Code: AC-15                                                                           Subject: COMPUTER GRAPHICS

Time: 3 Hours                                                                                                     Max. Marks: 100

NOTE: There are 9 Questions in all.

· Question 1 is compulsory and carries 20 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.

· Out of the remaining EIGHT Questions answer any FIVE Questions. Each question carries 16 marks.

· Any required data not explicitly given, may be suitably assumed and stated.

Q.1       Choose the correct or best alternative in the following:                                         (2x10)

a. One advantage of raster CRT is

(A)  Solid area representation             

                   (B)  Aliasing effect detection and removal

(C)   Low cost

(D) All of the above

b. In RGB colour system, for N bit planes/colour with w bit wide colour lookup table, how many colours can be shown at a time.

(A) (2³)^W (B)  (2³)^N

(C)  (2³)^W–N (D)  (2³)^N–W

             c.   If the starting point of the line is to be left of terminating point and slope of line is less than one then (in x-y plane) we have

(A) (B)

(C) (D)

d.    The transformation matrix for rotating an object about a point (15,12) on the object through an angle of 90° in clockwise direction is

(A)  0                                                      (B)  1

(C)  2                                                 (D)  3       

             e.   For c' parametric continuity at the point of join for two Bezier Curves with control points P₀, P₁, P₂, P₃ and Q₀, Q₁, Q₂, Q₃ we must have

(A)

(B) P₃ is mid point of line joining P₂ and Q₁

(C) P₃(=Q₀) is midpoint of line joining P₂ and Q₁

(D) P₁, P₂, P₃,Q₀, Q₁, Q₂ are collinear

  f.    If  is a vector in the viewing direction of the eye and  is normal vector to a polygon surface then the condition . > 0

(A) Front face                                    (B)  Back face

(C)  Side face                                      (D)  Top face

             g.   Conversion of a 3-D image to 2-D is

(A) Transformation                             (B) Projection

(C)  Half toning                                    (D) Clipping

             h.   Oblique projection of an object with projection angle α such that =1 is called.

(A) Cabinet projection                        (B) Orthographic projection

(C)  Cavilier projection                        (D) None

             i.    The persistence of a phosphore coated screen is related to

(A) intensity of light emitted by it

(B)  intensity of electron beam

(C)  size of the screen                         

(D)  thickness of the phosphose coated screen

             j.   

(A) perspective projection on view plane z=d and centre of projection at origin      

(B) parallel projection on view plane z=d

(C) perspective projection on view plane z=0 and centre of projection (0,0,d)

(D) None of the above

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q.2     a.   Describe interlacing procedure for CRT virtual display unit. Why is it required?                   (6)

             b.   Describe the technology of liquid crystal display.                                                 (6)

             c.   Differentiate between raster and random display devices                                     (4)

Q.3     a.   What are fractals? Briefly explain self-similar, self-affine and invariant fractals with the help of examples.                                                                 (8)

             b.   What do you mean by animation? Derive necessary equations to model deceleration in the movement of key frames.                                                (8)

Q.4     a.   Derive the necessary transformation matrix for reflection about an arbitrary line. What is the reflection of line joining (2,2) and (5,3) with respect to line y = x + 1?                                                           (8)

             b.   What will be pixel locations of the line with the end points (2,3) and (6,6) using DDA algorithm?     .                                                           (8)

Q.5     a.   What do you understand by Bezier Curves? What are the properties of cubic Bezier Curves which makes them useful for curve design? How do they differ from B-splines?                                       (10)

     b.   What are Bernstein polynomials? Where do we require them?                             (6)

  Q.6     a.   Describe the Cohen-Sutherland technique for clipping a line with respect to a rectangular window.                                                             (8)

b.    Write scan line seed filling algorithm. Compare it with seed fill algorithm.             (8)

Q.7     a.   What is the perspective projection of the line joining (-1,1,–10) and

(2,–2,0) onto the plane z = –5?                                                                          (8)

             b.   Define perspective and parallel projections. Give various types of perspective and parallel projections.                                                                   (8)

Q.8     a.   How can we calculate the depth values for a surface position (x,y) along a scan line and in the different scan lines for buffer algorithm?                     (8)

             b.   Give the steps for removing hidden surfaces using back face detection.                (8)

Q.9     a.   What are operations which are frequently used in constructive solid geometry? Give an example showing the construction of a solid with these operations.                                                                      (8)

b.   Discuss the derivation of total diffuse reflection equation in terms of light source direction vector and unit surface normal vector.                          (8)