Introduction to Computer Graphics
Que 1. Define Computer Graphics? Explain Applications of Computer Graphics? What is computer graphics? List any four areas of applications of computer graphics.
List the uses of computer graphics. Computer graphics is the art of drawing pictures on computer screens with the help of programming.
It involves computations, creation, and manipulation of data.
In other words, we can say that computer graphics is a rendering tool for generating and manipulating images. Applications of Computer Graphics:
Computer Art:
● Using computer graphics we can create fine and commercial art which includes animation
packages, paint packages.
● These packages provide facilities for designing object shapes and specifying object motion.
Cartoon drawings, paintings, and logo designs can also be done.
Computer-Aided Drawing:
● Designing of buildings, and aircraft is done with the help of computer-aided drawing.
● This helps in providing minute details to the drawing and producing more accurate and sharp
drawings with better specifications.
Presentation Graphics:
● For the preparation of reports or summarizing the financial, statistical, mathematical,
scientific, economic data for research reports, creation of bar graphs, pie charts, time charts,
can be done using the tools present in computer graphics.
Entertainment:
● Computer graphics find a major part of its utility in the movie industry and game industries.
● Used for creating motion pictures, music videos, television shows, and cartoon animation films.
● In the game industry where focus and interactivity are the key players, computer graphics helps in providing such features in an efficient way. The above are genuine uses of computer graphics.
Education:
● Computer-generated models are beneficial for teaching a huge number of concepts and
fundamentals in an easy-to-understand and learn manner.
● Using computer graphics many educational models can be created through which more
interest can be generated among the students regarding the subjects.
Training:
● Specialized systems for training like simulators can be used for training the candidates in a
way that can be grasped quickly with better understanding.
● Creation of training modules using computer graphics is simple and very useful.
Visualization:
● Today the need of visualizing things have increased drastically, the need of visualization can
be seen in many advanced technologies.
● data visualization helps in finding insights into the data, to check and study the behavior of
processes around us we need appropriate visualization which can be achieved through
proper usage of computer graphics
Image Processing:
● Various kinds of photographs or images require editing in order to be used in different places.
● Processing of existing images into refined ones for better interpretation is one of the many
applications of computer graphics.
Machine Drawing:
● Computer graphics are very frequently used for designing, modifying, and creating various
parts of machines and the whole machine itself,
● The main reason behind using computer graphics for this purpose is the precision and clarity
we get from such drawing is ultimately and highly desired for the safe manufacturing of
machines using these drawings.
Advantages of computer graphics
- Computer graphics is one of the most effective and commonly used ways of communication with
- computer.
- It provides tools for producing pictures of the “real world” as well as synthetic objects such as mathematical
- surfaces in 4D and of data that have no inherent geometry such as survey results.
- It has the ability to show moving pictures thus making it possible to produce animations with computer graphics.
Que 2. Explain the working of the cathode ray tube with a suitable diagram.
Ans:
Working of Cathode ray tube:
● An electron gun emits a beam of electrons, which passes through focusing and deflection
systems and hits on the phosphor-coated screen.
● The number of points displayed on a CRT is referred to as resolutions (eg. 1024×768).
● Different phosphors emit small light spots of different colors, which can combine to form a
range of colors.
● A common methodology for color CRT display is the Shadow-mask meth
● The light emitted by phosphor fades very rapidly, so it needs to redraw the picture
repeatedly.
● There are 2 kinds of redrawing mechanisms: Raster-Scan and Random-Scan
Main Components of Cathode ray tube:
Electron Gun:
● Electron gun consisting of a series of elements, primarily a heating filament (heater) and a
cathode.
● The electron gun creates a source of electrons which are focused into a narrow beam
directed at the face of the CRT.
Control Electrode:
● It is used to turn the electron beam on and off.
Focusing system:
● It is used to create a clear picture by focusing the electrons into a narrow beam.
Deflection Yoke:
● It is used to control the direction of the electron beam.
● It creates an electric or magnetic field that will bend the electron beam as it passes
through the area.
