# Example: poses_sog_merge_example

Example of how to merge overlapping modes of a Sum Of Gaussians (SOG) representation of a pose, in this case, a SE(2) SoG probability distribution function.

C++ example source code:

```/* +------------------------------------------------------------------------+
|                     Mobile Robot Programming Toolkit (MRPT)            |
|                          https://www.mrpt.org/                         |
|                                                                        |
| Copyright (c) 2005-2022, Individual contributors, see AUTHORS file     |
+------------------------------------------------------------------------+ */

#include <mrpt/gui/CDisplayWindow3D.h>
#include <mrpt/io/CFileGZOutputStream.h>
#include <mrpt/opengl/CGridPlaneXY.h>
#include <mrpt/poses/CPosePDFSOG.h>
#include <mrpt/serialization/CArchive.h>
#include <mrpt/system/os.h>

#include <iostream>

using namespace mrpt;
using namespace mrpt::poses;
using namespace mrpt::opengl;
using namespace mrpt::gui;
using namespace mrpt::io;
using namespace mrpt::system;
using namespace mrpt::serialization;
using namespace std;

/* ------------------------------------------------------------------------
Test_SoG_Merge
------------------------------------------------------------------------ */
void Test_SoG_Merge()
{
CPosePDFSOG pdf;

CPosePDFSOG::TGaussianMode m;
m.mean = CPose2D(1.1, -0.1, -2.0_deg);

m.cov.setIdentity();
m.cov(0, 0) = m.cov(1, 1) = square(0.1);
m.cov(2, 2) = square(2.0_deg);
m.log_w = 0;

pdf.clear();
pdf.push_back(m);

m.mean = CPose2D(1.1, 0.1, 2.0_deg);
pdf.push_back(m);

m.mean = CPose2D(2, 0, 20.0_deg);
pdf.push_back(m);

cout << "Initial PDF: mean: " << pdf.getMeanVal() << endl;
cout << pdf.getCovariance() << endl << endl;

#if MRPT_HAS_WXWIDGETS
CDisplayWindow3D win_before("Before merge");
CDisplayWindow3D win_after("After merge");
#endif

{
COpenGLScene scene;
CSetOfObjects::Ptr o = CSetOfObjects::Create();
pdf.getAs3DObject(o);
scene.insert(o);
scene.insert(CGridPlaneXY::Create(-5, 5, -5, 5, 0, 1));

CFileGZOutputStream f("sog_before.3Dscene");
archiveFrom(f) << scene;

#if MRPT_HAS_WXWIDGETS
COpenGLScene::Ptr sc = win_before.get3DSceneAndLock();
*sc = scene;
win_before.unlockAccess3DScene();
win_before.setCameraZoom(5);
win_before.setCameraPointingToPoint(1, 0, 0);
win_before.forceRepaint();
#endif
}

cout << "Merging...";
pdf.mergeModes(0.9, true);
cout << " # modes after: " << pdf.size() << endl;

cout << "Final PDF: mean: " << pdf.getMeanVal() << endl;
cout << pdf.getCovariance() << endl << endl;

{
COpenGLScene scene;
CSetOfObjects::Ptr o = CSetOfObjects::Create();
pdf.getAs3DObject(o);
scene.insert(o);
scene.insert(CGridPlaneXY::Create(-5, 5, -5, 5, 0, 1));

CFileGZOutputStream f("sog_after.3Dscene");
archiveFrom(f) << scene;

#if MRPT_HAS_WXWIDGETS
COpenGLScene::Ptr sc = win_after.get3DSceneAndLock();
*sc = scene;
win_after.unlockAccess3DScene();
win_after.setCameraZoom(5);
win_after.setCameraPointingToPoint(1, 0, 0);
win_after.forceRepaint();
#endif
}

#if MRPT_HAS_WXWIDGETS
cout << "Push any key to exit..." << endl;
mrpt::system::os::getch();
#endif
}

// ------------------------------------------------------
//                      MAIN
// ------------------------------------------------------
int main(int argc, char** argv)
{
try
{
Test_SoG_Merge();

return 0;
}
catch (const std::exception& e)
{
std::cerr << "MRPT error: " << mrpt::exception_to_str(e) << std::endl;
return -1;
}
catch (...)
{
printf("Untyped exception!");
return -1;
}
}```