# 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

### 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);

// 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();
vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
vtkSmartPointer<vtkRenderWindowInteractor>::New();
renderWindowInteractor->SetRenderWindow(renderWindow);

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
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
target_link_libraries(KochanekSpline PRIVATE ${VTK_LIBRARIES}) # vtk_module_autoinit is needed vtk_module_autoinit( TARGETS KochanekSpline MODULES${VTK_LIBRARIES}
)
endif ()


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.