# CenterOfMass

VTKExamples/Cxx/PolyData/CenterOfMass

### Code

CenterOfMass.cxx

    #include <vtkVersion.h>
    #include <vtkCenterOfMass.h>
    #include <vtkDoubleArray.h>
    #include <vtkPoints.h>
    #include <vtkPointData.h>
    #include <vtkPolyData.h>
    #include <vtkSmartPointer.h>

    #include <limits>
    #include <cmath>

    int main(int, char*[])
    {
      // Create a point set of a square
      vtkSmartPointer<vtkPoints> points =
        vtkSmartPointer<vtkPoints>::New();
      points->InsertNextPoint(0,0,0);
      points->InsertNextPoint(1,0,0);
      points->InsertNextPoint(0,1,0);
      points->InsertNextPoint(1,1,0);

      vtkSmartPointer<vtkPolyData> polydata =
        vtkSmartPointer<vtkPolyData>::New();
      polydata->SetPoints(points);

      // Compute the center of mass
      vtkSmartPointer<vtkCenterOfMass> centerOfMassFilter =
        vtkSmartPointer<vtkCenterOfMass>::New();
    #if VTK_MAJOR_VERSION <= 5
      centerOfMassFilter->SetInput(polydata);
    #else
      centerOfMassFilter->SetInputData(polydata);
    #endif
      centerOfMassFilter->SetUseScalarsAsWeights(false);
      centerOfMassFilter->Update();

      double center[3];
      centerOfMassFilter->GetCenter(center);

      std::cout << "Center of mass is " << center[0] << " " << center[1] << " " << center[2] << std::endl;

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(CenterOfMass)

    find_package(VTK REQUIRED)
    include(${VTK_USE_FILE})

    add_executable(CenterOfMass MACOSX_BUNDLE CenterOfMass.cxx)

    target_link_libraries(CenterOfMass ${VTK_LIBRARIES})

### Download and Build CenterOfMass

Danger

The generation of tar files has not been ported to the new VTKExamples. Some tarballs may be missing or out-of-date.

Click here to download CenterOfMass and its CMakeLists.txt file. Once the tarball CenterOfMass.tar has been downloaded and extracted,

    cd CenterOfMass/build

If VTK is installed:

    cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

    cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

Build the project:

    make

and run it:

    ./CenterOfMass

WINDOWS USERS PLEASE NOTE: Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.