Computer Graphics and Vision

Exam paper 2003 Questions and Answers from the Web

Question 1

(1)

(a)  Computer graphic devices can be categorized mainly into two types as raster devices and vector devices. Explain these two types of devices

Give two examples of output devices for each of the above device types. Explain how output is produced by them

INFORMATION:

Raster graphics - Wikipedia, the free encyclopedia.htm

Vector graphics - Wikipedia, the free encyclopedia.htm

(8 marks)

(b) What is mean by gamma correction  of display devices?

Gamma correction - Wikipedia, the free encyclopedia.htm

(4 marks)

(‘c) What is mean by clipping in 2D computer graphics?

Computer Graphics - Clipping.htm

Clipping (computer graphics) - Wikipedia, the free encyclopedia.htm

(5 marks)

(d) Describe the Cohen - Sutherland algorithm for clipping. Give this algorithm in pseudo code form

Cohen-Sutherland Algorithm.htm

Computer Graphics - Clipping.htm

(8 marks)

Question 2

(a) Describe the 3D graphic viewing pipeline explaining the operations taking place in each of the stages of the pipeline

graphics pipeline definition of graphics pipeline in computing dictionary - by the Free Online Dictionary, Thesaurus and Encyclopedia.htm

Graphics pipeline - Wikipedia, the free encyclopedia.htm

Pipeline (computer) - Wikipedia, the free encyclopedia.htm

(6 marks)

(b) Explain the parallel projection and perspective projection used in 3D graphics viewing. Give these two projection transformations as matrices using homogeneous coordinates

(5 marks)

(c) Obtain the Bezier curve function for four control pints. Show the curve passes through the start and ending control points

(6 marks)

(d)

Ray Tracing is the most accomplished technique to obtain photo quality images. Explain the process of ray tracing. Explain how the pixel intensity is calculated considering only the direct illumination of a single light

Ray tracing - Wikipedia, the free encyclopedia.mht

(8 marks)

Question 3

(a) Describe how grey scale and color images are displayed in the computer

(5 Marks)

(b) Explain how color lookup tables can be used to represent color of a color image. Give an example

( 7 Marks)

(‘c) “ the Intensity histogram of an image gives some useful clues about the shape of objects in the image” . Would you agree with the above statement ? Explain your reasoning with an example

( 7 Marks)

(c) Explain the contrast stretching operation on digital images. This operation would give wrong results if there are outer pixels with very large or very small grey-levels. Explain a technique to solve this problem

(8 marks)

Question 4

(a) An image has been taken using a rotated camera. As a result of this the image is distorted. Explain how you would correct this distortion. Give a pseudo code program for your operation.

(b) Identify a 3x3 filter suitable for each of the following operations

(i) Image smoothing

(ii) Detecting horizontal lines

(iii) Detecting vertical edges

(iv) Laplacian Edge detection

(‘c) Edges and segments are used as useful features in many computer vision systems. Describe two computer vision applications where on e uses edges and features and the other uses segments as features. Explain how these features can be extracted and interpretations about the objects in the images can be obtained

(d) Explain the goals of computer vision. It is difficult to achieve general purpose computer vision.