ReadLegacyUnstructuredGrid

VTKEx/Cxx/IO/ReadLegacyUnstructuredGrid

Description

This example displays a vtkUnstructuredGrid that contains eleven linear cells. We use a number of techniques to visualize the cells.

  1. vtkUnstructuredGridReader reads the file VTKCellTypes.vtk.
  2. vtkExtractEdges extracts the edges of the 2 and 3 dimensional cells. vtkTubeFilter wraps each edge with tubes.
  3. vtkGlyph3DMapper displays each point as a vtkSphere.
  4. vtkShrinkFilter highlights the cell faces by pulling them in towards their centroid.
  5. vtkLabeledDataMapper shows the point ids.
  6. vtkProperty::EdgeVisibilityOn() shows the edges of the cells after shrinking.
  7. vtkCellData colors each cell with a different color.

The example also shows how to add a vtkCategoryLegend to a visualization. The vtkCategoryLegend has a vtkLookupTable that must be Indexed for categorical data. Since the vtkDataSetMapper for the geometry uses the lookup table to color each cell, we use vtkLookupTable::DeepCopy to copy the input vtkLookupTable and apply vtkLookupTable::IndexedLookupOn().

The sample file is taken from the VTKFileFormats document.

Other languages

See (Python)

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

ReadLegacyUnstructuredGrid.cxx

#include <vtkUnstructuredGridReader.h>
#include <vtkUnstructuredGrid.h>

#include <vtkGenericCell.h>

#include <vtkExtractEdges.h>
#include <vtkTubeFilter.h>
#include <vtkPolyDataMapper.h>

#include <vtkGlyph3DMapper.h>
#include <vtkSphereSource.h>
#include <vtkPolyData.h>

#include <vtkTextMapper.h>
#include <vtkShrinkFilter.h>

#include <vtkCategoryLegend.h>
#include <vtkBrush.h>
#include <vtkCellData.h>
#include <vtkColor.h>
#include <vtkContextScene.h>
#include <vtkContextTransform.h>
#include <vtkContextView.h>
#include <vtkLookupTable.h>
#include <vtkScalarsToColors.h>
#include <vtkVariant.h>
#include <vtkVariantArray.h>

#include <vtkActor.h>
#include <vtkActor2D.h>
#include <vtkCamera.h>
#include <vtkDataSetMapper.h>
#include <vtkNamedColors.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>

#include <vtkCellIterator.h>
#include <vtkCellTypes.h>
#include <vtkLabeledDataMapper.h>

int main (int argc, char *argv[])
{
  if (argc < 2)
  {
    std::cout << "Usage: " << argv[0] << " filename.vtk" << std::endl;
    return EXIT_FAILURE;
  }
  vtkSmartPointer<vtkNamedColors> colors =
    vtkSmartPointer<vtkNamedColors>::New();

  // Create the reader for the data.
  std::string filename = argv[1];
  std::cout << "Loading " << filename.c_str() << std::endl;
  vtkSmartPointer<vtkUnstructuredGridReader> reader =
    vtkSmartPointer<vtkUnstructuredGridReader>::New();
  reader->SetFileName(filename.c_str());
  reader->Update();

  vtkSmartPointer<vtkExtractEdges> extractEdges =
    vtkSmartPointer<vtkExtractEdges>::New();
  extractEdges->SetInputConnection(reader->GetOutputPort());

  vtkSmartPointer<vtkVariantArray> legendValues =
    vtkSmartPointer<vtkVariantArray>::New();
  auto it =
    reader->GetOutput()->NewCellIterator();
  for (it->InitTraversal(); !it->IsDoneWithTraversal(); it->GoToNextCell())
  {
    vtkSmartPointer<vtkGenericCell> cell =
      vtkSmartPointer<vtkGenericCell>::New();
    it->GetCell(cell);
    std::string cellName = vtkCellTypes::GetClassNameFromTypeId(cell->GetCellType());
#if 0
    std::cout << cellName
              << " NumberOfPoints: " << cell->GetNumberOfPoints()
              << " CellDimension: " << cell->GetCellDimension()
              << std::endl;
#endif
    legendValues->InsertNextValue(vtkVariant(cellName));
  }
  it->Delete();

  // Tube the edges
  vtkSmartPointer<vtkTubeFilter> tubes =
    vtkSmartPointer<vtkTubeFilter>::New();
  tubes->SetInputConnection(extractEdges->GetOutputPort());
  tubes->SetRadius(.05);
  tubes->SetNumberOfSides(21);

  vtkSmartPointer<vtkPolyDataMapper> edgeMapper =
    vtkSmartPointer<vtkPolyDataMapper>::New();
  edgeMapper->SetInputConnection(tubes->GetOutputPort());
  edgeMapper->SetScalarRange(0, 26);

  vtkSmartPointer<vtkActor> edgeActor =
    vtkSmartPointer<vtkActor>::New();
  edgeActor->SetMapper(edgeMapper);
  edgeActor->GetProperty()->SetSpecular(.6);
  edgeActor->GetProperty()->SetSpecularPower(30);
;

  // Glyph the points
  vtkSmartPointer<vtkSphereSource> sphere =
    vtkSmartPointer<vtkSphereSource>::New();
  sphere->SetPhiResolution(21);
  sphere->SetThetaResolution(21);
  sphere->SetRadius(.08);

  vtkSmartPointer<vtkGlyph3DMapper> pointMapper =
    vtkSmartPointer<vtkGlyph3DMapper>::New();
  pointMapper->SetInputConnection(reader->GetOutputPort());
  pointMapper->SetSourceConnection(sphere->GetOutputPort());
  pointMapper->ScalingOff();
  pointMapper->ScalarVisibilityOff();

  vtkSmartPointer<vtkActor> pointActor =
    vtkSmartPointer<vtkActor>::New();
  pointActor->SetMapper(pointMapper);
  pointActor->GetProperty()->SetDiffuseColor(colors->GetColor3d("Banana").GetData());
  pointActor->GetProperty()->SetSpecular(.6);
  pointActor->GetProperty()->SetSpecularColor(1.0,1.0,1.0);
  pointActor->GetProperty()->SetSpecularPower(100);
;

