Code: DC-09                                                                          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. The picture is repeatedly drawn by quickly directing the electron beam back over all the points on the screen in

(A)  Random scan                               (B)  Shadow mask

(C)   Raster scan                                  (D)  Beam penetration

b. This consists of a small, vertical lever on a base that is used to steer the screen cursor around.

(A) Trackball                                      (B)  Spaceball

(C)  Mouse                                         (D)  Joystick

             c.   Straight lines can be constructed and positioned using __________ which stretch out a line from a starting position as the screen cursor is moved.

(A)  Rubber band methods                 (B) Dragging

(C)  Painting                                        (D) Drawing

             d.   A transformation that distorts the shape of an object such that the transformed shape appears as if the object were composed of internal layers that had been caused to slide over each other is called a __________.

(A)  Translation                                  (B)  Rotation

(C)  Shear                                          (D)  Scaling           

             e.   __________ generate curve sections which have continuous slopes so that they fit together smoothly.

(A) Lines                                            (B)  B splines

(C)  Planes                                          (D)  Polygons

             f.    In Cohen-Sutherland line clipping algorithm, assuming region code in the order of top, bottom, right, left; a point that is below and to the left of the rectangle has a region code of

(A) 0101                                            (B)  1010

(C)  1111                                            (D)  0000

             g.   The set of characters is called a(n) _________ if the character shapes are described using straight line and curve sections.

(A) Typeface                                      (B) Bitmap font

(C)  Outline font                                  (D) Marker

             h.   Front, side and rear orthographic projections of an object are called _________.

(A) Plan                                             (B) Axonometric

(C) Elevation                                       (D) Isometric

             i.    This modelling method creates a new volume by applying the union, intersection or difference operation of two specified volumes.

(A) Constructive solid geometry          (B)  Ray casting

(C) Sweep representation                    (D)  Fractals

             j.    A nearby source such as the long fluorescent light is more accurately modelled as a ________

(A)  Point source                                 (B)   Diffuse reflection

(C)  Specular reflection                        (D)   Distributed source

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q.2     a.   Calculate the required communication bandwidth between the host CPU and the graphics device for updating a curved line with 250 points describing it.  Each point is described by 3 coordinates.  Assume that a floating-point representation with 6 significant figures is used, a single      8-bit byte is used to represent a character and a refresh rate of 30 frames per second is used.                                              (6)

             b.   Explain flat-panel displays with suitable diagrams.  Indicate the different types of flat-panel displays with their applications.                                        (10)

Q.3     a.   Explain the following with neat schematic diagrams

                   (i)  Light pen                                        (ii)  Digitising tablet.                                 (8)

             b.   With suitable diagram derive the transformation matrix for a counterclockwise rotation about a point .                                            (8)

Q.4     a.   Explain Bezier curves with necessary equations and figures and describe the method for generating these curves.                                                (8)

b.   Describe Bresenham’s circle drawing algorithm.                                                  (8)

Q.5     a.   Consider the clipping window with diagonally opposite edges and .  For the lines with end points given below, determine the intersections with the window edges and the clipping results employing explicit two dimensional clipping algorithm. 

(i)                   (ii)  (8)

     b.   Describe Seed fill algorithms.  Compare a simple seed fill algorithm with a scan line seed fill algorithm with necessary figures.                                 (8)

  Q.6     a. What are the coordinates of a square with vertices (0,0) (3,0) (0,3) and (3,3), when it is transformed into a shifted parallelogram using parameter value  and ?                               (8)

             b.   How can scaling with respect to a point  be defined in terms of scaling with respect to the origin?                                                 Derive the necessary matrix.                    (8)

Q.7     a.   Explain perspective and parallel projections.  Provide mathematical descriptions with neat diagrams.                                                                      (8)

b.   Explain floating horizon algorithm to remove hidden lines from three-dimensional representations of surface functions of the form .     (8)

Q.8     a.   Describe hierarchical tree structures used to represent solid objects in graphics systems with an example.                                                               (8)

             b.   Illustrate the different basic illumination models for calculating light intensities with necessary figures.                                                            (8)

Q.9     a.   Describe the concepts of hypertext and hypermedia. Where are they used?         (8)

b.   Explain MIDI audio file format.                                                                          (8)