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vpFeatureMomentCommon Class Reference
Visual features

#include <visp3/visual_features/vpFeatureMomentCommon.h>

+ Inheritance diagram for vpFeatureMomentCommon:

Public Member Functions

 vpFeatureMomentCommon (vpMomentDatabase &moments, double A=0.0, double B=0.0, double C=1.0)
 
void updateAll (double A, double B, double C)
 
vpFeatureMomentAlpha & getFeatureAlpha ()
 
vpFeatureMomentAreaNormalized & getFeatureAn ()
 
vpFeatureMomentBasic & getFeatureMomentBasic ()
 
vpFeatureMomentCentered & getFeatureCentered ()
 
vpFeatureMomentCInvariant & getFeatureCInvariant ()
 
vpFeatureMomentGravityCenterNormalized & getFeatureGravityNormalized ()
 
vpFeatureMomentArea & getFeatureArea ()
 
vpFeatureMomentGravityCenter & getFeatureGravityCenter ()
 
vpFeatureMoment & get (const char *type, bool &found)
 

Detailed Description

This class allows to access common vpFeatureMoments in a pre-filled database.

It is a vpMomentDatabase filled with the following moments:

There is no need to do the linkTo operations manually nor is it necessary to care about the order of feature computation.

This class has an vpMomentCommon::updateAll method capable of updating the plane parameters AND computing interaction matrices inside the features.

The moment features computed by this class are classical moments features used in moment-based visual servoing. For more information see [30].

To initialize this feature set, the user needs to supply a vpMomentDatabase containing at least the contents of vpMomentCommon.

The features can be retrieved like from a normal vpFeatureMomentDatabase. However, some shortcuts to retrieve the features are provided.

Attention
Make sure your object is at least of order 6 when using this pre-filled database.

The following code demonstrates the construction of a 6x6 interaction matrix as described in [1].

#include <visp3/core/vpMomentObject.h>
#include <visp3/core/vpMomentCommon.h>
#include <visp3/core/vpPoint.h>
#include <visp3/visual_features/vpFeatureMoment.h>
#include <visp3/visual_features/vpFeatureMomentCommon.h>
#include <visp3/vs/vpServo.h>
#include <iostream>
#include <vector>
int main()
{
// Define source polygon
vpPoint p;
std::vector<vpPoint> vec_p; // vector that contains the vertices of the contour polygon
p.set_x(-0.2); p.set_y(0.1); // coordinates in meters in the image plane (vertex 1)
vec_p.push_back(p);
p.set_x(+0.3); p.set_y(0.1); // coordinates in meters in the image plane (vertex 2)
vec_p.push_back(p);
p.set_x(+0.2); p.set_y(-0.1); // coordinates in meters in the image plane (vertex 3)
vec_p.push_back(p);
p.set_x(-0.2); p.set_y(-0.15); // coordinates in meters in the image plane (vertex 4)
vec_p.push_back(p);
p.set_x(-0.2); p.set_y(0.1); // close the contour (vertex 5 = vertex 1)
vec_p.push_back(p);
vpMomentObject src(6); // Create a source moment object with 6 as maximum order
src.setType(vpMomentObject::DENSE_POLYGON); // The object is defined by a countour polygon
src.fromVector(vec_p); // Init the dense object with the source polygon
vec_p.clear();
//Define destination polygon. This is the source polygon translated
//of 0.1 on x-axis
p.set_x(-0.1); p.set_y(0.1); // coordinates in meters in the image plane (vertex 1)
vec_p.push_back(p);
p.set_x(+0.4); p.set_y(0.1); // coordinates in meters in the image plane (vertex 2)
vec_p.push_back(p);
p.set_x(+0.3); p.set_y(-0.1); // coordinates in meters in the image plane (vertex 3)
vec_p.push_back(p);
p.set_x(-0.1); p.set_y(-0.15); // coordinates in meters in the image plane (vertex 4)
vec_p.push_back(p);
p.set_x(-0.1); p.set_y(0.1); // close the contour (vertex 5 = vertex 1)
vec_p.push_back(p);
vpMomentObject dst(6); // Create a destination moment object with 6 as maximum order
dst.setType(vpMomentObject::DENSE_POLYGON); // The object is defined by a countour polygon
dst.fromVector(vec_p); // Init the dense object with the destination
// polygon
//init classic moment primitives (for source)
vpMomentCommon mdb_src(vpMomentCommon::getSurface(dst),vpMomentCommon::getMu3(dst),vpMomentCommon::getAlpha(dst),1.);
//Init classic features
vpFeatureMomentCommon fmdb_src(mdb_src);
vpMomentCommon mdb_dst(vpMomentCommon::getSurface(dst),vpMomentCommon::getMu3(dst),vpMomentCommon::getAlpha(dst),1.);
//Init classic features
vpFeatureMomentCommon fmdb_dst(mdb_dst);
//update+compute moment primitives from object (for source)
mdb_src.updateAll(src);
//update+compute features (+interaction matrices) from plane
fmdb_src.updateAll(0.,0.,1.);
//update+compute moment primitives from object (for destination)
mdb_dst.updateAll(dst);
//update+compute features (+interaction matrices) from plane
fmdb_dst.updateAll(0.,0.,1.);
//define visual servoing task
vpServo task;
task.setServo(vpServo::EYEINHAND_CAMERA);
task.setInteractionMatrixType(vpServo::CURRENT);
//Add all classic features to the task
//In this example, source and destination features are translated by 0.1
//will produce a movement of 0.1 on x-axis.
task.addFeature(fmdb_src.getFeatureGravityNormalized(),fmdb_dst.getFeatureGravityNormalized());
task.addFeature(fmdb_src.getFeatureAn(),fmdb_dst.getFeatureAn());
//the object is NOT symmetric
//select C4 and C6
task.addFeature(fmdb_src.getFeatureCInvariant(),fmdb_dst.getFeatureCInvariant(),(1 << 3) | (1 << 5));
task.addFeature(fmdb_src.getFeatureAlpha(),fmdb_dst.getFeatureAlpha());
task.setLambda(1) ;
vpColVector v = task.computeControlLaw() ;
task.print();
task.kill();
return 0;
}

