Code: AC15                                                                            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. Absolute co-ordinates and Relative co-ordinates are the ways of     

(A) Specifying points on a screen              (B)  Specifying line on a screen

                   (C) Specifying a window on a screen         (D) Specifying a curve on a screen                  

b. Window and viewport are important concepts associated with

(A) Ray tracing                                          (B)  Picture

(C) Ray casting                                         (D)  None of the above

             c.   If an image is of 16 inch by k inch and aspect ratio is then the value of k is

(A) 80 inch                                               (B)  40 inch

(C) 20 inch                                                (D)  10 inch

             d.   For resizing the image of size  pixels to the image of size  pixels, with same aspect ratio, the value of k is      

(A) 1024                                                 (B)  780

(C) 512                                                    (D)  256

             e.   To avoid unwanted artifacts in ____________, the pattern should not be symmetrical.

(A) JPEG                                                 (B)  GIF

(C)  BMP                                                 (D)  Halftoning

             f.    The  pattern given below in halftoning  represents.

(A) (B)

(C) (D)

             g.   The condition for a line trivially outside the polygon, in cyrus Beck algorithm is    

(A) t > 1                                            (B)  t < 1

(C)  (D)  None of the above

             h.   The homogenous co-ordinate for (x, y) is

(A) (x, y, w)                                       (B) (hx, hy, h)

(C)  (hx, hy, w)                                    (D)  None

             i.    If a quadtree has 5 levels then an area represented by this quadtree will have at most _______ pixels. 

(A)	512	(B)	256
(C)	1024	(D)	None

             j.    To model increasing speed between frames of an animation we use the function  

(A)  (B)

(C) (D)  None

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q.2     a.   Describe the working of display processor.  Give an architecture of a raster graphics system including display processor.                                           (8)

             b.   What do you mean by Knot vector of a B-spline?  Give examples of three types of B-splines with their Knot vectors.                                               (8)

Q.3     a.   What do you mean by aliasing?  How is it tackled in raster scan systems?            (6)

             b.   Using 4-connected pixels, fill the region with vertices (5, 5) (10, 5)

                   (10, 10) (20, 10) (20, 12) (5, 12) using seed fill algorithm.  The seed is

                   (9, 8).                                                                                                              (10)

Q.4     a.   Write Bresenham circle generation algorithm with centre at origin (0, 0) and radius r.                       (6)

b.   Using Cyrus Beck algorithm clip the line joining (8, 12) and (24, 16) with respect to window (10, 10) (20, 10) (20, 20) (10, 20).  How is it better than Cohen Sutherland algorithm?                          (8+2)

  Q.5     a. Give the composite transformation matrix for the rotation about a fixed point on the object followed by translation transformation.                    (8)

             b.   If the projection plane is z = 0 and the projectors are inclined to it at an angle of , what will be the co-ordinates of oblique projection of the point (3, 4, 6) on to the plane of projection. (8)

  Q.6     a.   What do you mean by vanishing points, in perspective projection?  How many vanishing points are possible?  Draw the diagrams depicting one, two and three vanishing points.                                       (8)

     b.   Derive the transformation matrix for reflection about a line y = mx + b  and b > 0.                                                                       (8)

Q.7     a.   What is a Bezier Curve?  Give the polynomial of degree n representing a Bezier Curve.  Derive the properties for first order continuity for joining two cubic Bezier Curve sections.                   (8)

b.   Describe briefly octree representation of solids.                                                  (8)

Q.8     a.   Describe the scanline z-buffer algorithm for removing hidden surfaces.                 (9)

             b.   Describe Phong shading model for rendering objects.  How is it better than Gourad shading model?                                                                       (7)

Q.9     a.   What is Lambert’s cosine law and what is it used for?                                         (4)

b.   Compare Painters algorithm with z-buffer algorithm.                                            (4)

c. What do you mean by morphing?  Describe rules for equalizing key frames in terms of number of edges and vertices.                                               (8)