Computer Science 455

Instructor: R. P. Burton

Second Quiz

February 6-7, 2006

Name _________________________________________ Score ____________/47

1. Some mechanism (shutters, colored filters, polarized filters, etc.) must be provided to separate the left-eye and right-eye components on an image to produce a stereo effect. The eye (and mind) simply cannot look at a computer screen and, unaided, separate the presentation into left- and right-eye images.

   1. true

   2. false

(b)

2. (Continuing the previous question) Not only must some mechanism be provided, but the mechanism must have either mechanically moving or electrically changing parts (think “liquid crystal). A passive device, such as a box sitting in front of a screen, falls short of the mark.

   1. true

   2. false

(b)

3. The 3D movies of the 1950s become unpopular (and disappeared all together) when the citizenry of America began to realize that the technology used in 3D movies was carcinogenic, especially considering that the citizenry was already sensitized by the link between asbestos and cancer.

   1. true

   2. false

(b)

4. The notion of taking a “goo” or a mist and solidifying regions of it to produce 3D output remains one of the pipe dreams from the 1980s that is yet to be realized in any commercially viable form.

   1. true

   2. false

(b)

5. The use of “glowing seaweed” for a 3D output device was doomed

   1. by the vocal environmentalists of the early 1970s

   2. by the long persistence of the glow

   3. by the seasonal availability of the seaweed

   4. by the toxic spores produced by the seaweed

   5. because the idea lacked serious merit

   6. because the Loch Ness monster ate all the seaweed

(e)

6. A computer properly programmed and connected to a numerically controlled milling machine can produce true 3D output.

   1. true

   2. false

(a)

7. A head-mounted display is capable of

   1. producing left- and right-eye images for a stereo effect

   2. determining the position and orientation of the user’s head, and producing a corresponding view

   3. both (a) and (b)

(c)

8. The real strength of the Bresenham line-drawing algorithm lies in the fact that

   1. it capitalizes on the fact that after plotting a pixel, there are only two possible successor pixels

   2. the successor pixel can be determined with simple (and hence fast) operations

(b)

9. Parallel line algorithms are designed for

   1. thick lines

   2. multiple parallel (but not touching) lines

   3. multiple processors

(c)

10. When loading the frame buffer with the pixels that approximate a line,

    1. approximately the same amount of time is required to calculate the memory location of the first, the last, or an intermediate pixel

    2. different amounts of time are needed to calculate the memory locations of different pixels

(b)

11. When the implicit equation for a circle is used to determine pixels which approximate the circle, the result is

    1. slow and nonuniform

    2. slow, but uniform

    3. fast, but nonuniform

    4. fast and uniform

(a)

12. When the parametric equation for a circle is used to determine pixels which approximate the circle, the result is

    1. slow and nonuniform

    2. slow, but uniform

    3. fast, but nonuniform

    4. fast and uniform

(b)

13. The circle-generating DDA algorithm discussed in class

    1. produces a helix

    2. produces an oval

    3. produces a circle and is fast and uniform

(b)

14. When the Bresenham algorithm is used to generate a circle, typically, as each point is computed, _____ more point(s) is/are determined with relatively minimal computation.

    1. 1

    2. 3

    3. 7

    4. 15

(c)

15. All the (steps and values in) Bresenham algorithms for generating lines, circles, and ellipses are

    1. intuitively meaningful

    2. not meaningful intuitively

(b)

16. Suppose that a line is to be drawn from mathematical point (0,0) to (10,0). The space of the intended points is exactly the same scale as the pixel grid. How many total pixels should be plotted?

    1. 9

    2. 10

    3. 11

(b)

17. When using the odd-even rule to do inside-outside tests, vertices should be counted as

    1. one intersection

    2. two intersections

    3. depends

(c)

18. When using the winding number rule to do inside-outside tests,

    1. negative means in and positive means out

    2. odd means in and even means out

    3. zero means in and nonzero means out

(c)

19. The odd-even rule and the winding number rule always make the same inside-outside determinations.

    1. true

    2. false

(b)

20. A boundary-fill algorithm requires the interior of the polygon to be filled to be either void, or of homogeneous content.

    1. true

    2. false

(b)

21. 21. A flood fill algorithm requires the interior of the polygon to be filled to be either void, or of homogeneous content.

    1. true

    2. false

(b)

22. “8-connect” fill can “seep” through a “4-connect” boundary, but “4-connect” fill cannot “seep through an “8-connect” boundary.

