CS 184 Midterm (Fall 94)
UNIVERSITY OF CALIFORNIA
College of Engineering
Department of Electrical Engineering
and Computer Sciences
Computer Science Division
Computer Science 184  Foundations of Computer Graphics
Fall 1994  Midterm Exam
Professor Brian A Barksy
TAs: Dan Garcia and Zijiang Yang
Relax. You have 80 minutes. You will be graded on the best 4 out of 5 problems. This means you should allocate
about 16 minutes per question. Remember to pace yourself. Feel free to use the back of each page for additional
answer space. Do not panic. You will have time.
GOOD SKILL
Page 1
Question 1:
Scan Conversion
[25 points]
In the figure to the right, the grey area represents a dense
concentration of edges of a very degenerate polygon. You
cannot
tell how many edges there are within that region, nor
the direction of them. There are two edges we
are
sure of 
these are labeled in bold with the directions specified. There
are two topologically distinct regions we care about, X and
Y. Each of AD is worth 3 points for a correct answer, 1
point for a wrong answer, and 0 points if left blank. This is
so that a random guessing strategy will, on average, yield 0
overall points. In the future, this will be written [3/1 points]
to indicate the value of a correct/incorrect answer, and will
be used for multiplechoice questions.
A)
For the
Odd/Even
rule,
is
X
: (circle one)
IN
OUT
dependswhat'sinthe
greyregion
B)
For the
NonZero
Winding
rule, is
X
:
(circle one)
IN
OUT
dependswhat'sinthe
greyregion
C)
For the
Odd/Even
rule,
is
Y
: (circle one)
IN
OUT
dependswhat'sinthe
greyregion
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CS 184 Midterm (Fall 94)
D)
For the
NonZero
Winding
rule, is
Y
:
(circle one)
IN
OUT
dependswhat'sinthe
greyregion
Questions EG concern rotational invariance (i.e. does the category
in question remain constant after an arbitrary rotation)
E)
Is
region classification
(i.e. whether a region is in or out) by
the
NonZeroWinding
rule
rotationally invariant
? [3/1 points]
(circle
one)
Yes
No
Depends on
___________________________
F)
We specify the color (R,G,B) for every corner of a polygon (as
in one of you assignments). We are then given an ideal system
in which each pixel is infinitely small (thus we don't have to
worry about all of the nitpicky details that arise due to corners
falling between scanlines like special cases for convex corners,
incrementing the attributes by that additional wierd factor
when first added to the edge_y_start list, etc.). We then color
the inside of the polygon using a linear interpolation
("lerping") strategy exactly as in your handout. Think very
carefully of different types of polygons and the colors that
could be chosen when you answer this question. Is the
color
inside the polygon
rotationally invariant
? ("Yes" mean that
EVERY polygon's color is rotationally invariant, regardless of
the colors and type/size of the polygon, "No" means that NO
polygon's color is rotationally invariant, regardless of the
colors and type/size of polygon)[6/2 points]
(circle
one)
Yes
No
Depends on
___________________________
G)
Why
? (provide a sketch if it helps)[4 points]
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