Computer
Science 455
Instructor: R. P. Burton
Fifth Quiz
Name ____________________________________ Score ____________/47 (ugh!)
1. What is a principal advantage of parallel projection?
a. It simulates the way the eye and mind receive projections.
b. It preserves relative proportions.
c. (both (a) and (b))
(b)
2. Which of the following 3D graphics activities is most without counterpart in other disciplines?
a. mapping from 3D to 2D (for display purposes)
b. modeling solid objects
c. removing hidden lines and hidden surfaces
(c)
3. Suppose you have a vertex table, an edge table, a polygon table, and a polyhedron table. Which is/are likely to be changed by transformations which are represented in matrix form? The contents of
a. none of these tables
b. the vertex table
c. the edge table
d. the polygon table
e. the polyhedron table
f. the vertex, edge, polygon, and polyhedron tables
(b)
4. The equation Ax + By + Cz + D = 0 represents
a. a plane with just one side
b. a plane with two sides
(a)
5. Suppose the following are vertices of a triangle: (1,2,3), (3,2,1), and (2,2,2). Do any of the coefficients in the equation of the associated plane have a value of 0?
a. yes
b. no
(a)
6. What can you say about a point (x,y,z) if Ax + BY + Cz + D > 0
a. nothing
b. the point is on the plane
c. the point is outside the plane
d. the point is inside the plane
(c)
7. Suppose you have triangle in a plane whose equation is Ax + By + Cz + D = 0, and a transformation matrix M which transforms the vertices of a triangle. What matrix can be used to transform [A B C D] to determine [A’ B’ C’ D’] of the new plane of the transformed triangle?
a. M
b. M inverse
c. M transpose
d. (none of the above)
(b)
8. What is the relationship between quadrics and superquadrics?
a. superquadrics are higher-dimensional counterparts of quadrics
b. superquadrics have additional shape adjusting features
c. superquadrics are the parent class and quadrics are the child classes
(b)
9. On what axis is the parameter in a parametric equation plotted?
a. x
b. y
c. z
d. (it isn’t plotted)
(d)
10. Two curves which touch and have common tangents at the joint exhibit _______ continuity.
a. zero order
b. first order
c. second order
d. no
(b)
11. Which is the more popular usage? Control points which are _______.
a. interpolated
b. approximated
(b)
12. The Bezier coordinate function presented in class can handle (pick the most inclusive correct answer)
a. curves in the plane
b. curves in three-dimensional space
c. curves in n-dimensional space
(c)
13. Suppose a Bezier curve is determined by five control points. Moving one control points affects _____ of the curve.
a. approximately one fifth
b. approximately half
c. virtually all
(c)
14. Suppose you have found the blending functions for a Bezier curve with five control points. If you are given a second set of five control points, two of which are the same as the control points in the first set, how many new blending functions do you need to determine?
a. none
b. three if the matching points are in the same positions in both sets
c. five if the matching points are in different positions in the sets
(a)
15. A Bezier curve is ______ guaranteed to be inside its ______ which is guaranteed to be inside its _________.
a. always, convex hull, bounding box
b. always, bounding box, convex hull
c. never, bounding box, convex hull
(a)
16. A Bezier curve ____ be closed; the ending points ____ be tangent to a common line.
a. can, can
b. can, cannot
c. cannot, can
d. cannot, cannot
(a)
17. A particular Bezier curve is determined by 10 control points. What is the maximum degree of the associated polynomial?
a. 11
b. 10
c. 9
d. 3
e. 2
(c)
18. Bezier curves can be pieced together with zero-order or first-order continuity.
a. true
b. false
(a)
19. The B-spline coordinate function is fundamentally equivalent to the Bezier coordinate function except that a different blending function is used.
a. true
b. false
(a)
20. Suppose the 0th B-spline control point (of 5 control points) is moved. How much of the curve changes?
a. none
b. some
c. most
d. all
(b)
21. An increase in the number of B-spline control points ________ the degree of the curve.
a. does not change
b. linearly changes
c. quadratically changes
(a)
22. How are Bezier surfaces determined?
a. by several parallel Bezier curves (one for each set of “parallel” control points)
b. by a 2D grid or “net” of control points
c. by a 3D lattice of control points
d. (there are no such things as Bezier surfaces)
(b)
23. As a general rule, a curve which interpolates control points does so at the expense of the convex hull and variation diminishing property.