This code produces the following output:

Visual servoing task:
Type of control law
Eye-in-hand configuration
Control in the camera frame
List of visual features : s
0.0166667,-0.00833333,
1,
-0.312148,0.0249916,
-1.43449,
List of desired visual features : s*
0.116667,-0.00833333,
1,
-0.312148,0.0249916,
-1.43449,
Interaction Matrix Ls
-1 0 -6.938893904e-18 0.007291666667 -1.06875 -0.008333333333
0 -1 3.469446952e-18 1.0171875 -0.007291666667 -0.01666666667
0 0 -1 0.0125 0.025 0
0 0 -4.585529113e-15 -0.2983860943 0.5832596643 -4.376751552e-16
0 0 -3.58244462e-15 0.08633028234 -0.2484618767 3.63421192e-16
4.353086256e-17 -1.339411156e-16 -0 -0.03019436997 -0.0168230563 -1
Error vector (s-s*)
-0.1 0 0 1.831867991e-15 -1.072059108e-15 0
Gain : Zero= 1 Inf= 1 Deriv= 0
Examples:
manServoMomentsSimple.cpp, servoMomentImage.cpp, servoMomentPoints.cpp, and servoMomentPolygon.cpp.

Definition at line 217 of file vpFeatureMomentCommon.h.

Constructor & Destructor Documentation

vpFeatureMomentCommon::vpFeatureMomentCommon ( vpMomentDatabase &  moments,
double  A = 0.0,
double  B = 0.0,
double  C = 1.0 
)

Constructor which initializes and links all common features in the database

Parameters
moments: database for moment primitives
A: first plane coefficient for a plane equation of the following type Ax+By+C=1/Z
B: second plane coefficient for a plane equation of the following type Ax+By+C=1/Z
C: third plane coefficient for a plane equation of the following type Ax+By+C=1/Z

Definition at line 48 of file vpFeatureMomentCommon.cpp.

References vpFeatureMoment::linkTo().

Member Function Documentation

vpFeatureMoment & vpFeatureMomentDatabase::get ( const char *  type,
bool &  found 
)
inherited

Retrieves a moment feature from the database

Parameters
type: the name of the feature, the one specified when using add
found: true if the type string is found inside the database, false otherwise
Returns
the moment feature corresponding to the type string

Definition at line 60 of file vpFeatureMomentDatabase.cpp.

Referenced by vpFeatureMomentCentered::compute_interaction(), and vpFeatureMomentCInvariant::compute_interaction().

vpFeatureMomentAlpha& vpFeatureMomentCommon::getFeatureAlpha ( )
inline

Returns alpha.

Examples:
servoMomentImage.cpp, servoMomentPoints.cpp, and servoMomentPolygon.cpp.

Definition at line 234 of file vpFeatureMomentCommon.h.

vpFeatureMomentAreaNormalized& vpFeatureMomentCommon::getFeatureAn ( )
inline

Returns normalized surface.

Examples:
servoMomentImage.cpp, servoMomentPoints.cpp, and servoMomentPolygon.cpp.

Definition at line 239 of file vpFeatureMomentCommon.h.

vpFeatureMomentArea& vpFeatureMomentCommon::getFeatureArea ( )
inline

Returns the area

Definition at line 260 of file vpFeatureMomentCommon.h.

vpFeatureMomentCentered& vpFeatureMomentCommon::getFeatureCentered ( )
inline

Returns centered moments.

Definition at line 247 of file vpFeatureMomentCommon.h.

vpFeatureMomentCInvariant& vpFeatureMomentCommon::getFeatureCInvariant ( )
inline

Returns non-symmetric invariants.

Examples:
servoMomentImage.cpp, servoMomentPoints.cpp, and servoMomentPolygon.cpp.

Definition at line 252 of file vpFeatureMomentCommon.h.

vpFeatureMomentGravityCenter& vpFeatureMomentCommon::getFeatureGravityCenter ( )
inline

Returns gravity center

Definition at line 264 of file vpFeatureMomentCommon.h.

vpFeatureMomentGravityCenterNormalized& vpFeatureMomentCommon::getFeatureGravityNormalized ( )
inline

Returns normalized gravity center.

Examples:
servoMomentImage.cpp, servoMomentPoints.cpp, and servoMomentPolygon.cpp.

Definition at line 256 of file vpFeatureMomentCommon.h.

vpFeatureMomentBasic& vpFeatureMomentCommon::getFeatureMomentBasic ( )
inline

Returns basic moment.

Definition at line 243 of file vpFeatureMomentCommon.h.

void vpFeatureMomentCommon::updateAll ( double  A,
double  B,
double  C 
)
virtual

Update all moment features in the database with plane coefficients

Parameters
A: first plane coefficient for a plane equation of the following type Ax+By+C=1/Z
B: second plane coefficient for a plane equation of the following type Ax+By+C=1/Z
C: third plane coefficient for a plane equation of the following type Ax+By+C=1/Z

Reimplemented from vpFeatureMomentDatabase.

Examples:
servoMomentImage.cpp, servoMomentPoints.cpp, and servoMomentPolygon.cpp.

Definition at line 75 of file vpFeatureMomentCommon.cpp.

References vpFeatureMoment::update().