Past Midterm and Exam Questions (PDF) - Student.cs.uwaterloo.ca ...

CS488/688 Introduction to Computer Graphics 11
2. If we clip a polygon to a window, it is inadequate to merely perform repeated half-space
clipping on each polygon line segment independently. Give an example illustrating why
independent clipping of polygon line segments may fail to correctly clip a convex polygon. A
picture alone is inadequate; you should also give a short answer describing the picture and
why it illustrates the problem, noting both the incorrectly clipped polygon and what the
correctly clipped polygon should be.
4.16 Line Clipping [Last Used: Fall 2012 Final]
In assignment 2, you implemented a line clipping algorithm by repeatedly clipping to half-spaces.
Suppose we want to clip a polygon to a rectangular window. One approach would be to just clip
each line segment to the window independently, and use the resulting clipped line segments as our
clipped polygon.
Given an example illustrating that this algorithm may give an incorrect result.
5 Colour
5.1 Colour Coordinate Systems [Last Used: Spring 1986 Final]
Name three colour coordinate systems and describe their defining axes. For each system, indicate
the shape of the region containing the colours they can define.
5.2 Additive and Subtractive Colour [Last Used: ?]
Explain the difference between additive and subtractive colour mixing.
(a) According to the opponent-colour theory of vision, what information is passed on to the brain
from the eye and how is it generated from cone excitations?
(b) Explain the relevance of opponent-colour theory to computer graphics.
5.3 Colour Space Mapping [Last Used: Winter 1986 Final]
The colours D, E, F are defined in terms of the R, G, B primaries as:
D = 1.0R + 0.5G (1)
E = 1.0R − 0.5B (2)
F = 1.0R (3)
(a) What are D, E, F values that produce an equivalent stimulus to the eye as R = 0.0, G = 1.0,
and B = 1.0?
(b) Write the equations that map from three values in DEF colour space into RGB colour space.
(c) Can the colours D, E, F be considered as primaries? Justify your answer.