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ch8 Graphics Flashcards

(101 cards)

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1
Q

Q

A

A

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2
Q

Why is lighting important in computer graphics?

A

It makes objects appear three-dimensional by creating shadows, highlights, and brightness variations.

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3
Q

What does the human eye actually see when observing an object?

A

Light reflected off objects, not the light source itself.

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4
Q

What are the three parameters involved in lighting models?

A

Light, reflection, and surface.

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5
Q

Name four types of light sources in computer graphics.

A

Ambient light, point light source, distant light source, spotlight.

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6
Q

What is ambient light?

A

A global light that illuminates all objects equally, without direction.

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7
Q

How does a point light source behave?

A

Emits light from a single point in all directions, like a bulb.

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8
Q

What characterizes a distant light source?

A

Light rays are parallel, like sunlight.

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9
Q

What is a spotlight in graphics?

A

Focused light in a cone shape, like a flashlight.

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10
Q

What is diffuse reflection?

A

Light scattering equally in all directions from a rough surface.

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11
Q

What is specular reflection?

A

Mirror-like reflection creating bright spots (highlights) on shiny surfaces.

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12
Q

How does material affect light reflection?

A

Surface type (metal, wood, glass) and texture (smooth or rough) influence reflection.

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13
Q

What happens when white light hits a green object?

A

Green wavelengths are reflected, and other colors are absorbed.

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14
Q

What components make up the basic illumination model?

A

Ambient light, diffuse reflection, specular reflection.

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15
Q

Why do we initially assume monochromatic light?

A

To simplify lighting calculations before adding color channels.

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16
Q

What is ambient light responsible for?

A

Ensuring surfaces not directly hit by light are still visible.

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17
Q

How does diffuse reflection affect appearance?

A

It makes brightness uniform from many viewing angles.

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18
Q

What surfaces typically show diffuse reflection?

A

Matte or non-shiny surfaces like paper or walls.

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19
Q

What surfaces show specular reflection?

A

Smooth, shiny surfaces like polished metal.

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20
Q

What is the formula component F_att in the specular model?

A

Models how intensity decreases with the square of distance.

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21
Q

What does the ka coefficient represent?

A

The ambient reflection coefficient.

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22
Q

What does the kd coefficient represent?

A

The diffuse reflection coefficient.

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23
Q

What does the ks coefficient represent?

A

The specular reflection coefficient.

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24
Q

What is θ (theta) in lighting models?

A

The angle between surface normal and light source direction.

