lecture2 computer graphics graphics hardware(Computer graphics tutorials)

31
Comp 430 Computer Graphics Lecture 2: Hardware Overview

description

presentation By Daroko blog-where IT learners Apply skills. This topic an presentation will introduce you to Computer graphics hardware types. --------------------------------- • Daroko blog (www.professionalbloggertricks.com) • Presentation by Daroko blog, to see More tutorials more than this one here, Daroko blog has all tutorials related with IT course, simply visit the site by simply Entering the phrase Daroko blog (www.professionalbloggertricks.com) to search engines such as Google or yahoo!, learn some Blogging, affiliate marketing ,and ways of making Money with the computer graphic Applications(it is useless to learn all these tutorials when you can apply them as a student you know),also learn where you can apply all IT skills in a real Business Environment after learning Graphics another computer realate courses.ly • Be practically real, not just academic reader Do Not just learn computer graphics an close your computer tab and go away.. APPLY them in real business, Visit Daroko blog for real IT skills applications,androind, Computer graphics,Networking,Programming,IT jobs Types, IT news and applications,blogging,Builing a website, IT companies and how you can form yours, Technology news and very many More IT related subject. -simply google:Daroko blog(professionalbloggertricks.com)

Transcript of lecture2 computer graphics graphics hardware(Computer graphics tutorials)

Page 1: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Comp 430Computer Graphics

Lecture 2:

Hardware Overview

Page 2: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Daroko blog-where IT leaners apply skills Do Not just learn computer graphics an close your

computer tab and go away.. APPLY them in real business, Visit Daroko blog for real IT skills

applications,androind, Computer graphics,Networking,Programming,IT jobs Types, IT news and applications,blogging,Builing a website, IT companies and how you can form yours, Technology news and very many More IT related subject.

-simply google:Daroko blog(professionalbloggertricks.com)

Jan 2009 - Lecture2 CSC406 Computer Graphics 2

Page 3: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 3

Lecture 2:

Scope: Graphics hardware.

Objectives: To determine the characteristics of graphics

display hardware.

Page 4: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 4

Computer Hardware:

Output Devices:Output Devices: Computer Graphics can use many different

output devices: Video display devices

Cathode Ray Tube (CRT) Liquid Crystal Display (LCD) Plasma panels Thin-film electroluminescent displays Light-emitting diodes (LED)

Page 5: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 5

Hard-copy devices Ink-jet printer Laser printer Film recorder Electrostatic printer Pen plotter

The most common display device is the Cathode Ray Tube (CRT) monitor.

Page 6: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 6

The Cathode Ray Tubes (CRTs) Most common display device today Characterized by:

Evacuated glass bottle Extremely high voltage Heating element (filament) Electrons pulled towards anode focusing cylinder Vertical and horizontal deflection plates Beam that strikes phosphor coating on front of

tube

Page 7: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 7

Page 8: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 8

CRT-2

Page 9: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 9

How CRT works-1

The electron gun contains a filament that, when heated, emits a stream of electrons

Electrons are focused with an electromagnet into a sharp beam and directed to a specific point of the face of the picture tube

The front surface of the picture tube is coated with small phospher dots

When the beam hits a phospher dot it glows with a brightness proportional to the strength of the beam and how long it is hit

Page 10: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 10

How CTR works - 2

In a CRT the focusing system acts like a light lens with a focal length such that the center of focus is the screen.

The horizontal and vertical deflectors allow the electron beam to be focused on any spot on the screen.

The screen is coated with a special organic compound called a phosphor.

For color systems there are groups of three different phosphors, one to produce red shades, one for green shades, and one for blue shades.

Page 11: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 11

How CRT works - 3

Electrons hit the screen phosphor molecules and cause a ground state to singlet excited state transition.

Most of the phosphors relax back to the ground state by emitting a photon of light which is called fluorescence. This happens very rapidly so that all of the molecules which

fluoresce do so in under a millisecond. These phosphors then emit light, called

phosphorescence, that decays slower but still rapidly (in about 15-20 milliseconds)… so there is the need to refresh the screen by redrawing the

image.

Page 12: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 12

CRT details…

Phosphors are characterized by color (usually red, green, or blue) and persistence, which is the time for the emitted light to decay to 10 % of the initial intensity.

High persistence phosphors allow for a lower refresh rate to avoid flicker, e.g., the original IBM PC monochrome monitor had a high

persistence phosphor. This allowed it to have good resolution for text with

inexpensive electronics. However, this is poor for animation since a "trail" is left with

moving objects.

Page 13: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 13

CRT details…

Low persistence phosphors are good for animation but require a high refresh rate to prevent flicker. A refresh rate of 50 - 60 Hz is usually sufficient to

prevent flicker, but some systems refresh at even higher rates

such as 72-76 Hz.

