Computer Graphics VIVA Questions and Answers:

Computer Graphics

 1. What is scan conversion?
A major task of the display processor is digitizing a picture definition given in an application program into a set of pixel-intensity values for storage in the frame buffer. This digitization process is called scan conversion.

2. Write the properties of video display devices?
Properties of video display devices are persistence,resolution, and aspect ratio.

3. What is rasterization?
The process of determining the appropriate pixels for representing picture or graphics object is known as rasterization.

4. Define Computer graphics.
Computer graphics remains one of the most existing andrapidly growing computer fields. Computer graphics maybe defined as a pictorial representation or graphicalrepresentation of objects in a computer.

5. Name any four input devices?
Four input devices are keyboard, mouse, image scanners,and trackball.

6. Write the two techniques for producing color displays with a CRT?
Beam penetration method, shadow mask method.

7. What is vertical retrace of the electron beam?
In raster scan display, at the end of one frame, the electron beam returns to the left top corner of the screen to start the next frame.

8. Short notes on video controller?
Video controller is used to control the operation of the display device. A fixed area of the system is reserved for the frame buffer, and the video controller is given direct access to the frame buffer memory.

9. What is bitmap?
Some system has only one bit per pixel; the frame buffer is often referred to as bitmap.

10. Differentiate plasma panel display and thin film electro luminescent display?
In plasma panel display, the region between two glass plates is filled with neon gas. In thin film electro luminescent display, the region between two glasses plates are filled with phosphor, such as zinc sulphide doped with manganese.

11. What is resolution?
The maximum number of points that can be displayed without overlap on a CRT is referred to as the resolution.

12. What is horizontal retrace of the electron beam?
In raster scan display, the electron beam return to the left of the screen after refreshing each scan line, is called horizontal retrace of the electron beam.

13. What is filament?
In the CRT, heat is applied to the cathode by directing a current through a coil of wire, is called filament.

14. What is pixel map?
Some system has multiple bits per pixel, the frame buffer is often referred to as pixel map.

15. Write the types of clipping?
Point clipping, line clipping, area clipping, text clipping and curve clipping.

16. What is meant by scan code?
When a key is pressed on the keyboard, the keyboard controller places a code carry to the key pressed into a part of the memory called as the keyboard buffer. This code is called as the scan code.

17. List out the merits and demerits of Penetration techniques?
The merits and demerits of the Penetration techniques areas follows. It is an inexpensive technique. It has only four colors. The quality of the picture is not good when it is compared to other techniques. It can display color scans in monitors. Poor limitation etc.

18. List out the merits and demerits of DVST?
The merits and demerits of direct view storage tubes[DVST] are as follows. It has a flat screen. Refreshing of screen is not required. Selective or part erasing of screen is not possible. It has poor contrast Performance is inferior to the refresh CRT.

19. What do you mean by emissive and non-emissivedisplays?
The emissive display converts electrical energy into lightenergy. The plasma panels, thin film electro-luminescent displays are the examples.The Non-emissive are optical effects to convert the sunlightor light from any other source to graphic form. Liquid crystal display is an example

20. List out the merits and demerits of Plasma paneldisplay?
Merits. Refreshing is not required. Produce a very steady image free of Flicker. Less bulky than a CRT.Demerits. Poor resolution of up to 60 d.p.i. It requires complex addressing and wiring. It is costlier than CRT.

21. What is persistence?
The time it takes the emitted light from the screen to decay one tenth of its original intensity is called as persistence.

 22. What is Aspect ratio?
The ratio of vertical points to the horizontal points necessary to produce length of lines in both directions of the screen is called the Aspect ratio. Usually the aspect ratio is ¾.

23. What is the difference between impact and non-impactprinters?
Impact printer press formed character faces against an inked ribbon on to the paper. A line printer and dot-matrix printer are examples.Non-impact printer and plotters use Laser techniques,inkjet sprays, Xerographic process, electrostatic method sand electrothermal methods to get images onto the papers. Examples are: Inkjet/Laser printers.

24. Define pixel?
Pixel is shortened forms of picture element. Each screen point is referred to as pixel or pixel.

25. What is frame buffer?
Picture definition is stored in a memory area called frame buffer or refresh buffer.

26. Where the video controller is used?
A special purpose processor, which is used to control the operation of the display device, is known as video controller or display controller.

27. What is run length encoding?
Run length encoding is a compression technique used to store the intensity values in the frame buffer, which store search scan line as a set of integer pairs. One number each pair indicates an intensity value, and second number specifies the number of adjacent pixels on the scan line that are to have that intensity value.

28. What is point in the computer graphics system?
The point is a most basic graphical element & is completely defined by a pair of user coordinates (x, y).

29. Write short notes on lines?
A line is of infinite extent can be defined by an angle of slope q and one point on the line P=P(x,y). This can also be defined as y=mx+C where C is the Y intercept.

30. Define Circle?
Circle is defined by its center xc, yc and its radius in user coordinate units. The equation of the circle is (x-xc) + (yyc)= r2.

31. What are the various attributes of a line?
The line type, width and color are the attributes of the line.The line type include solid line, dashed lines, and dotted lines.

32. What is anti aliasing?
The process of adjusting intensities of the pixels along the line to minimize the effect of aliasing is called anti aliasing.

33. What is Transformation?
Transformation is the process of introducing changes in the shape size and orientation of the object using scaling rotation reflection shearing & translation etc.

34. What is translation?
Translation is the process of changing the position of an object in a straight-line path from one coordinate location to another. Every point (x , y) in the object must under go a displacement to (x|,y|). the transformation is:x| = x + tx ; y| = y+ty

35. What is rotation?
A 2-D rotation is done by re positioning the coordinates along a circular path, in the x-y plane by making an angle with the axes. The transformation is given by:X| = r cos (q + f) and Y| = r sin (q + f).

36. What is scaling?
A 2-D rotation is done by re positioning the coordinates along a circular path, in the x-y plane by making an angle with the axes. The transformation is given by:X| = r cos (q + f) and Y| = r sin (q + f).

37. What is shearing?
The shearing transformation actually slants the object along the X direction or the Y direction as required. ie; this transformation slants the shape of an object along a required plane.

38. What is reflection?
The reflection is actually the transformation that produces a mirror image of an object. For this use some angles and lines of reflection.

39. What are the two classifications of shear transformation?
X shear, y shear

40. A point (4,3) is rotated counterclockwise by an angle of 45°. Find the rotation matrix and the resultant 
point

41. Name any three font editing tools.
ResEdit, FONTo grapher

42. Differentiate serif and sans serif fonts. 
Give one example Serif fonts has a little decoration at the end of the letter,but serif font has not. Times, new century schoolbook is the examples of serif fonts. Arial, optima are examples for sanserif fonts.

43. Distinguish between window port & view port?
A portion of a picture that is to be displayed by a window is known as window port. The display area of the part selected or the form in which the selected part is viewed is known as view port.

44. Define clipping?
Clipping is the method of cutting a graphics display to neatly fit a predefined graphics region or the view port.

45. What is the need of homogeneous coordinates?
To perform more than one transformation at a time, use homogeneous coordinates or matrixes. They reduce unwanted calculations intermediate steps saves time and memory and produce a sequence of transformations.