Computer Science 455
Instructor: R. P. Burton
Sixth Quiz
June 7-8, 2004
Name _________________________________________ Score ____________/20
1. The visible surface algorithms discussed in class were
a. all image-space algorithms
b. mostly image-space algorithms
c. mostly object-space algorithms
d. all object-space algorithms
(b)
2. If a scene consists of a single convex polyhedron or hyperpolyhedron, back-face removal by itself is sufficient to perform hidden-element removal.
a. true
b. false
(a)
3. Back-face removal requires at least ____ of the plane containing the polygon that is a candidate for removal
a. substitution of the viewing position into the equation
b. consideration of the normal
c. consideration of the value of one of the elements of the normal
d. consideration of the sign of one of the elements of the normal
(d)
4. The depth-buffer algorithm processes _____ at a time.
a. one surface
b. one scan line (for all surfaces)
c. one slice of the view volume (for all polyhedra)
(a)
5. The z-buffer algorithm requires
a. surfaces to be sorted in increasing z (assume left-handed coordinates)
b. surfaces to be sorted in decreasing z
c. polyhedra to be convex
d. (none of the above)
(d)
6. The scan-line method processes ____ at a time.
a. one surface
b. one scan line (for all surfaces)
c. one slice of the view volume (for all polyhedra)
(b)
7. When using the scan line method in a scene consisting of h closed polyhedra each with g polygons, what is the maximum number of edges that can be “on” at any point in time?
a. just one
b. h
c. g
d. more than h or g, but less than h * g
e. h * g
(d)
8. For the depth-sorting method, suppose surfaces are sorted according to the maximum z value of each surface. Suppose further that several surfaces overlap in z, but not in y. Then
a. the surfaces can be written into the frame buffer in their current order
b. the surfaces must be reordered before they can be written into the frame buffer
c. neither (a) not (b) always holds
(a)
9. For painter’s method, if surfaces overlap in x, y, and z, then the surfaces can be ordered properly by first attempting to assure that all the vertices of each subject (assumed to be of greater depth) are on the far side of the plane of the neighbor, or that the vertices of each neighbor are on the near side of the plane of each subject; one of these two conditions will always exist.
a. true
b. false
(b)
10. All of the following handle partially transparent polygons with only minor changes EXCEPT
a. the depth-buffer algorithm
b. the scan-line algorithm
c. the Newell Newell Sancha algorithm
d. the area subdivision algorithm
e. (no exceptions here)
(a)
11. Which of the following conditions requires further subdivision when the area subdivision algorithm is used?
a. no surfaces intersect the area
b. one surface intersects the area, but is completely contained in the area
c. one surface intersects the area, but is not completely contained in the area
d. multiple surfaces intersect the area, and the closest one surrounds the area
e. (none of these conditions requires further subdivision)
(e)
12. The speed with which the Warnock algorithm executes is determined most significantly by
a. the visual complexity of the scene
b. the number of subdivisions required
c. the maximum height of the associated quadtree
(a)
13. To produce a scene without hidden elements, typically it is necessary to traverse ______ of an octree containing the scene.
a. none
b. only part
c. all
(b)
14. Which of the following algorithms does NOT lend itself to the presentation of “opaque” polygons presented with their bounding edges (i.e. line drawings)?
a. the z-buffer method
b. the scan-line method
c. painter’s algorithm
d. the area subdivision method
e. (no exceptions here)
(e)
15. Point light sources are suitable for modeling (pick the most inclusive answer)
a, point light sources
b. (a) and linear light sources
c. (b) and area light sources
d. (c) and volume light sources
e. (d) and hypervolume light sources
(e)
16. Light which produces diffuse reflection comes from
a. point light sources
b. ambient light sources
c. either (a) or (b), but not both
d. either (a) or (b) and possibly both
(d)
17. Light which produces specular reflection comes from
a. point light sources
b. ambient light sources
c. either (a) or (b), but not both
d. either (a) or (b) and possibly both
(a)
18. The amount of reflected light at a point on a surface _______ the angle of incidence of the incoming light.
a. depends on
b. is independent of
(a)
19. Graphics techniques which simulate reflection from similarly colored materials (nickel, aluminum, silver, titanium, platinum, etc.) lose the subtle differences in the appearance of materials when the associated objects are represented by a polygonal “skin” as opposed to an octree.
a. true
b. false
(b)
20. Light passing through a thick pane of glass
a. enters and exits along collinear paths
b. enters and exits along parallel paths
c. enters and exists along paths which are neither collinear nor parallel
(b)