Set of flashcards Interactive Computer Graphics (Page 7 of 7)

Flashcards	272
Language	English
Category	Computer Science
Level	University
Created / Updated	27.07.2022 / 31.07.2022
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Blendshapes or Delta-Blendshapes, Which method is more expressive, i.e., can produces more/richer expressions?

Blendshapes

Delta-Blendshapes

Both produce equivalent expressions.

You want to simulate the effects of strong winds on human faces.

Which of the following assumptions hold true?

My FACS encoding of blendshapes is sufficient, however, I might have to go beyond the given weight limits.

My 600+ blendshapes are sufficient since they go far beyond the FACS encoding.

I will have to do this with a physical simulation to be on the safe side.

What are correct statements about skinning weights (bone weights, joint weights)?

Weight wᵢₐ defines influence of bone a on vertex i.

Weight wᵢₐ defines influence of vertex a on bone i.

Weights build a concave combination per vertex.

Weights build a convex combination per vertex.

Weights can be computed by the bone Heat method or by bounded biharmonic weights.

What are correct statements about skinning weights (bone weights, joint weights)?

Weights must sum up to one as ∑ₐwᵢₐ = 1.

Weights could be negative: -1 <= wᵢₐ <= 1

Weight should be positive: wᵢₐ >= 0

Weights can't be painted manually.

Which facts are correct for inverse kinematics (IK)?

Leave the ones that are correct for forward kinematics (FK) unchecked.

... determines effector positions xᵢ from joint angles θₐ.

... determines joint angles θₐ such that effector positions xᵢ reach specified target positions tₐ.

Analytic solutions for ... exist for simple skeleton configurations only.

Numerical approach for ... solver iteratively updates angles to minimize errors .

Which coordinate system transition is done in the model-view transformation stage of the rasterization pipeline?

camera coordinate system to normalized device coordinate system

world coordinate system to camera coordinate system

normalized device coordinate system to object coordinate system

object coordinate system to world coordinate system

object coordinate system to camera coordinate system

Which coordinate system transition is done in the rasterization and interpolation stage of the rasterization pipeline?

normalized device coordinate system to image coordinate system

camera coordinate system to normalized device coordinate system

world coordinate system to camera coordinate system

object coordinate system to world coordinate system

object coordinate system to camera coordinate system

How is the FoV (Field of View) β of a pinhole camera of height h and depth d calculated?

β = tan(2h/d)

β = 2tan(h/2d)

β = 2arctan(h/2d)

β = arctan(2h/d)

β = 2arctan(h/d)

What is a projection?

A transformation which maps from a higher to a lower dimensional space (e.g., 3D to 2D).

How is Slerp (Spherical Linear Interpolation) s(q, r, t) defined?

(rq⁻¹)ᵗq

(qr⁻¹)ᵗr

(rqᵗ)⁻¹q

(qrᵗ)⁻¹r

What is blending?

the combination of lighting and texture

Bump Mapping: What's Normal Mapping?

Texture values as normals applied during shading to mimic irregularities on the surface.

Distorts the u, v coordinates of the normal map and diffuse texture to add illusion of depth.

Additonally cast rays against a hightfield texture.

Use multiple depth samples checks to distort u, v coordinates of normal map and diffuse texture.

Displaces surface by modifying triangle heights of model.

Bump Mapping: What's Parallax Mapping?

Texture values as normals applied during shading to mimic irregularities on the surface.

Distorts the u, v coordinates of the normal map and diffuse texture to add illusion of depth.

Additonally cast rays against a hightfield texture.

Use multiple depth samples checks to distort u, v coordinates of normal map and diffuse texture.

Displaces surface by modifying triangle heights of model.

Bump Mapping: What's Parallax Occlusion Mapping?

Texture values as normals applied during shading to mimic irregularities on the surface.

Distorts the u, v coordinates of the normal map and diffuse texture to add illusion of depth.

Additonally cast rays against a hightfield texture.

Use multiple depth samples checks to distort u, v coordinates of normal map and diffuse texture.

Displaces surface by modifying triangle heights of model.

Bump Mapping: What's Relief Mapping?

Texture values as normals applied during shading to mimic irregularities on the surface.

