Computer Science 455

Instructor: R. P. Burton

Fourth Quiz

March 3-4, 2008 

Name _________________________________________ Score ____________/29 

1. The clipping window determines what we see, and the viewport determines where we see it.

1. true

2. false

 

(a) 

2. It makes sense to rotate  ____,.

1. the viewport but not the window.

2. the window, but not the viewport.
3. the window and the vieport.
4. neither the window nor the viewport.

 

(b) 

3. The window-to-viewport transformation typically consists of a scaling and a translation and, hence, can be represented with a 3 x 3 matrix for 2D scenes.

1. true

2. false

 

(a) 

4. Changes to the viewport result in _______ changes to the displayed image; changes to the window result in _______ changes to the displayed image.

1. corresponding, inverse

2. inverse, corresponding
3. corresponding, corresponding
4. inverse, inverse

 

(a) 

5. The transformation of a 2D object from master coordinates all the way to device coordinates can be represented as a single 3x3 matrix.

1. true

2. false

 

(a) 

 

6. It never makes sense to clip in master coordinates.

1. true

2. false

 

(b) 

7. Clipping is applicable to all of the following except

1. points

2. line segments
3. areas
4. curves
5. text
6. (no exceptions here)

 

(f) 

8. A point is rejected if it fails at least ____ of four standard tests.

1. one

2. two
3. three
4. four

 

(a) 

9. In Cohen-Sutherland clipping, which if the following is attempted first?

1. trivial rejection

2. trivial acceptance
3. suddivision

 

(b) 

10. In Cohen-Sutherland clipping with midpoint subdivision, which of the following is attempted first?

1. trivial rejection

2. trivial acceptance
3. subdivision

 

(b) 

11. For purposes of the Liang and Barsky algorithm, the line segment to be clipped is represented

1. explicitly

2. implicitly
3. parametrically

 

(c)

12. Nicholl-Lee-Nicholl clips a line segment only by rejecting it trivially.

1. True

2. False

 

(a) 

13. The results of clipping a set of objects of a particular type (dimensionality) should result in a set of objects of that same type (where the type may be points, lines, areas, etc.)

1. True

2. False

 

(a) 

14. In Sutherland-Hodgman clipping, the order in which the edges are processed makes no difference.

1. True

2. False

 

(a) 

15. _______ can result in new lines which were not part of the original scene.

1. Sutherland Hodgman

2. Weiler Atherton
3. Both Sutherland Hodgman and Weiler Atherton
4. Neither Sutherland nor Weiler Atherton

 

(a) 

16. To do “all or nothing” text clipping for “aligned” text, clip

1. the major diagonal of the bounding box

2. the minor diagonal of the bounding box
3. either diagonal of the bounding box
4. both diagonals of the bounding box

 

(c) 

17. Points, lines, areas, and text are amenable to clipping using the algorithms mentioned above, but curves cannot be clipped using the algorithms discussed above.

1. True

2. False

 

(b) 

 

18. ALL of the clipping algorithms discussed above are adaptable to blanking.

1. True

2. False

 

(a) 

19. Digitizing an existing automobile for subsequent representation in a computer is an example of a(n) ________ activity.

1. analytic

2. synthetic

 

(a) 

20. Graphics systems often use left-handed coordinates because

1. it’s more natural to think in terms of z going into (rather than out of) the screen

2. Sutherland, the father of computer graphics, was left-handed
3. left-handed coordinates are the coordinates of master coordinate space.

 

(a) 

21. Be they left-handed or right-handed, coordinate systems always are Cartesian.

1. true

2. false

 

(b) 

22. Parallel axis coordinates allows for up to ____ independent directions.

1. only two

2. three
3. four
4. more than four

 

(d) 

23. Visible element determination in 2D almost always is temporal: the younger you are, the more likely you are to be visible.

1. True

2. False

 

(a) 

24. The projection of an object without hidden lines removed generally is sufficient to indicate whether the object is being viewed from above or below.

1. true

2. false

 

(b) 

25. Darker/thicker lines always are perceived to be closer than lighter/thinner lines.

1. true

2. false

 

(b) 

26. The human visual system produces a ______ projection.  A telescope produces a ______ projection.

1. parallel, parallel

2. parallel, perspective
3. perspective, parallel
4. perspective, perspective

 

(d) 

27. Parallel projections represent a nearly obsolete carryover from the days when computing resources were insufficient to compute perspective projections at an acceptable rate.

1. true

2. false

 

(b) 

28. Producing stereo views is as simple as computing the view from two different (but typically close) viewpoints.

1. True

2. False

 

(a) 

29. Orthogonal and oblique projections are kinds of ________ projections.

1. parallel

2. perspective
3. parallel and/or perspective

 

(c)