KDTreeAccessPoints

#include <vtkDataSetCollection.h>
#include <vtkKdTree.h>
#include <vtkNew.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkVertexGlyphFilter.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};

  vtkNew<vtkPoints> points;
  points->InsertNextPoint(x);
  points->InsertNextPoint(y);
  points->InsertNextPoint(z);

  vtkNew<vtkPolyData> polydata;
  polydata->SetPoints(points);

  // The tree needs cells, so add vertices to each point.
  vtkNew<vtkVertexGlyphFilter> vertexFilter;
  vertexFilter->SetInputData(polydata);
  vertexFilter->Update();

  // Create the tree.
  vtkNew<vtkKdTree> kDTree;
  kDTree->AddDataSet(vertexFilter->GetOutput());
  kDTree->BuildLocator();

  // Get the number of points in the tree like this:
  kDTree->GetDataSets()->InitTraversal();
  std::cout << "Number of points in tree: "
            << kDTree->GetDataSets()->GetNextDataSet()->GetNumberOfPoints()
            << std::endl;

  // Or you can get the number of points in the tree like this:
  std::cout << "Number of points in tree: "
            << kDTree->GetDataSet(0)->GetNumberOfPoints() << std::endl;

  // Get the 0th point in the tree.
  double p[3];
  kDTree->GetDataSet(0)->GetPoint(0, p);
  std::cout << "p: " << p[0] << " " << p[1] << " " << p[2] << std::endl;

  return EXIT_SUCCESS;
}

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(KDTreeAccessPoints)

find_package(VTK COMPONENTS 
  CommonCore
  CommonDataModel
  FiltersGeneral
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "KDTreeAccessPoints: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(KDTreeAccessPoints MACOSX_BUNDLE KDTreeAccessPoints.cxx )
  target_link_libraries(KDTreeAccessPoints PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS KDTreeAccessPoints
  MODULES ${VTK_LIBRARIES}
)

cd KDTreeAccessPoints/build

cmake ..

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

make

./KDTreeAccessPoints