Computer Graphics

What is Computer Graphics? What are its types? Discuss the importance of Computer Graphics.

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.

What are its types?

Different types of Computer Graphics

Computer Graphics can be broadly divided into two

a) Non Interactive Computer Graphics

b) Interactive Computer Graphics

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 takeoff 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.

Discuss the important uses of Computer Graphics.

The importance of computer graphics lies in its applications. In engineering applications (e.g. automotive and aeorspace), the ability to quickly visualize newly designed shapes is indispensible. Before the advent of computer graphics, designers built expensive prototypes and time-consuming clay models. Now, designers can interactively view and modify models of their shapes using a computer.

Medical imaging is another application where computer graphics has proven valuable. Recent advances in imaging technology such as computer tomography and magnetic resonance imaging allow physicians to take 3D Xrays of the human body. Interactive computer graphics allows the physician to interpret this large volume of data in new and useful ways.

Computer graphics has also expanded the boundaries of art and entertainment. Movies such as Jurassiac Park make extensive use of computer graphics to create images that test the bounds of imagination. The development of computer graphics has made possible virtual reality, a synthetic reality that exists only inside a computer. Virtual reality is fast becoming an indispensable tool in education. Flight simulators are used to train pilot for extreme conditions. Surgical simulators are used to train novice surgeons without endangering patients.

Computer has become a powerful tool for the rapid and economical production of pictures. Computer Graphics remains one the most exciting and rapidly growing fields. Old Chinese saying”One picture is worth of thousand words” can be modified in this computer era into “One picture is worth of many kilobytes of data”.

Computer has become a powerful tool for the rapid and economical production of pictures. Computer Graphics remains one the most exciting and rapidly growing fields. Old Chinese saying”One picture is worth of thousand words” can be modified in this computer era into “One picture is worth of many kilobytes of data”. It is natural to expect that graphical communication will often be more convenient when computers are utilized for this purpose. This is true because one must represent objects in two-dimensional and three-dimensional spaces. Computer Graphics has revolutionized almost every computer-based application in science and technology.

Information technology is a trend today. As the volume of information increases, problem of storage arises. As time is money, in the 21st century people doesn’t have the time to read huge number of pages. So this problem is solved by Computer Graphics. . Picture can represent a huge database like bar charts, pie charts etc. suppose, we have to show the performance of some factory related with profit since 1980. One requires large number of pages to store this huge information related with financial, numerical and statistical information. A common man requires a lot of time to understand it. There is an alternative to show or represent this information with the help of graphical tools such as bar chart or pie chart i.e. we can express this data in pictorial forms.

Computer Graphics methods are utilized in Computer Aided Design (CAD) to produce the drawings of certain parts of a machine from any viewing angel. Another area in the field of Computer Aided Manufacturing (CAM) where by employing computer graphics techniques, one may display the manufacturing layout for a given part and trace the path taken by machine tools for a given manufacturing process. Architects can use computer graphics to produce layout of building and utilized them for Computer-Aided-Design (CAD). Virtual reality can take you one more step to further. Your architect can take you to walk in the simulated building to see and feel how accessible are the light switches and selves and so on.

Many people for different domain of applications use interactive graphics. For example, structural engineering use for efficient design of structures on the basis of the analysis of stress in various elements of the structure. From the survey it is evident that in future, engineers, designers etc, will be using computer graphics quite extensively. There is virtually no area in which graphical displays can not be used to some advantage, and so it is not surprising to find the use of computer graphics so widespread. Today, we find Computer Graphics used routinely in such diverse areas such as science, engineering, medicine, business, industry, government, art, entertainment, advertising, education, training, etc.

Applications of Computer Graphics

The following are also considered graphics applications

Paint programs: Allow you to create rough freehand drawings. The images are stored as bit maps and can easily be edited. It is a graphics program that enables you to draw pictures on the display screen which is represented as bit maps (bit-mapped graphics). In contrast, draw programs use vector graphics (object-oriented images), which scale better.

Most paint programs provide the tools shown below in the form of icons. By selecting an icon, you can perform functions associated with the tool.In addition to these tools, paint programs also provide easy ways to draw common shapes such as straight lines, rectangles, circles, and ovals.

Sophisticated paint applications are often called image editing programs. These applications support many of the features of draw programs, such as the ability to work with objects. Each object, however, is represented as a bit map rather than as a vector image.

Illustration/design programs: Supports more advanced features than paint programs, particularly for drawing curved lines. The images are usually stored in vector-based formats. Illustration/design programs are often called draw programs. Presentation graphics software: Lets you create bar charts, pie charts, graphics, and other types of images for slide shows and reports. The charts can be based on data imported from spreadsheet applications.

A type of business software that enables users to create highly stylized images for slide shows and reports. The software includes functions for creating various types of charts and graphs and for inserting text in a variety of fonts. Most systems enable you to import data from a spreadsheet application to create the charts and graphs. Presentation graphics is often called business graphics.

