Computer Science 455
Instructor: R. P. Burton
Third Quiz
May 17-18, 2004
Name _________________________________________ Score ____________/40
1. The principles for producing graphic output for hardcopy devices are fundamentally different from the principles for producing graphic output for a monitor.
a. true
b. false
(b)
2. How is the ink in an ink jet printer directed?
a. by micropositioning the jet
b. by electrically deflecting the ink
c. by micropositioning the paper
(b)
3. Which coordinate system is farthest from the display device?
a. device coordinates
b. master coordinates
c. normalized device coordinates
d. world coordinates
(b)
4. What is the primary purpose of graphics standards?
a. decorum
b. compliance with government requirements
c. maintenance of quality levels
d. portability
(d)
5. The presentation of a point on the screen anticipates no attributes other than position.
a. true
b. false
(b)
6. A pixel mask such as “00001111” would be sufficient for representing a line to be presented with equally sized and uniform dashes and spaces; the pattern is simply repeated and applied to lines or any length or orientation.
a. true
b. false
(b)
7. The DDA and Bresenham algorithms for lines can be modified to present lines whose thicknesses are odd multiples. Presenting lines whose thicknesses are even multiples requires shifting of the line one line thickness either up or down.
a. true
b. false
(b)
8. When a manufacturer tells you that his computer can present a small fraction of its available colors, he’s probably telling you that
a. the additional colors must be purchased, and are not included in the base price
b. that he picked, and provided you, with the small collection of colors most suited to your needs
c. that he is using a color table whose size is exactly the same as the number of colors available to you
d. you are getting the “budget” version of his hardware
(c)
9. When you fill a polygon with “tiles,” the starting point of a tile
a. must be coincident with a vertex of the polygon
b. must be interior to the polygon
c. can be anywhere
(c)
10. When a polygon is “soft filled,”
a. It is scan-converted at lower resolution, making the “jaggies” more apparent, but reducing the scan conversion time
b. It is “flood filled”
c. Its fill color is diluted
d. Its fill color is textured to produce a fuzzy appearance
(c)
11. What is kerning?
a. “soft-filling”
b. beveling joints between line segments
c. adjusting inter-character spacing
d. achieving compatibility among attributes
(c)
12. What is a “marker”?
a. a “current position,” relative to which other positions are determined
b. any symbol placed to “mark” a position
c. a felt-tipped cylinder filled with ink and used to write on a chalkboard
d. a field indicating a self-intersecting polygon
(b)
13. What is the primary purpose of bundled attributes?
a. To prevent the setting of incompatible attributes
b. To provide for the interpretation of attributes on different devices
c. To collect together otherwise unrelated attributes (such as line style and polygon fill pattern) for selection as a group
(b)
14. What is the primary purpose of an inquiry function?
a. To determine and save a current setting
b. To discover the collection of attributes used to achieve a particular effect
c. To verify that all appropriate attributes have been given values
(a)
15. How large is the Nyquist sampling interval?
a. half the size of the cycle interval
b. no larger than the cycle interval
c. not more than twice the cycle interval
(a)
16. Supersampling is also known as
a. area sampling
b. prefiltering
c. postfiltering
(c)
17. What is the purpose of pixel-weighted masks?
a. to implement supersampling by giving more weight to subpixels near the center of the pixel area
b. to implement area sampling by giving more weight to subpixels near the center of the primitive
c. to enhance the contribution of subpixels around the perimeter of the pixel
(a)
18. What is pixel phasing?
a. making intensity proportional to proximity to the center of the pixel
b. pixel masking
c. micropositioning the electron beam
(c)
19. The boundary between a blue polygon and a red polygon can be made less obvious by turning it various shades of purple.
a. true
b. nonsense!
