# QuantizePolyDataPoints

VTKExamples/Cxx/PolyData/QuantizePolyDataPoints

### Description

This example demonstrates how to "snap" points onto a discrete grid. This example rounds the coordinates of each point the the nearest .1

### Code

QuantizePolyDataPoints.cxx

    #include <vtkSmartPointer.h>
    #include <vtkQuantizePolyDataPoints.h>

    #include <vtkPoints.h>
    #include <vtkPolyData.h>
    #include <vtkPointSource.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkProperty.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>
    #include <vtkXMLPolyDataReader.h>
    #include <vtkSphereSource.h>
    #include <vtkGlyph3DMapper.h>
    #include <vtkCamera.h>

    int main(int, char *[])
    {
      vtkSmartPointer<vtkPointSource> pointSource =
        vtkSmartPointer<vtkPointSource>::New();
      pointSource->SetNumberOfPoints(100);
      pointSource->Update();

      std::cout << "There are " << pointSource->GetNumberOfPoints()
                << " points." << std::endl;

      vtkSmartPointer<vtkQuantizePolyDataPoints> quantizeFilter =
        vtkSmartPointer<vtkQuantizePolyDataPoints>::New();
      quantizeFilter->SetInputConnection(pointSource->GetOutputPort());
      quantizeFilter->SetQFactor(.1);
      quantizeFilter->Update();

      vtkPolyData* quantized = quantizeFilter->GetOutput();
      std::cout << "There are " << quantized->GetNumberOfPoints()
                << " quantized points." << std::endl;

      for(vtkIdType i = 0; i < pointSource->GetOutput()->GetNumberOfPoints(); i++)
      {
        double pOrig[3];
        double pQuantized[3];
        pointSource->GetOutput()->GetPoint(i,pOrig);
        quantized->GetPoints()->GetPoint(i,pQuantized);

        std::cout << "Point " << i << " : ("
                  << pOrig[0] << ", " << pOrig[1] << ", " << pOrig[2] << ")"
                  << " (" << pQuantized[0] << ", " << pQuantized[1] << ", " << pQuantized[2]
                  << ")" << std::endl;
      }

      double radius = .02;
      vtkSmartPointer<vtkSphereSource> sphereSource =
        vtkSmartPointer<vtkSphereSource>::New();
      sphereSource->SetRadius(radius);

      vtkSmartPointer<vtkGlyph3DMapper> inputMapper =
        vtkSmartPointer<vtkGlyph3DMapper>::New();
      inputMapper->SetInputConnection(pointSource->GetOutputPort());
      inputMapper->SetSourceConnection(sphereSource->GetOutputPort());
      inputMapper->ScalarVisibilityOff();
      inputMapper->ScalingOff();

      vtkSmartPointer<vtkActor> inputActor =
        vtkSmartPointer<vtkActor>::New();
      inputActor->SetMapper(inputMapper);

      vtkSmartPointer<vtkGlyph3DMapper> quantizedMapper =
        vtkSmartPointer<vtkGlyph3DMapper>::New();
      quantizedMapper->SetInputConnection(quantizeFilter->GetOutputPort());
      quantizedMapper->SetSourceConnection(sphereSource->GetOutputPort());
      quantizedMapper->ScalarVisibilityOff();
      quantizedMapper->ScalingOff();

      vtkSmartPointer<vtkActor> quantizedActor =
        vtkSmartPointer<vtkActor>::New();
      quantizedActor->SetMapper(quantizedMapper);

      // There will be one render window
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->SetSize(640, 360);

      // And one interactor
      vtkSmartPointer<vtkRenderWindowInteractor> interactor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      interactor->SetRenderWindow(renderWindow);

      // Define viewport ranges
      // (xmin, ymin, xmax, ymax)
      double leftViewport[4] = {0.0, 0.0, 0.5, 1.0};
      double rightViewport[4] = {0.5, 0.0, 1.0, 1.0};

      // Setup both renderers
      vtkSmartPointer<vtkRenderer> leftRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      renderWindow->AddRenderer(leftRenderer);
      leftRenderer->SetViewport(leftViewport);
      leftRenderer->SetBackground(.6, .5, .4);

      vtkSmartPointer<vtkRenderer> rightRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      renderWindow->AddRenderer(rightRenderer);
      rightRenderer->SetViewport(rightViewport);
      rightRenderer->SetBackground(.4, .5, .6);

      // Add the sphere to the left and the cube to the right
      leftRenderer->AddActor(inputActor);
      rightRenderer->AddActor(quantizedActor);

      leftRenderer->ResetCamera();

      rightRenderer->SetActiveCamera(leftRenderer->GetActiveCamera());

      renderWindow->Render();
      interactor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(QuantizePolyDataPoints)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkCommonDataModel
      vtkFiltersGeneral
      vtkFiltersSources
      vtkIOXML
      vtkInteractionStyle
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping QuantizePolyDataPoints: ${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(QuantizePolyDataPoints MACOSX_BUNDLE QuantizePolyDataPoints.cxx )
      target_link_libraries(QuantizePolyDataPoints PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(QuantizePolyDataPoints MACOSX_BUNDLE QuantizePolyDataPoints.cxx )
      target_link_libraries(QuantizePolyDataPoints PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS QuantizePolyDataPoints
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build QuantizePolyDataPoints

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

    cd QuantizePolyDataPoints/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:

    ./QuantizePolyDataPoints

WINDOWS USERS

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