a. true
b. false
(a)
24. What are the requirements for blending B-spline curves?
a. none – they don’t need to be blended
b. coincident connection points
c. coincident connection points and colinear adjacent points
(a)
25. A 2D shape which is swept (pick the richest answer) ______ during sweeping.
a. can only be translated
b. can be translated and rotated
c. can be translated, rotated, and scaled
d. can be translated, rotated, scales, and sheared
(d)
26. The unioning, intersecting, and differencing of a basic collection of shapes is called
a. binary space partitioning
b. boundary representation partitioning
c. constructive solid geometry
(c)
27. Which of the following are likely to be of uniform dimensions?
a. octants (in an octree representation)
b. voxels
c. dexels
d. (all are of uniform dimensions)
(b)
28. Under what circumstance is a leaf node in an octree realized?
a. when pixel size is achieved
b. only when the contents of the octant is void
c. what the contents of the octant is homogeneous
d. When the predetermined octant size is reached
(c)
29. Suppose 12-dimensional data (not including the homogeneous coordinate) is to be translated or scaled, but not both. How many entries in the transformation matrix can have a value other than zero?
a. 12
b. 13
c. 24
d. 25
e. 26
f. none of the above
(d)
30. Suppose 12-dimensional data (not including the homogeneous coordinate) is to be rotated. How many entries in the transformation matrix can have a value other than zero?
a. 2
b. 4
c. 12
d. 13
e. 144
f. none of the above
(f - 15)
31. Suppose you wish to rotate about an axis which is neither a principal axis, nor is it parallel to a principal axis. How many basic transformation matrices are you likely to compose to produce the desired transformation matrix?
a. 3
b. 4
c. 5
d. 6
e. 7
f. more than 7
(e)
32. Suppose you wish to rotate the (European style) doorknob about its axis the position, orientation, and scale of which is defined relative to the origin of door coordinates, the position, orientation, and scale of which is defined relative to room coordinates which, fortunately, happens to be the same as world coordinates since this is a room in the solitary confinement section of the prison. How many basic transformation matrices need to be composed to produce the desired transformation matrix?
a. less than 10
b. 10 to 19
c. 20 to 29
d. 30 to 39
e. 40 or more
(b)
33. Suppose points P1 and P2 in viewing coordinates are ten units apart before they are projected to the screen. After projection to the screen, they are nine units apart. The projection could be any of the following EXCEPT
a. parallel orthographic
b. parallel oblique
c. perspective orthographic
d. perspective oblique
e. (no exceptions here)
(e)
34. Two line segments of identical lengths and identical orientations are projected to the screen, but their projections appear to be of different lengths. The projection is
a. parallel
b. perspective
c. parallel or perspective
d. impossible
(b)
35. Which of the following are represented appropriately by 4x4 transformation matrices?
a. parallel projections
b. perspective projections
c. both
d. neither
(a)
36. The x and y coordinates of the projection are exactly the same as the x and y coordinates of the original point, and they are not zero. The projection is
a. parallel orthographic
b. parallel oblique
c. perspective orthographic
d. perspective oblique
e. impossible
(a)
37. What is the immediate “parent” of cavalier and cabinet projections?
a. parallel
b. perspective
c. parallel orthographic
d. parallel oblique
e. perspective orthographic
f. perspective oblique
(d)
38. In a perspective projection, the x and y coordinates are divided by the z coordinate where z is measured from
a. the projection plane
b. the eye
(a)
39. After picking a “look from” point and a “look at” point, the viewing transformation is uniquely determined (i.e. the relationship between the viewing coordinate system and the world coordinate system is uniquely determined).
a. true
b. false
(b)
40. The view volume for parallel oblique projection is converted to a view volume for parallel orthographic projection by
a. scaling
b. shearing
c. scaling and shearing
d. no known means
(b)
41. The view volume for perspective oblique projection is converted to a view volume for parallel orthographic projection by
a. scaling
b. shearing
c. scaling and shearing
d. no known means
(c)
42. Which of the following is NOT a function of the near and/or far planes?
a. taking cross sections
b. focusing the precision of the machine on the region of interest
c. indicating the range of positions of the view plane
d. (all are functions of the near and/or far planes)
(c)
43. Where is the center of projection for a parallel projection?
a. on the screen
b. at the eye of the viewer
c.
far, far away (but not on
(c)
44. Which of the following is MOST difficult to extend to 3D?
a. Cohen-Sutherland
b. Liang-Barsky
c. Nicholl-Lee-Nicholl
d. (all extend easily to 3D)
(c)
45. The intensity of point-source light diminishes in proportion to the __________ between the surface normal and the vector to the point source light.
a. angle
b. the cosine of the angle
c. the sine of the angle
(b)
46. Where does Gouraud first compute intensities?
a. for each plane
b. at vertices
c. along edges
d. at individual pixels along scan lines
(b)
47. Where does Phong first compute intensities?
a. for each plane
b. at vertices
c. along edges
d. at individual pixels along scan lines
(d)