**UNIVERSITY EXAMINATIONS: 2018/2019**

**EXAMINATION FOR THE DEGREES OF BACHELOR OF SCIENCE IN**

**INFORMATION TECHNOLOGY**

**BIT2301A COMPUTER GRAPHICS**

**FULLTIME/ PART TIME/DISTANCE LEARNING**

**ORDINARY EXAMINATIONS**

**DATE: DECEMBER, 2018 TIME: 2 HOURS**

**INSTRUCTIONS: Answer Question One & ANY OTHER TWO questions.**

**QUESTION ONE [30 MARKS]**

a) Define the term ‘shearing’ and explain TWO main types. (6 Marks)

b) Explain the operation of the cathode ray tube. (4 Marks)

c) Discuss each of the following primitives as used in computer graphics:

i) Mesh (2 Marks)

ii) Facet (2 Marks)

iii) Edge (2 Marks)

d) Describe THREE text clipping algorithms and illustrate each. (6 Marks)

e) Explain and illustrate the phenomenon of local illumination. (4 Marks)

f) Which are the applications of computer graphics? Discuss any FOUR of these. (4 Marks)

**QUESTION TWO [20 MARKS]**

a) Explain what happens during the following stages of the rendering pipeline: (6 Marks)

i) Application stage

ii) Geometry stage

iii) Rasterization stage

b) Explain the concept of clipping and why it is necessary in computer graphics. (2 Marks)

c) Consider the triangle below undergoing a series of transformations. Showing all your

calculations, calculate and plot the new vertices after the following:

i) Scaling by (0.5, 1.5) (3 Marks)

ii) Translation of (-3, 3) (3 Marks)

iii) Rotation of 45ᵒ anticlockwise about the origin (3 Marks)

Plot the transformed images on a Cartesian plane. (3 Marks)

**QUESTION THREE [20 MARKS]**

a) Explain and illustrate the following light sources:

i) Point light

ii) Directional light

iii) Spotlight (9 Marks)

b) Distinguish between zooming and panning. (4 Marks)

c) The Area Subdivision method of hidden surface elimination describes four possible

relationships that a surface can have with a specified area boundary. Describe any THREE

of these relationships. (3 Marks)

d) Discuss any TWO shading models. (4 Marks)

**QUESTION FOUR [20 MARKS]**

a) Explain and illustrate the following types of reflections:

i) Diffuse reflection (3 Marks)

ii) Specular reflection (3 Marks)

iii) Ambient light reflection (3 Marks)

b) Illustrate reflections with respect to X and Y axes, and about the origin respectively.

(5 Marks)

c) Consider the pentagon below that needs to be clipped using the Sutherland-Hodgman

algorithm. Illustrate the clipping process clearly showing the steps. Present both the original

and the clipped objects. (6 Marks)

**QUESTION FIVE [20 MARKS]**

b) Consider a line with endpoints (3,2) and 11,8). Which intermediate points will be required to

draw this line using DDA and Bresenham algorithms? Show your calculations. (6 Marks)

c) Distinguish between ‘object space’ and ‘image space’ methods of removing hidden surfaces

and offer an example of each method. (6 Marks)

d) Discuss in detail the TWO ways of displaying an object on the screen (8 Marks)