Computer Science 455
Instructor: R. P. Burton
Fourth Quiz
March 1-2, 2004
Name _________________________________________ Score ____________/35
1. Let min be the minimum number of comparisons sufficient to clip a point to a rectangular clipping region. Let max be the maximum number of comparisons needed to clip the point. What is the sum of min and max?
a. two
b. four
c. five
d. eight
(c)
2. To determine if a line segment can be trivially accepted by the Cohen Sutherland clipping algorithm, the endpoint codes are
a. ANDed
b. NANDed
c. ORed
d. NORed
e. XORed
(c)
3. To determine if a line segment can be trivially rejected by the Cohen Sutherland clipping algorithm, the endpoint codes are
a. ANDed
b. NANDed
c. ORed
d. NORed
e. XORed
(a)
4. Using the Cohen Sutherland approach, a line segment which cannot be trivially accepted or trivially rejected crosses one or more window boundaries.
a. true
b. false
(b)
5. Using the Cohen Sutherland approach, the window boundaries which a line segment crosses can be determined from the two endpoint codes.
a. true
b. false
(a)
6. Suppose line segments have a maximum delta-x or delta-y of 1000. If midpoint subdivision is used, what is the maximum number of subdivisions required to find where a line segment intersects a window boundary? (pick the correct range)
a. 0 to 5
b. 6 to 10
c. 11 to 50
d. 51 to 500
e. 501 to 1000
f. more than 1000
(b – 10)
7. Without midpoint subdivision, the x and y coordinates of the intersection of the line segment with the window boundary are both calculated using “similar triangle” techniques.
a. true
b. false
(b)
8. If your do your “p’s and q’s” correctly using the Liang and Barsky method, you can determine all of the following EXCEPT
a. if a line segment is parallel to a window boundary
b. (if not parallel) whether the (extended) line segment crosses the (extended) boundary from inside to outside, or from outside to inside
c. (if not parallel), the point of (extended) intersection
d. (no exceptions here)
(d)
9. The Nicholl Lee Nicholl algorithm
a. executes faster than Cohen-Sutherland or Liang-Barsky for large numbers of line segments
b. executes faster than Cohen-Sutherland or Liang-Barsky independent of the number of line segments
c. does not actually perform any clipping
(c)
10. Nicholl Lee Nicholl attempts to classify a line segment in one of ____ categories.
a. two
b. three
c. four
d. eight
e. nine
(b)
11. If the window is rotated, none of the clipping algorithms discussed above is of any value.
a. true
b. false
(b)
12. Suppose a polygon of n vertices is passed to the Sutherland-Hodgman algorithm for clipping. How many vertices does the resulting polygon have?
a. less than n
b. less than or equal to n
c. exactly n
d. greater than or equal to n
e. greater than n
f. can’t say in general
(f)
13. The Weiler-Atherton algorithm is
a. conceptually much simpler than Sutherland-Hodgman
b. much easier to code than Sutherland-Hodgman
c. more accurate than Sutherland-Hodgman in the results it produces
d. less accurate than Sutherland-Hodgman in the results it produces
(c)
14. ALL of the clipping algorithms discussed above are adaptable to blanking.
a. true
b. true except for Cohen-Sutherland
c. true except for Liang-Barsky
d. true except for Nicholl Lee Nicholl
e. true except for Sutherland-Hodgman and Weiler-Atherton
f. false
(a)
15. What is the dimensionality of a matrix representing translation of six-dimensional data?
a. 3x3
b. 4x4
c. 5x5
d. 6x6
e. 7x7
(e)
16. How many non-zero values are in a matrix for doing translation of six-dimensional data?
a. 11
b. 12
c. 13
d. 14
e. 15
f. 16
(c)
17. How many non-zero values are in a matrix for rotating six-dimensional data in the xw-plane?
a. 6
b. 7
c. 8
d. 9
e. 10
f. 11
(d)
18. Suppose x points left, y points up, and z points in, and you want to rotate counterclockwise about the y axis. In which position does the minus sign go?
a. (1,2)
b. (1,3)
c. (2,1)
d. (2,2)
e. (3,1)
f. (3,2)
(e)
19. Suppose you are deriving a 2-degree rotation of the earth about its axis, with its poles defined relative to the origin of universe coordinates. How many transformation matrices are composed in the derivation?
a. two or less
b. three
c. four
d. five
e. six
f. seven or more
(f)
20. Suppose the earth’s axis extends between (0,0,0) and (a,b,c). To determine the angle through which you need to rotate the axis to place it in the xy-plane, you find an angle whose hypotenuse is the square root of
a. (a2 + b2)
b. (a2 + c2)
c. (b2 + c2)
d. (a2 + b2 + c2)
(a)
21. Suppose a group of points is defined in right-handed universe coordinates and you wish to know their coordinates in left-handed moon coordinates. How many transformation matrices are composed in the derivation?
a. two or less
b. three
c. four
d. five
e. six
f. seven or more
(d)
22. Suppose the details of Mars’ surface are stored in left-handed coordinates and you wish to have them in right-handed coordinates. How many transformation matrices are composed in the derivation?
a. two or less
b. three
c. four
d. five
e. six
f. seven or more
(a)
23. Which class of graphics applications is likely to be the more challenging?
a. analytic
b. synthetic
(b)
24. Of necessity, 3D graphics is Cartesian.
a. true
b. false
(b)
25. As an intensity queue, thicker lines appear
a. closer
b. farther away
c. (can’t say in general)
(c)
26. “Hidden” lines are never displayed; otherwise they are not “hidden.”
a. true
b. false
(b)
27. Geometric transformations are likely to affect
a. vertex table data
b. edge table data
c. polygon-surface data
d. (all of the above)
(a)
28. How many sides does the plane Ax + By + Cz + D have?
a. none
b. one
c. two
(b)
29. The equation Ax + By + Cz + D = 0 is
a. implicit
b. explicit
c. parametric
(a)
30. Suppose you have a collection of vertices from which a planar equation is determined. Suppose these vertices are subjected to a transformation M. The new planar equation can NOT be determined by
a. using the transformed vertices to determine the planar equation
b. transforming the planar coefficients with transformation M
c. transforming the planar coefficients with transformation M-inverse.
d. either (c) or (d)
(b)
31. A superquadric has additional parameters for
a. representing a three-dimensional object
b. representing an object of more than three dimensions
c. adjusting the shape of the quadric
d. “sweeping” the quadric
(c)
32. What is least likely to remain constant in a “blobby” object?
a. its topology
b. its geometry
c. its volume
(b)
33. Suppose a circle of diameter 10 is approximated by a 20-sided polygon. Suppose the polygon is swept translationally so that its x-coordinates change by 100, its y-coordinates by 200, and its z-coordinates by 300. How many four-sided polygons should be generated to produce the sides (but not the ends) of the resulting cylinder?
a. 20
b. 100
c. 200
d. 300
e. 600
f. (none of the above)
(a)
34. Suppose a triangle is swept rotationally through 360 degrees, to approximate a torus using a collection of connected prisms, each of which is a chord across 20 degrees. How many polygons represent the resulting “torus?” (pick the interval in which the answer lies)
a. 0 to 25
b. 26 to 50
c. 51 to 100
d. 101 to 500
e. 501 or more
(c- 54)
35. All of the following can be done while sweeping a polygon EXCEPT
a. rotation about an arbitrary axis
b. scaling
c. movement along an arbitrary path
d. reflection
e. shearing
f. (no exceptions here)
(f)