Animation software: Enables you to chain and sequence a series of images to simulate movement. Each image is like a frame in a movie. It can be defined as a simulation of movement created by displaying a series of pictures, or frames. A cartoon on television is one example of animation. Animation on computers is one of the chief ingredients of multimedia presentations. There are many software applications that enable you to create animations that you can display on a computer monitor.

There is a difference between animation and video. Whereas video takes continuous motion and breaks it up into discrete frames, animation starts with independent pictures and puts them together to form the illusion of continuous motion.

CAD software: Enables architects and engineers to draft designs. It is the acronym for computer-aided design. A CAD system is a combination of hardware and software that enables engineers and architects to design everything from furniture to airplanes. In addition to the software, CAD systems require a high-quality graphics monitor; a mouse, light pen, or digitizing tablet for drawing; and a special printer or plotter for printing design specifications.

CAD systems allow an engineer to view a design from any angle with the push of a button and to zoom in or out for close-ups and long-distance views. In addition, the computer keeps track of design dependencies so that when the engineer changes one value, all other values that depend on it are automatically changed accordingly. Until the mid 1980s, all CAD systems were specially constructed computers. Now, you can buy CAD software that runs on general-purpose workstations and personal computers.

Desktop publishing: Provides a full set of word-processing features as well as fine control over placement of text and graphics, so that you can create newsletters, advertisements, books, and other types of documents. It means by using a personal computer or workstation high-quality printed documents can be produced. A desktop publishing system allows you to use different typefaces, specify various margins and justifications, and embed illustrations and graphs directly into the text. The most powerful desktop publishing systems enable you to create illustrations; while less powerful systems let you insert illustrations created by other programs.

As word-processing programs become more and more powerful, the line separating such programs from desktop publishing systems is becoming blurred. In general, though, desktop publishing applications give you more control over typographical characteristics, such as kerning, and provide more support for full-color output.

A particularly important feature of desktop publishing systems is that they enable you to see on the display screen exactly how the document will appear when printed. Systems that support this feature are called WYSIWYGs (what you see is what you get). Until recently, hardware costs made desktop publishing systems impractical for most uses. But as the prices of personal computers and printers have fallen, desktop publishing systems have become increasingly popular for producing newsletters, brochures, books, and other documents that formerly required a typesetter.

Once you have produced a document with a desktop publishing system, you can output it directly to a printer or you can produce a PostScript file which you can then take to a service bureau. The service bureau has special machines that convert the PostScript file to film, which can then be used to make plates for offset printing. Offset printing produces higher-quality documents, especially if color is used, but is generally more expensive than laser printing.

In general, applications that support graphics require a powerful CPU and a large amount of memory. Many graphics applications—for example, computer animation systems—require more computing power than is available on personal computers and will run only on powerful workstations or specially designed graphics computers. This is true of all three-dimensional computer graphics applications.

In addition to the CPU and memory, graphics software requires a graphics monitor and support for one of the many graphics standards. Most PC programs, for instance, require VGA graphics. If your computer does not have built-in support for a specific graphics system, you can insert a video adapter card.

The quality of most graphics devices is determined by their resolution—how many pixels per square inch they can represent—and their color capabilities.

Advantages of Interactive on Passive Graphics

1.     High quality of image produces.

2.     More reliable results.

3.     Lower cost.

4.     Large productivity.

5.     Lower analysis.

What is Wire-frame model ?

Wireframe systems were developed in the early 1960's to automate design drafting. Most of the early 3D CAD systems used wireframe models. The very first systems were only 2D and the user had to construct a model point by point and line by line.

A wireframe model is represented by tables defining edges and points. The start point and the end point of each edge are stored in the edge table. An edge may be a line or a curve. The coordinates of each point are stored in the point table. This representation is natural for a designer who is familiar with mechanical drawings, since it is the lines and curves in a drawing which define 3D shape. A wireframe model is stored very simply in a computer as a data structure. The storage space is small and the access time very short.

When one attempts to use pure wireframe representations to model 3D solids, one is confronted with four problems:

• The possibility of creating ambiguous models;
• The possibility of creating nonsense objects;
• The lack of graphic or visual coherence;
• The possibility that the wireframe model approximating a solid is verbose.

What is Z-buffering algorithm?

 Z-buffering is an algorithm used in 3-D graphics to ensure that perspective works the same way in the virtual world as it does in the real one: a solid object in the foreground will block the view of one behind it. You've seen this illustrated in the real world when someone stands between you and the television screen. Z-buffering is a type of algorithm known as a Visual Surface Determination (VSD) algorithm.

Z-buffering works by testing pixel depth and comparing the current position ( z coordinate ) with stored data in a buffer (called a z-buffer ) that holds information about each pixel's last postion. The pixel in the closer position to the viewer is the one that will be displayed, just as the person in front of the television is what the viewer sees rather than the screen.

Z-buffering is one of three VSD algorithms commonly used for this purpose. The other two, BSP trees and depth sorting, work with polygons and consequently are less effective for portrayal of movement and overlap. Since it works at the pixel level, z-buffering can be demanding in terms of memory and processing time. Nevertheless, its more complex and life-like simulation of real-world object dynamics ensures its continuing popularity as a 3-D graphics development tool.