Computer
Science 455
Instructor: R. P. Burton
Fourth Quiz
Name
_________________________________________ Score
____________/18
1.
The Weiler & Atherton
polygon clipping algorithm is easy to implement (relative to the
Sutherland & Hodgman
algorithm).
a.
true
b.
false
(b)
2.
The algorithm more suitable to an arbitrary clipping
boundary is
a.
Sutherland & Hodgman
b.
Weiler & Atherton
(b)
3.
Suppose a point-plotted string of characters (i.e. a
piece of text) consists of 1000 points – an average of 100 points per
character. To do all-or-nothing text
clipping, how many points (whether or not they are part of the text) need to be
checked against the boundaries of the clipping region?
a.
1000
b.
100
c.
10
d.
4
e.
2
f.
1
(e)
4.
Which of the following approaches is least appropriate for curve clipping?
a.
clip individual points for point-plotted curves
b.
clip individual lines for curves consisting of short
line segments
c.
use the Cooprider-Crow
algorithm presented in the text and discussed in class
d.
(all are appropriate)
(c)
5.
What is “blanking?”
a.
another name for clipping
b.
reverse clipping
c.
adding texture (dashes, specifically) to lines
(b)
6.
The lowest level “object” or “segment” should be
a.
a point
b.
a line segment
c.
a polygon
d.
a polyhedron
e.
the smallest entity which might be manipulated by
itself
(e)
7.
Which of the following is least desirable from the
point of view of efficiency?
a.
posted and painted
b.
posted but not painted
c.
painted but not posted
d.
neither posted nor painted
e.
(all are equivalently efficient)
(c)
8.
When the user determines to create a “segment”
interactively, how much memory should be made available as the “segment” is
being created (i.e. how large should the “segment” be allowed to be)?
a.
a fixed minimum
b.
enough to accommodate the largest conceivable
“segment”
c.
“chunks” as needed, consolidating them when the
“segment” is “closed”
(c)
9.
Suppose a facility consists of three work areas,
each of which can contain worktables, chairs, file cabinets and shelves. Subsequently the facility is placed in world
coordinates and ultimately the facility is rendered in physical device
coordinates. Which of the following
represent(s) master coordinates?
a.
the worktables, chairs, file cabinets and shelves
b.
(a) and the work areas
c.
(b) and the facility
d.
(c) and the world coordinate representation
(c)
10.
Suppose the worktables, chairs, file cabinets and
shelves are represented with physical descriptions (points, lines, polygons,
etc). By what are the other parts of the
hierarchy (the work areas, the facility, etc.) of the previous question
represented?
a.
physical descriptions again
b.
transformations and references to the worktables,
chairs, etc.
c.
locations and bounding boxes of these other parts of
the hierarchy
(b)
11.
Suppose transformation matrix M takes a worktable
description in master coordinates and transforms it through Work Area 1
coordinates, through Facility coordinates, through world coordinates, through
normalized device coordinates, and into physical device coordinates, i.e. M
consists of 5 transformation matrices which have been composed. How many matrices need to be composed to
transform a chair description in master coordinates into Work Area 1 and all
the way to physical device coordinates?
a.
five
b.
four
c.
three
d.
two
(d)
12.
Any student who has completed a course in computer
graphics (such as CS 455) should have the skill to use a graphics package to
arrange furniture (such as chairs, tables, file cabinets, etc.) tastefully and functionally in a work
area.
a.
true
b.
false
(b)
13.
The user has an input device with which he may drag,
sketch, or rubber band. If he does so,
he will be using his input device in ______ mode.
a.
request
b.
sample
c.
event
(c)
14.
Suppose a user uses his input device to provide
several sequential pieces of input, and does so faster than the system is able
to process the input, but not faster than the system is able to buffer it (i.e.
the user tires of providing input before the buffer fills). Which piece of input should the system
process?
a.
the oldest
b.
the youngest
c.
can’t say in general
(c)
15.
Suppose a system permits the user to draw horizontal
and vertical lines by clicking to indicate endpoints. Suppose the user provides 10 clicks to
produce a polyline of 9 segments. The first click provides x and y coordinates
(i.e. 2 coordinate values) for the starting point. How many individual coordinates are needed by
the system from the 9 subsequent clicks, each of which may indicate a
horizontal or vertical continuation of the polyline?
a.
20
b.
18
c.
10
d.
9
(b)
16.
Which of the following is least efficient for a rubberband line
which does not progressively obliterate the scene as the rubberband
line is moved?
a.
drawing the line in XOR mode
b.
storing the contents of the frame buffer under the
line before the line is drawn, and then restoring the contents when the line is
moved
c.
allocating a priority plane of one or more bits for
the rubberband line
d.
drawing the rubberband
line, and then, when the line is moved, re-scan-converting any objects which
fell under the line
e.
(all are equivalently efficient)
(d)
17.
Pick the best statement related to Cartesian
coordinate systems for computer graphics:
a.
Cartesian coordinate systems should be right-handed
to be consistent with the Cartesian coordinates systems of mathematics and
science to which most of us became accustomed before we studied graphics.
b.
Cartesian coordinate systems should be left-handed,
so that objects with greater depth have a greater “positive” depth rather than
a greater “negative” depth.
c.
Both (a) and (b) have defensible merit.
(c)
18.
For plotting five points in five-dimensional space,
_______ coordinates should be used.
a.
right-handed Cartesian
b.
left-handed Cartesian
c.
polar
d.
spherical
e.
cylindrical
f.
parallel axes
(f)