CellTypeSource

Description¶

This example uses vtkCellTypeSource to generate a vtkUnstructuredGrid. If a cell does not fill a rectangular area or volume, then multiple cells will be generated. For example, a vtkTetra requires 12 cells to fill a cube. A vtkTriangle requires two cells to fill a square. vtkCellTypeSource generates a uniform set of coordinates. The example perturbs those coordinates to illustrate the results of the vtkTessellatorFilter. Also, each cell is passed through vtkShrinkFilter to help identify the cells. Each generated cell also has a unique color.

The example takes an optional argument, a vtkCell name.

For example, to generate vtkTriangles, run

CellTypeSource [vtkTriangle](https://www.vtk.org/doc/nightly/html/classvtkTriangle.html)

Other languages

See (Python), (PythonicAPI)

Question

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

Code¶

CellTypeSource.cxx

#include <vtkActor.h>
#include <vtkActor2D.h>
#include <vtkCamera.h>
#include <vtkCellData.h>
#include <vtkCellTypeSource.h>
#include <vtkCellTypes.h>
#include <vtkColorSeries.h>
#include <vtkDataSetMapper.h>
#include <vtkIntArray.h>
#include <vtkLookupTable.h>
#include <vtkMinimalStandardRandomSequence.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkShrinkFilter.h>
#include <vtkTessellatorFilter.h>
#include <vtkTextMapper.h>
#include <vtkTextProperty.h>
#include <vtkUnstructuredGrid.h>

#include <map>

int main(int argc, char* argv[])
{
  std::string cellName = "vtkTetra";
  if (argc > 1)
  {
    cellName = std::string(argv[1]);
  }

  // Store cell class names in a map
  std::map<std::string, int> cellMap;
  cellMap[vtkCellTypes::GetClassNameFromTypeId(VTK_LINE)] = VTK_LINE;
  cellMap[vtkCellTypes::GetClassNameFromTypeId(VTK_QUADRATIC_EDGE)] =
      VTK_QUADRATIC_EDGE;
  cellMap[vtkCellTypes::GetClassNameFromTypeId(VTK_CUBIC_LINE)] =
      VTK_CUBIC_LINE;

  cellMap[vtkCellTypes::GetClassNameFromTypeId(VTK_TRIANGLE)] = VTK_TRIANGLE;
  cellMap[vtkCellTypes::GetClassNameFromTypeId(VTK_QUADRATIC_TRIANGLE)] =
      VTK_QUADRATIC_TRIANGLE;
  cellMap[vtkCellTypes::GetClassNameFromTypeId(VTK_QUAD)] = VTK_QUAD;
  cellMap[vtkCellTypes::GetClassNameFromTypeId(VTK_QUADRATIC_QUAD)] =
      VTK_QUADRATIC_QUAD;

  cellMap[vtkCellTypes::GetClassNameFromTypeId(VTK_TETRA)] = VTK_TETRA;
  cellMap[vtkCellTypes::GetClassNameFromTypeId(VTK_HEXAHEDRON)] =
      VTK_HEXAHEDRON;
  cellMap[vtkCellTypes::GetClassNameFromTypeId(VTK_WEDGE)] = VTK_WEDGE;
  cellMap[vtkCellTypes::GetClassNameFromTypeId(VTK_PYRAMID)] = VTK_PYRAMID;
  cellMap[vtkCellTypes::GetClassNameFromTypeId(VTK_QUADRATIC_WEDGE)] =
      VTK_QUADRATIC_WEDGE;
  cellMap[vtkCellTypes::GetClassNameFromTypeId(VTK_QUADRATIC_PYRAMID)] =
      VTK_QUADRATIC_PYRAMID;
  cellMap[vtkCellTypes::GetClassNameFromTypeId(VTK_QUADRATIC_HEXAHEDRON)] =
      VTK_QUADRATIC_HEXAHEDRON;
  cellMap[vtkCellTypes::GetClassNameFromTypeId(VTK_QUADRATIC_TETRA)] =
      VTK_QUADRATIC_TETRA;

  if (cellMap.find(std::string(cellName)) == cellMap.end())
  {
    std::cout << "Cell type " << cellName << " is not supported." << std::endl;
    return EXIT_FAILURE;
  }
  vtkNew<vtkCellTypeSource> source;
  source->SetCellType(cellMap[cellName]);
  source->Update();
  std::cout << "Cell: " << cellName << std::endl;

