Exam number 1:

There are four questions, 25 points per question. Give a 
brief and clear answer.


1. Assume a graphics board with 8 bit per pixel and a 
color lookup table. Given an image with 24 bits per 
pixel, how can one display the image with a reasonable 
visual quality? Describe in few words what is the 
process of choosing the best colors for the lookup 
table and how to set the pixel colors in the displayed 
image.

2.  In the Mid-point line algorithm the update of the 
decision variable requires one addition in each 
incremental step. Why drawing a circle requires two 
additions? Can it be done with only one? 

3.  Define the following terms in two sentences each:

(a) dithering
(b) rigid transformation (Also give an example such 
transformation)
(c) affine transformation (Also give an example such 
transformation)
(d) oblique projection
(e) specular reflection
(f) ambient light
(g) smooth shading
(h) z-buffer
(i) image-space algorithm
(j) fixed-point (in the context of geometric 
transformations)


4.  Given two rectangular windows, which may overlap. 
Given a line segment, we need to clip the line against 
the overlapping rectangle. How the Cyrus-Beck 
(parametric) line-clipping algorithm can be extended 
to deal with the above problem? Note that the two 
windows might not intersect at all.