Visual Servoing Platform  version 3.6.1 under development (2024-04-23)

Minimalist example of moment-based visual servoing with polygon and a simple robot

* ViSP, open source Visual Servoing Platform software.
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* Campus Universitaire de Beaulieu
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* Description:
* Example of visual servoing with moments using a polygon as object container
#include <visp3/core/vpPoint.h> //the basic tracker
#include <iostream> //some console output
#include <limits>
#include <vector> //store the polygon
#include <visp3/core/vpException.h>
#include <visp3/core/vpMomentCommon.h> //update the common database with the object
#include <visp3/core/vpMomentObject.h> //transmit the polygon to the object
#include <visp3/core/vpPlane.h>
#include <visp3/robot/vpSimulatorCamera.h>
#include <visp3/visual_features/vpFeatureMomentCommon.h> //init the feature database using the information about moment dependencies
#include <visp3/vs/vpServo.h> //visual servoing task
// this function converts the plane defined by the cMo to 1/Z=Ax+By+C plane
// form
void cMoToABC(vpHomogeneousMatrix &cMo, double &A, double &B, double &C);
void cMoToABC(vpHomogeneousMatrix &cMo, double &A, double &B, double &C)
vpPlane pl;
pl.setABCD(0, 0, 1.0, 0);
if (fabs(pl.getD()) < std::numeric_limits<double>::epsilon()) {
std::cout << "Invalid position:" << std::endl;
std::cout << cMo << std::endl;
std::cout << "Cannot put plane in the form 1/Z=Ax+By+C." << std::endl;
throw vpException(vpException::divideByZeroError, "invalid position!");
A = -pl.getA() / pl.getD();
B = -pl.getB() / pl.getD();
C = -pl.getC() / pl.getD();
int main()
try {
double x[8] = { 1, 3, 4, -1, -3, -2, -1, 1 };
double y[8] = { 0, 1, 4, 4, -2, -2, 1, 0 };
double A, B, C, Ad, Bd, Cd;
int nbpoints = 8;
std::vector<vpPoint> vec_p,
vec_p_d; // vectors that contain the vertices of the contour polygon
vpHomogeneousMatrix cMo(0.1, 0.0, 1.0, vpMath::rad(0), vpMath::rad(0), vpMath::rad(0));
vpHomogeneousMatrix wMo; // Set to identity
vpHomogeneousMatrix wMc; // Camera position in the world frame
cMoToABC(cMo, A, B, C);
cMoToABC(cdMo, Ad, Bd, Cd);
// Define source and destination polygons
for (int i = 0; i < nbpoints; i++) {
vpPoint p(x[i], y[i], 0.0);
vpMomentObject cur(6); // Create a source moment object with 6 as maximum order
cur.setType(vpMomentObject::DENSE_POLYGON); // The object is defined by a
// countour polygon
cur.fromVector(vec_p); // Init the dense object with the source polygon
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_d); // Init the dense object with the destination polygon
// init classic moment primitives (for source)
vpMomentCommon::getAlpha(dst)); // Init classic features
vpFeatureMomentCommon fmdb_cur(mdb_cur);
vpMomentCommon::getAlpha(dst)); // Init classic features
vpFeatureMomentCommon fmdb_dst(mdb_dst);
// update+compute moment primitives from object (for destination)
// update+compute features (+interaction matrixes) from plane
fmdb_dst.updateAll(Ad, Bd, Cd);
// define visual servoing task
vpServo task;
task.addFeature(fmdb_cur.getFeatureGravityNormalized(), fmdb_dst.getFeatureGravityNormalized());
task.addFeature(fmdb_cur.getFeatureAn(), fmdb_dst.getFeatureAn());
// the object is NOT symmetric
// select C4 and C6
task.addFeature(fmdb_cur.getFeatureCInvariant(), fmdb_dst.getFeatureCInvariant(),
task.addFeature(fmdb_cur.getFeatureAlpha(), fmdb_dst.getFeatureAlpha());
vpBasicFeature *al = new vpFeatureMomentAlpha(mdb_dst, 0, 0, 1.);
// param robot
float sampling_time = 0.010f; // Sampling period in seconds
wMc = wMo * cMo.inverse();
do {
wMc = robot.getPosition();
cMo = wMc.inverse() * wMo;
for (int i = 0; i < nbpoints; i++) {
vpPoint p(x[i], y[i], 0.0);
cMoToABC(cMo, A, B, C);
// update+compute moment primitives from object (for source)
// update+compute features (+interaction matrixes) from plane
fmdb_cur.updateAll(A, B, C);
double t = vpTime::measureTimeMs();
vpTime::wait(t, sampling_time * 1000); // Wait 10 ms
} while ((task.getError()).sumSquare() > 0.005);
std::cout << "final error=" << (task.getError()).sumSquare() << std::endl;
catch (const vpException &e) {
std::cout << "Catch an exception: " << e << std::endl;
class that defines what is a visual feature
virtual vpColVector error(const vpBasicFeature &s_star, unsigned int select=FEATURE_ALL)
virtual void init()=0
Implementation of column vector and the associated operations.
Definition: vpColVector.h:163
error that can be emitted by ViSP classes.
Definition: vpException.h:59
@ divideByZeroError
Division by zero.
Definition: vpException.h:82
Functionality computation for in-plane rotation moment feature : computes the interaction matrix asso...
This class allows to access common vpFeatureMoments in a pre-filled database.
Implementation of an homogeneous matrix and operations on such kind of matrices.
vpHomogeneousMatrix inverse() const
static double rad(double deg)
Definition: vpMath.h:127
This class initializes and allows access to commonly used moments.
static std::vector< double > getMu3(vpMomentObject &object)
static double getAlpha(vpMomentObject &object)
static double getSurface(vpMomentObject &object)
Class for generic objects.
This class defines the container for a plane geometrical structure.
Definition: vpPlane.h:54
void changeFrame(const vpHomogeneousMatrix &cMo)
Definition: vpPlane.cpp:372
double getD() const
Definition: vpPlane.h:106
double getA() const
Definition: vpPlane.h:100
double getC() const
Definition: vpPlane.h:104
void setABCD(double a, double b, double c, double d)
Definition: vpPlane.h:88
double getB() const
Definition: vpPlane.h:102
Class that defines a 3D point in the object frame and allows forward projection of a 3D point in the ...
Definition: vpPoint.h:77
void setVelocity(const vpRobot::vpControlFrameType frame, const vpColVector &vel) vp_override
Definition: vpRobot.h:82
void setInteractionMatrixType(const vpServoIteractionMatrixType &interactionMatrixType, const vpServoInversionType &interactionMatrixInversion=PSEUDO_INVERSE)
Definition: vpServo.cpp:378
Definition: vpServo.h:155
void addFeature(vpBasicFeature &s_cur, vpBasicFeature &s_star, unsigned int select=vpBasicFeature::FEATURE_ALL)
Definition: vpServo.cpp:329
void print(const vpServo::vpServoPrintType display_level=ALL, std::ostream &os=std::cout)
Definition: vpServo.cpp:169
void setLambda(double c)
Definition: vpServo.h:976
void setServo(const vpServoType &servo_type)
Definition: vpServo.cpp:132
vpColVector getError() const
Definition: vpServo.h:504
vpColVector computeControlLaw()
Definition: vpServo.cpp:703
Definition: vpServo.h:196
Class that defines the simplest robot: a free flying camera.
VISP_EXPORT int wait(double t0, double t)
VISP_EXPORT double measureTimeMs()