# 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.

Other Languages

See (Java)

Question

If you have a simple question about this example contact us at VTKExamplesProject If your question is more complex and may require extended discussion, please use the VTK Discourse Forum

### 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 3.3 FATAL_ERROR)

project(KochanekSpline)

find_package(VTK COMPONENTS
vtkCommonColor
vtkCommonComputationalGeometry
vtkCommonCore
vtkCommonDataModel
vtkFiltersSources
vtkInteractionStyle
vtkRenderingCore
vtkRenderingFreeType
vtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
message("Skipping KochanekSpline: ${VTK_NOT_FOUND_MESSAGE}") return () endif() message (STATUS "VTK_VERSION:${VTK_VERSION}")
if (VTK_VERSION VERSION_LESS "8.90.0")
# old system
include(${VTK_USE_FILE}) add_executable(KochanekSpline MACOSX_BUNDLE KochanekSpline.cxx ) target_link_libraries(KochanekSpline PRIVATE${VTK_LIBRARIES})
else ()
# include all components
add_executable(KochanekSpline MACOSX_BUNDLE KochanekSpline.cxx )
target_link_libraries(KochanekSpline PRIVATE ${VTK_LIBRARIES}) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS KochanekSpline MODULES${VTK_LIBRARIES}
)
endif ()


### 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

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