Computer Science 455
Instructor: R. P. Burton
Seventh Quiz
April 12-13, 2004
Name _________________________________________ Score ____________/31
1. The point of diminishing returns is reached when the number of primary colors (for a monitor, for example) exceeds
a. one
b. two
c. three
d. four
e. eight
(c)
2. What is the source of the standard primary colors?
a. the sun
b. refraction produced by water
c. Roy G. Biv
d. a committee
(d)
3. The number of primary colors used to produce the chromaticity diagram is _____ the dimensionality of the chromaticity diagram.
a. less than
b. the same as
c. greater than
(c)
4. A dominant wavelength is associated with ______ of the chromaticity diagram.
a. every point
b. all except one point
c. the points around the outside
(b)
5. Sally Brown adjusts a pure hue by adding black pigment. Sally Brown is
a. shading
b. tinting
c. toning
d. torquing
(a)
6. The phosphors used in color monitors are chosen to
a. maximize coverage of the chromaticity diagram
b. maximize the response of the cones of the retina
c. represent the standard primary colors
d. represent what most cultures commonly call red, green, and blue
(b)
7. What shape is the CMY color model?
a. a sphere
b. a cube
c. a cone
d. a double cone
e. a frustum
f. (none of the above)
(b)
8. Where are the pure hues in the HSV hexacone?
a. on the flat, hexagonal top
b. around the perimeter of the flat, hexagonal top
c. along the vertical axis
d. on the outside between the flat, hexagonal top and the point at the bottom
e. throughout the interior
f. (the HSV hexacone does not represent pure hues)
(b)
9. Where are the tints in the HSV hexacone?
a. on the flat, hexagonal top
b. around the perimeter of the flat, hexagonal top
c. along the vertical axis
d. on the outside between the flat, hexagonal top and the point at the bottom
e. throughout the interior
f. (the HSV hexacone does not represent pure hues)
(a)
10. Which of the following approaches works well for aesthetic color selection?
a. select points evenly distributed on the exterior of the RGB color model
b. select points evenly distributed along an edge of the CMY color model
c. select points evenly distributed on the flat, hexagonal top of the HSV hexacone
d. select points along the vertical axis of the HLS color model
e. (all these approaches work equally well)
(b)
11. A pinhole camera inverts the image. Similarly, raytracing inverts the image, but compensation is made by writing into the frame buffer “upside down.”
a. true
b. false
(b)
12. For raytracing purposes, each pixel can be thought of as an independent window onto the scene. In theory, if you had enough processors (one for each pixel), they could all execute simultaneously and independently.
a. true
b. false
(a)
13. The principal advantage of tracing rays backwards is
a. the fact that it models reality; like electricity, light actually travels backwards.
b. fewer rays to process
c. conformity, but no other advantage; it’s like choosing what side of the street people should drive on (and conformity is a good idea there, too)
(b)
14. In pure ray tracing, if a ray (represented as a polyline) passing through a pixel doesn’t encounter a light source, then that ray doesn’t “add” any light to the pixel.
a. true
b. false
(a)
15. Suppose a ray bounces off several surfaces, finally striking a light source. Which surface(s) determine(s) the color of the ray’s pixel?
a. only the surface “closest” to the eye
b. only the surface “closest” to the light source
c. most of the surfaces
d. all of the surfaces
(d)
16. How is the aliasing problem solved in raytracing?
a. by supersampling
b. by stochastic sampling
c. by statistical sampling
d. (it isn’t solved, but it can be reduced)
(d)
17. The primary objective of an algorithm which determines the intersection of a ray with an object is
a. speed
b. both speed and mathematical elegance, since mathematically elegant solutions yield fast algorithms
c. reduction of memory demands, since raytracing can require literally millions of polyline segments.
(a)
18. To test for the intersection of a ray and a sphere (as discussed in class), the ray is represented ______ and the sphere is represented _______.
a. explicitly, explicitly
b. parametrically, parametrically
c. implicitly, implicitly
d. implicitly, parametrically
e. parametrically, implicitly
f. explicitly, implicitly
(e)
19. How many solutions are there when attempting to find the intersection of a ray and a sphere?
a. always at least none
b. always at least one
c. always exactly two
(a)
20. How is the normal at the point of intersection of a ray and a sphere found?
a. the ray is assumed to be tangent to the sphere
b. the ray is assumed to be perpendicular to the sphere
c. from the equation for the ray
d. from the equation for the sphere
e. from the equation for the sphere and the point of intersection
f. (none of the above)
(e)
21. Relative to the algebraic solution discussed in class, the geometric solution for finding the intersection of a ray and a sphere is
a. more accurate
b. more efficient
c. more elegant mathematically
d. (all of the above)
(b)
22. In the geometric solution, which of the following is likely to be determined last?
a. the distance from the ray’s origin to the point on the ray closest to the sphere’s center
b. the distance between the closest approach of the ray to the sphere’s center and the sphere’s surface
(b)
23. What is the purpose of spherical inverse mapping?
a. to accommodate refracted rays and rays which emanate inside a sphere by treating the sphere as two-sided and by inverting the surface normal
b. to accommodate texture and color
c. to trace rays backwards from the sphere to other surfaces and/or a light source
(b)
24. For raytracing purposes, a ray extended infinitely (both positively and negatively) always intersects a plane, independent of the orientation of the ray or the plane.
a. true
b. true unless the plane is considered to be one-sided
c. false
(c - parallel)
25. The approach discussed in class for finding the intersection of a ray and a plane is fundamentally ______ approach for finding the intersection of a ray and a sphere.
a. the same as the algebraic
b. the same as the geometric
c. different from both the algebraic and geometric
(a)
26. To find the intersection of a ray with a polygon (in a plane)
a. a 3D inside-outside test is required which requires rotation of the polygon to align it with a principal plane
b. a 2D inside-outside test will suffice, with the polygon and the point of intersection being projected to a principal plane
c. the distance of the point of intersection from each edge of the polygon must be determined, and that distance must be positive for all edges
(b)
27. The algorithm for quadrilateral inverse mapping can be used for triangle inverse mapping with only a minor of adjustment.
a. true
b. false
(a)
28. Ray/box intersection techniques are important primarily because
a. a box represents a commonly occurring shape
b. bounding boxes can increase the efficiency of raytracing
(b)
29. Given any slab and a ray not parallel to it, there is a value of t where the ray enters the slab and a value of t where the ray exits the slab.
a. true
b. false
(a)
30. If a ray has positive t values when it enters and exits each of the x-, y-, and z-slabs, then the ray intersects the box which determines the slabs.
a. true
b. false
(b)
31. The approach discussed in class for finding the intersection of a ray and a quadric is fundamentally ______ approach for finding the intersection of a ray and a sphere.
d. the same as the algebraic
e. the same as the geometric
f. different from both the algebraic and geometric
(a)