Keyboards• Mouse, Trackball & Spaceball, Joysticks• Data glove• Digitizers• Image scanners• Touch panels• Light pens• Voice systems



Graphics software

• Graphics pipeline …

• Coordinates representations …

• Transformation pipeline …

• Graphics functions

• Standards



Graphics pipeline …

App’n Model

App’n Program

Graphics System

Device Independent

Device Dependent

App Prog: Use Package

Graphics Sys implementor: Alg’s to scan convert primitives to pixels



Coordinate rep’s …

• Modeling / Local / Master (mc)

• World (wc)

• Physical device / screen (dc)

• Normalized device (nc)



Transformation pipeline …

• mc --> wc --> nc --> dc



Graphics functions

• Output primitives …

• Attributes …

• Transformations …

• Segmentation

• Objects, structures



Output primitives …

• Character string

• Geometric entities

• Point

• Line

• Curve

• Filled area (polygon, circle, ...)

• General



Attributes

• Color

• Line style, thickness

• Text style

• Area-filling patterns



Transformations

• Geometric ...

• Modeling ...

• Viewing ...



Geometric

• Translate

• Rotate

• Scale

• Sheer



Modeling

• Construct object / scene

• Object description

• Modeling coo’s



Viewing …

• Project view of picture

• Specify views

• Selected portion of output



Standards

• Portability

• Core

• GKS

• PHIGS, PHIGS+ …

• Language binding …

• Interface: CGI

• Store / transmit: CGM



PHIGS ...

• Programmer’s Hierarchical Interactive Graphics Standard

• Extension of GKS• Modeling• Color• Surface rendering• Picture manipulation



PHIGS+

• 3-D surface shading extension



Language binding …

• Syntax to access standard graphics functions from a particular language

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