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Comp 414: Computer Graphics Question Paper

Comp 414: Computer Graphics

Course:Bachelor Of Computer Science

Institution: Kabarak University question papers

Exam Year:2008

COURSE CODE: COMP 414
COURSE TITLE: COMPUTER GRAPHICS
STREAM: Y4S1
DAY: TUESDAY
TIME: 8.30 -10.30 A.M.
DATE: 16/12/2008
INSTRUCTIONS:
ANSWER QUESTION 1 AND ANY OTHER TWO QUESTIONS.

Question 1 (30 Marks)
(a). (i). Define the following graphics terms.
(I). Persistence (II). Shear (III). GLUT (IV). Data glove (2 Marks)
(ii). Explain the meanings of the following graphics terms.
(I). Interlacing (II). View port (III). Trichomatic theory
(IV). Homogenous co-ordinates (4 Marks)
(b). (i). Presentation graphics is an important area of application of computer graphics. Write
notes to describe it. (3 Marks)
(ii). Apart from presentation graphics, list four other areas of applications of computer
graphics. (1 Mark)
(c). (i). Give four advantages of the flat panel displays over the traditional CRT technology.
(2 Marks)
(ii). Describe the things that take place inside the CRT in order to output a spot of light at a
particular pixel on the screen. (4 Marks)
(d). (i). Briefly explain the importance of the following in computer graphics.
(I). Loading identity matrix (II). Defining the matrix mode. (2 Marks)
(ii). What are the 2-D non-homogenous representations for the following two 2-D
homogenized points?
(I). [-6, 4, 2] (II). [8, 9, 0] (1 Marks)
(iii). Assume we rotate the point (4, 6) about the origin and through the angle 90 degrees
anticlockwise. Derive the new point using matrices. (2 Marks)
(iv). Distinguish between modeling and viewing transformations. (1 Mark)
(e). What is texture mapping? Write notes to describe the properties of texture maps.
(3 Marks)
(f). (i). State the work of the following functions in Open GL.
(I). glutMainLoop() (II). glutInit()
(III). glutSwapBuffers() (IV). glClear() (2 Marks)
(ii). (I). Write down a OPENGL user-defined function that uses the mouse down event to
output either the message “Button pressed down” or “Button released” when the user
either presses down the centre button or releases it respectively. (2.5 Marks)
(II). Write the statement that invokes the above function. (0.5 Mark)

Question 2 (20 Marks)
(a). (i). Describe the main difference between a raster scan display system and a random scan
display system. (2 Marks)
(ii). How does the CRT output color? Describe one technique. (4 Marks)
(b). Write short notes to describe how we represent color using the HSL system. (3 Marks)
(c). (i). What are projections? Why are they necessary in computer graphics? (2 Marks)
(ii). Give the difference between parallel projection orthographic projection. (1 Marks)
(iii). Give the prototype of an OPEN GL function used to implement each of the above two
projection methods (in c(ii)). (2 Marks)
(d). (i). List the sequence of transformations necessary to implement the transformation of the
triangle ABC to A’B’C’ shown below, given that the length A’B’=B’C’=2. Note that A’ is at
(4.0, 0.0), B’ is 6.8, 2.8), while C’ is at (4.0, 5.7). (1.5 Marks)
(ii). Derive the effective transformation matrix using homogenized values. (3.0 Marks)
(iii). List the OPENGL commands equivalent to the sequence of transformations in part
d(i) above. (1.5 Marks)
Question 3 (20 Marks)
(a). Describe how plasma panels operate. (4 Marks)
(b). Describe the Digital Differential Analyzer algorithm. (3 Marks)
(c). (i). Explain the transformation accomplished by each of the following matrices.
(I). 0 -1 0 (II). 2 0 0 (III). 1 0 2
1 0 0 0 4 0 0 1 1
0 0 1 0 0 1 0 0 1
(3 Marks)
(ii). Assume we apply the above transformations (in 3.c(i)) in sequence (starting with I, then
II then III) on a 2D line (0,0), (2, 1). Derive the effective transformation matrix, and hence
the new point. (3 Marks)
(d). A 2D line has vertices (4, 2), and (8, 6). Assume we want to rotate the line about the vertex
(4, 2) and though the angle 180 degrees anti clockwise.
(i). List the sequence of operations needed. (1.5 Mark)
(ii). Give the OPEN GL statements for the above sequence of operations (in d(i)).
(1.5 Marks)
(iii). Derive the transformation matrix using homogenous coordinates and hence the coordinates
of the new line. (3 Marks)
(e). List any four GLUT constants. (1 Mark)
Question 4 (20 Marks)
(a). Briefly describe how the following graphics devices operate.
(i). Trackball (ii). Light pens (iv). Dot matrix printer (6 Marks)
(b). Assume we rotate the 3D point (0, 1, 2) through an angle 60 degrees (anti clockwise) about
the z axis.
Derive the transformation matrix, and hence the new point. (3 Marks)
(c). Assume we apply the following OPEN GL transformation functions (in sequence) on a line
with vertices (1, 0, 3), (3, 1, 0).
glScalef(1, 3, 1);
glRotatef(180, 1, 0, 0);
Required: Derive the transformation matrix and hence the vertices of the new line.
(4 Mar ks)
(d). Write OpenGL functions to do the following. Assume a complete program.
(i). A function to output a green line with end points (4, 6) and (-7, 3) (2 Marks)
(ii). A function to output a 3-sided figure with vertices (-5, -4), (6, 4), (3, 1). (2 Marks)
(iii). A user defined function to handle keyboard events. The function should call the above
two functions when the user presses either key 1 or 2 respectively. It should also change
the drawing color to yellow when the user types key ‘y’, and exit on pressing key ‘e’.
(3 Marks)

Comp 414: Computer Graphics Question Paper

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