  vtkPoints* originalPoints = source->GetOutput()->GetPoints();
  vtkNew<vtkPoints> points;
  points->SetNumberOfPoints(source->GetOutput()->GetNumberOfPoints());
  vtkNew<vtkMinimalStandardRandomSequence> rng;
  rng->SetSeed(5070); // for testing
  for (auto i = 0; i < points->GetNumberOfPoints(); ++i)
  {
    double perturbation[3];
    for (auto j = 0; j < 3; ++j)
    {
      rng->Next();
      perturbation[j] = rng->GetRangeValue(-0.1, 0.1);
    }
    double currentPoint[3];
    originalPoints->GetPoint(i, currentPoint);
    points->SetPoint(i, currentPoint[0] + perturbation[0],
                     currentPoint[1] + perturbation[1],
                     currentPoint[2] + perturbation[2]);
  }
  source->GetOutput()->SetPoints(points);

  int numCells = source->GetOutput()->GetNumberOfCells();
  std::cout << "Number of cells: " << numCells << std::endl;
  vtkNew<vtkIntArray> idArray;
  idArray->SetNumberOfTuples(numCells);
  for (auto i = 0; i < numCells; ++i)
  {
    idArray->InsertTuple1(i, i + 1);
  }
  idArray->SetName("Ids");
  source->GetOutput()->GetCellData()->AddArray(idArray);
  source->GetOutput()->GetCellData()->SetActiveScalars("Ids");

  vtkNew<vtkShrinkFilter> shrink;
  shrink->SetInputConnection(source->GetOutputPort());
  shrink->SetShrinkFactor(.8);

  vtkNew<vtkTessellatorFilter> tessellate;
  tessellate->SetInputConnection(shrink->GetOutputPort());
  tessellate->SetMaximumNumberOfSubdivisions(3);

  // Create a lookup table to map cell data to colors
  vtkNew<vtkLookupTable> lut;

  vtkNew<vtkColorSeries> colorSeries;
  int seriesEnum = colorSeries->BREWER_QUALITATIVE_SET3;
  ;
  colorSeries->SetColorScheme(seriesEnum);
  colorSeries->BuildLookupTable(lut, colorSeries->ORDINAL);

  // Fill in a few known colors, the rest will be generated if needed
  vtkNew<vtkNamedColors> colors;

  // Create a mapper and actor
  vtkNew<vtkDataSetMapper> mapper;
  mapper->SetInputConnection(source->GetOutputPort());
  mapper->SetInputConnection(shrink->GetOutputPort());
  mapper->SetScalarRange(0, numCells + 1);
  mapper->SetLookupTable(lut);
  mapper->SetScalarModeToUseCellData();
  mapper->SetResolveCoincidentTopologyToPolygonOffset();
  if (source->GetCellType() == VTK_QUADRATIC_PYRAMID ||
      source->GetCellType() == VTK_QUADRATIC_WEDGE)
  {
    mapper->SetInputConnection(shrink->GetOutputPort());
  }
  else
  {
    mapper->SetInputConnection(tessellate->GetOutputPort());
  }
  vtkNew<vtkActor> actor;
  actor->SetMapper(mapper);
  actor->GetProperty()->EdgeVisibilityOn();
  //  actor->GetProperty()->SetLineWidth(3);

  vtkNew<vtkTextProperty> textProperty;
  textProperty->SetFontSize(20);
  textProperty->SetJustificationToCentered();
  textProperty->SetColor(colors->GetColor3d("Lamp_Black").GetData());

  vtkNew<vtkTextMapper> textMapper;
  textMapper->SetInput(cellName.c_str());
  textMapper->SetTextProperty(textProperty);

  vtkNew<vtkActor2D> textActor;
  textActor->SetMapper(textMapper);
  textActor->SetPosition(320, 20);

  // Create a renderer, render window, and interactor
  vtkNew<vtkRenderer> renderer;
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->SetWindowName("CellTypeSource");
  renderWindow->AddRenderer(renderer);
  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
  renderWindowInteractor->SetRenderWindow(renderWindow);

  // Add the actors to the scene
  renderer->AddViewProp(textActor);
  renderer->AddActor(actor);
  renderer->SetBackground(colors->GetColor3d("Silver").GetData());

  renderer->ResetCamera();
  renderer->GetActiveCamera()->Azimuth(30);
  renderer->GetActiveCamera()->Elevation(30);
  renderer->ResetCameraClippingRange();

  // Render and interact
  renderWindow->SetSize(640, 480);
  renderWindow->Render();
  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(CellTypeSource)

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

if (NOT VTK_FOUND)
  message(FATAL_ERROR "CellTypeSource: 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(CellTypeSource MACOSX_BUNDLE CellTypeSource.cxx )
  target_link_libraries(CellTypeSource PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS CellTypeSource
  MODULES ${VTK_LIBRARIES}
)

Download and Build CellTypeSource¶

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

cd CellTypeSource/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:

./CellTypeSource

WINDOWS USERS

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