# PointInsideObject2

VTKExamples/Cxx/PolyData/PointInsideObject2

### Description

This example creates a volume (convex hull-ish) out of a mesh object. It then uses FindCell (which determines if a point is inside of a cell) to determine if a point is inside of any of the 3D cells created by Delaunay3D or not. This could potentially lead to false positives - that is, points that are outside the mesh but inside the convex hull.

### Code

PointInsideObject2.cxx

    #include <vtkVersion.h>
    #include <vtkProperty.h>
    #include <vtkCellArray.h>
    #include<vtkPolyDataMapper.h>
    #include<vtkDelaunay3D.h>
    #include <vtkSphereSource.h>
    #include <vtkPolyData.h>
    #include <vtkSmartPointer.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkUnstructuredGrid.h>
    #include <vtkVertexGlyphFilter.h>

    int main(int , char *[])
    {
      // Create a sphere
      vtkSmartPointer<vtkSphereSource> bigSphereSource =
        vtkSmartPointer<vtkSphereSource>::New();
      bigSphereSource->SetCenter(0.0, 0.0, 0.0);
      bigSphereSource->SetRadius(4);
      bigSphereSource->SetThetaResolution(20);
      bigSphereSource->SetPhiResolution(20);
      bigSphereSource->Update();

      vtkSmartPointer<vtkPolyDataMapper> bigSphereMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      bigSphereMapper->SetInputConnection(bigSphereSource->GetOutputPort());

      vtkSmartPointer<vtkActor> bigSphereActor =
        vtkSmartPointer<vtkActor>::New();
      bigSphereActor->SetMapper(bigSphereMapper);
      bigSphereActor->GetProperty()->SetOpacity(.5);

      vtkSmartPointer<vtkSphereSource> smallSphereSource =
        vtkSmartPointer<vtkSphereSource>::New();
      smallSphereSource->SetCenter(1, 2, 1);
      smallSphereSource->SetRadius(2);
      smallSphereSource->SetThetaResolution(20);
      smallSphereSource->SetPhiResolution(20);
      smallSphereSource->Update();

      vtkSmartPointer<vtkPolyDataMapper> smallSphereMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      smallSphereMapper->SetInputConnection(smallSphereSource->GetOutputPort());

      vtkSmartPointer<vtkActor> smallSphereActor =
        vtkSmartPointer<vtkActor>::New();
      smallSphereActor->SetMapper(smallSphereMapper);

      vtkSmartPointer<vtkPoints> pointsInside = vtkSmartPointer<vtkPoints>::New();
      vtkSmartPointer<vtkPolyData> polyDataInside = vtkSmartPointer<vtkPolyData>::New();
      double point[3];

      vtkSmartPointer<vtkDelaunay3D> delaunay3D = vtkSmartPointer<vtkDelaunay3D>::New();
      delaunay3D->SetInputConnection (bigSphereSource->GetOutputPort());
      delaunay3D->Update();

      for(vtkIdType i = 0; i < smallSphereSource->GetOutput()->GetNumberOfPoints(); i++)
      {
        smallSphereSource->GetOutput()->GetPoint(i,point);

        double pcoords[3];
        // The number of weights >= max number of nodes in each cell
        double weights[4];

        int subId;
        vtkIdType cellId = delaunay3D->GetOutput()->FindCell(point,NULL, 0, .1,subId, pcoords, weights);

        if (cellId>=0)
        {
          std::cout << "In cell " << cellId << std::endl;
          std::cout << "inside" << std::endl;
          pointsInside->InsertNextPoint(point);
        }
        else
        {
          std::cout << "outside" << std::endl;
        }
      }

      polyDataInside->SetPoints(pointsInside);

      vtkSmartPointer<vtkVertexGlyphFilter> vertexGlyphFilter = vtkSmartPointer<vtkVertexGlyphFilter>::New();
    #if VTK_MAJOR_VERSION <= 5
      vertexGlyphFilter->SetInputConnection(polyDataInside->GetProducerPort());
    #else
      vertexGlyphFilter->SetInputData(polyDataInside);
    #endif
      vertexGlyphFilter->Update();

      // Mapper and actor for points inside
      vtkSmartPointer<vtkPolyDataMapper> pointsInsideMapper = vtkSmartPointer<vtkPolyDataMapper>::New();
      pointsInsideMapper->SetInputConnection(vertexGlyphFilter->GetOutputPort());
      vtkSmartPointer<vtkActor> pointsInsideActor = vtkSmartPointer<vtkActor>::New();
      pointsInsideActor->SetMapper(pointsInsideMapper);
      pointsInsideActor->GetProperty()->SetPointSize(6);
      pointsInsideActor->GetProperty()->SetColor(1,0,1);

      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);
      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      renderWindowInteractor->SetRenderWindow(renderWindow);

      renderer->AddActor(smallSphereActor);
      renderer->AddActor(bigSphereActor);
      renderer->AddActor(pointsInsideActor);
      renderer->SetBackground(.3, .6, .3); // Background color green
      renderWindow->Render();
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(PointInsideObject2)

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

    add_executable(PointInsideObject2 MACOSX_BUNDLE PointInsideObject2.cxx )

    target_link_libraries(PointInsideObject2 ${VTK_LIBRARIES})

### Download and Build PointInsideObject2

Click here to download PointInsideObject2 and its CMakeLists.txt file. Once the tarball PointInsideObject2.tar has been downloaded and extracted,

    cd PointInsideObject2/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:

    ./PointInsideObject2

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.