VTK/Examples/Cxx/PolyData/ThresholdPoints

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ThresholdPoints.cxx

#include <vtkVersion.h>
#include <vtkIntArray.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkPointData.h>
#include <vtkSmartPointer.h>
#include <vtkThresholdPoints.h>
 
int main(int, char *[])
{
  vtkSmartPointer<vtkPoints> points = 
    vtkSmartPointer<vtkPoints>::New(); 
  points->InsertNextPoint(0,0,0);
  points->InsertNextPoint(1,1,1);
  points->InsertNextPoint(2,2,2);
  points->InsertNextPoint(3,3,3);
  points->InsertNextPoint(4,4,4);
 
  std::cout << "There are " << points->GetNumberOfPoints() 
            << " points before thresholding." << std::endl;
 
  //setup position index
  vtkSmartPointer<vtkIntArray> index = 
    vtkSmartPointer<vtkIntArray>::New();
  index->SetNumberOfComponents(1);
  index->SetName("index");
  index->InsertNextValue(0);
  index->InsertNextValue(1);
  index->InsertNextValue(2);
  index->InsertNextValue(3);
  index->InsertNextValue(4);
 
  vtkSmartPointer<vtkPolyData> polydata = 
    vtkSmartPointer<vtkPolyData>::New();
  polydata->SetPoints(points);
  polydata->GetPointData()->AddArray(index);
 
  vtkSmartPointer<vtkThresholdPoints> threshold = 
    vtkSmartPointer<vtkThresholdPoints>::New();
#if VTK_MAJOR_VERSION <= 5
  threshold->SetInput(polydata);
#else
  threshold->SetInputData(polydata);
#endif
  threshold->ThresholdByLower(2);
  threshold->SetInputArrayToProcess(0, 0, 0, vtkDataObject::FIELD_ASSOCIATION_POINTS, "index");
  threshold->Update();
 
  //vtkPolyData* thresholdedPolydata = threshold->GetOutput();
  vtkPolyData* thresholdedPolydata = threshold->GetOutput();
  std::cout << "There are " << thresholdedPolydata->GetNumberOfPoints() 
            << " points after thresholding." << std::endl;
  for(vtkIdType i = 0; i < thresholdedPolydata->GetNumberOfPoints(); i++)
    {
    double p[3];
    thresholdedPolydata->GetPoint(i,p);
    std::cout << "Point " << i << " : " << p[0] << " " << p[1] << " " << p[2] << std::endl;
    }
 
  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 2.8)
 
PROJECT(ThresholdPoints)
 
find_package(VTK REQUIRED)
include(${VTK_USE_FILE})
 
add_executable(ThresholdPoints MACOSX_BUNDLE ThresholdPoints.cxx)
 
if(VTK_LIBRARIES)
  target_link_libraries(ThresholdPoints ${VTK_LIBRARIES})
else()
  target_link_libraries(ThresholdPoints vtkHybrid vtkWidgets)
endif()

Download and Build ThresholdPoints

Click here to download ThresholdPoints. and its CMakeLists.txt file.

Once the tarball ThresholdPoints.tar has been downloaded and extracted,

cd ThresholdPoints/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:

./ThresholdPoints

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.