Page 14: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 14

CRT details…

Phosphers – terms… Flourescence: Light emitted while the

phosphor is being struck by electrons Phosphorescence: Light emitted once the

electron beam is removed Persistence: The time from the removal of the

excitation to the moment when phospherescence has decayed to 10% of the initial light output

Page 15: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 15

CRTs - Display Technologies… Two main types:

Vector display. Raster display.

Page 16: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 16

CRTs - Vector Displays

Early computer displays: basically an oscilloscope Control X,Y with vertical/horizontal plate voltage Often used intensity as Z (close things were

brighter) Often termed random scan displays.

Page 17: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 17

Vector displays:

Here the electron gun of a CRT illuminates points and straight lines in any order.

The display processor repeatedly reads a variable 'display file' defining a sequence of X,Y coordinate pairs and brightness or color values, and converts these to voltages controlling the electron gun.

Page 18: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 18

Vector Display…

Advantages of random scan: very high resolution, limited only by monitor easy animation, just draw at different positions requires little memory (just enough to hold the display

program) Disadvantages:

requires "intelligent electron beam, i.e., processor controlled

limited screen density before have flicker, can't draw a complex image

limited color capability (very expensive)

Page 19: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 19

A Random Scan Display (outline)…

Page 20: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 20

Display technologies: CRTsRaster Displays Raster: a raster is a series of adjacent parallel 'lines'

which together form an image on a display screen. Pixel: One dot or picture element of the raster Scan line: A row of pixels

Page 21: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 21

Display technologies: CRTsRaster Displays Black and white television: an oscilloscope with a fixed

scan pattern: left to right, top to bottom As beam sweeps across entire face of CRT, beam

intensity changes to reflect brightness Analog signal vs. digital display

Page 22: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 22

Rasters:Rasters:

Lexically, a raster is a series of adjacent parallel 'lines' which together form an image on a display screen.

In early analogue television sets each such line is scanned continuously, not broken up into distinct units.

In computer or digital displays these lines are composed of independently coloured pixels (picture elements).

Page 23: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 23

A Raster

Page 24: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 24

Resolution…

The maximum number of points that can be displayed without overlap is called the resolution.

Usually given as the number of horizontal points versus the number of vertical points

These are called pixels (picture elements), E.g. a monitor might have a resolution of 1024 X 768

pixels.

Page 25: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 25

The maximum resolution may be determined by the characteristics of the monitor for a random

scan system or by a combination of the monitor and graphics card

memory for a raster scan system. For a random scan system the resolution can be

up to 4096 X 4096

Page 26: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 26

Aspect Ratio:

The aspect ratio equals the ratio of vertical pixels/horizontal pixels for an equal length line.

It sometimes refers to the ratio of the horizontal dimension/vertical dimension.

Examples:

Page 27: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 27

If have the above monitor and a resolution of 640 X 480 pixels

==> horizontal --> 640/8 = 80 pixels/inch ==> vertical --> 480/6 = 80 pixels/inch

Therefore, it has "square" pixels, i.e. the same size in the vertical and horizontal directions.

If the resolution is 320 X 200 pixels, then: ==> horizontal --> 320/8 = 40 pixels/inch ==> vertical --> 200/6 = 33 1/3 pixels/inch

So the size of a horizontal pixel does not equal the size of a vertical pixel. We must correct for this in our image display, e.g. line or

object drawing. Otherwise all of the drawings will be distorted.

Page 28: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 28

Mathematically we consider a raster to be a rectangular grid or array of pixel positions:

Pixel positions have X,Y coordinates. Usually Y points down - This may reflect early use

to display text to western readers. When considering 3D, right-handed coordinates

imply Z - represents depth.

Page 29: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 29

Pixel Values:Pixel Values:

The colour of each pixel of a display is controlled by a distinct digital memory element.

Each such element holds a pixel value encoding a monochrome brightness or colour to be displayed.

With respect to color/pixel value, displays can be classified into two broad categories: Monochrome. Non-monochrome.

Page 30: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 30

Monochrome displays…

Are of two types. Bi-level displays - have 1-bit pixels and have been

green or orange as well as black-and-white. Greyscale displays - usually have 8 to 16 bit pixel

values encoding brightness.

Page 31: lecture2  computer graphics graphics hardware(Computer graphics tutorials)

Jan 2009 - Lecture2 CSC406 Computer Graphics 31

Non-monochrome displays… Also have two types.

True-colour Displays have pixel values divided into three component

intensities, usually red, green and blue Often of 8 bits each - This used to be very costly. Alternatively the pixel values may index into a fixed or

variable colour map defining a limited colour palette. Pseudo-colour

Displays with 8-bit pixels indexing a variable colour map of 256 colours have been common.