Distorts the u, v coordinates of the normal map and diffuse texture to add illusion of depth.

Additonally cast rays against a hightfield texture.

Use multiple depth samples checks to distort u, v coordinates of normal map and diffuse texture.

Displaces surface by modifying triangle heights of model.

Bump Mapping: What's Displacement Mapping?

Texture values as normals applied during shading to mimic irregularities on the surface.

Distorts the u, v coordinates of the normal map and diffuse texture to add illusion of depth.

Additonally cast rays against a hightfield texture.

Use multiple depth samples checks to distort u, v coordinates of normal map and diffuse texture.

Displaces surface by modifying triangle heights of model.

How are texture coordinates u = (u, v) interpolated by barycentric coordinates?

u(X) = αu(A) + βu(B) + γu(C)

u(X) = αβu(A) + α(1- β)u(B) + (1 - α)(1 - β)u(C)

u(X) = u(A) + u(B) + u(C)

What are options to define texture coordinates for each vertex?

Manual assignment

Procedural generation

3D scan techniques

Photmetric assignment

Wrapping algorithms

What are options to define texture coordinates for each vertex?

Sequential generation

3D print techniques

Projector functions

Mesh unwrapping algorithms

Self-aware vertex solution

Which operation/s translate/s the object space location into parameter space coordinates in the Texture Pipeline?

Projector Function

Corresponder Function(s)

Obtain Value

Value Transform Function

Mapping Function

Which operation/s translate/s the parameter space coordinates into the texture space location in the Texture Pipeline?

Projector Function

Corresponder Function(s)

Obtain Value

Value Transform Function

Mapping Function

Which operation/s translate/s the texture space location into a texture value in the Texture Pipeline?

Projector Function

Corresponder Function(s)

Obtain Value

Value Transform Function

Mapping Function

Which operation/s transform/s the texture value in the Texture Pipeline?

Projector Function

Corresponder Function(s)

Obtain Value

Value Transform Function

Mapping Function

What are input or putput of the projector function in the Texture Pipeline?

Object Space Location

Parameter Coordinates

Texture Space Location

Texture Value

Transformed Texture Value

What are input or putput of the corresponder function(s) in the Texture Pipeline?

Object Space Location

Parameter Coordinates

Texture Space Location

Texture Value

Transformed Texture Value

What are input or putput of the obtain value operation in the Texture Pipeline?

Object Space Location

Parameter Coordinates

Texture Space Location

Texture Value

Transformed Texture Value

What are input or putput of the value transform function in the Texture Pipeline?

Object Space Location

Parameter Coordinates

Texture Space Location

Texture Value

Transformed Texture Value

What are examples of the corresponder function in the Texture Pipeline?

Selecting a portion of a larger texture used for improved memory management.

Using a matrix transformation in the vertex or pixel shader.

Controlling the way an image is applied when out of range [0, 1].

Use simple parameterizations for geometric shapes.

User surface normales to calculate texture space locations.

What are examples for Out-of-Range Corresponder Functions?

Texture repeat

Texture clamp

Texture border

Texture mirror

Texture skew

What is a common example or true about the value transform function in the Texture Pipeline?

Remapping from unsigned [0.0, 1.0] to signed [-1.0, 1.0] to use as normals.

Conversion to linear space (recall Gamma correction) for shading equations.

Typically performed in shader program.

Often paired with tesselation process.

Linear scale by matrix multiplication.

Was ergibt die bilineare Interpolation der Koordinate (81.8, 74.6), wenn folgende Pixelfarben der Textur gegeben sind?

(81, 74): RGB(1.0, 0.0, 0.0)
(82, 74): RGB(0.0, 1.0, 0.0)
(81, 75): RGB(0.0, 0.0, 1.0)
(82, 75): RGB(0.5, 0.5, 0.5)

(0.645, 0.285, 0.085)

(0.285, 0.645, 0.085)

(0.645, 0.085, 0.285)

(0.285, 0.085, 0.645)

(0.085, 0.645, 0.285)

Which of these formats primarily use raster graphics?

CGM

IGES

DWF

GCM

DGS

Interactive Computer Graphics

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