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Introduction to Computer Graphics
Today there are very few aspects of our lives not affected by computers. Practically every cash or monetary transaction that takes place daily involves a computer. In many cases, the same is true of computer graphics. Whether you see them on television, in newspapers, in weather reports or while at the doctor’s surgery, computer images are all around you.
“A picture is worth a thousand words” is a well-known saying and highlights the advantages and benefits of the visual presentation of our data. We are able to obtain a comprehensive overall view of our data and also study features and areas of particular interest.
A well-chosen graph is able to transform a complex table of numbers into meaningful results. You know that such graphs are used to illustrate papers, reports and thesis, as well as providing the basis for presentation material in the form of slides and overhead transparencies. A range of tools and facilities are available to enable users to visualize their data, and this document provides a brief summary and overview.
Computer graphics can be used in many disciplines. Charting, Presentations, Drawing, Painting and Design, Image Processing and Scientific Visualization are some among them.
In particular, we will emphasize the following
a) Basic concepts of Computer Graphics
b) Different types of Computer Graphics
c) Origin of Computer Graphics
d) Working of an interactive graphics display
e) Importance of speed in displaying pictures
f) The change in size an orientation of pictures
g) Applications of Computer Graphics
Basic concepts of Computer Graphics
I hope all of you are fond of video games and you may be good at playing them. Have you seen the game of ping-pong? It’s a game played by two people with a pair video game controller and a home television set. You can see that when a game is switched on, a small bright spot , representing a ball, is seen bouncing to and fro across the screen.
Now each player uses his video game controller to position a paddle to bounce the ball back to his opponent. The player who hits the ball past his opponent wins a point and the one who gains 15 points wins the game. Now how did you invent this video game? This has been done with the aid of Computer Graphics. Video games represent a major use in the home of computer graphics. Computer graphics helps to create and manipulate pictures with the aid of computers.
Computer graphics is concerned with all aspects of producing images using a computer. It concerns with the pictorial synthesis of real or imaginary objects from their computer-based models.
Different types of Computer Graphics
Computer Graphics can be broadly divided into two
Non Interactive Computer Graphics: In non interactive computer graphics otherwise known as passive computer graphics, the observer has no control over the image. Familiar examples of this type of computer graphics include the titles shown on TV and other forms of computer art. Interactive Computer Graphics: Interactive Computer Graphics involves a two way communication between computer and user.
Here the observer is given some control over the image by providing him with an input device for example the video game controller of the ping pong game. This helps him to signal his request to the computer. The computer on receiving signals from the input device can modify the displayed picture appropriately. To the user it appears that the picture is changing instantaneously in response to his commands. He can give a series of commands, each one generating a graphical response from the computer. In this way he maintains a conversation, or dialogue, with the computer.
Interactive computer graphics affects our lives in a number of indirect ways. For example, it helps to train the pilots of our airplanes. We can create a flight simulator which may help the pilots to get trained not in a real aircraft but on the grounds at the control of the flight simulator.
The flight simulator is a mock up of an aircraft flight deck, containing all the usual controls and surrounded by screens on which we have the projected computer generated views of the terrain visible on take off and landing. Flight simulators have many advantages over the real aircrafts for training purposes, including fuel savings, safety, and the ability to familiarize the trainee with a large number of the world’s airports.
Origin of Computer Graphics
Years of research and development were made to achieve the goals in the field of computer graphics. In 1950 the first computer driven display was used to generate only simple pictures. This display made use of a cathode ray tube similar to the one used in television sets. During 1950’s interactive computer graphics made little progress because the computers of that period were so unsuited to interactive use. These computers were used to perform only lengthy calculations.
The single vent that did the most to promote interactive computer graphics as an important new field was the publication in 1962 of a brilliant thesis by Ivan E. Sutherland. His thesis, entitled ‘Sketchpad: A Man- Machine Graphical Communication System proved to many readers that interactive computer graphics was a viable, useful, and exciting field of research. By the mid -1960’s large computer graphics research projects were under taken at MIT, Bell Telephone Labs and General Motors. Thus the golden age of computer graphics began. In 1970’s thee researches began to bear fruit.
The instant appeal of computer graphics to users of all ages has helped it to spread into many applications throughout the world.
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Different Kinds of Resolutions in the Monitor
Resolution refers to the sharpness, or detail of the usual image. It’s a primary function of the monitor & it’s determined by the beam size & dot pitch. The screen is made up of a number of pixels.
A completes screen image consists of thousand of pixels & the screen resolution in the maximum no. of displayable pixels. Higher the resolution, the more pixels can be displayed. Resolutions are of different for different video standards as listed below :
(a) VGA : 1640 x 480
(b) SVGA : 800 x 600
(c) XGA : 1024 x 768
(d) SXGA : 1400 x 1050
Applications of Computer Graphics.