// Label the points
  vtkSmartPointer<vtkLabeledDataMapper> labelMapper = 
    vtkSmartPointer<vtkLabeledDataMapper>::New();
  labelMapper->SetInputConnection(reader->GetOutputPort());
  vtkSmartPointer<vtkActor2D> labelActor = 
    vtkSmartPointer<vtkActor2D>::New();
  labelActor->SetMapper(labelMapper);

// The geometry
  vtkSmartPointer<vtkShrinkFilter> geometryShrink = 
    vtkSmartPointer<vtkShrinkFilter>::New();
  geometryShrink->SetInputConnection(reader->GetOutputPort());
  geometryShrink->SetShrinkFactor(.8);

// NOTE: We must copy the originalLut because the CategorialLegend
// needs an indexed lookup table, but the geometryMapper uses a
// non-index lookup table
  vtkSmartPointer<vtkLookupTable> categoricalLut =
    vtkSmartPointer<vtkLookupTable>::New();
  vtkSmartPointer<vtkLookupTable> originalLut =
    reader->GetOutput()->GetCellData()->GetScalars()->GetLookupTable();

  categoricalLut->DeepCopy(originalLut);
  categoricalLut->IndexedLookupOn();

  vtkSmartPointer<vtkDataSetMapper> geometryMapper = 
    vtkSmartPointer<vtkDataSetMapper>::New();
  geometryMapper->SetInputConnection(geometryShrink->GetOutputPort());
  geometryMapper->SetScalarModeToUseCellData();
  geometryMapper->SetScalarRange(0,11);

  vtkSmartPointer<vtkActor> geometryActor = 
    vtkSmartPointer<vtkActor>::New();
  geometryActor->SetMapper(geometryMapper);
  geometryActor->GetProperty()->SetLineWidth(3);  
  geometryActor->GetProperty()->EdgeVisibilityOn();
  geometryActor->GetProperty()->SetEdgeColor(0,0,0);

  // Legend
  for (int v = 0; v < legendValues->GetNumberOfTuples(); ++v)
  {
    categoricalLut->SetAnnotation(legendValues->GetValue(v),
                       legendValues->GetValue(v).ToString());
  }
  vtkSmartPointer<vtkCategoryLegend> legend =
    vtkSmartPointer<vtkCategoryLegend>::New();
  legend->SetScalarsToColors(categoricalLut);
  legend->SetValues(legendValues);
  legend->SetTitle("Cell Type");
  legend->GetBrush()->SetColor(colors->GetColor4ub("Silver").GetData());

  vtkSmartPointer<vtkContextTransform> placeLegend =
    vtkSmartPointer<vtkContextTransform>::New();
  placeLegend->AddItem(legend);
  placeLegend->Translate(640 - 20, 480 - 12 * 16);

  vtkSmartPointer<vtkContextView> contextView =
    vtkSmartPointer<vtkContextView>::New();
  contextView->GetScene()->AddItem(placeLegend);

  vtkSmartPointer<vtkRenderer> renderer =
    contextView->GetRenderer();

  vtkSmartPointer<vtkRenderWindow> renderWindow =
    contextView->GetRenderWindow();

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

  renderer->AddActor(geometryActor);
  renderer->AddActor(labelActor);
  renderer->AddActor(edgeActor);
  renderer->AddActor(pointActor);
  renderer->SetBackground(colors->GetColor3d("SlateGray").GetData());

  vtkSmartPointer<vtkCamera> aCamera =
    vtkSmartPointer<vtkCamera>::New();
  aCamera->Azimuth(-40.0);
  aCamera->Elevation(50.0);

  renderer->SetActiveCamera(aCamera);
  renderer->ResetCamera ();

  renderWindow->SetSize(640, 480);
  renderWindow->Render();

  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(ReadLegacyUnstructuredGrid)

find_package(VTK COMPONENTS 
  vtkvtkChartsCore
  vtkvtkCommonColor
  vtkvtkCommonCore
  vtkvtkCommonDataModel
  vtkvtkFiltersCore
  vtkvtkFiltersExtraction
  vtkvtkFiltersGeneral
  vtkvtkFiltersSources
  vtkvtkIOLegacy
  vtkvtkInteractionStyle
  vtkvtkRenderingContext2D
  vtkvtkRenderingContextOpenGL2
  vtkvtkRenderingCore
  vtkvtkRenderingFreeType
  vtkvtkRenderingGL2PSOpenGL2
  vtkvtkRenderingLabel
  vtkvtkRenderingOpenGL2
  vtkvtkViewsContext2D QUIET)
if (NOT VTK_FOUND)
  message("Skipping ReadLegacyUnstructuredGrid: ${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(ReadLegacyUnstructuredGrid MACOSX_BUNDLE ReadLegacyUnstructuredGrid.cxx )
  target_link_libraries(ReadLegacyUnstructuredGrid PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(ReadLegacyUnstructuredGrid MACOSX_BUNDLE ReadLegacyUnstructuredGrid.cxx )
  target_link_libraries(ReadLegacyUnstructuredGrid PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS ReadLegacyUnstructuredGrid
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build ReadLegacyUnstructuredGrid

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

cd ReadLegacyUnstructuredGrid/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:

./ReadLegacyUnstructuredGrid

WINDOWS USERS

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