# SignedDistance

VTKExamples/Cxx/Points/SignedDistance

### Description

Contrast this with the UnsignedDistance example.

The image was created using the Armadillo dataset

Warning

The classes used in this example require vtk 7.1 or later.

### Code

SignedDistance.cxx

    #include <vtkSmartPointer.h>

    #include <vtkBYUReader.h>
    #include <vtkOBJReader.h>
    #include <vtkPLYReader.h>
    #include <vtkPolyDataReader.h>
    #include <vtkSTLReader.h>
    #include <vtkXMLPolyDataReader.h>

    #include <vtkPointSource.h>
    #include <vtkPCANormalEstimation.h>
    #include <vtkSignedDistance.h>
    #include <vtkImageMapToColors.h>
    #include <vtkLookupTable.h>
    #include <vtkImageData.h>

    #include <vtkScalarBarActor.h>
    #include <vtkImageActor.h>

    #include <vtkImageMapper3D.h>
    #include <vtkProperty.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>
    #include <vtkCamera.h>

    #include <vtksys/SystemTools.hxx>

    namespace
    {
    vtkSmartPointer<vtkPolyData> ReadPolyData(const char *fileName);
    }

    int main (int argc, char *argv[])
    {
      vtkSmartPointer<vtkPolyData> polyData = ReadPolyData(argc > 1 ? argv[1] : "");;

      double bounds[6];
      polyData->GetBounds(bounds);
      double range[3];
      for (int i = 0; i < 3; ++i)
      {
        range[i] = bounds[2*i + 1] - bounds[2*i];
      }

      int sampleSize = polyData->GetNumberOfPoints() * .00005;
      if (sampleSize < 10)
      {
        sampleSize = 10;
      }
      std::cout << "Sample size is: " << sampleSize << std::endl;
      vtkSmartPointer<vtkPCANormalEstimation> normals =
        vtkSmartPointer<vtkPCANormalEstimation>::New();
      normals->SetInputData (polyData);
      normals->SetSampleSize(sampleSize);
      normals->SetNormalOrientationToGraphTraversal();
      normals->FlipNormalsOn();
      std::cout << "Range: "
                << range[0] << ", "
                << range[1] << ", "
                << range[2] << std::endl;
      int dimension = 256;
      dimension = 128;
      double radius = range[0] * .02;
      radius = range[0] / static_cast<double>(dimension) * 5;; // ~5 voxels
      std::cout << "Radius: " << radius << std::endl;
      vtkSmartPointer<vtkSignedDistance> distance =
        vtkSmartPointer<vtkSignedDistance>::New();
      distance->SetInputConnection (normals->GetOutputPort());
      distance->SetRadius(radius);
      distance->SetDimensions(dimension, dimension, dimension);
      distance->SetBounds(
        bounds[0] - range[0] * .1,
        bounds[1] + range[0] * .1,
        bounds[2] - range[1] * .1,
        bounds[3] + range[1] * .1,
        bounds[4] - range[2] * .1,
        bounds[5] + range[2] * .1);

      // Create a lookup table that consists of the full hue circle
      // (from HSV).
      vtkSmartPointer<vtkLookupTable> hueLut =
        vtkSmartPointer<vtkLookupTable>::New();
      hueLut->SetTableRange (-.99 * radius, .99 * radius);
      hueLut->SetHueRange (.667, 0);
      hueLut->SetSaturationRange (1, 1);
      hueLut->SetValueRange (1, 1);
      hueLut->UseBelowRangeColorOn();
      hueLut->SetBelowRangeColor(0, 0, 0, 0);
      hueLut->UseAboveRangeColorOn();
      hueLut->SetAboveRangeColor(0, 0, 0, 0);
      hueLut->SetNumberOfColors(5);
      hueLut->Build();
      double *last = hueLut->GetTableValue(4);
      hueLut->SetAboveRangeColor(last[0], last[1], last[2], 0);

      vtkSmartPointer<vtkImageMapToColors> sagittalColors =
        vtkSmartPointer<vtkImageMapToColors>::New();
      sagittalColors->SetInputConnection(distance->GetOutputPort());
      sagittalColors->SetLookupTable(hueLut);
      sagittalColors->Update();

      vtkSmartPointer<vtkImageActor> sagittal =
        vtkSmartPointer<vtkImageActor>::New();
      sagittal->GetMapper()->SetInputConnection(sagittalColors->GetOutputPort());
      sagittal->SetDisplayExtent(dimension/2, dimension/2, 0, dimension - 1, 0, dimension - 1);
      sagittal->ForceOpaqueOn();

      vtkSmartPointer<vtkImageMapToColors> axialColors =
        vtkSmartPointer<vtkImageMapToColors>::New();
      axialColors->SetInputConnection(distance->GetOutputPort());
      axialColors->SetLookupTable(hueLut);
      axialColors->Update();

      vtkSmartPointer<vtkImageActor> axial =
        vtkSmartPointer<vtkImageActor>::New();
      axial->GetMapper()->SetInputConnection(axialColors->GetOutputPort());
      axial->SetDisplayExtent(0, dimension - 1, 0, dimension - 1, dimension/2, dimension/2);
      axial->ForceOpaqueOn();

      vtkSmartPointer<vtkImageMapToColors> coronalColors =
        vtkSmartPointer<vtkImageMapToColors>::New();
      coronalColors->SetInputConnection(distance->GetOutputPort());
      coronalColors->SetLookupTable(hueLut);
      coronalColors->Update();

      vtkSmartPointer<vtkImageActor> coronal =
        vtkSmartPointer<vtkImageActor>::New();
      coronal->GetMapper()->SetInputConnection(coronalColors->GetOutputPort());
      coronal->SetDisplayExtent(0, dimension - 1, dimension/2, dimension/2, 0, dimension - 1);
      coronal->ForceOpaqueOn();