As ancient says “ a pixel is worth thousand words”, graphics is essential everywhere to understand the things, concepts, etc easily. Computer graphics is useful in almost all part of our life. In the following sections we are discussing some of the popular areas of computer graphics.
Design and Drawing : In almost all areas of engineering, be it civil, mechanical, electronic etc., drawings are of prime importance. In fact, drawing is said to be the language of engineers. The ability of computers to store complex drawings and display them on demand was one of the major attractions for using computers in graphic mode. However, these were further advantages.
Most of these drawings were the result of engineering calculations. In fact, programs can be written to make these calculations and the results can be used to draw diagrams on the screen. If changes are to be made, one can get back to the design formulae and so on. Thus, the are of design and drawing was one of the earliest and most useful applications of graphics.
Animation: But what brought the computers pretty close to the average individuals is the concept of animation moving pictures. It is the well known principle of moving pictures that a succession of related pictures, when flashed with sufficient speed will make the succession of pictures appear to be moving. In movies, a sequence of such pictures is shot and are displayed with sufficient speed to make them appear moving. Computers can do it in another way.
The properties of the picture can be modified at a fairly fast rate to make it appear moving. For example, if a hand is to be moved, say, the successive positions of the hand at different periods of time can be computed and pictures showing the position of the hand at these positions can be flashed on the screen. This led to the concept of “animation” or moving pictures. In the initial stages, animation was mainly used in computer games.
However, this led to a host of other possibilities. As we see later on in this course, computers not only allow you to display the figures but also offer you facilities to manipulate them in various ways – you can enlarge, reduce, rotate, twist, morph (make one picture gradually change to another – like an advertisement showing a cheetah change into a motor bike) and do a whole lot of other things.
Thus, a whole lot of films made use of computers to generate tricks. In fact, several advertisement films and cartons strips are built with no actors at all – only the computer generated pictures.
Multimedia applications : The use of sound cards to make computers produce sound effect led to other uses of graphics. The concept of virtual reality, where in one can be taken through an unreal experience, like going through an unbuilt house ( to see how it feels inside, once it is built ) are possible by the use of computer graphics technology .
In fact the ability of computers to convert electronic signals (0 & 1) to data and then on to figures and pictures has made it possible for us to get photographs of distant planets like mars being reproduced here on the earth in almost real time.
Simulation : The other revolutionary change that graphics made was in the area of simulation. Basically simulation is a mockup of an environment elsewhere to study or experience it. The availability of easily interactive devices (mouse is one of them, we are going to see a few other later in the course) made it possible to build simulators.
One example is of flight simulators, wherein the trainee, sitting in front of a computer, can operate on the interactive devices as if he were operating on the flight controls and the changes he is expected to see outside his window are made to appear on the screen, so that he can master the skills of flight operations before actually trying his hand on the actual flights.
The graphic capabilities of computers are used in a very large variety of areas like criminology (to recreate faces of victims, assailants etz.,) medical fields (recreating pictures of internal cavities, using signals sent by miniature cameras), recreation of Satellite pictures etc.
What is computer Graphics? Explain Interactive and Non-interactive
Computer graphics is an art of drawing pictures, lines, charts, etc using computers with the help of programming. Computer graphics is made up of number of pixels. Pixel is the smallest graphical picture or unit represented on the computer screen. Basically there are two types of computer graphics namely.
Interactive Computer Graphics: Interactive Computer Graphics involves a two way communication between computer and user. Here the observer is given some control over the image by providing him with an input device for example the video game controller of the ping pong game. This helps him to signal his request to the computer.
The computer on receiving signals from the input device can modify the displayed picture appropriately. To the user it appears that the picture is changing instantaneously in response to his commands. He can give a series of commands, each one generating a graphical response from the computer. In this way he maintains a conversation, or dialogue, with the computer.
Interactive computer graphics affects our lives in a number of indirect ways. For example, it helps to train the pilots of our airplanes. We can create a flight simulator which may help the pilots to get trained not in a real aircraft but on the grounds at the control of the flight simulator. The flight simulator is a mock up of an aircraft flight deck, containing all the usual controls and surrounded by screens on which we have the projected computer generated views of the terrain visible on take off and landing.
Flight simulators have many advantages over the real aircrafts for training purposes, including fuel savings, safety, and the ability to familiarize the trainee with a large number of the world’s airports.
Non Interactive Computer Graphics: In non interactive computer graphics otherwise known as passive computer graphics. it is the computer graphics in which user does not have any kind of control over the image. Image is merely the product of static stored program and will work according to the instructions given in the program linearly. The image is totally under the control of program instructions not under the user. Example: screen savers.