# DownsamplePointCloud

VTKExamples/Cxx/PolyData/DownsamplePointCloud

### Description

This example downsamples a point cloud by specifying the minimum distance two points can be from each other. The filter will delete points so that this criterion is met.

### Code

DownsamplePointCloud.cxx

    #include <vtkSmartPointer.h>
    #include <vtkPointSource.h>
    #include <vtkPolyData.h>
    #include <vtkCleanPolyData.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>

    int main(int, char *[])
    {
      vtkSmartPointer<vtkPointSource> pointSource =
        vtkSmartPointer<vtkPointSource>::New();
      pointSource->SetNumberOfPoints(1000);
      pointSource->SetRadius(1.0);
      pointSource->Update();

      vtkSmartPointer<vtkCleanPolyData> cleanPolyData =
        vtkSmartPointer<vtkCleanPolyData>::New();
      cleanPolyData->SetInputConnection(pointSource->GetOutputPort());
      cleanPolyData->SetTolerance(0.1);
      cleanPolyData->Update();

      vtkSmartPointer<vtkPolyDataMapper> inputMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      inputMapper->SetInputConnection(pointSource->GetOutputPort());
      vtkSmartPointer<vtkActor> inputActor =
        vtkSmartPointer<vtkActor>::New();
      inputActor->SetMapper(inputMapper);

      vtkSmartPointer<vtkPolyDataMapper> cleanedMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      cleanedMapper->SetInputConnection(cleanPolyData->GetOutputPort());
      vtkSmartPointer<vtkActor> cleanedActor =
        vtkSmartPointer<vtkActor>::New();
      cleanedActor->SetMapper(cleanedMapper);

       // There will be one render window
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->SetSize(600, 300);

      // 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);

      leftRenderer->AddActor(inputActor);
      rightRenderer->AddActor(cleanedActor);

      leftRenderer->ResetCamera();
      rightRenderer->ResetCamera();

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

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(DownsamplePointCloud)

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

### Download and Build DownsamplePointCloud

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

    cd DownsamplePointCloud/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:

    ./DownsamplePointCloud

WINDOWS USERS

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