Computer Science 455

Instructor: R. P. Burton

Fourth Quiz

March 5-6, 2007

Name _________________________________________ Score ____________/31

1. Liang & Barsky can do all of the following except

   1. identify line segments parallel to clipping region boundaries

   2. identify line segments completely inside (or outside) clipping region boundaries

   3. determine the direction from which the extension of a line segment crosses the extension of a clipping region boundary

   4. produce a parameter which indicates the point of crossing

   5. (no exceptions here)

(e)

2. Which of the following algorithms is best at determining whether or not a line segment crosses a (nonextended) clipping region boundary?

   1. Cohen Sutherland

   2. Liang & Barsky

   3. Nicholl Lee Nicholl

(c)

3. The line clipping algorithms of the preceding question typically assume clipping region boundaries parallel to the principal axes, and hence are useless if the clipping region is rotated.

   1. true

   2. false

(b)

4. A general rule for a clipping algorithm is, “points in, points out,” “lines in, lines out,” and “polygons in, polygons out.”

   1. true

   2. false

(a)

5. Which of the following can produce line segments that really shouldn’t be there?

   1. Sutherland Hodgman

   2. Weiler Atherton

   3. both

   4. neither

(a)

6. With all-or-nothing string clipping, it is sufficient (pick the most inclusive, correct answer) to clip

   1. the major diagonal

   2. the minor diagonal

   3. either (a) or (b)

   4. both (a) and (b)

   5. any of the above

(e)

7. All of the preceding algorithms lend themselves to blanking except

   1. Cohen Sutherland

   2. Liang & Barsky

   3. Nicholl Lee Nicholl

   4. Sutherland Hodgman

   5. Weiler Atherton

   6. (no exceptions here)

(f)

8. Algorithms for clipping curves are beyond the scope of CS 455.

   1. true

   2. false

(b)

9. How many (“principal plane”) rotations are required to align an arbitrary axis with a principal axis (for the purposes of 3D rotation)?

   1. one

   2. two

   3. three

   4. more than three

(b)

10. The first of these rotations involves a hypotenuse that considers _____ of delta x, delta y, and delta z.

    1. just one

    2. two

    3. all three

(b)

11. How many (“principal plane”) rotations are required to align an arbitrary Cartesian coordinate frame with another arbitrary Cartesian coordinate frame?

    1. one

    2. two

    3. three

    4. more than three

    5. (it can’t always be done)

(c)

12. If we determine a representation (for computer graphics purposes) of an object which already exists, likely we are engaged in a(n) _______ activity.

    1. analytic

    2. synthetic

(a)

13. Computer graphics is Cartesian. Period. The user should limit his thinking to Cartesian coordinates.

    1. true

    2. false

(b)

14. A user lacking binocular vision cannot reasonably hope to see 3D in a scene rendered using computer graphics techniques.

    1. true

    2. false

(b)

15. Extreme intensity cuing provides a form of

    1. transparency

    2. translucency

    3. hidden element removal

    4. shading

(c)

16. Where is the viewpoint for a parallel projection?

    1. on the projection plane

    2. one screen-width away from the projection plane

    3. far, far away – even beyond Judea’s plains (actually, Judea is hilly)

(c)

17. House plans typically are _______ projections.

    1. parallel

    2. perspective

(a)

18. A parallel projection is _____ the projection plane.

    1. always parallel to

    2. always perpendicular to

    3. sometimes perpendicular to

    4. never perpendicular to

(c)

19. What is the relationship between axonometric projections and isometric projections?

    1. they are siblings

    2. axonometric projections are specialized isometric projections

    3. isometric projections are specialized axonometric projections

    4. there is no relationship

(c)

20. What is the relationship between cavalier and cabinet projections?

    1. they are siblings

    2. cavalier projections are specialized cabinet projections

    3. cabinet projections are specialized cavalier projections

    4. there is no relationship

(a)

21. A perspective projection involves a simple division by depth.

    1. true

    2. false

(a)

22. A cube in an arbitrary orientation has ___ vanishing point(s).

    1. no

    2. one

    3. two

    4. three

    5. more than three

(d)

23. The transformation from world coordinates to viewing coordinates involves a conventional transformation from one coordinate system to another coordinate system.

    1. true

    2. false

(a)

24. What is the shape of the view volume for a parallel projection?

    1. a parallelepiped

    2. a cone

    3. a frustum

(a)

25. What is the purpose of near and far planes?

    1. to take cross sections

    2. to make greater use of the available precision

    3. to eliminate the processing of items which can be expected to be imperceptibly small

    4. all of the above

(d)

26. All of the following view volumes can be normalized except the view volume resulting from (pick the most complete, correct answer)

    1. any perspective projection

    2. any oblique projection

    3. an oblique perspective projection

    4. (no exceptions here)

(d)

27. Which is better for doing arbitrary curves in two-dimensional space?

    1. let y be a function of x

    2. let x be a function of y

    3. (neither works satisfactorily in general)

(c)

28. Which of the following is NEVER satisfactory for piecing together curve sections?

    1. zero-order continuity

    2. first-order continuity

    3. second-order continuity

    4. (each can be satisfactory)

(d)

29. All things considered, the better approach usually involves curves which _____ the control points.

    1. approximate

    2. interpolate

(a)

30. Bézier curves date from

    1. the ancient Greeks

    2. the era of wooden sailing ships

    3. the era of the automobile

    4. the most recent decade

(c)

31. The Bézier curve formulation is

    1. algebraically correct, but lacking in intuitive meaning

    2. intuitively meaningful

(b)