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ch7Graphics Flashcards

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1
Q

What defines the position of the camera in 3D space?

A

Camera Position.

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2
Q

What is the ‘Look At’ point in camera setup?

A

The point the camera is aimed at, often the origin.

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3
Q

What is the View Vector?

A

A vector from the camera position to the look-at point.

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4
Q

What does the Up Vector define?

A

The upward orientation of the camera.

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5
Q

What is the Image Plane?

A

The 2D surface where the 3D scene is projected.

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6
Q

Why must the image plane be perpendicular to the View Vector?

A

To ensure accurate projection from the camera’s perspective.

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7
Q

What is the Up Direction of the Image Plane?

A

It reflects the vertical direction on the image plane, derived from the up vector.

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8
Q

What is the Viewing Transformation?

A

Mapping of world coordinates to device coordinates.

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9
Q

What are local/object coordinates?

A

Coordinates relative to an object’s own origin.

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10
Q

What are world coordinates?

A

Global coordinates for placing objects in the scene.

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11
Q

What is the normalized coordinate range?

A

Typically from 0 to 1 or -1 to 1.

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12
Q

What is the final step before rendering on screen?

A

Viewport transformation.

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13
Q

What does viewport transformation do?

A

Maps normalized coordinates to device coordinates.

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14
Q

What is modeling transformation?

A

Transformation that positions and orients objects in the world.

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15
Q

What are viewing coordinates in 2D?

A

Clipped world coordinates.

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16
Q

What are device coordinates?

A

Final coordinates mapped to the display hardware.

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17
Q

Why are normalized coordinates useful?

A

They make rendering device-independent.

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18
Q

Which transformations are applied in 3D viewing?

A

Rotation, translation, and scaling.

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19
Q

What transformation makes 3D scenes fit within a unit cube?

A

Normalization.

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20
Q

What is clipping?

A

Removing parts of the scene outside the viewing volume.

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21
Q

What does 2D modeling coordinate represent?

A

Each part’s local coordinates.

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22
Q

What is the purpose of translation in viewing?

A

To position the camera or object.

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23
Q

What does scaling do in viewing transformation?

A

Adjusts scene size.

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24
Q

What does rotation do in 3D viewing?

A

Aligns the camera with the scene.

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25
What is camera/viewing coordinate system?
A coordinate system with the camera at the origin.
26
What does perspective projection mimic?
Human visual perception with depth.
27
In which projection are lines parallel and perpendicular to the view plane?
Orthographic projection.
28
What does the function gluPerspective() do?
Sets up a perspective projection.
29
What does gluLookAt() define?
The camera’s position and orientation.
30
What is a frustum?
The visible volume of space in a perspective view.
31
What is a screen-space view?
The final 2D rendering seen on screen.
32
What does the command window typically display?
Projection and camera parameters.
33
What happens in image plane projection?
The 3D scene is projected onto a 2D surface.
34
What are projection rays?
Lines from 3D points to the image plane.
35
What is the center of projection (COP)?
The camera's eye, where projection rays converge.
36
What is the main characteristic of perspective projection?
Projection lines converge at a finite point (COP).
37
What is the key trait of parallel projection?
All projection lines are parallel.
38
What is foreshortening?
The visual effect that makes distant objects appear smaller.
39
Which projection avoids foreshortening?
Parallel projection.
40
What are the two subtypes of parallel projection?
Orthographic and oblique.
41
What is the angle of projection lines in orthographic projection?
90° to the projection plane.
42
What is the projection center in orthographic projection?
At infinity.
43
What does orthographic projection preserve?
The true size and shape of objects.
44
What does the orthographic projection matrix do to a point (x, y, z)?
Converts it to (x, y, 0).
45
What defines oblique projection?
Projection lines are parallel but not perpendicular.
46
What does oblique projection reveal?
More sides of the object.
47
What controls slant in oblique projection?
Parameters L and α.
48
What is the role of L in oblique projection?
Determines shift amount per unit of z-depth.
49
What does α represent in oblique projection?
The direction of the shift in the XY-plane.
50
What is the result of oblique projection on (x, y, z)?
(x + Lcosα, y + Lsinα, 0).
51
What is a practical use of oblique projection?
Visualizing depth in schematics.
52
Which projection best represents mechanical parts?
Orthographic.
53
Which projection is used for realistic scenes?
Perspective projection.
54
How does z-depth affect oblique projection?
It modifies the final x and y values.
55
Which projection type is free from distortion?
Parallel projection.
56
Where are parallel projections used most?
Engineering and architectural drawings.
57
Why is COP considered to be at infinity in parallel projection?
So that rays remain parallel.
58
What does the z-coordinate become after orthographic projection?
Zero.
59
What differentiates oblique from orthographic projection?
The angle of projection lines to the view plane.
60
How is object size affected in parallel projection?
Size remains constant regardless of depth.
61
What is the key idea of perspective projection?
Objects farther from the camera appear smaller.
62
What are the two placements of COP?
At origin or at -D on the Z-axis.
63
What happens when COP is at the origin?
The projection plane is at distance D along the Z-axis.
64
What is the Z value of the projection plane in this case?
Z = D.
65
What is the 2D projected point formula with COP at origin?
P' = (xD/z, yD/z, D).
66
What does D represent?
Distance between COP and the projection plane.
67
Where is the projection plane placed when COP is at -D?
At the origin (z = 0).
68
What is the eye position when COP = -D?
At (0, 0, -D).
69
What is the Z value of the projection in this case?
Zero.
70
Why use different COP placements?
For mathematical simplicity or simulation accuracy.
71
Which coordinate changes the most during perspective projection?
X and Y (they are scaled by Z).
72
What does perspective projection simulate?
Depth perception.
73
What is the effect of small z-values in perspective projection?
Larger X and Y values (objects appear bigger).
74
What creates a sense of depth in 3D viewing?
Perspective projection.
75
What is projection distortion called?
Foreshortening.
76
When is perspective projection mathematically complex?
When the COP isn't at the origin.
77
What helps simplify the math in projections?
Placing the COP at the origin.
78
Where do all projection rays meet in perspective projection?
At the center of projection.
79
What does the term 'viewing plane' refer to?
The 2D surface onto which the 3D scene is projected.
80
What is the main advantage of perspective projection?
Realism.
81
What are the steps of 3D viewing transformation?
Rotate, translate, scale, project.
82
What tool helps visualize camera setup?
Frustum.
83
Which function defines camera orientation in OpenGL?
gluLookAt().
84
What does gluPerspective() accept as parameters?
Field of view, aspect ratio, near and far planes.
85
What view shows final 2D rendering?
Screen-space view.
86
What is the purpose of the command window in 3D editors?
Adjust camera and projection parameters.
87
Why is foreshortening important?
It enhances depth realism.
88
Which coordinate system does the camera become the origin?
Viewing coordinate system.
89
Why normalize coordinates?
To simplify rendering across devices.
90
What is a virtual camera?
A simulated viewpoint used for rendering.
91
What does the projection matrix do?
Converts 3D coordinates into 2D.
92
Which transformation flattens the z-dimension?
Orthographic projection.
93
What component gives direction to the image plane?
Up vector.
94
What allows rotation of the entire scene in world space?
Modeling transformation.
95
What are dashed lines in projection diagrams?
Projection rays.
96
Why are object coordinates local?
To allow individual object manipulation.
97
How is a 3D model transformed for display?
Through modeling, viewing, and projection transformations.
98
Which projection shows multiple sides of an object clearly?
Oblique.
99
Why is perspective used in games and simulations?
It creates depth and realism.
100
What’s the final output of all transformations in graphics?
2D image on a device screen.

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