Computer Science 455
Instructor: R. P. Burton
Sixth Quiz
November 21-22, 2005

Name _________________________________________	Score ____________/43

1.	In a properly coded painter’s algorithm, one of the tests will determine the nearer of two polygons; no subdivision of polygons is ever required.
a.true
b.false

(b)

2.Which of the following ALWAYS requires further subdivision when the area subdivision algorithm is used?
a.all surfaces are outside the area
b.only one surface intersects the area
c.multiple surfaces intersect the area
d.(none of these ALWAYS requires further subdivision)

(d)

3.The time required by the area subdivision method is proportional to
a.the number of subdivisions
b.the visual complexity of the scene

(b)

4.When an octree approach is taken to hidden element removal, how many times is the value of a pixel written from the octree (for a single, static scene)?
a.at most once
b.perhaps many times, depending on the complexity of the scene
c.perhaps many times, depending on the number of subdivisions in the octree

(a)

5.An octree can be expected to be used to produce a ________ projection. (pick the most specific answer)
a.parallel
b.perspective
c.parallel orthographic
d.parallel oblique
e.perspective orthographic
f.perspective oblique

(c)

6.Of the algorithms listed below, all can be adapted to produce line-drawn images except
a.the depth-buffer algorithm
b.the scan-line algorithm
c.painter’s algorithm
d.the area subdivision algorithm
e.(no exceptions here)

(e)

7.Of the algorithms listed below, all can accommodate transparency except
a.the z-buffer algorithm
b.the scan-line algorithm
c.the depth-sorting algorithm
d.the Warnock algorithm
e.(no exceptions here)

(a)


8.All of the following can have an effect on the color of a pixel EXCEPT
a.light-emitting sources
b.light-reflecting sources
c.light-transmitting sources
d.(no exceptions here)

(d)

9.Translucency _______ transparency.
a.is the same as
b.is richer in information and easier to calculate than
c.is richer in information but more difficult to calculate than
d.is leaner in information and easier to calculate than
e.is leaner in information and more difficult to calculate than

(e)

10.What feature(s) of reflection can be determined (at least in part) by the surface?
a.whether it is diffuse of specular
b.what color it is
c.both (a) and (b)

(c)

11.Light reflected diffusely comes from ______ light sources.
a.ambient
b.point
c.both ambient and point

(c)

12.The diffuse intensity of a point on a surface is determined by all of the following EXCEPT
a.a coefficient of reflection
b.the distance to the light source
c.the angle between the surface normal and the direction to a point light source
d.the angle between the reflected light and the direction to the viewer
e.(no exceptions here)

(d)

13.The intensity of a specular reflection is determined by all of the following EXCEPT
a.a coefficient of reflection
b.the distance to the light source
c.the angle between the surface normal and the direction to a point light source
d.the angle between the reflected light and the direction to the viewer
e.(no exceptions here)

(e)

14.The color of a specular reflection of a very shiny Christmas tree ornament is determined primarily by 
a.the color of the incident light
b.the color of the surface of the ornament

(a)

15.The color of a point on a partially transparent surface is determined by _____ light.
a.reflected
b.refracted
c.both reflected and refracted

(c)

16.Which of the following approaches is least satisfactory for achieving texture?
a.micropolygonization of the surface
b.altering surface normals as a function of position
c.altering reflections coefficients as a function of position

(a)

17.Which of the following approaches is most satisfactory for achieving surface patterns?
a.micropolygonization of the surface
b.applying bitmaps/pixmaps
c.fractalization of the surface

(b)

18.Shadows occur because
a.all or a portion of a surface is darkened
b.light fails to reach all or a portion of a surface
c.light intensity is reduced due to the orientation of a surface

(b)

19.Shadows are independent of
a.the positions of light sources
b.the position of the viewer
c.both (a) and (b)
d.neither (a) nor (b)

(b)

20.What is the “price” of halftoning?
a.fewer colors
b.lower resolution
c.aliasing

(b)

21.What is the primary purpose of dithering?
a.to extend the apparent range of colors
b.to restore lost resolution
c.to antialias by doing more accurate calculations
d.to antialias by adding noise

(d)

22.Constant shading, while relatively inexpensive, does not produce realistic scene elements.
a.true
b.false

(b)

23.Gourand shading improves the visual quality of
a.interiors of curved surfaces approximated by polyhedra
b.boundaries (i.e. silhouettes) of polyhedra approximated by surface patches
c.both (a) and (b)
d.neither (a) nor (b)

(a)

24.Gouraud shading determines and uses “normals” at each of the following EXCEPT
a.surfaces
b.vertices
c.(points along) edges and scanlines
d.(no exceptions here)

(c)

25.Phong shading determines and uses “normals” at each of the following EXCEPT
a.surfaces
b.vertices
c.(points along) edges and scanlines
d.(no exceptions here)

(d)

26.Ray-tracing naturally accommodates all of the following EXCEPT
a.curved surfaces
b.transparent solids
c.diffuse reflection
d.intersurface reflection
e.(no exceptions here)

(c)

27.For purposes of ray tracing, how is the normal at a point on the surface of a sphere determined?
a.from the normal of the polygon approximating the sphere at that point on the sphere
b.from an interpolated normal, considering the polygons that approximate the sphere
c.without consideration of the polygons approximating the sphere
d.sphere surfaces don’t have normals; hence none is determined

(c)

28.If a surface lies within the volume for which a ray is responsible and is the closest surface within that volume, a conventional raytracer will always detect intersection with that surface and will always detect it first.
a.true
b.false	

(b)

29.A raytracer produced by a competent professional either works or it does not.  There is no such thing as “good enough.”
a.true
b.false

(b)

30.The normals to the octants of an octree have one of only six directions.  Hence, it is not possible to think in terms of the orientation of a surface represented in an octree.
a.true
b.false

(b)

31.Radiosity precalculates intensities in a view-______ manner
a.dependent
b.independent

(b)

32.Radiosity models
a.diffuse reflection
b.specular reflection

(a)

33.A scene to be rendered using radiosity and consisting of approximately n surface patches calculates approximately _____ form factors.
a.log n
b.n
c.n log n
d.n2
e.n!

(d)

34.If rays are sent through pixel corners (and averaged) instead of through pixel centers, the number of rays approximately
a.stays the same
b.doubles
c.four-folds
d.five-folds

(a)

35.Perceived light is a narrow band in the electromagnetic spectrum.
a.true
b.false

(a)

36.If “the eye can perceive 400,000 distinct colors,” there could never be a box of crayons with more than 400,000 crayons of different colors.
a.true
b.false

(b)

37.Continuing the previous question, white is a “distinct color.”
a.true
b.false

(b)

38.A large color gamut (representing many of the colors which you and I see) requires at least ____ primary colors.
a.two
b.three
c.100
d.several thousand

(b)

39.What is the source of the standard primary colors?
a.a committee
b.Mother Nature
c.The landmark work of Roy G. Biv

(a)

40.The material used for screen phosphors is chosen to produce (three) colors at the “extremes” of the chromaticity diagram.
a.true
b.false

(b)

41.__________ the chromaticity diagram is/are associated with a dominant wavelength.
a.Each color in
b.Each color except one in
c.Only the colors on the perimeter of

(b)

42.Pick the better synonym for “shades.”
a.tints
b.tones
c.(no synonyms here)

(c)

43.The visual pigments in the cones of the retina have peak sensitivities at the extremes of the chromaticity diagram.
a.true
b.false

(b)