# KochanekSpline

VTKExamples/Cxx/PolyData/KochanekSpline

### Description

The vtkKochanekSpline provides three parametes to control the shape of the spline:

1. tension - Changes the length of the tangent vector
2. bias - Primarily changes the direction of the tangent vector
3. continuity - Changes the sharpness in change between tangents

Seealso

KochanekSplineDemo provides sliders to change the three parameters.

Seealso

This wikipedia article describes the controlsin detail.

### Code

KochanekSpline.cxx

    #include <vtkSmartPointer.h>
    #include <vtkKochanekSpline.h>
    #include <vtkParametricSpline.h>
    #include <vtkParametricFunctionSource.h>

    #include <vtkPointSource.h>
    #include <vtkPoints.h>
    #include <vtkPolyData.h>
    #include <vtkPolyDataMapper.h>
    #include <vtkProperty.h>
    #include <vtkActor.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindowInteractor.h>

    #include <vtkGlyph3DMapper.h>
    #include <vtkSphereSource.h>
    #include <vtkNamedColors.h>

    int main(int, char *[])
    {
      vtkSmartPointer<vtkNamedColors> colors =
        vtkSmartPointer<vtkNamedColors>::New();

      int numberOfPoints = 10;
      vtkSmartPointer<vtkPointSource> pointSource =
        vtkSmartPointer<vtkPointSource>::New();
      pointSource->SetNumberOfPoints(numberOfPoints);
      pointSource->Update();

      vtkPoints* points = pointSource->GetOutput()->GetPoints();

      vtkSmartPointer<vtkKochanekSpline> xSpline =
        vtkSmartPointer<vtkKochanekSpline>::New();
      vtkSmartPointer<vtkKochanekSpline> ySpline =
        vtkSmartPointer<vtkKochanekSpline>::New();
      vtkSmartPointer<vtkKochanekSpline> zSpline =
        vtkSmartPointer<vtkKochanekSpline>::New();

      vtkSmartPointer<vtkParametricSpline> spline =
        vtkSmartPointer<vtkParametricSpline>::New();
      spline->SetXSpline(xSpline);
      spline->SetYSpline(ySpline);
      spline->SetZSpline(zSpline);
      spline->SetPoints(points);

      vtkSmartPointer<vtkParametricFunctionSource> functionSource =
          vtkSmartPointer<vtkParametricFunctionSource>::New();
      functionSource->SetParametricFunction(spline);
      functionSource->SetUResolution(50 * numberOfPoints);
      functionSource->SetVResolution(50 * numberOfPoints);
      functionSource->SetWResolution(50 * numberOfPoints);
      functionSource->Update();

      // Setup actor and mapper
      vtkSmartPointer<vtkPolyDataMapper> mapper =
        vtkSmartPointer<vtkPolyDataMapper>::New();
      mapper->SetInputConnection(functionSource->GetOutputPort());

      vtkSmartPointer<vtkActor> actor =
        vtkSmartPointer<vtkActor>::New();
      actor->SetMapper(mapper);
      actor->GetProperty()->SetColor(colors->GetColor3d("DarkSlateGrey").GetData());
      actor->GetProperty()->SetLineWidth(3.0);

      // Glyph the points
      vtkSmartPointer<vtkSphereSource> sphere =
        vtkSmartPointer<vtkSphereSource>::New();
      sphere->SetPhiResolution(21);
      sphere->SetThetaResolution(21);
      sphere->SetRadius(.02);

      // Create a polydata to store everything in
      vtkSmartPointer<vtkPolyData> polyData =
        vtkSmartPointer<vtkPolyData>::New();
      polyData->SetPoints(points);

      vtkSmartPointer<vtkGlyph3DMapper> pointMapper =
        vtkSmartPointer<vtkGlyph3DMapper>::New();
      pointMapper->SetInputData(polyData);
      pointMapper->SetSourceConnection(sphere->GetOutputPort());

      vtkSmartPointer<vtkActor> pointActor =
        vtkSmartPointer<vtkActor>::New();
      pointActor->SetMapper(pointMapper);
      pointActor->GetProperty()->SetColor(colors->GetColor3d("Peacock").GetData());

      // 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(actor);
      renderer->AddActor(pointActor);;
      renderer->SetBackground(colors->GetColor3d("Silver").GetData());

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

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(KochanekSpline)

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

    add_executable(KochanekSpline MACOSX_BUNDLE KochanekSpline.cxx )

    target_link_libraries(KochanekSpline ${VTK_LIBRARIES})

### Download and Build KochanekSpline

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

    cd KochanekSpline/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:

    ./KochanekSpline

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.