● In a conventional CRT, the yoke is linked to a sweep or scan generator.
● The deflection yoke which is connected to the sweep generator creates a fluctuating
electric or magnetic potential.
Phosphor-coated screen:
● The inside front surface of every CRT is coated with phosphors.
● Phosphors glow when a high-energy electron beam hits them.
● Phosphorescence is the term used to characterize the light given off by a phosphor after
it has been exposed to an electron beam.
5. Differentiate between Random (Vector) scan display and Raster scan display?
Ans:
NOTE: A vector scan is also called a Random Scan.
| Vector scan (Random) Display | Raster Scan Display |
| 1) In Random Scan Display the resolution is higher than raster scan. | 1) In Raster Scan Display the resolution of raster scan is lower than random scan. |
| 2) It is more expensive. | 2) It is affordable as compared to the random scan. |
| 3) In a random scan, it is easy to proceed with modifications. | 4) In raster scans, we prefer interlacing. |
| 4) In random scans, we don’t prefer interlacing. | 8) Example of a raster scan is TV Sets. |
| 5) When it comes to image rendering, we prefer mathematical functions. | 5) When it comes to image rendering, we prefer pixels here. It is good for constructing lifelike scenes. |
| 6) In a random scan, only an area of the screen with a picture is displayed. | 6) In a raster scan, the entire screen is scanned. |
| 7) In a random scan, it is difficult to fill the solid pattern. | 7) In a raster scan, it is easy to fill the solid pattern. |
| 9) Refresh rate depends on resolution, | 10) the Whole screen is scanned. |
| 10) Only a screen with a view of an area is displayed. | 9) Refresh rate does not depend on the picture. |
| 11) Beam Penetration technology comes under it. | 8) Example of a random scan is Pen Plotter. |
| 14) It is used for photos. That is Why Photoshop is a Raster editing program. | 11) Shadow mark technology came under this. |
| 12) It is restricted to line drawing applications. | 12) It is suitable for realistic display. |
| 13) Screen points/pixels are used to draw an image. | 13) Mathematical functions are used to draw an image. |
| 14) It is used for photos. That is Why Photoshop is Raster editing program. | 14) It is used for text, logs, and letterheads. |
| 15) Raster Scan Mainly in photos like JPG, PNG, GIF File Format. | 15) Random Scan system High Quality Images In SVG, the Size is Rescaleable like Logo in sites. |
- Describe the Architecture of a raster graphics system with a display processor.
- What is the role of a video controller in a raster scan system?
Ans:
● Interactive raster graphics systems typically employ several processing units.
● In addition to the CPU, a special-purpose processor called the video controller or display
controller is used to control the operation of the display device.
● The figure shows the organization of a raster system.
● The frame buffer can be anywhere in the system memory, and the video controller accesses
the frame buffer to refresh the screen.
Video Controller:
● A fixed area of the system memory is reserved for the frame buffer, and the video controller
is given direct access to the frame buffer memory.
● The coordinates of the graphics monitor starts at the lower left-screen corner.
● Positive x values increase to the right and y values increase from bottom to top.
● The above diagram shows the refresh operation of the video controller.
● Two registers are used to store the coordinates of the screen pixels.
● Initially X=0 and Y=Ymax.
● The value stored in the frame buffer corresponding to this pixel position is retrieved.
● And the x value is incremented by 1 and the corresponding y value is retrieved, like the
pixel values are retrieved line by line.
● Once the last pixel is reached again the registers are reset to the initial value to repeat the
process.
8. Explain Raster Scan Display & Random Scan Display. Explain with a diagram the Random scan display technique. Explain with diagram Vector scan display technique Explain with diagram Raster scan display technique.
Ans:
Raster Scan Display:
● A rectangular pattern of image capture on television is known as a raster scan.
● It is one of the most popular and standard types of graphics monitors which operates CRT.
● Through the raster scan, we can display real-life images with a variety of shades.
● Also, it comprises a massive color range.
The basic working of Raster Scan:
● In a raster scan system, the electron beam is swept across the screen, one row at a time from
top to bottom.
