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Top 5 Most Important Question of Computer Graphics

Top 5 Most Important Question of Computer Graphics 

Q1- Prove that

Fraction of total refresh time per frame Spent
in plotter of the e- beam = r(m-1) sh +(r-1) xv  
Where    r =
refresh rate of r-frame in per second
               sh = time required to retrace in horizontal
               xv = time require to retrace in
vertical direction
               n*m is the resolution of raster monitor system

Given that 
            Resolution is n*m
system contains m- scan lines because number of columns are m.
             Scan line 1,2, 3……., m    

is going to perform (m-1) horizontal retraces.

          As time
taken for horizontal retrace is sh 
          Therefore total time takes for
horizontal retrace = (m-1)* sh
          If there are r frames then Time taken become = r *(m-1)
* sh.
is r- frames then there will be (r-1) vertical retraces because number of vertical  retrace  and vertically we scan the frame is equal

time for vertical retrace = (r-1) xv
          Total time for retrace (for r-frames) = r(m-1) sh
+ (r-1) x
          Total time require of retrace on frame = [r(m-1) sh
+ (r-1) xv ]/r … (1)

refresh time of one frame = 1/r ……………(2)
           From equation 1 and 2
   fraction of Total time requires of retrace on frame to Total refresh time of
one frame is
sh + (r-1) xv

Q2- Difference between Printer
and Plotter?

They produce continuous
They draw dots (Pixel) to
draw any figure or image.
They are expensive.
They are less expensive.
Large number of print outs
can be produced.
Lesser printouts than a
Mainly used for CAD, CAM and
Auto Cad Application
They are used for all
Lesser human interventions.
More human interventions

Q3- Draw and explain the basic structure of DVST . Also discuss its
working ?
Direct View Storage Tube (DVST) –
DVST has inherent capability to storage store image
information. It stores image information as a charge distribution, just behind
the coating of phosphors. It is very similar to CRT but using long persistence
It consists of two electron guns-
Primary gun / writing
It is used to store the image pattern.
Flood gun: It is used to refresh
the Image display.
In DVST there
is no need to put refresh buffer. The images are created by drawing line
segment with a slow-moving electron beam.
The beam writes
directly on the fine mesh wire grid coated with dielectric not to phosphorus
directly and placed just behind the phosphor of screen. A pattern of positive
charge is deposited on the mesh wire grid and which is further transferred to
the phosphor by a continuous flood of electrons emitted from the flood gun.
There is one more
grid which is mounted just behind the storage grid that is called as a
collector. The main purpose of the collector is to maintain the flow of
electrons from flood gun.
These electrons pass
the collector get attracted to the positively charged portions of storage mesh
and strike the phosphor in order to draw the object.

Q4- Write a short note on any four of the following
Frame buffer
Refresh rate
Vector Scan display device
Aspect Ratio
Display file

1. Frame buffer: 
Frame Buffer is the large and contiguous memory area which is used to store color intensity value of every pixel in the array. It can be represented like a multi dimension array that is used by display devices in order to draw object or image.
2. Refresh rate:
 It can be defined as the number of times the electronic beam strike the pixels per second so that the image does not flicker or dulled. For a monitor, it is measured in Hertz (Hz) or Frame per Second. Here it is also known by the name of frame rate. generally, the refresh rate for monitor screen is lying between 60 to 75 Hz. If the refresh rate of 75 Hz meaning of this statement is, we have to refresh the 75 times in a second. If we talk about relation between refresh rate and flicking the lower the refresh rate, the higher is the flicking or vice versa. The refresh rate increase as the bit depth decrease.
3. Vector Scan display device: 
In the case of vector Scan display the object is generated by drawing a set of straight lines in way as draw image on paper using pen. It is also known by the name of calligraphic or vector or stroke displays.
4. Aspect ratio:
The ratio of number of horizontal pixels to that of vertical pixel is known as Aspect ratio.
5. Display File: 
Basically, there are two type of display system, random scan display system and raster scan display system. As we know that the raster scan system makes use of frame buffer to store intensity value for all pixels on the object. On the other hand, vector or random refresh display stores only the commands for drawing the line segments. The file in which all these are saved is called as a display file. the concept of display file is to provides an interface between image display process and image specification process. It also defines a compressed or compact description of image which may be saved for further use. These files are known as meta files or pseudo-display files.

Briefly discuss the following

1) CRT
2) Plasma
3) Locator Input Device
4) Valuator Input
5) Scan Conversion

1. CRT

Cathode Ray Tube (CRT) is a one of the simplest computer display screen
work on the principle of beam penetration. Its display the object by moving an
electron beam horizontally and vertically with the help of deflection plate.
Intensity of light at particular pixel is controlled by Control grid which is
positively charged. More the number of electron strike the phosphors more time
it grow. 


A plasma display is a computer video display in which each pixel on the
screen is illuminated by a tiny bit of plasma or charged gas, somewhat like a
tiny neon light. cathode ray tube ( CRT ) displays is thinker than Plasma
displays and also brighter than liquid crystal displays ( LCD ).

Locator Input Device

 These are the input device which give coordinate value as
input. Example mouse, trackball, joystick and tablet

Input Device

These are the input device which give a real and analog value as
a single input. Example rotary potentio meter.

Scan Conversion

The process of converting the rasterized picture stored in a
frame buffer to the rigid display pattern of video is called as scan conversion
or rasterization. It is a continuous to discrete transformation. A display list
contains the information about every pixel on the screen.

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