# TubesFromSplines

VTKExamples/Cxx/VisualizationAlgorithms/TubesFromSplines

### Description

This example shows how to interpolate a set of points and generate tubes around the resulting polyline. Scalars associated with the points are also interpolated and used to vary the radius of the tube.

'''NOTE:''' This example was inspired by a question asked by ''Adam Sankowski''.

### Code

TubesFromSplines.cxx

    #include <vtkSmartPointer.h>
    #include <vtkVersion.h>

    #include <vtkParametricFunctionSource.h>
    #include <vtkTupleInterpolator.h>
    #include <vtkTubeFilter.h>
    #include <vtkParametricSpline.h>

    #include <vtkDoubleArray.h>
    #include <vtkPoints.h>
    #include <vtkPolyData.h>
    #include <vtkPointData.h>

    #include <vtkPolyDataMapper.h>
    #include <vtkActor.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>

    int main(int, char *[])
    {
      vtkSmartPointer<vtkPoints> points =
        vtkSmartPointer<vtkPoints>::New();
      points->InsertPoint(0,1,0,0);
      points->InsertPoint(1,2,0,0);
      points->InsertPoint(2,3,1,0);
      points->InsertPoint(3,4,1,0);
      points->InsertPoint(4,5,0,0);
      points->InsertPoint(5,6,0,0);

      // Fit a spline to the points
      vtkSmartPointer<vtkParametricSpline> spline =
        vtkSmartPointer<vtkParametricSpline>::New();
      spline->SetPoints(points);
      vtkSmartPointer<vtkParametricFunctionSource> functionSource =
        vtkSmartPointer<vtkParametricFunctionSource>::New();
      functionSource->SetParametricFunction(spline);
      functionSource->SetUResolution(10 * points->GetNumberOfPoints());
      functionSource->Update();

      // Interpolate the scalars
      double rad;
      vtkSmartPointer<vtkTupleInterpolator> interpolatedRadius =
        vtkSmartPointer<vtkTupleInterpolator> ::New();
      interpolatedRadius->SetInterpolationTypeToLinear();
      interpolatedRadius->SetNumberOfComponents(1);
      rad = .2; interpolatedRadius->AddTuple(0,&rad);
      rad = .2; interpolatedRadius->AddTuple(1,&rad);
      rad = .2; interpolatedRadius->AddTuple(2,&rad);
      rad = .1; interpolatedRadius->AddTuple(3,&rad);
      rad = .1; interpolatedRadius->AddTuple(4,&rad);
      rad = .1; interpolatedRadius->AddTuple(5,&rad);

      // Generate the radius scalars
      vtkSmartPointer<vtkDoubleArray> tubeRadius =
        vtkSmartPointer<vtkDoubleArray>::New();
      unsigned int n = functionSource->GetOutput()->GetNumberOfPoints();
      tubeRadius->SetNumberOfTuples(n);
      tubeRadius->SetName("TubeRadius");
      double tMin = interpolatedRadius->GetMinimumT();
      double tMax = interpolatedRadius->GetMaximumT();
      double r;
      for (unsigned int i = 0; i < n; ++i)
      {
        double t = (tMax - tMin) / (n - 1) * i + tMin;
        interpolatedRadius->InterpolateTuple(t, &r);
        tubeRadius->SetTuple1(i, r);
      }

      // Add the scalars to the polydata
      vtkSmartPointer<vtkPolyData> tubePolyData =
        vtkSmartPointer<vtkPolyData>::New();
      tubePolyData = functionSource->GetOutput();
      tubePolyData->GetPointData()->AddArray(tubeRadius);
      tubePolyData->GetPointData()->SetActiveScalars("TubeRadius");

      // Create the tubes
      vtkSmartPointer<vtkTubeFilter> tuber =
        vtkSmartPointer<vtkTubeFilter>::New();
    #if VTK_MAJOR_VERSION <= 5
      tuber->SetInput(tubePolyData);
    #else
      tuber->SetInputData(tubePolyData);
    #endif
      tuber->SetNumberOfSides(20);
      tuber->SetVaryRadiusToVaryRadiusByAbsoluteScalar();

      //--------------
      // Setup actors and mappers
      vtkSmartPointer<vtkPolyDataMapper> lineMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
    #if VTK_MAJOR_VERSION <= 5
      lineMapper->SetInput(tubePolyData);
    #else
      lineMapper->SetInputData(tubePolyData);
    #endif
      lineMapper->SetScalarRange(tubePolyData->GetScalarRange());

      vtkSmartPointer<vtkPolyDataMapper> tubeMapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      tubeMapper->SetInputConnection(tuber->GetOutputPort());
      tubeMapper->SetScalarRange(tubePolyData->GetScalarRange());

      vtkSmartPointer<vtkActor> lineActor = vtkSmartPointer<vtkActor>::New();
      lineActor->SetMapper(lineMapper);
      vtkSmartPointer<vtkActor> tubeActor = vtkSmartPointer<vtkActor>::New();
      tubeActor->SetMapper(tubeMapper);

      // Setup render window, renderer, and interactor
      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);
      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      renderWindowInteractor->SetRenderWindow(renderWindow);
      renderer->AddActor(lineActor);
      renderer->AddActor(tubeActor);
      renderer->SetBackground(.4, .5, .6);
      renderWindow->Render();
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(TubesFromSplines)

    find_package(VTK REQUIRED)
    include(${VTK_USE_FILE})

    add_executable(TubesFromSplines MACOSX_BUNDLE TubesFromSplines.cxx)

    target_link_libraries(TubesFromSplines ${VTK_LIBRARIES})

### Download and Build TubesFromSplines

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

    cd TubesFromSplines/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:

    ./TubesFromSplines

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.