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# BuildLocatorFromKClosestPoints

VTKEx/Cxx/DataStructures/BuildLocatorFromKClosestPoints

Question

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### Code

BuildLocatorFromKClosestPoints.cxx

    #include <vtkSmartPointer.h>
    #include <vtkPoints.h>
    #include <vtkPointSource.h>
    #include <vtkIdList.h>
    #include <vtkKdTree.h>

    int main(int, char *[])
    {
      // Create some points
      double origin[3] = {0.0, 0.0, 0.0};
      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();
      points->InsertNextPoint(origin);
      points->InsertNextPoint(x);
      points->InsertNextPoint(y);
      points->InsertNextPoint(z);

      // Create the tree
      vtkSmartPointer<vtkKdTree> pointTree =
        vtkSmartPointer<vtkKdTree>::New();
      pointTree->BuildLocatorFromPoints(points);

      // Find the 2 closest points to (0.5,0,0)
      vtkIdType k = 2;
      double testPoint[3] = {0.5, 0.0, 0.0};
      vtkSmartPointer<vtkIdList> result =
        vtkSmartPointer<vtkIdList>::New();

      pointTree->FindClosestNPoints(k, testPoint, result);

      for(vtkIdType i = 0; i < k; i++)
      {
        vtkIdType point_ind = result->GetId(i);
        double p[3];
        points->GetPoint(point_ind, p);
        std::cout << "Closest point "
                  << i << ": Point " << point_ind << ": ("
                  << p[0] << ", " << p[1] << ", " << p[2] << ")" << std::endl;
      }

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(BuildLocatorFromKClosestPoints)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkCommonDataModel
      vtkFiltersSources QUIET)
    if (NOT VTK_FOUND)
      message("Skipping BuildLocatorFromKClosestPoints: ${VTK_NOT_FOUND_MESSAGE}")
      return ()
    endif()
    message (STATUS "VTK_VERSION: ${VTK_VERSION}")
    if (VTK_VERSION VERSION_LESS "8.90.0")
      # old system
      include(${VTK_USE_FILE})
      add_executable(BuildLocatorFromKClosestPoints MACOSX_BUNDLE BuildLocatorFromKClosestPoints.cxx )
      target_link_libraries(BuildLocatorFromKClosestPoints PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(BuildLocatorFromKClosestPoints MACOSX_BUNDLE BuildLocatorFromKClosestPoints.cxx )
      target_link_libraries(BuildLocatorFromKClosestPoints PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS BuildLocatorFromKClosestPoints
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build BuildLocatorFromKClosestPoints

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

    cd BuildLocatorFromKClosestPoints/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:

    ./BuildLocatorFromKClosestPoints

WINDOWS USERS

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