Cg pre-board 2018

5th Semester

Asian 1
Animation is the process used for generating animated images using computer graphics.
Steps used in animation sequence are: –

  • Storyboard Layout
  • Object definitions
  • Key frame specifications
  • Generation of –in between frames 4
Uses of OCR: OCR technology is used to convert virtually any kind of images containing written text (typed, handwritten or printed) into machine-readable text data.
Uses of OMR: This technology is useful for applications in which large numbers of hand-filled forms need to be processed quickly and with great accuracy, such as surveys, reply cards, questionnaires and ballots. 6
Disadvantages of DDA algorithm are:

  • Floating point arithmetic in DDA algorithm is still time consuming.
  • The algorithm is orientation dependent. Hence end point accuracy is poor.
  • Although DDA is fast, the accumulation of round-off error in successive additions of floating point increment, however can cause the calculation pixel position to drift away from the true line path for long line segment.
  • Rounding-off in DDA is time consuming. 9
Raster scan display system: In a raster scan system, the electron beam is swept across the screen, one row at a time from top to bottom. 10
Methods for representing 3D objects are:

  • Polygon and Quadric surfaces: For simple Euclidean objects
  • Spline surfaces and construction: For curved surfaces
  • Procedural methods: Eg. Fractals, Particle systems
  • Physically based modeling methods
  • Octree Encoding
  • Isosurface displays, Volume rendering, etc.



1)How light pen works?
-Light pen works by sensing the sudden small change in brightness of a point on the screen when the electron refreshes that spot.
2)Differentiate between cavalier and cabinet parallel projection?
-The only difference between the two is that cavalier shows full depth and cabinet parallel projection show half depth. Front view height and width are the same between the two.
3)What is region code?
-Region code is the method to selectively enable or disable rendering operations within a defined region of interest.
4)Define touch panel?
-A touch panel is equipment that lets users interact with a computer by touching the screen directly.
5)Make distinctive between image space and object space method?

Image space method Object image method
1)Depth-Buffer method 1)Back-face Detection
2)A buffer method 2)Bsp-tree method
3)Scan-line method 3)Area-sub division

6)Write homogeneous matrix for 3D scaling about arbitrary point?
                                         sx            0           0           0
0            s        0           0
0            0           s        0
0           0            0           1
7)Define specular highlights?
-Specular highlights is the bright spot of light that appears on shiny objects when illuminated.
8)Who was the inventor of sketch pad?
-Ivan Southerland was the inventor of sketch pad.
9)How Image is formed in random scan display?
-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.
1.What is aliasing and anti-aliasing?
The process by which smooth curves and other lines become jagged.It is due to the resolution of thegraphic device is not high enough to represent a smooth curve.
Anti –aliasing is the technique of minimizing blocky patterns when representing a high-resolution signal at a lower resolution.
2 Write a piece of code in java to specify the simple line?
 To specify the simple dash line in java code as:
Public void paint(Graphics g)
4 Write down the basic steps of animation?
 The basic steps of animation are as follows:

  •  Storyboard layout
  • Object definitions
  • Key-frame Specifications
  • Generation of in-between frames

5 Define Mach band effect.
Highlights on the surface are displayed with anomalous shapes and linear intensity can cause bright or dark intensity streaks called Mach band. These effect is due to the spatial high boost filtering performed by the human visual system on the luminance channel of the image captured by the retina. These effect can be reduced by dividing the surface into a greater number of polygon faces .
6 How aspect ratio and resolution are important in display device?
Aspect ratio is the proportion of the vertical point to horizontal point which produce equal length line in both direction on screen. Resolution is the number of points used to display an image.High resolution is important for projecting detailed charts and graphs text.
7 How bar code reader and optical character recognition are worked?
 When the barcode scanner reads the bar code,it translates the bars into number or letters.It sends that information into computer or terminal or whatever device it is attached.OCR converts image containing texts into format witheditable text.
8 Which class is used in java 2D for coloring?
 Color class is used in java 2D for coloring.
For eg: Color col=new Color(r,g,b)
9 Explain how color is manipulated in color CRT?
A Color CRT monitor displays color by using combination of phosphors that emit different-colored light.By combining the emitted light from the different phosphors a range of color can be generated.There are two basic technique:
 Beam penentration-two layers of phosphoros usually green and red
 Shadow-mask:three phosphors color dots red,green,blue