Computer Graphics Lecture 02 Graphics Systems Taqdees A. Siddiqi

With the massive development in the field of computer graphics a broad range of graphics hardware and software systems are available. With personal computers… usage of variety of interactive input devices and graphics software packages Higher-quality applications… usage of special-purpose graphics hardware systems and technologies Introduction to Graphics Systems

 VIDEO DISPLAY DEVICES  RASTER-SCAN SYSTEMS  RANDOM-SCAN SYSTEMS  GRAPHICS MONITORS AND WORKSTATIONS  INPUT DEVICES  HARD-COPY DEVICES  GRAPHICS SOFTWARE Graphics Systems

 Refresh Cathode-Ray Tubes  Raster-Scan Displays  Random-Scan Displays  Color CRT Monitors  Direct-View Storage Tubes  Flat-Panel Displays  Three-Dimensional Viewing Devices Video Display Devices

Refresh Cathode-Ray Tubes Refresh CRT  Control Grid  Focusing System  Focusing in High Precision System  Construction of Cathode-Ray Tubes  Persistence  Resolution  Aspect Ratio

Refresh Cathode-Ray Tubes

Refresh Cathode-Ray Tubes Cont..

Refresh Cathode-Ray Tubes Refresh CRT  Control Grid  Focusing System  Focusing in High Precision System  Construction of Cathode-Ray Tubes  Persistence  Resolution  Aspect Ratio

Refresh Cathode-Ray Tubes

Raster-Scan Displays  Refresh Buffer or Frame Buffer  Pixel  Bitmap vs. Pixmap  Horizontal Retrace & Vertical Retrace  Interlaced vs. Non-interlaced Display

Random-Scan Displays  Vector Display  Refresh Display File  Random-Scan vs. Raster-Scan

Color CRT Monitors  Beam Penetration Method  Shadow Mask Method

CRT Displays Advantages  Fast response (high resolution possible)  Full colour (large modulation depth of E- beam)  Saturated and natural colours  Inexpensive, matured technology  Wide angle, high contrast and brightness Disadvantages  Large and heavy (typ. 70x70 cm, 15 kg)  High power consumption (typ. 140W)  Harmful DC and AC electric and magnetic fields  Flickering at Hz (no memory effect)  Geometrical errors at edges

Direct View Storage Devices  Primary Gun  Flood Gun  Advantages & Disadvantages

Flat-Panel Displays  Properties Volume, Weight, Power  Emissive Display Plasma Panels  Non-Emissive Display Liquid Crystal Display

Plasma-panel Displays  Similar in principle to fluorescent light tubes  Small gas-filled capsules are excited by electric field, emits UV light  UV excites phosphor  Phosphor relaxes, emits some other color

Plasma-panel Displays  Two glass plates separated by neon gas  Vertical and horizontal conductors  Very rugged  No refreshing  Screens can be transparent and overlay documents  Used to be available in monochrome (Orange)  Now available in colour

Plasma-panel Displays  Advantages –Large viewing angle –Good for large-format displays –Fairly bright  Disadvantages –Expensive –Large pixels (~1 mm versus ~0.2 mm) –Phosphors gradually deplete –Less bright than CRTs, using more power

Liquid Crystal Displays  Liquid Crystal Display  A transmissive technology  Works by letting varying amounts of a fixed-intensity white backlight through an active filter  Organic crystals that align themselves together  When external force is applied they realign themselves  This is used to change polarisation and filter light

Liquid Crystal Displays

 Transmissive & reflective LCDs: – LCDs act as light valves, not light emitters, and thus rely on an external light source. – Laptop screen: backlit, transmissive display – Palm Pilot/Game Boy: reflective display

Advantages  Small footprint (approx 1/6 of CRT)  Light weight (typ. 1/5 of CRT)  Low power consumption (typ. 1/4 of CRT)  Completely flat screen - no geometrical errors  Crisp pictures - digital and uniform colours  No electromagnetic emission  Fully digital signal processing possible  Large screens (>20 inch) on desktops Liquid Crystal Displays

Disadvantages  High price (presently 3x CRT)  Poor viewing angle (type. +/- 50 degrees)  Low contrast and luminance (type. 1:100)  Low luminance (Natural light) (type. 200 cd/m2) Liquid Crystal Displays

Three-Dimensional Viewing Devices  Vibrating flexible mirror  Stereoscopic and virtual -reality systems -shutter glasses (with tracking) -headset with tracking -other VR devices  Holograms  NC-mills + soft material  Stereo-lithographic apparatus (SLA)

Virtual reality = stimulation of the human senses to simulate a fictive environment eyes: private eye, head mounted displays (hmd) ears: headphones, loudspeakers in hmd tactile sense: data glove, data suit, treadmill Virtual Reality Devices

2 small screens display images for both eyes: high immersion degree head movement controls virtual camera artificial image only low resolution (e.g. 256 x 210) very expensive narrow view-angle Head Mounted Display

ultrasound tracking device used with stereoscopic glasses to track head position Light Weight HMD

Interactive Walkthrough

Data Glove

Computer Graphics Lecture 02 Graphics Systems Taqdees A. Siddiqi