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TubesFromSplines

vtk-examples/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.

Question

If you have a question about this example, please use the VTK Discourse Forum

Code

TubesFromSplines.cxx

#include <vtkActor.h>
#include <vtkDoubleArray.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkParametricFunctionSource.h>
#include <vtkParametricSpline.h>
#include <vtkPointData.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkTubeFilter.h>
#include <vtkTupleInterpolator.h>

int main(int, char*[])
{
  vtkNew<vtkPoints> points;
  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
  vtkNew<vtkParametricSpline> spline;
  spline->SetPoints(points);
  vtkNew<vtkParametricFunctionSource> functionSource;
  functionSource->SetParametricFunction(spline);
  functionSource->SetUResolution(10 * points->GetNumberOfPoints());
  functionSource->Update();

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

  // Add the scalars to the polydata
  auto tubePolyData = functionSource->GetOutput();
  tubePolyData->GetPointData()->AddArray(tubeRadius);
  tubePolyData->GetPointData()->SetActiveScalars("TubeRadius");

  // Create the tubes
  vtkNew<vtkTubeFilter> tuber;
  tuber->SetInputData(tubePolyData);
  tuber->SetNumberOfSides(20);
  tuber->SetVaryRadiusToVaryRadiusByAbsoluteScalar();

  //--------------
  // Setup actors and mappers
  vtkNew<vtkPolyDataMapper> lineMapper;
  lineMapper->SetInputData(tubePolyData);
  lineMapper->SetScalarRange(tubePolyData->GetScalarRange());

  vtkNew<vtkPolyDataMapper> tubeMapper;
  tubeMapper->SetInputConnection(tuber->GetOutputPort());
  tubeMapper->SetScalarRange(tubePolyData->GetScalarRange());

  vtkNew<vtkActor> lineActor;
  lineActor->SetMapper(lineMapper);
  lineActor->GetProperty()->SetLineWidth(3);
  vtkNew<vtkActor> tubeActor;
  tubeActor->SetMapper(tubeMapper);
  tubeActor->GetProperty()->SetOpacity(0.6);

  // Setup render window, renderer, and interactor
  vtkNew<vtkNamedColors> colors;
  vtkNew<vtkRenderer> renderer;
  renderer->UseHiddenLineRemovalOn();
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->AddRenderer(renderer);
  renderWindow->SetSize(640, 480);
  renderWindow->SetWindowName("TubesFromSplines");

  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
  renderWindowInteractor->SetRenderWindow(renderWindow);
  renderer->AddActor(lineActor);
  renderer->AddActor(tubeActor);
  renderer->SetBackground(colors->GetColor3d("SlateGray").GetData());

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

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(TubesFromSplines)

find_package(VTK COMPONENTS 
  CommonColor
  CommonComputationalGeometry
  CommonCore
  CommonDataModel
  FiltersCore
  FiltersSources
  InteractionStyle
  RenderingContextOpenGL2
  RenderingCore
  RenderingFreeType
  RenderingGL2PSOpenGL2
  RenderingOpenGL2
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "TubesFromSplines: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(TubesFromSplines MACOSX_BUNDLE TubesFromSplines.cxx )
  target_link_libraries(TubesFromSplines PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS TubesFromSplines
  MODULES ${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

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