1-cse455-introduction-crt-and-other-devices - · PDF file2016-10-01 · Introduction •Computer Graphics : It involves display manipulation and ... • CAD/CAM Design(VLSI, Construction,

Computer Graphics

Introduction

Introduction

• Computer Graphics : It involves display manipulation and storage of pictures and experimental data for proper visualization using a computer.

• Typically graphics system comprises of the host computers with support of – fast processor, – large memory, – frame buffer– display devices, – input devices, – output devices – interface devices.

1/13/2011 2Gaurav Raj, Lovely Professional University,

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Conceptual Framework for Interactive Graphics

Application Model

Application Program

Graphics System

Input Devices

Output devices


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Typical Application Areas• GUI• Plotting in business• Office Automation• Desktop Publishing • Plotting in Science and Technology • Web/Commercial/Business publishing and advertisements • CAD/CAM Design(VLSI, Construction, Circuits)• Scientific visualization• Entertainment• Simulation and Simulation Study• Cartography • Multimedia • Virtual reality • Process monitoring• Digital Image processing• Education and Training


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GUI – Graphics User Interface

• Typical Component used-– Menus

– Icons

– Cursors

– Dialog Boxes

– Scroll Bars

– Buttons

– Valuators

– Grids

– 3-D Interfaces


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Application Packages

• Various application package and standards available

– Core Graphics

– GKS

– SRGP

– PHIGS, SPHIGS and PEX 3D

– OpenGL(With ActiveX and Direct3D)

– X11 Based Systems


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• GKS- Graphics Kernel System – Developed by ISO and ANSI

• SRGP- Simple Raster Graphics Package

• PHIGS- Programmers Hierarchical IntaractiveGraphics Systems

– Various tools and utilities available for web based design include – JAVA, XML, VRML and GIF Animators

– Certain compilers with their own graphics libraries, API support and help for programming 2D/3D graphics.


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Display

• A graphics display is a drawing area comprised of an array of fine points called pixels (picture elements).

• At the heart of a graphics system there is a magic pen,

– move at lightning speed to a specific pixel

– draw the pixel with a specific color — a red, green, and blue (RGB) vector value.

– Computer graphics is about using this pen automatically through programming.


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Object, Model, and Image

• A real or imaginary object is represented in a computer as amodel, and is displayed as an image.

• A model is an abstract description of the object’s shape(vertices) and attributes (colors),

– which can be used to find all the points on the object corresponding tothe pixels in the drawing area.

– Given a model, the application program will control the pen through agraphics library to generate the corresponding image.

• An image is simply a 2D array of pixels.


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Primitive and Graphics Library• A graphics library provides a set of graphics commands or

functions.

– bound in C, Java, or other programming languages on differentplatforms.

– specify primitive 2D and 3D geometric models to be digitized anddisplayed.

• Primitive models or simply primitives stand for some simpleshapes (such as points, lines, and polygons)

• OpenGL is a graphics library; DirectX includes a graphicslibrary Direct3D


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Brief History

• 1963 Evan Sutherland’s seminal doctoral work “Sketchpad: a man-machine graphical communication system”

• 1977 3D Core Graphics System by ACM SIGGRAPH Committee• 1980’s, hardware expensive & graphics app. programs were few• 1985 GKS (the Graphical Kernel System), 2D • 1987 MIT’s X lib for windows under UNIX OS• 1988 GKS-3D, PHIGS (ANSI and ISO standard); SGI’s GL; • 1993 OpenGL (Open standard from SGI) • Since then, OpenGL supported on PC, MAC, Sun work-stations, SGI

work-stations, special purpose image generators (ESIG)• Since then, Evolution of advanced GUI’s and graphics

environments; Software from low-level, device dependent packages to higher-level device-independent packages

• 2003 JOGL – Java for OpenGL from Sunmicrosystem


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1/13/2011Gaurav Raj, Lovely Professional University,

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Cathode Ray Tube (CRT)


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Color CRT


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Type of CRT Display Devices

1. DVST (Direct View Storage Tube)2. Calligraphic or Random Scan Display System3. Refresh and Raster Scan Display System

DVST(Direct View Storage Tube)

1. Storage Tube – It is a CRT with a long persistence phosphor2. Provides Flicker – Free Display3. No refreshing necessary4. A slow moving electron beam draws a line on the screen.5. Screen has a storage mesh in which the phosphor is embedded.6. Image is stored as a distribution of charges on the inside surface of the

screen.7. Limited interactive support.


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Phosphor Coated Screen

DVST- Drawbacks

• Modifying any part of the image requires redrawing the entire image.

• Change in the image requires to generate new charge distribution in the DVST.

• Slow process of drawing- typically a few seconds are necessary for a complex image.

• Erasing takes approx. 0.5 second. All lines and character must be erased.

• No animation possible with DVST.


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Calligraphic or Random Scan Display System

• Also called vector , stroke, line drawing displays.

• Characters are also made of sequence of strokes (or short lines)

• Vectored – Electron beam deflected from end- point to end-point.

• Random Scan - Order of deflection is dictated by the arbitrary order of the display commands.

• Phosphor has short persistence – delay in 10 -100 micro seconds


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• Display must be refreshed at regular interval minimum of 30 Hz(fps) for flicker free display.

• Refresh Buffer- Memory space allocated to store the display list or display program for the display processor to draw the image.

• The display processor interprets the commands in the refresh buffer for plotting.

• The display processor must cycle through the display list to refresh the phosphor.

• Display program has the commands for point, line and character plotting.


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Conceptual Block Diagram

Calligraphic Refresh Display I


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Conceptual Block Diagram

Calligraphic Refresh Display II


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• The Display processor sends digital and point coordinate values to the vector display.

• The vector generator converts the digital coordinate values to analog voltages for the beam deflection circuits.

• The Beam deflection circuits displays the electron beam for writing on the CRT’s phosphor coating.

• Recommended refresh rate is 40 -50 Hz.

• Scope of animation with segmentation mixture of static and dynamic parts of the picture.


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RASTER DISPLAYS

• Store the primitives in a famebuffer, or refresh buffer which is RAM with 1024*1280, or V*H addressable pixels.

• Bitmap – array of 1/0 (pixels)• Pixmap- array of gray-scale pixels• Monocrome – Bi-level • Gray Scale – multiple level(1-15)• Color – (R,G,B)• Scan-Conversion(rasterization ) – Objects are converted

into discrete pixels in frame buffer.• Aliasing – Jagging or Stair casing of lines/ edges• Anti-Aliasing - Dealing with aliasing• Resolution - # of distingushable lines per inch


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CRT (CATHODE RAY TUBE)

LASER PRINTER (HARD COPY DISPLAY DEVICE)

Framebuffer


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RASTER DISPLAY SYSTEMS

• Graphics card: handle scan-conversion and other advanced graphics functions

Graphics Card (Video Card)


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• Frame Buffer(Bit Planes) : RAM with the generated pixmap and attribute ready to display.

• Video Controller : refresh the display.

• Interlaced: fine as long as adjacent scan lines display similar information

• # of bits for color : Direct(RGB Mode) and indirect(Index Mode)


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Documents

1-cse455-introduction-crt-and-other-devices - · PDF file2016-10-01 · Introduction •Computer Graphics : It involves display manipulation and ... • CAD/CAM Design(VLSI, Construction,