Computer Science 455
Quiz 2
Instructor: R. P. Burton
1. What is scan conversion?
a. changing a refresh display file (for a vector display) to a memory representation suitable for a raster display
b. determining the pixels that correspond to an entity such as a line or a circle
c. conversion from one output protocol to a different output protocol
(b)
2. In the context of cell encoding, a cell typically is _______ a pixel.
a. smaller than
b. the same size as
c. larger than
(c)
3. Ivan Sutherland, the father of computer graphics, did his pioneering work
a. during the 1800s
b. between 1900 and 1950
c. between 1950 and 2000
(c)
4. All of the following are technologies applicable to touch panels EXCEPT
a. optical
b. electrical
c. acoustical
d. (no exceptions here)
(d)
5. Which is likely to require the greater knowledge of computer science?
a. special purpose packages (CAD, painting programs, etc.)
b. general purpose librarires (OpenGL, Java 3D, etc.)
(b)
6. What is the primary purpose of graphics standards?
a. portability
b. control
c. enforcement of a minimum standard of quality
(a)
7. In developing your graphics software this semester, likely you will work in
a. master coordinates
b. world coordinates
c. viewing coordinates
d. device coordinates
e. (all of the above)
(e)
8. ____ of the logical devices discussed in class can be modeled by any of the physical devices discussed in class (pick the most complete true statement).
a. none
b. some
c. most
d. all
(d)
9. Almost all graphics systems are capable of plotting
a. true points
b. true lines
c. true areas
d. all of the above
(c)
10. Which typically comes first?
a. hidden element removal
b. conversion to viewing coordinates
(b)
11. When plotting a line segment using the DDA algorithm, how many of the points are centered exactly on the true line?
a. possibly none
b. at least two
c. some, but not most
d. most, but not all
e. all
(a)
12. Why would the Bresenham algorithm be faster than the DDA algorithms?
a. exploitation of symmetry
b. fewer calculations
c. simpler calculations
d. (it isn’t faster; it’s just different)
(c)
13. Using the explicit equation for a circle (x2 + y2 = r2) the results are
a. shoddy and slow
b. shoddy, but not slow
c. slow, but not shoddy
d. neither slow nor shoddy
(a)
14. Using the polar parametric form for a circle (x = x + r cos ?; y = y + r sin?), the results are
a. shoddy and slow
b. shoddy, but not slow
c. slow, but not shoddy
d. neither slow nor shoddy
(c)
15. For a Bresenham line, the successor pixel is one of two pixels. For a Bresenham circle, the successor pixel is one of ___ pixels.
a. two
b. three
c. four
d. more than four
(a)
16. The initial value of the decision variable for one implementation of the Bresenham circle algorithm is 1.25 – r. What does the 1.25 represent?
a. the aspect ratio for a typical monitor
b. the incremental advancement of the x variable relative to the y variable at the “top” of a circle
c. the incremental advancement of the x variable relative to the y variable at the “side” of a circle
d. (none of the above)
(d)
17. The pixels lying along only _____ of an ellipse (in standard position) need to be determined. The remaining pixels can be determined by symmetry.
a. ½
b. ¼
c. 1/8
(b)
18. If you are using the DDA algorithm and you want a double thickness line segment with positive slope < 1 (but you are not worried about the end caps), you can achieve it accurately by
a. plotting either the pixel above or the pixel below the calculated pixels
b. alternating between plotting the pixels above or below the calculated pixels
c. omitting the addition of ½ to the initial y value, truncating, and adding the pixel above
d. omitting the addition of ½ to the initial y value, rounding, and adding the pixel below
(c)
19. The preferable location for a pixel is the location of its
a. center
b. lower left corner
(b)
20. The pixels used to represent a polygon should be chosen so that
a. the centers along the boundary are as close as possible to the true boundary
b. the centers of the pixels defining the boundary as either on or exterior to the true boundary
c. the centers of all pixels are interior to the true boundary
(c)
21. To scan convert a polygon with the intent of representing a filled polygon in the frame buffer
a. find all the intersections of all edges with all scan lines, sort them on y, then sort them on x, and pull them off in pairs (with special consideration for vertices), and fill in between
b. put all the edges in an active edge list (ordered based on max y, then on change in y), find intersection points, and pull them off in pairs (ordered on x) (with special consideration for vertices), and fill in between
c. either (a) or (b)
(c)
22. The scan-line fill algorithm discussed in class ____ work for self-intersecting polygons.
a. does
b. does not
(a)
23. The “edge crossing” inside-outside test works only for convex polygons. Concave polygons must be broken up into a collection of convex polygons.
a. true
b. false
(b)
24. If the “edge crossing” technique determines that a point is interior to a polygon, the “winding number” technique will determine that the same point is interior to the same polygon.
a. true
b. false
(b)
25. Why bother to convert a polygon with more than three vertices into a collection of triangles?
a. because a triangle always has a normal determined by the equation of its plane, whereas a polygon may not have such a normal
b. because the scan-fill, boundary-fill, and flood-fill algorithms work only for triangles
c. no particular reason; more than anything else it’s a carry-over of a tradition
(a)
26. The equation Ax + By + Cz + D = 0 is
a. explicit
b. implicit
c. parametric
(b)
27. The planar coefficients A, B, C, and D can be determined using the coordinates of the vertices of a polygon.
a. true
b. false
(a)
28. The equations Ax + By + Cz + D = 0 and -Ax - By - Cz - D = 0 represent the same side of the same plane.
a. true
b. false
(b)