    1. true

    2. false

(b)

23. When doing boundary-fill across pixel spans, how large can the stack become?

    1. never more than 1

    2. at most 2

    3. arbitrarily large

(c)

24. Which of the following operations is most likely to be used when tiles are used to fill a polygon?

    1. trunc

    2. round

    3. mod

(c)

25. The width of a stroke, as a percentage of the width of a character, is independent of the point size of the character.

    1. true

    2. false

(b)

26. The possible disadvantages of run-length encoding include

    1. more decoding time

    2. more storage

    3. both (a) and (b)

(c)

27. By what means are markers typically connected?

    1. line segments

    2. dashed line segments

    3. (they are not typically connected)

(c)

28. The equations Ax + By + Cz + D = 0 and –Ax – By – cZ – D = 0 represent

    1. one plane with one normal

    2. two distinct planes

    3. two coincident planes with different normals

(c)

29. As represented on a computer screen ______ have attributes of position, width, and length.

    1. points

    2. lines segments

    3. neither points nor line segments

    4. both points and line segments

(d)

30. As measured in pixels, the horizontal line drawn along the base of a square is ______ the 45 degree line drawn between opposite corners of the square

    1. shorter than

    2. longer than

    3. the same length as

(c)

31. The slope of the line is m. What is the slope of the butt cap?

    1. m

    2. 1/m

    3. –m

    4. -1/m

(d)

32. If a manufacturer told you that he can offer you 4096 out of more than 16 million colors, how wide is the color look-up table?

    1. 24 bits

    2. 16 bits

    3. 12 bits

    4. 8 bits

(c)

33. “Soft fill” refers to

    1. antialiasing by including adjacent pixels which may be partially overlapped

    2. antialiasing by diminishing the intensity of pixels

    3. mixing background and foreground colors

(c)

34. Attributes are bundled to

    1. facilitate their interpretations, depending on the output device

    2. prevent the use of conflicting attributes

    3. avoid aesthetically displeasing or information-diminishing combinations

(a)

35. Which typically produces the more accurate information?

    1. postfiltering /supersampling

    2. prefiltering/area sampling

    3. (they produce equivalent results)

(b)

36. How is pixel phasing achieved?

    1. using pixel-weighting masks

    2. micropositioning of the electron beam

    3. area sampling

(b)

37. To antialias the boundary between a red polygon and a blue polygon.

    1. make sure that each pixel along the boundary is either red or blue

    2. allow the pixels along the boundary to be purple

    3. (there is no need to antialias; the eye & brain will smooth the boundary)

(b)

38. Matrices are _____ for doing translation, scaling, and rotation.

    1. necessary

    2. useful

    3. both necessary and useful

(b)

39. All of the following 2D transformations can be represented (functionally) in a 2 x 2 matrix except _____.

    1. translation

    2. scaling

    3. rotation

    4. (no exceptions here)

(a)

40. Which of the following transformations does not always facilitate subsequent inversion?

    1. translation

    2. scaling

    3. rotation

    4. (all facilitate subsequent inversion)

(b)

41. All of the following anticipate transformation relative to a fixed point except ____.

    1. translation

    2. scaling

    3. rotation

    4. (no exceptions here)

(a)

42. Scaling in 2D can take place

    1. only along the positive x- and y-axes.

    2. only along the positive or negative x- and y-axes

    3. in any direction in the 2D plane

(c)

43. How many points in homogeneous coordinate space correspond to an arbitrary point (x,y) in 2D space?

    1. just 1

    2. exactly two

    3. infinitely many

(c)

44. Suppose you have several matrices to be composed, representing a translation, a scaling, a rotation, and the data. Which matrix should NOT be part of the first composition (i.e. matrix multiplication)?

    1. the translation

    2. the scaling

    3. the rotation

    4. the data

    5. (any is appropriate for the first composition)

(d)

45. If TSR represents a composition of transformations, what represents the inverse?

    1. RST

    2. R^-1 S^-1 T^-1

    3. T^-1 S^-1 R^-1

    4. (there is no inverse)

(b)

46. The most desirable approach for inverting a matrix involves

1. Cramer’s rule

b. Gauss elimination with partial pivoting

c. Gauss elimination with full pivotint

(b)

47. A matrix for doing translation of nD data likely is

a. n x n

b. n+1 x n+1

(b)