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KochanekSpline

vtk-examples/Cxx/PolyData/KochanekSpline


Description

The vtkKochanekSpline provides three parameters 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 question about this example, please use the VTK Discourse Forum

Code

KochanekSpline.cxx

#include <vtkActor.h>
#include <vtkGlyph3DMapper.h>
#include <vtkKochanekSpline.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkParametricFunctionSource.h>
#include <vtkParametricSpline.h>
#include <vtkPointSource.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSphereSource.h>

int main(int, char*[])
{
  vtkNew<vtkNamedColors> colors;

  int numberOfPoints = 10;
  vtkNew<vtkPointSource> pointSource;
  pointSource->SetNumberOfPoints(numberOfPoints);
  pointSource->Update();

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

  vtkNew<vtkKochanekSpline> xSpline;
  vtkNew<vtkKochanekSpline> ySpline;
  vtkNew<vtkKochanekSpline> zSpline;

  vtkNew<vtkParametricSpline> spline;
  spline->SetXSpline(xSpline);
  spline->SetYSpline(ySpline);
  spline->SetZSpline(zSpline);
  spline->SetPoints(points);

  vtkNew<vtkParametricFunctionSource> functionSource;
  functionSource->SetParametricFunction(spline);
  functionSource->SetUResolution(50 * numberOfPoints);
  functionSource->SetVResolution(50 * numberOfPoints);
  functionSource->SetWResolution(50 * numberOfPoints);
  functionSource->Update();

  // Setup actor and mapper
  vtkNew<vtkPolyDataMapper> mapper;
  mapper->SetInputConnection(functionSource->GetOutputPort());

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

  // Glyph the points
  vtkNew<vtkSphereSource> sphere;
  sphere->SetPhiResolution(21);
  sphere->SetThetaResolution(21);
  sphere->SetRadius(.02);

  // Create a polydata to store everything in
  vtkNew<vtkPolyData> polyData;
  polyData->SetPoints(points);

  vtkNew<vtkGlyph3DMapper> pointMapper;
  pointMapper->SetInputData(polyData);
  pointMapper->SetSourceConnection(sphere->GetOutputPort());

  vtkNew<vtkActor> pointActor;
  pointActor->SetMapper(pointMapper);
  pointActor->GetProperty()->SetColor(colors->GetColor3d("Peacock").GetData());

  // Setup render window, renderer, and interactor
  vtkNew<vtkRenderer> renderer;
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->AddRenderer(renderer);
  renderWindow->SetWindowName("KochanekSpline");

  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
  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
  vtkRenderingContextOpenGL2
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingGL2PSOpenGL2
  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.