Computer Science 455
Instructor: R. P. Burton
Sixth Quiz
November 22-23, 2004

Name _________________________________________	Score ____________/38


1.	What are the dimensions of a "point" light source for the purposes of computer 
        graphics?
	a.	infinitesimally small
	b.	not greater than one pixel when projected
	c.	small relative to the scene

(c)

2.	What kind of light can result in diffuse reflection?
	a.	point sources
	b.	distributed sources
	c.	transparent sources
	d.	any of the above

(d)

3.	The intensity of reflected light falls off ____ between the surface normal and the 
        direction to the light source.
	a.	as the square of the angle
	b.	linearly with the angle
	c.	as the square root of the angle
	d.	as the cosine of the angle

(d)

4.	If a scene consists of ambient light and 10 point light sources, the total diffuse 
        reflection can be determined by adding _____ terms together.
	a.	10
	b.	11
	c.	20

(b)

5.	Light from specular reflections is
	a.	white
	b.	the same color as the incident light
	c.	the same color as the surface

(b)

6.      Specular reflections vary with
	a.	the angle of the incident light (relative to the surface normal)
	b.	the direction to the viewer (relative to the primary reflection direction)
	c.	both (a) and (b)

(c)

7.	Texture is efficiently implemented using all of the following EXCEPT
	a.	surface micropolygonization
	b.	pattern mapping
	c.	surface normal perturbation
	d.	reflection coefficient perturbation
	e. 	(no exceptions here)

(a)

8.	Shadows are better determined by
        a.	projecting one object onto another object and by diminishing the intensity 
                of the surface(s) receiving the projection
        b.	omitting point source light contributions for surfaces which cannot be 
                "seen" from the point light source

(b)

9.	Given a system where each pixel is either "on" or "off," 5 x 5 "megapixels" could 
        have _____ different intensity levels.
	a.	just 2
	b.	10
	c.	25
	d.	more than 25

(d)

10.	Dithering
	a.	adds noise
	b.	thresholds
	c.	either (a) or (b)

(c)

11.	Constant intensity shading of a surface is relatively efficient, but never realistic.
	a.	true
	b.	false

(b)

12.	Gouraud shading determines intensities for the first time at
	a.	each pixel
	b.	each intersection of each scan line with each edge
	c.	each vertex
	d.	each polygonal surface

(c)

13.	Phong shading determines intensities for the first time at
	a.	each pixel
	b.	each intersection of each scan line with each edge
	c.	each vertex
	d.	each polygonal surface

(a)

14.	Which of the following is a NOT characteristic of Gouraud shading?
a.	the ability to suspend smooth shading across boundaries (such as across 
        the boundary between the cheek and the lip)
b.	the ability to animate (e.g. rotate) a smooth-shaded polyhedron without 
        further revealing the polygonal nature of the surface
c.	the sufficiency of linear (as opposed to higher-order) interpolation
d.	(all are characteristic of Gouraud shading)

(b)

15.	Ray tracing traces rays
	a.	from the light source toward the eye
	b.	from the eye toward the light source(s)

(b)

16.	Traced rays
	a.	never split
	b.	sometimes split
	c.	always split

(b)

17.	One serious disadvantage of an octree representation is the impossibility of 
        calculating or estimating a surface normal.
	a.	true
	b.	false

(b)

18.	A principal advantage of radiosity is
	a.	the speed with which illumination can be calculated
	b.	the fact that illumination is independent of viewpoint
	c.	the extraordinary realism of the rendering
	d.	(all of the above)

(b)

19.	A scene of n polygonal patches requires the calculation of _____ (radiosity) form factor(s).
	a.	one
	b.	log n
	c.	n log n
	d.	n2
	e.	n!

(d)

20.	If rays pass through pixel corners rather than through pixel centers, the number of 
        rays to be traced for a typical display surface
	a.	stays about the same
	b.	is four times as great

(a)

21.	The human eye can ___ approximately 400,000 distinct hues.
	a.	distinguish
	b.	perceive

(b)

22.	Most perceived colors are
	a.	pure hues
	b.	combinations of pure hues

(b)

23.	Which is the least pure of the following colors in an additive model:
	a.	black
	b.	white
	c.	red
	d.	pink

(b)

24.	Complementary colors of light combine to produce
	a.	black
	b.	white
	c.	gray
	d.	something other than black, white, or gray

(b)

25.	What is the source of the standard primaries?
	a.	the three frequencies to which the human eye has peak sensitivity
	b.	the 1931 landmark work of Nobel prize recipient Roy G. Biv
	c.	a committee

(c)

26.	What is the dimensionality of the chromaticity diagram?
	a.	1
	b.	2
	c.	3
	d.	4

(b)

27.	The chromaticity diagram presents
	a.	pure hues only
	b.	pure hues and tints only
	c.	pure hues and shades only
	d.	pure hues and tones

(b)

28.	A "best buy" (i.e. "best dollar value") of primary colors would include ___ 
        primary colors.
	a.	2
	b.	3
	c.	4
	d.	more than 4

(b)

29.	Suppose each pixel consists of a red phosphor, a green phosphor, and a blue 
        phosphor, each of which is either on or off, resulting in 8 different colors.  
        Suppose "megapixels" measure 3 x 3.  How many different colors are possible?
	a.	still just 8
	b.	more than 8, but less than 100
	c.	101 to 499
	d.	500 to 999
	e.	1000 or more

(e)

30.	Where is white in the CMY color cube?
	a.	at the origin
	b.	diagonally opposite the origin
	c.	out on the x, y, or z axis
	d.	none of the above

(a)

31.	In the HSV color model, the user tints by decreasing
	a.	hue
	b.	saturation
	c.	value
	d.	a combination of hue, saturation, and value

(b)

32.	In the HSV color model, the user shades by decreasing
	a.	hue
	b.	saturation
	c.	value
	d.	a combination of hue, saturation, and value

(c)

	
33.	Where are the tints on the HLS color model?
	a.	inside between the two cones
	b.	inside just one of the cones
	c.	on the outside of one of the cones
	d.	along the vertical axis

(c)

34.	Coordinating colors should be selected
	a.	randomly from the RGB cube
	b.	uniformly from a straight line in the RGB cube
	c.	uniformly from a plane in the RGB cube
	d.	uniformly from the volume of the RGB cube

(b)
35.	In the context of ray tracing, aliases are removed completely only by
	a.	supersampling
	b.	adaptive supersampling
	c.	statistical supersampling
	d.	stochastic supersampling
	e.	(none of the above)

(e)

36.	If something is invisible (or never drawn), there is no point in finding the 
        intersection of a ray with this "something."
	a.	true
	b.	false

(b)

37.	To test for the intersection of a ray and a sphere, the ray should be represented 
        ____ and the sphere should be represented ____.
	a.	implicitly, explicitly
	b.	explicitly, implicitly
	c.	implicitly, parametrically
	d.	parametrically, implicitly
	e.	parametrically, parametrically

(d)

38.	Given an arbitrary ray and an arbitrary sphere, the ray intersects the sphere in at 
        least _____ point(s).
	a.	zero
	b.	one
	c.	two
	d.	three

(a)