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25
What is α (alpha) in lighting models?
The angle between reflection vector and viewer direction.
26
What is the shininess factor (n)?
It controls the concentration of the specular highlight.
27
What happens with a higher shininess factor?
Creates a smaller, sharper highlight.
28
What is a surface normal?
A vector perpendicular to a surface at a given point.
29
How is the surface normal for a polygon found?
By taking the cross product of two edges of the polygon.
30
What is normalization in vector math?
Making a vector have length 1 while keeping its direction.
31
What does the dot product of two unit vectors represent?
The cosine of the angle between them.
32
How do we convert lighting intensity to an 8-bit grayscale value?
Multiply the intensity by 255.
33
What three components are added together for final lighting?
Ambient + Diffuse + Specular.
34
What is flat shading?
Lighting is calculated once per polygon; the whole surface has the same color.
35
What is Gouraud shading?
Lighting calculated at vertices and interpolated across surfaces.
36
What is Phong shading?
Lighting is calculated per pixel, using interpolated normals.
37
Which shading technique is the fastest?
Flat shading.
38
Which shading technique provides the smoothest highlights?
Phong shading.
39
Why does Gouraud shading sometimes miss highlights?
Highlights may fall between vertices, not at them.
40
What are Mach bands?
Optical illusions where smooth gradients look like bands in Gouraud shading.
41
What major problem does Gouraud shading have?
Poor handling of specular reflections.
42
Who developed Gouraud shading?
Henri Gouraud.
43
Who developed Phong shading?
Phong Bui Tuong.
44
What does Phong shading interpolate?
Normal vectors across the polygon.
45
What does Gouraud shading interpolate?
Light intensities across the polygon.
46
What is bilinear interpolation used for?
Estimating intensity inside polygons using known vertex intensities.
47
What are scanlines?
Horizontal lines across the screen used to fill polygons.
48
What is the first step in bilinear interpolation?
Sorting vertices by y-coordinate.
49
How are trapezoids created in scan-line interpolation?
By slicing the polygon with horizontal scanlines.
50
How is intensity interpolated vertically?
Along the edges of the trapezoid.
51
How is intensity interpolated horizontally?
Along each scanline between two edge points.
52
What determines the slope 'a' in interpolation?
The change in intensity divided by the change in y.
53
What determines the intercept 'b' in interpolation?
The starting intensity value.
54
How is the intensity I at a point calculated in linear interpolation?
I = a * y + b.
55
What happens to the light vector L in illumination models?
It's normalized before calculations.
56
What does ambient light simulate in real scenes?
Light that has bounced around the environment.
57
What happens to intensity with distance from a point light source?
It decreases with the square of the distance.
58
What is the purpose of the reflection vector R?
It shows the direction light would reflect perfectly off a surface.
59
What lighting model is used in most 3D graphics systems?
The basic illumination model.
60
Why are lighting calculations computationally expensive?
Simulating realistic light behavior involves complex math.
61
How is general brightness achieved without direction?
Using ambient light.
62
Why does flat shading look unrealistic?
It doesn’t account for surface curvature.
63
What can overcome the limits of flat shading?
Increasing the number of polygons.
64
What happens when polygons have more vertices?
Smoother, more realistic surfaces.
65
What is intensity interpolation across edges called?
Linear interpolation.
66
What is the purpose of using a normalized normal vector?
Simplifies cosine angle calculations.
67
What does specular exponent control?
Sharpness of highlights.
68
What happens with a low specular exponent?
Broad, dull highlights.
69
Why is Phong shading more realistic than Gouraud shading?
It computes lighting at every pixel.
70
What is a visible surface detection technique?
Algorithms to determine which surfaces are visible to the camera.
71
What happens in interpolation between two points?
Values are blended proportionally based on distance.
72
What does 'rendering' mean in graphics?
Generating an image from a 3D scene.
73
What technique can cause specular highlights to appear more accurately?
Phong shading.
74
Why is ambient light essential even in dark scenes?
It prevents surfaces from appearing completely black.
75
What defines the surface color we perceive?
The wavelengths of light reflected.
76
How does a flashlight simulate a spotlight?
By focusing light in a cone shape.
77
Why are unit vectors important in graphics?
They ensure consistent directional calculations.
78
What are the three components of final light intensity in the specular model?
Ambient, diffuse, and specular.
79
What happens when specular highlights are missed in Gouraud shading?
The surface appears less shiny or realistic.
80
What does Phong shading require more of compared to Gouraud shading?
Computational power.
81
In what situation is flat shading acceptable?
When rendering simple or stylized objects quickly.
82
What is interpolated during Gouraud shading?
Intensity (color/brightness).
83
What is interpolated during Phong shading?
Surface normals.
84
Which shading method best shows curved surfaces?
Phong shading.
85
What does normalization do to a vector?
Makes its magnitude equal to 1.
86
What role does the reflection vector play in specular reflection?
Helps calculate the highlight based on viewer position.
87
What does a high shininess factor n produce?
A small, sharp specular highlight.
88
How is light intensity typically represented in computers?
As an 8-bit value from 0 to 255.
89
What happens to parallel light rays?
They maintain a constant direction.
90
How is a surface normal at a shared vertex usually calculated?
As the average of adjacent polygons' normals.
91
What is constant shading another name for?
Flat shading.
92
What is the goal of using lighting models?
To simulate realistic interaction of light and surfaces.
93
Which shading method is best for real-time applications needing speed?
Flat shading.
94
Which shading method balances realism and performance?
Gouraud shading.
95
Which shading method prioritizes realism over speed?
Phong shading.
96
What visual artifact results from interpolation errors?
Mach bands.
97
What is the first action when interpolating within a polygon?
Sort vertices by y-coordinate.
98
What is calculated when doing bilinear interpolation?
Intensities at any pixel.
99
What kind of surfaces show prominent specular highlights?
Smooth, polished surfaces.
100
Why use specular reflection in shading models?
To simulate shiny, glossy surfaces.
101
What do shading models significantly affect in 3D graphics?
Surface realism and depth perception.

ch3 (12 decks)

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