# BuildOctree

VTKExamples/Cxx/DataStructures/BuildOctree

### Code

BuildOctree.cxx

    #include <vtkSmartPointer.h>
    #include <vtkPoints.h>
    #include <vtkCellArray.h>
    #include <vtkPolyData.h>
    #include <vtkXMLPolyDataReader.h>
    #include <vtkIdList.h>
    #include <vtkOctreePointLocator.h>
    #include <vtkDataSetCollection.h>

    int main(int, char *[])
    {
      // Setup point coordinates
      double x[3] = {1.0, 0.0, 0.0};
      double y[3] = {0.0, 1.0, 0.0};
      double z[3] = {0.0, 0.0, 1.0};

      vtkSmartPointer<vtkPoints> points =
        vtkSmartPointer<vtkPoints>::New();
      vtkSmartPointer<vtkCellArray> vertices =
        vtkSmartPointer<vtkCellArray>::New();

      for(unsigned int i = 0; i < 3; ++i)
      {
        points->InsertNextPoint ( x[i], y[i], z[i] );
      }

      std::cout << "There are " << points->GetNumberOfPoints() << " points." << std::endl;

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

      //Create the tree
      vtkSmartPointer<vtkOctreePointLocator> octree =
          vtkSmartPointer<vtkOctreePointLocator>::New();
      octree->SetDataSet(polydata);
      octree->BuildLocator();

      std::cout << "Number of points in tree: " << octree->GetDataSet()->GetNumberOfPoints() << std::endl;

      double p[3];
      octree->GetDataSet()->GetPoint(0,p);
      std::cout << "p: " << p[0] << " " << p[1] << " " << p[2] << std::endl;

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(BuildOctree)

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

    add_executable(BuildOctree MACOSX_BUNDLE BuildOctree.cxx )

    target_link_libraries(BuildOctree ${VTK_LIBRARIES})

### Download and Build BuildOctree

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

    cd BuildOctree/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:

    ./BuildOctree

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.