      // Create a scalar bar
      vtkSmartPointer<vtkScalarBarActor> scalarBar =
        vtkSmartPointer<vtkScalarBarActor>::New();
      scalarBar->SetLookupTable(hueLut);
      scalarBar->SetTitle("Distance");
      scalarBar->SetNumberOfLabels(5);

      // Create graphics stuff
      //
      vtkSmartPointer<vtkRenderer> ren1 =
        vtkSmartPointer<vtkRenderer>::New();
      ren1->SetBackground(.3, .4, .6);

      vtkSmartPointer<vtkRenderWindow> renWin =
        vtkSmartPointer<vtkRenderWindow>::New();
      renWin->AddRenderer(ren1);
      renWin->SetSize(512,512);

      vtkSmartPointer<vtkRenderWindowInteractor> iren =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      iren->SetRenderWindow(renWin);

      // Add the actors to the renderer, set the background and size
      //
      ren1->AddActor(sagittal);
      ren1->AddActor(axial);
      ren1->AddActor(coronal);
      ren1->AddActor2D(scalarBar);

      // Generate an interesting view
      //
      ren1->ResetCamera();
      ren1->GetActiveCamera()->Azimuth(120);
      ren1->GetActiveCamera()->Elevation(30);
      ren1->GetActiveCamera()->Dolly(1.5);
      ren1->ResetCameraClippingRange();

      renWin->Render();
      iren->Initialize();
      iren->Start();
      std::cout << distance->GetOutput()->GetScalarRange()[0] << ", "
                << distance->GetOutput()->GetScalarRange()[1] << std::endl;
      return EXIT_SUCCESS;
    }

    namespace
    {
    vtkSmartPointer<vtkPolyData> ReadPolyData(const char *fileName)
    {
      vtkSmartPointer<vtkPolyData> polyData;
      std::string extension = vtksys::SystemTools::GetFilenameExtension(std::string(fileName));
      if (extension == ".ply")
      {
        vtkSmartPointer<vtkPLYReader> reader =
          vtkSmartPointer<vtkPLYReader>::New();
        reader->SetFileName (fileName);
        reader->Update();
        polyData = reader->GetOutput();
      }
      else if (extension == ".vtp")
      {
        vtkSmartPointer<vtkXMLPolyDataReader> reader =
          vtkSmartPointer<vtkXMLPolyDataReader>::New();
        reader->SetFileName (fileName);
        reader->Update();
        polyData = reader->GetOutput();
      }
      else if (extension == ".vtk")
      {
        vtkSmartPointer<vtkPolyDataReader> reader =
          vtkSmartPointer<vtkPolyDataReader>::New();
        reader->SetFileName (fileName);
        reader->Update();
        polyData = reader->GetOutput();
      }
      else if (extension == ".obj")
      {
        vtkSmartPointer<vtkOBJReader> reader =
          vtkSmartPointer<vtkOBJReader>::New();
        reader->SetFileName (fileName);
        reader->Update();
        polyData = reader->GetOutput();
      }
      else if (extension == ".stl")
      {
        vtkSmartPointer<vtkSTLReader> reader =
          vtkSmartPointer<vtkSTLReader>::New();
        reader->SetFileName (fileName);
        reader->Update();
        polyData = reader->GetOutput();
      }
      else if (extension == ".g")
      {
        vtkSmartPointer<vtkBYUReader> reader =
          vtkSmartPointer<vtkBYUReader>::New();
        reader->SetGeometryFileName (fileName);
        reader->Update();
        polyData = reader->GetOutput();
      }
      else
      {
        vtkSmartPointer<vtkPointSource> points =
          vtkSmartPointer<vtkPointSource>::New();
        points->SetNumberOfPoints(100000);
        points->SetRadius(10.0);
        points->SetCenter(vtkMath::Random(-100, 100),
                          vtkMath::Random(-100, 100),
                          vtkMath::Random(-100, 100));
        points->SetDistributionToShell();
        points->Update();
        polyData = points->GetOutput();
      }
      return polyData;
    }
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(SignedDistance)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkCommonDataModel
      vtkFiltersPoints
      vtkFiltersSources
      vtkIOGeometry
      vtkIOLegacy
      vtkIOPLY
      vtkIOXML
      vtkImagingCore
      vtkInteractionStyle
      vtkRenderingAnnotation
      vtkRenderingContextOpenGL2
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingGL2PSOpenGL2
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping SignedDistance: ${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(SignedDistance MACOSX_BUNDLE SignedDistance.cxx )
      target_link_libraries(SignedDistance PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(SignedDistance MACOSX_BUNDLE SignedDistance.cxx )
      target_link_libraries(SignedDistance PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS SignedDistance
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build SignedDistance

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

    cd SignedDistance/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:

    ./SignedDistance

WINDOWS USERS

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