(a)
20. The Bresenham algorithm can be adapted to determine the extent to which a pixel is overlapped.
a. true
b. false; it is designed only to select between one of two potential successor pixels and cannot be adapted to make more than a binary selection
(a)
21. A change in “orientation” is a change in
a. position
b. the direction something is “pointing”
c. size
d. position and/or the directions something is “pointing”
(b)
22. Suppose you have a matrix M for translating 100 points. How many elements of M need to be changed to produce a matrix M-inverse that will take these 100 points back to their original positions?
a. 1 or 2
b. 3 or 4
c. 5 or 6
d. 7 or more
(a)
23. Suppose you have a matrix M for rotating 100 points. How many elements of M need to be changed to produce a matrix M-inverse that will take these 100 points back to their original positions?
a. 1 or 2
b. 3 or 4
c. 5 or 6
d. 7 or more
(a)
24. Without homogeneous coordinates, it is not reasonable to include _____ in composable matrix form.
a. translation
b. scaling
c. rotation
d. (no exceptions here)
(a)
25. What is the minimum number of 3x3 matrices needed to represent rotation about an arbitrary point and scaling with a different point remaining fixed?
a. one
b. three
c. six
(a)
26. How many points in homogeneous coordinate space map to the point (1,2) in two-dimensional space?
a. none
b. one
c. two
d. a buhzillion or more
(d)
27. To scale an object leaving a chosen point fixed in position after scaling, it is necessary to 1) translate the fixed point to the origin, 2) scale, and 3) translate the fixed point back to its original location.
a. true
b. false
(b)
28. Suppose a collection C of 100 points is to be translated by matrix T, scaled by matrix S, and rotated by matrix R, i.e. C’ = R x S x T x C. What multiplication should NOT be done first?
a. R x S
b. S x T
c. T x C
d. Any of these multiplications can be done first, with no loss
(c)
29. Composite transformation T1 is determined by taking a fixed point to the origin, scaling, and taking the fixed point back to its original position. Composite transformation T2 is determined by scaling, and then translating the fixed point back to its original position. Pick the correct characterization:
a. Transformation T1 will not work
b. Transformation T2 will not work
c. T1 and T2 are identical
(c)
30. Suppose composite transformation M needs to be undone/reversed/inverted. This can be done effectively by
a. using Cramer’s rule
b. inverting each of the matrices used to build M, composing these inverses in the same order
c. inverting each of the matrices used to build M, composing these inverses in the opposite order
d. M cannot be inverted
(c)
31. Independent of what the scale factors are – even if they are zero or negative – a scaling matrix always has a usable inverse.
a. true
b. false
(b)
32. Rotation through 180 degrees could also be called
a. Scaling by –1
b. Reflection through the origin
c. Either (a) or (b)
d. (none of the above)
(c)
33. Reflection across the x axis is achieved by
a. complimenting x values
b. complimenting y values
c. complimenting both x and y values
d. (none of the above)
(b)
34. Reflection can occur relative to any of the following EXCEPT
a. the origin
b. an arbitrary point in the plane
c. a line which is not a principal axis
d. a line which does not pass through the origin
e. a line which is not parallel to a principal axis
f. (no exceptions here)
(f)
35. The inverse of a shearing matrix is produced by
a. negating the shearing value
b. inverting the shearing value
c. transposing the shearing value
d. none of the above
(a)
36. The x axis points down, the y axis points left, the rotation is intended to be counterclockwise. Where is the minus sign?
a. (1,1)
b. (1,2)
c. (2,1)
d. (2,2)
(c)
37. If stepped an instruction at a time, a polygon rotated about point would reveal that the arbitrary point moves to the origin, the polygon rotates, and the arbitrary point moves back to its original position.
a. true
b. false
(b)
38. If A and B are transformations such as translation, scaling, rotation, reflection, and shear, then AB = BA.
a. true
b. false
(b)
39. To transform one region of the frame buffer to a same-alignment, same-size, but overlapping region of the frame buffer
a. you must use auxiliary memory at least as large as the region
b. you can do it using the frame buffer if you start with a nonoverlapped corner of the source
c. you can do it using the frame buffer if you start with an overlapped corner of the source
(c)
40. To align an arbitrary line (defined by its endpoints P1 and P2) with the x axis, _____ and use a conventional rotation matrix.
a. find the angle whose tangent is delta-y / delta-x, then determine the sines and cosines of the angle
b. find the angle whose tangent is delta-x / delta-y, then determine the sines and cosines of the angle
c. determine the sines and cosines directly using delta-x and delta y
(c)