KDTreeAccessPoints

VTKEx/Cxx/DataStructures/KDTreeAccessPoints

Description

This example demonstrates how to build a KDTree, get its number of points, and get a point by ID.

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

KDTreeAccessPoints.cxx

#include <vtkSmartPointer.h>
#include <vtkPoints.h>
#include <vtkCellArray.h>
#include <vtkPolyData.h>
#include <vtkXMLPolyDataReader.h>
#include <vtkIdList.h>
#include <vtkKdTree.h>
#include <vtkDataSetCollection.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};

  vtkSmartPointer<vtkPoints> points = 
    vtkSmartPointer<vtkPoints>::New();
  points->InsertNextPoint (x);
  points->InsertNextPoint (y);
  points->InsertNextPoint (z);

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

  //the tree needs cells, so add vertices to each point
  vtkSmartPointer<vtkVertexGlyphFilter> vertexFilter = 
    vtkSmartPointer<vtkVertexGlyphFilter>::New();
  vertexFilter->SetInputData(polydata);
  vertexFilter->Update();

  //Create the tree
  vtkSmartPointer<vtkKdTree> kDTree = 
    vtkSmartPointer<vtkKdTree>::New();
  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;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(KDTreeAccessPoints)

find_package(VTK COMPONENTS 
  vtkvtkCommonCore
  vtkvtkCommonDataModel
  vtkvtkFiltersGeneral
  vtkvtkIOXML QUIET)
if (NOT VTK_FOUND)
  message("Skipping KDTreeAccessPoints: ${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(KDTreeAccessPoints MACOSX_BUNDLE KDTreeAccessPoints.cxx )
  target_link_libraries(KDTreeAccessPoints PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  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}
    )
endif ()

Download and Build KDTreeAccessPoints

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

cd KDTreeAccessPoints/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:

./KDTreeAccessPoints

WINDOWS USERS

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