FeatureMomentAlpha¶

class FeatureMomentAlpha¶

Bases: FeatureMoment

Functionality computation for in-plane rotation moment feature \(\alpha\) : computes the interaction matrix associated with vpMomentAlpha .

The interaction matrix for the feature can be deduced from [42] .

This class computes the interaction matrix associated to \(\alpha = \frac{1}{2} arctan(\frac{2\mu_{11}}{\mu_{20}-\mu_{02}})\) moment primitive.

The interaction matrix for the feature has the following form:

\[\begin{split}{ \left[ \begin {array}{c} {\frac {\mu_{{1,1}}{\it DA}\,A}{d}}+{\frac { \left( {\it DA}\,\mu_{{0,2}}+1/2\,d-1/2\,{{\it DA}}^{2} \right) B}{d} }\\\noalign{\medskip}{\frac { \left( {\it DA}\,\mu_{{0,2}}-1/2\,d-1/2 \,{{\it DA}}^{2} \right) A}{d}}-{\frac {B\mu_{{1,1}}{\it DA}}{d}} \\\noalign{\medskip}Bw_{{x}}-Aw_{{y}}\\\noalign{\medskip}{\frac { \beta\, \left( \mu_{{1,2}} \left( \mu_{{2,0}}-\mu_{{0,2}} \right) +\mu _{{1,1}} \left( \mu_{{0,3}}-\mu_{{2,1}} \right) \right) +\gamma\,x_{{ g}} \left( \mu_{{0,2}} \left( \mu_{{2,0}}-\mu_{{0,2}} \right) -2\,{\mu _{{1,1}}}^{2} \right) +\gamma\,y_{{g}}\mu_{{1,1}} \left( \mu_{{2,0}}+ \mu_{{0,2}} \right) }{d}}\\\noalign{\medskip}{\frac {\beta\, \left( \mu_{{2,1}} \left( \mu_{{0,2}}-\mu_{{2,0}} \right) +\mu_{{1,1}} \left( \mu_{{3,0}}-\mu_{{1,2}} \right) \right) +\gamma\,x_{{g}}\mu_{ {1,1}} \left( \mu_{{2,0}}+\mu_{{0,2}} \right) +\gamma\,y_{{g}} \left( \mu_{{2,0}} \left( \mu_{{0,2}}-\mu_{{2,0}} \right) -2\,{\mu_{{1,1}}}^{ 2} \right) }{d}}\\\noalign{\medskip}-1\end {array} \right] }^t \end{split}\]

with \({\it DA} = \mu_{{2,0}}-\mu_{{0,2}}\) and \({\it d} = DA^2+4{\mu_{1,1}}^2\) .

In the discrete case: \(beta = 4\) , \(gamma = 2\) .
In the dense case: \(beta = 5\) , \(gamma = 1\) .

The interaction matrix computed is single-dimension (no selection possible) and can be obtained by calling vpFeatureMomentAlpha::interaction() .

This feature is often used in moment-based visual servoing to control the planar rotation parameter.

Minimum vpMomentObject order needed to compute this feature: 4.

This feature depends on:

vpMomentCentered
vpMomentGravityCenter

Methods

`__init__`
`compute_interaction`	Overloaded function.
`error`	Compute the error between two visual features from a subset of the possible features.
`momentName`	Associated moment name.
`name`	Feature name.

Inherited Methods

`printDependencies`	Interface function to display the moments and other interaction matrices on which a particular vpFeatureMoment is dependent upon Not made pure to maintain compatibility Recommended : Types inheriting from vpFeatureMoment should implement this function.
`BasicFeatureSelect`	Indicates who should deallocate the feature.
`vpServo`
`deallocate`
`dimension_s`	Return the dimension of the feature vector \(\bf s\) .
`linkTo`	Links the feature to the feature's database.
`s`
`user`
`getDeallocate`
`nbParameters`
`print`	Outputs the content of the feature: it's corresponding selected moments.
`BasicFeatureDeallocatorType`	Indicates who should deallocate the feature.
`selectAll`	Select all the features.
`setDeallocate`
`dim_s`
`interaction`	Retrieves the interaction matrix.
`get_s`	Get the feature vector \(\bf s\) .
`update`	Updates the interaction matrices with the image plane the camera is facing.
`FEATURE_ALL`
`setFlags`	Set feature flags to true to prevent warning when re-computing the interaction matrix without having updated the feature.
`display`	Overloaded function.
`init`	Initialize common parameters for moment features.
`getDimension`	Overloaded function.

Operators

`__doc__`
`__init__`
`__module__`

Attributes

`FEATURE_ALL`
`__annotations__`
`deallocate`
`dim_s`
`nbParameters`
`s`
`user`
`vpServo`

class BasicFeatureDeallocatorType(self, value: int)¶

Bases: pybind11_object

Indicates who should deallocate the feature.

Values:

user
vpServo

__and__(self, other: object) → object¶

__eq__(self, other: object) → bool¶

__ge__(self, other: object) → bool¶

__getstate__(self) → int¶

__gt__(self, other: object) → bool¶

__hash__(self) → int¶

__index__(self) → int¶

__init__(self, value: int)¶

__int__(self) → int¶

__invert__(self) → object¶

__le__(self, other: object) → bool¶

__lt__(self, other: object) → bool¶

__ne__(self, other: object) → bool¶

__or__(self, other: object) → object¶

__rand__(self, other: object) → object¶

__ror__(self, other: object) → object¶

__rxor__(self, other: object) → object¶

__setstate__(self, state: int) → None¶

__xor__(self, other: object) → object¶

property name : str¶

class BasicFeatureSelect(self, value: int)¶

Bases: pybind11_object

Indicates who should deallocate the feature.

