TubesWithVaryingRadiusAndColors

VTKEx/Cxx/VisualizationAlgorithms/TubesWithVaryingRadiusAndColors

Description¶

This example shows how to vary the radius of a tube with one scalar and color the tube with another.

Contributed by Marcus Thamson

Note

This original source code for this example is here.

Question

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

Code¶

TubesWithVaryingRadiusAndColors.cxx

#include <math.h>

#include <vtkCellArray.h>
#include <vtkDoubleArray.h>
#include <vtkPointData.h>
#include <vtkPoints.h>
#include <vtkPolyData.h>
#include <vtkUnsignedCharArray.h>

#include <vtkCell.h>
#include <vtkCellData.h>
#include <vtkDataSet.h>
#include <vtkDataSetAttributes.h>
#include <vtkProperty.h>
#include <vtkSmartPointer.h>
#include <vtkTubeFilter.h>

#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkDataSetMapper.h>
#include <vtkInteractorStyleTrackballCamera.h>
#include <vtkPolyDataMapper.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>

#include <vtkMath.h>

int main(int, char*[])
{
  // Spiral tube
  unsigned int nV = 256;       // No. of vertices
  unsigned int nCyc = 5;       // No. of spiral cycles
  double rT1 = 0.1, rT2 = 0.5; // Start/end tube radii
  double rS = 2;               // Spiral radius
  double h = 10;               // Height
  unsigned int nTv = 8;        // No. of surface elements for each tube vertex

  // Create points and cells for the spiral
  auto points =
    vtkSmartPointer<vtkPoints>::New();
  for (unsigned int i = 0; i < nV; i++)
  {
    // Spiral coordinates
    auto vX = rS * cos(2 * vtkMath::Pi() * nCyc * i / (nV - 1));
    auto vY = rS * sin(2 * vtkMath::Pi() * nCyc * i / (nV - 1));
    auto vZ = h * i / nV;
    points->InsertPoint(i, vX, vY, vZ);
  }

  auto lines =
    vtkSmartPointer<vtkCellArray>::New();
  lines->InsertNextCell(nV);
  for (unsigned int i = 0; i < nV; i++)
  {
    lines->InsertCellPoint(i);
  }

  auto polyData =
    vtkSmartPointer<vtkPolyData>::New();
  polyData->SetPoints(points);
  polyData->SetLines(lines);

  // Varying tube radius using sine-function
  auto tubeRadius =
    vtkSmartPointer<vtkDoubleArray>::New();
  tubeRadius->SetName("TubeRadius");
  tubeRadius->SetNumberOfTuples(nV);
  for (unsigned int i = 0; i < nV; i++)
  {
    tubeRadius->SetTuple1(
        i, rT1 + (rT2 - rT1) * sin(vtkMath::Pi() * i / (nV - 1)));
  }
  polyData->GetPointData()->AddArray(tubeRadius);
  polyData->GetPointData()->SetActiveScalars("TubeRadius");

  // RBG array (could add Alpha channel too I guess...)
  // Varying from blue to red
  auto colors =
    vtkSmartPointer<vtkUnsignedCharArray>::New();
  colors->SetName("Colors");
  colors->SetNumberOfComponents(3);
  colors->SetNumberOfTuples(nV);
  for (unsigned int i = 0; i < nV; i++)
  {
    colors->InsertTuple3(i, int(255 * i / (nV - 1)), 0,
                         int(255 * (nV - 1 - i) / (nV - 1)));
  }
  polyData->GetPointData()->AddArray(colors);

  auto tube =
    vtkSmartPointer<vtkTubeFilter>::New();
  tube->SetInputData(polyData);
  tube->SetNumberOfSides(nTv);
  tube->SetVaryRadiusToVaryRadiusByAbsoluteScalar();

  auto mapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  mapper->SetInputConnection(tube->GetOutputPort());
  mapper->ScalarVisibilityOn();
  mapper->SetScalarModeToUsePointFieldData();
  mapper->SelectColorArray("Colors");

  auto actor =
    vtkSmartPointer<vtkActor>::New();
  actor->SetMapper(mapper);

  auto renderer =
    vtkSmartPointer<vtkRenderer>::New();
  renderer->AddActor(actor);
  renderer->SetBackground(.2, .3, .4);

  // Make an oblique view
  renderer->GetActiveCamera()->Azimuth(30);
  renderer->GetActiveCamera()->Elevation(30);
  renderer->ResetCamera();

  auto renWin =
    vtkSmartPointer<vtkRenderWindow>::New();
  auto iren =
    vtkSmartPointer<vtkRenderWindowInteractor>::New();

  iren->SetRenderWindow(renWin);
  renWin->AddRenderer(renderer);
  renWin->SetSize(500, 500);
  renWin->Render();

  auto style =
    vtkSmartPointer<vtkInteractorStyleTrackballCamera>::New();
  iren->SetInteractorStyle(style);

  iren->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(TubesWithVaryingRadiusAndColors)

find_package(VTK COMPONENTS 
  vtkvtkCommonCore
  vtkvtkCommonDataModel
  vtkvtkFiltersCore
  vtkvtkInteractionStyle
  vtkvtkRenderingContextOpenGL2
  vtkvtkRenderingCore
  vtkvtkRenderingFreeType
  vtkvtkRenderingGL2PSOpenGL2
  vtkvtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
  message("Skipping TubesWithVaryingRadiusAndColors: ${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(TubesWithVaryingRadiusAndColors MACOSX_BUNDLE TubesWithVaryingRadiusAndColors.cxx )
  target_link_libraries(TubesWithVaryingRadiusAndColors PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(TubesWithVaryingRadiusAndColors MACOSX_BUNDLE TubesWithVaryingRadiusAndColors.cxx )
  target_link_libraries(TubesWithVaryingRadiusAndColors PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS TubesWithVaryingRadiusAndColors
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build TubesWithVaryingRadiusAndColors¶

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

cd TubesWithVaryingRadiusAndColors/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:

./TubesWithVaryingRadiusAndColors

WINDOWS USERS

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