● As the electron beam moves across each row, the beam intensity is turned on and off to
create a pattern of illuminated spots.
● Picture definition is stored in a memory area called the Refresh Buffer or Frame Buffer.
● This memory area holds the set of intensity values for all the screen points.
● Stored intensity values are then retrieved from the refresh buffer and “painted” on the
screen one-row scan line at a time as shown in the following illustration.
● Each screen point is referred to as a pixel picture element.
● At the end of each scan line, the electron beam returns to the left side of the screen to begin
displaying the next scan line.
Random Scan Display:
● The random scan is a technique in which the display is constructed through an electron
beam,
● This is directed only to the specific areas of the screen where the image is to be sketched
or drawn.
● The resolution of the random scan display is high, and thus it delivers smooth image drawing.
● One of the most attractive pointers about the random scan is that it requires less memory.
● However, the color range is minimal here.
The basic working of random scan display:
● In this technique, the electron beam is directed only to the part of the screen where the
picture is to be drawn rather than scanning from left to right and top to bottom as in a raster
scan.
● It is also called vector display, stroke-writing display, or calligraphic display.
● Picture definition is stored as a set of line-drawing commands in an area of memory referred
to as the refresh display file.
● To display a specified picture, the system cycles through the set of commands in the display
file, drawing each component line in turn.
● After all the line-drawing commands are processed, the system cycles back to the first line
command in the list.
● Random-scan displays are designed to draw all the component lines of pictures 30 to 60
times each second.
Explain 1] Pixel, 2] Resolution 3] PPi 4] Aspect Ratio 5] Frame Buffer.
Define (i) aspect ratio and (ii) resolution.
Define pixel and frame buffer.
Pixel:
● A pixel is the smallest unit of a digital image or graphic that can be displayed and represented
on a digital display device.
● A pixel is the basic logical unit in digital graphics. Pixels are combined to form a complete
image, video, text, or any visible thing on a computer display.
● A pixel is also known as a picture element (pix = picture, el = element).
Resolution:
● Resolution is a measure used to describe the sharpness and clarity of an image or picture.
● It is often used as a metric for judging the quality of monitors, printers, digital images, and
various other hardware and software technologies.
● The term is popular in the mobile industry for describing a mobile device’s display
capabilities, and also in the entertainment media to distinguish the visual quality of movies
to distinguish between high definition and standard definition movies.
● It is also used to determine the resolution of a screen, monitor, or TV.
● Resolution is also referred to as screen resolution.
Pixel per Inch:
● Pixels per inch (PPI) is a measurement used to define the resolution of a computer display.
● This metric evaluates the picture/image quality that a particular computing or output display
device is able to display.
● Pixels per inch is also known as pixel density.
Aspect Ratio:
● An aspect ratio is an attribute that describes the relationship between the width and height
of an image.
● Aspect ratio is expressed by the symbolic notation: X: Y. The values of X and Y are not the
actual width and height of the image, but describe the relationship between them.
Frame Buffer:
● It is a digital memory where the image is stored as a matrix of intensity values of pixels.
● The portion of the memory used to hold the pixel is called the frame buffer.
12. Scan Conversion in Computer Graphics?
Ans:
Scan Conversion Definition:
● It is a process of representing graphics objects a collection of pixels.
● The graphics objects are continuous. The pixels used are discrete.
● Each pixel can have either an on or off-state.
● The circuitry of the video display device of the computer is capable of converting binary
values (0, 1) into pixel-on and pixel-off information.
● 0 is represented by a pixel off. 1 is represented using pixel on.
● Using this ability graphics computers represent pictures having discrete dots.
● Any model of graphics can be reproduced with a dense matrix of dots or points.
● Most human beings think of graphics objects as points, lines, circles, and ellipses. For generating
graphical objects, many algorithms have been developed.
Advantages of developing algorithms for scan conversion:
● Algorithms can generate graphics objects at a faster rate.
● Using algorithms, memory can be used efficiently.
● Algorithms can develop a higher level of graphical objects.
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