Computer Science 455

Instructor: R. P. Burton

Second Quiz

January 31- February 1, 2005

Name _________________________________________ Score ____________/x

1. What is the decision variable in the Bresenham line algorithm?

   1. It is the slope

   2. It is the inverse of the slope

   3. It is the complement of the slope

   4. It is the inverse of the complement of the slope.

   5. (none of the above)

(e)

2. The parallel line algorithm is intended

   1. for lines thicker than one pixel

   2. for environments with multiple processors

(b)

3. If multiple processors are to be used to produce parts of a common line segment using the Bresenham algorithm, the repeating cycle of the Bresenham line algorithm should be identified so that each processor can be doing an identical task.

   1. true

   2. false

(b)

4. Suppose two additions and a multiplication are required to load the first point of a line segment into the frame buffer. The next point on the same line segment can be expected to require _______ calculation.

   1. less

   2. the same amount of

   3. more

(a)

5. When using the Bresenham algorithm efficiently to produce a circle, the roles of x and y are switched to calculate the 45-to-90 degree region relative to what they were when calculating the 0-to-45 degree region of the circle.

   1. true

   2. false

(b)

6. By general consensus, the pixels used to represent the circumference of a circle should lie

   1. as close as possible on the true circumference

   2. outside, but as close as possible to the true circumference

   3. inside, but as close as possible to the true circumference

(c)

7. For the scan-line polygon fill algorithm, vertices count as ____ intersection point(s).

   1. zero

   2. one

   3. two

   4. (can’t say in general)

(d)

8. To determine the order of edges (which proceed downward from a common vertex) in the active edge list (option E should read “shortest in y” )

   1. the leftmost edge is first

   2. the rightmost edge is first

   3. the edge encountered first in a counterclockwise traversal is first

   4. the edge encountered last in a counterclockwise traversal is first

   5. the shortest edge is first

   6. the longest edge is first

(e)

9. To determine if a point is inside a polygon, the point is extended beyond the boundaries of the polygon, counting the number of polygon edges that are encountered, with vertices always counting as two edges intersected.

   1. true

   2. false

(b)

10. The “count the edges crossed” and the “winding number” approach produce ______ results for self-intersecting polygons.

    1. identical

    2. different

(b)

11. For the boundary-fill algorithm, if the recursion is _____-directional, the boundary should be _____-connected.

    1. four, four (or eight, eight)

    2. four, eight (or eight, four)

    3. four or eight, four or eight (i.e. no correlation is needed)

(b)

12. For the flood-fill algorithm, if the recursion is _____-directional, the boundary should be _____-connected.

    1. four, four (or eight, eight)

    2. four, eight (or eight, four)

    3. four or eight, four or eight (i.e. correlation doesn’t matter)

(b) Note: the testing-center key was wrong on this question.

13. When filling a polygon with “tiles” (i.e. a cell array), the starting point must be

    1. a vertex

    2. a point interior to the polygon

    3. any point in the same plane as the polygon

(c)

14. “Tiles” can be used to with any of the following EXCEPT

    1. the scan-line polygon fill algorithm

    2. the boundary-fill algorithm

    3. the flood-fill algorithm

    4. (no exceptions here)

(d)

15. Ax + By + Cz + D = 0 and –Ax – By – Cz – D = 0 describe the same plane rather than two planes which have at least one different feature.

    1. true

    2. false

(b)

16. Given the equation of a plane and the coordinates of a point, you can determine

    1. if the point is in the plane

    2. which side of the plane the point is on, if it is not in the plane

    3. both (a) and (b)

(c)

17. Points, as represented on computer screens, can have attributes besides location.

    1. true

    2. false

(a)

18. The DDA and Bresenham algorithms lend themselves to lines that are 3 times as thick, 5 times as thick, etc. for odd multiples, but not 2 times as thick, four times as thick, etc. for even multiples.

    1. true

    2. false

(b)

19. When a manufacturer says that his graphics system can present 4,096 colors from a pallet of 16 million colors, either his system doesn’t really have 16 million colors or it is capable of presenting all 16 million colors simultaneously.

    1. true

    2. false

(b)

20. What is “soft fill”?

    1. Rendering a polygon by its outline only

    2. Rendering a polygon with some inaccuracies, for purposes of efficiency and preliminary assessment

    3. Rendering a polygon with a uniform color.

    4. (None of the above)

(d)

21. What is the purpose of bundling attributes?

    1. to avoid overconstrained specifications which the user might otherwise choose

    2. to avoid underconstrained specifications which the user might otherwise choose

    3. to achieve visual harmony among attributes

    4. to provide an interpretation of each attribute for each output device

    5. (None of the above)

(d)

22. What is the purpose of inquiry functions?

    1. to reveal the combination of attributes used to produce a particular (usually pleasing) effect

    2. to facilitate changing attributes temporarily

    3. to verify the correctness of the setting of the attributes

(b)

23. What is an alias?

    1. a residual image, usually from a previous frame

    2. an unintended artifact

    3. a correction of the features inherent in a raster display

(b)

24. Prefiltering would be associated more naturally with

    1. supersampling

    2. area sampling

    3. pixel phasing

(b)

25. Texture patterns should be adjusted, depending on the orientation of the _____ to which they are applied.

    1. lines

    2. polygons

    3. lines and polygons

(c)

26. What is pixel phasing?

    1. using masks to distribute the pixel’s intensity

    2. using filters to distribute the pixel’s intensity

    3. micropositioning the electron beam

(c)

27. If two polygons (one might be red and the other might be blue) share a common boundary which overlaps some pixels, a line of variable intensity (purple perhaps) will make the boundary

    1. become clear, because there a (purple) line along the boundary

    2. look clear because the line “covers up” the “jaggies”

    3. look clean and crisp with no apparent line along the boundary

(c)

28. Which algorithm lends itself most easily to antialiasing area boundaries?

    1. the DDA algorithm(s)

    2. the simple DDA algorithm(s)

    3. the Bresenham algorithm(s)

    4. (none of these algorithms)

(c)

29. To “reorient” is to change

    1. Position (i.e. translate)

    2. Direction (i.e. rotate)

    3. Size (i.e. scale)

(b)

30. The inverse of a translation, rotation, or scaling transformation is achieved by ______ the transformation parameter(s).

    1. negating

    2. inverting

    3. negating and inverting

    4. negating or inverting

(d)

31. When an object is to be rotated about a fixed point which is not the origin, the transformation MUST translate the fixed point to the origin, then the rotation MUST take place about the origin, and then the transformation MUST move the fixed point back to its original location, causing the object to assume two intermediate positions.

    1. true

    2. false

(b)

32. Scaling affects ______.

    1. sizes of objects

    2. displacement of objects relative to the origin

    3. both (a) and (b)

(c)

33. All translation, rotation, and scaling transformations are reversible.

    1. true

    2. false

(b)