Values:

user
vpServo

__and__(self, other: object) → object¶

__eq__(self, other: object) → bool¶

__ge__(self, other: object) → bool¶

__getstate__(self) → int¶

__gt__(self, other: object) → bool¶

__hash__(self) → int¶

__index__(self) → int¶

__init__(self, value: int)¶

__int__(self) → int¶

__invert__(self) → object¶

__le__(self, other: object) → bool¶

__lt__(self, other: object) → bool¶

__ne__(self, other: object) → bool¶

__or__(self, other: object) → object¶

__rand__(self, other: object) → object¶

__ror__(self, other: object) → object¶

__rxor__(self, other: object) → object¶

__setstate__(self, state: int) → None¶

__xor__(self, other: object) → object¶

property name : str¶

__init__(*args, **kwargs)¶

compute_interaction(*args, **kwargs)¶

Overloaded function.

compute_interaction(self: visp._visp.visual_features.FeatureMomentAlpha) -> None

Computes interaction matrix for alpha moment. Called internally. The moment primitives must be computed before calling this. This feature depends on:

vpMomentCentered
vpMomentGravityCenter

compute_interaction(self: visp._visp.visual_features.FeatureMoment) -> None

dimension_s(self) → int¶: Return the dimension of the feature vector \(\bf s\) .

display(*args, **kwargs)¶

Overloaded function.

display(self: visp._visp.visual_features.FeatureMoment, cam: visp._visp.core.CameraParameters, I: visp._visp.core.ImageGray, color: visp._visp.core.Color = vpColor::green, thickness: int = 1) -> None

Not implemented since visual representation of a moment doesn’t often make sense.

display(self: visp._visp.visual_features.FeatureMoment, cam: visp._visp.core.CameraParameters, I: visp._visp.core.ImageRGBa, color: visp._visp.core.Color = vpColor::green, thickness: int = 1) -> None

Not implemented since visual representation of a moment doesn’t often make sense.

error(self, s_star: visp._visp.visual_features.BasicFeature, select: int = FEATURE_ALL) → visp._visp.core.ColVector¶: Compute the error between two visual features from a subset of the possible features.

getDeallocate(self) → visp._visp.visual_features.BasicFeature.BasicFeatureDeallocatorType¶

getDimension(*args, **kwargs)¶

Overloaded function.

getDimension(self: visp._visp.visual_features.FeatureMoment, select: int = FEATURE_ALL) -> int

Feature’s dimension according to selection.

getDimension(self: visp._visp.visual_features.BasicFeature, select: int = FEATURE_ALL) -> int

Get the feature vector dimension.

get_s(self, select: int = FEATURE_ALL) → visp._visp.core.ColVector¶: Get the feature vector \(\bf s\) .

init(self) → None¶: Initialize common parameters for moment features.

interaction(self, select: int = FEATURE_ALL) → visp._visp.core.Matrix¶

Retrieves the interaction matrix. No computation is done.

There is no rule about the format of the feature selector. It may be different for different features. For example, for vpFeatureMomentBasic or vpFeatureMomentCentered features, select may refer to the \((i,j)\) couple in the \(j \times order + i\) format, but for vpFeatureMomentCInvariant the selector allows to select couples \((i,j,k,l...)\) in the following format: 1 << i

1 << j + 1 << k + 1 << l.

Parameters:

select: int = FEATURE_ALL¶: Feature selector.

Returns:

The corresponding interaction matrix.

linkTo(self, featureMoments: visp._visp.visual_features.FeatureMomentDatabase) → None¶

Links the feature to the feature’s database.

Note

The feature’s database is different from the moment’s database.

Parameters:

featureMoments: visp._visp.visual_features.FeatureMomentDatabase¶: database in which the moment features are stored.

momentName(self) → str¶: Associated moment name.

name(self) → str¶: Feature name.

print(self, select: int = FEATURE_ALL) → None¶: Outputs the content of the feature: it’s corresponding selected moments.

printDependencies(self: visp._visp.visual_features.FeatureMoment, os: std::ostream) → None¶: Interface function to display the moments and other interaction matrices on which a particular vpFeatureMoment is dependent upon Not made pure to maintain compatibility Recommended : Types inheriting from vpFeatureMoment should implement this function.

static selectAll() → int¶: Select all the features.

setDeallocate(self, d: visp._visp.visual_features.BasicFeature.BasicFeatureDeallocatorType) → None¶

setFlags(self) → None¶: Set feature flags to true to prevent warning when re-computing the interaction matrix without having updated the feature.

update(self, A: float, B: float, C: float) → None¶

Updates the interaction matrices with the image plane the camera is facing. The plane must be in the format: \(\frac{1}{Z}=Ax+By+C\) . The moment primitives MUST be updated before calling this function.

This method also computes the interaction matrix. Therefore, you must call vpFeatureMoment::update before calling vpFeatureMoment::interaction .

Warning

The behaviour of this method is not the same as vpMoment::update which only acknowledges the new object. This method also computes the interaction matrices.