Code: DC09                                                                            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 number of visibly distinct dots that can be displayed in a given area of the screen is called

(A)  coordinates                                  (B)  bit precision

(C)   screen resolution                          (D)  pixels

b. These displays are commonly used in small systems such as calculators and laptops computers.

(A) Composite Monitor                      (B)  Light Emitting Diode

(C)  Plasma panels                               (D)  Liquid Crystal Displays

             c.   Drawings can be stored for computer processing with a(n) ________ by passing an optical scanning mechanism over the information to be stored.

(A)  Image Scanner                            (B) Touch Panel

(C)  Printer                                          (D) Light Pen

             d.   The mirror image is generated by rotating the object 180° about the axis. This is termed as  __________.

(A)  Translation                                  (B)  Rotation

(C)  Reflection                                    (D)  Scaling           

             e.   This class of splines is used to set up paths for object motions or to provide representation for an existing object or drawing.

(A) Lines                                            (B)  Cubic splines

(C)  Planes                                          (D)  Polygons

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

(A) 0101                                            (B)  1010

(C)  1111                                            (D)  0000

             g.   The point at which a set of projected parallel lines appears to converge is called as a

(A) View point                                   (B) Projection point

(C)  Vanishing point                             (D) Parallel point

             h.   This algorithm is most frequently used to remove hidden lines from three dimensional representations of surface functions.

(A) Run length encoding                      (B) Bresenham’s algorithm

(C) Floating Horizon algorithm             (D) Midpoint subdivision algorithm

             i.    ____________ are generated by successively dividing a two dimensional region into quadrants.

(A) Quadtrees (B)  Constructive solid geometry

(C) Sweep representation                    (D)  Fractals

             j.    This is the result of total or near total reflection of the incident light in a concentrated region.

(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.   In raster scan displays, if pixels are accessed individually with an access time of 200 nanoseconds, what is the time required to access each of the pixel in a 4096 x 4096 display? Calculate the number of bits in the frame buffer if there are 8 bits for each of three colors. What is the equivalent frame refresh rate? To achieve a refresh rate of 30 frames per second what is the effective pixel access rate?                     (8)

             b.   Define the following terms:

                   (i) Resolution              (ii) Aspect Ratio                 (iii) Horizontal retrace

                   (iv) Vertical retrace                                                                                            (8)

Q.3     a.   Explain the following with neat diagrams

                   (i)  Mouse                  (ii)  Keyboard                    (iii) Joystick                            (9)

             b.   Show that two-dimensional scale and rotation do not commute that is, scaling followed by rotation is not equivalent to rotation followed by scaling.                                                                           (7)

Q.4     a.   What do you understand by B-spline curves? Briefly explain cubic, periodic B-spline. What are advantages of B-splines over Bezier curves?          (8)

b.   Explain the algorithm for the generation of ellipses via transformation of circles.                   (8)

Q.5     a.   Explain scan line seed fill algorithm.                                                                     (8)

     b.   Explain character generation algorithm with examples.                                         (8)

  Q.6     a. Explain homogeneous coordinates. What are their advantages? Write the transformation matrices for 2-D translation, scaling and rotation using homogeneous coordinates.                                         (8)

             b.   Derive the rotation matrix for any axis that does not coincide with a coordinate axis using composite transformations.                                   (8)

Q.7     a.   Derive the transformation matrix to obtain a perspective projection of a three dimensional object. Represent the transformation in homogeneous coordinates. Explain the special cases (i) if the view plane is the uv plane (ii) if the projection reference point is the viewing coordinate origin.                     (8)

b.   What are visible surface detection algorithms? Briefly explain the following surface detection algorithms (i) Back face detection (ii) Depth buffer method.                                                                     (8)

Q.8     a.   Explain sweep representations and constructive solid geometry methods for solid modeling.                                                                       (8)

             b.   Explain the terms illumination model and surface-rendering algorithm. Describe different types of light sources and reflections.                                    (8)

Q.9     a.   Explain the following hardware components of multimedia:

(i)   Audio Speakers             (ii) Sound Card              (iii) Video Cameras    

                   (iv) Scanners (8)

b.   Explain image bit maps and various image formats.                                              (8)