CS602 Midterm Subjective by Junaid

Q1. What are the two focusing methods in CRT? Explain briefly.

1. Electrostatic focusing
2. Magnetic focusing

In electrostatic focusing the electron beam passes through a positively charged metal cylinder that forms an electrostatic lens. Then electrostatic lens focuses the electron beam at the center of the screen. Similar task can be achieved with a magnetic field setup by a coil mounted around the outside of the CRT envelope. Magnetic lens focusing produces the smallest spot size on the screen and is used in special purpose devices

Q2. What is the relation between triads and shadow mask method?

Answer: Shadow mask methods can display a wide range of colors. In this technique each pixel position is made up of three phosphor dots called triads.

Q3. Discuss in brief the pixel drawing methods.

Answer: BIOS routines are standard routines built in VGA cards but these routines are very much slow. You will use pixel to draw filled triangle, rectangles and circles and these all will be much slower than direct memory access method. Direct memory access method allows you to write pixel directly by passing the complex BIOS routines. It is easy and faster but its programming is only convenient in mode 13h. Library functions are easier to use and even faster because these are optimized and provided with special drivers by different companies.

Q4. What are the steps involved in performing the boundary fill algorithm, also write the pseudo code for the steps you have mentioned above?

Answer: The Boundary fill algorithm performs the following steps: Check the pixel for boundary color Check the pixel for fill color Set the pixel in fill color Run the process for neighbors

The pseudo code for Boundary fill algorithm can be written as: boundaryFill (x, y, fillColor, boundaryColor) if ((x < 0) || (x >= width)) return if ((y < 0) || (y >= height)) return current = GetPixel(x, y) if ((current != boundaryColor) && (current != fillColor)) setPixel(fillColor, x, y) boundaryFill (x+1, y, fillColor, boundaryColor) boundaryFill (x, y+1, fillColor, boundaryColor) boundaryFill (x-1, y, fillColor, boundaryColor) boundaryFill (x, y-1, fillColor, boundaryColor)

Q5. How the locality of a point can be defined with respect to a plane?

Answer: One of the most important operations planes let you perform is defining the location of a point with respect to a plane. If you drop a point into the equation, it can be classified into three cases: in front of the plane, in back of the plane, or coplanar with the plane. Front is defined as the side of the plane the normal sticks out of.

Q6. Find in which quadrant the point (-2, 3) lies in 2D plane.

Answer: 2nd quadrant

Q7. Consider these 3-D vectors:

A = [9,8,7] B = [4,7,3] C = [2,9,6] Compute : i) A.BxC ii) AxB.C

BxC = [7x6 - 3x9 , 3x2 - 4x6 , 4x9 – 7x2]

=[15,-18,22]

A.BxC=9x15 +8x(-18)+7x22=135-144+154=145

AxB =[8x3 - 7x7 , 7x4 - 9x3 , 9x7 – 8x4]

=[-25,1,31]

AxB.C =-25x2+1x9+31x6 = -50 + 9+186=145