ClosestNPoints

VTKEx/Cxx/DataStructures/ClosestNPoints

Question

If you have a simple question about this example contact us at VTKExProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

Code¶

ClosestNPoints.cxx

#include <vtkCellArray.h>
#include <vtkIdList.h>
#include <vtkKdTreePointLocator.h>
#include <vtkPointSource.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkSmartPointer.h>

int main(int, char *[]) {
  // Create some random points
  vtkSmartPointer<vtkPointSource> pointSource =
      vtkSmartPointer<vtkPointSource>::New();
  pointSource->SetNumberOfPoints(10);
  pointSource->Update();

  // Create the tree
  vtkSmartPointer<vtkKdTreePointLocator> pointTree =
      vtkSmartPointer<vtkKdTreePointLocator>::New();
  pointTree->SetDataSet(pointSource->GetOutput());
  pointTree->BuildLocator();

  // Find the k closest points to (0,0,0)
  unsigned int k = 1;
  double testPoint[3] = {0.0, 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];
    pointSource->GetOutput()->GetPoint(point_ind, p);
    std::cout << "Closest point " << i << ": Point " << point_ind << ": ("
              << p[0] << ", " << p[1] << ", " << p[2] << ")" << std::endl;
  }

  // Should return:
  // Closest point 0: Point 2: (-0.136162, -0.0276359, 0.0369441)

  return EXIT_SUCCESS;
}

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(ClosestNPoints)

find_package(VTK COMPONENTS 
  vtkvtkCommonCore
  vtkvtkCommonDataModel
  vtkvtkFiltersSources QUIET)
if (NOT VTK_FOUND)
  message("Skipping ClosestNPoints: ${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(ClosestNPoints MACOSX_BUNDLE ClosestNPoints.cxx )
  target_link_libraries(ClosestNPoints PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(ClosestNPoints MACOSX_BUNDLE ClosestNPoints.cxx )
  target_link_libraries(ClosestNPoints PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS ClosestNPoints
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build ClosestNPoints¶

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

cd ClosestNPoints/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:

./ClosestNPoints

WINDOWS USERS

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