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ReadLegacyUnstructuredGrid

vtk-examples/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. [vtkUnstructuredGrid](https://www.vtk.org/doc/nightly/html/classvtkUnstructuredGrid.html#details)Reader reads the file src/Testing/Data/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 question about this example, please use the VTK Discourse Forum

Code

ReadLegacyUnstructuredGrid.cxx

#include <vtkBrush.h>
#include <vtkCategoryLegend.h>
#include <vtkCellData.h>
#include <vtkCellIterator.h>
#include <vtkCellTypes.h>
#include <vtkContextScene.h>
#include <vtkContextTransform.h>
#include <vtkContextView.h>
#include <vtkExtractEdges.h>
#include <vtkGenericCell.h>
#include <vtkGlyph3DMapper.h>
#include <vtkLabeledDataMapper.h>
#include <vtkLookupTable.h>
#include <vtkPolyDataMapper.h>
#include <vtkShrinkFilter.h>
#include <vtkSphereSource.h>
#include <vtkTubeFilter.h>
#include <vtkUnstructuredGrid.h>
#include <vtkUnstructuredGridReader.h>
#include <vtkVariantArray.h>

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

// Note that:
// vtkExtractEdges moved from vtkFiltersExtraction to vtkFiltersCore in
// VTK commit d9981b9aeb93b42d1371c6e295d76bfdc18430bd

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

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

  vtkNew<vtkExtractEdges> extractEdges;
  extractEdges->SetInputConnection(reader->GetOutputPort());

  vtkNew<vtkVariantArray> legendValues;
  auto it = reader->GetOutput()->NewCellIterator();
  for (it->InitTraversal(); !it->IsDoneWithTraversal(); it->GoToNextCell())
  {
    vtkNew<vtkGenericCell> cell;
    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
  vtkNew<vtkTubeFilter> tubes;
  tubes->SetInputConnection(extractEdges->GetOutputPort());
  tubes->SetRadius(.05);
  tubes->SetNumberOfSides(21);

  vtkNew<vtkPolyDataMapper> edgeMapper;
  edgeMapper->SetInputConnection(tubes->GetOutputPort());
  edgeMapper->SetScalarRange(0, 26);

  vtkNew<vtkActor> edgeActor;
  edgeActor->SetMapper(edgeMapper);
  edgeActor->GetProperty()->SetSpecular(0.6);
  edgeActor->GetProperty()->SetSpecularPower(30);
  ;

  // Glyph the points.
  vtkNew<vtkSphereSource> sphere;
  sphere->SetPhiResolution(21);
  sphere->SetThetaResolution(21);
  sphere->SetRadius(0.08);

  vtkNew<vtkGlyph3DMapper> pointMapper;
  pointMapper->SetInputConnection(reader->GetOutputPort());
  pointMapper->SetSourceConnection(sphere->GetOutputPort());
  pointMapper->ScalingOff();
  pointMapper->ScalarVisibilityOff();

  vtkNew<vtkActor> pointActor;
  pointActor->SetMapper(pointMapper);
  pointActor->GetProperty()->SetDiffuseColor(
      colors->GetColor3d("Banana").GetData());
  pointActor->GetProperty()->SetSpecular(0.6);
  pointActor->GetProperty()->SetSpecularColor(1.0, 1.0, 1.0);
  pointActor->GetProperty()->SetSpecularPower(100);
  ;

  // Label the points.
  vtkNew<vtkLabeledDataMapper> labelMapper;
  labelMapper->SetInputConnection(reader->GetOutputPort());
  vtkNew<vtkActor2D> labelActor;
  labelActor->SetMapper(labelMapper);

  // The geometry.
  vtkNew<vtkShrinkFilter> geometryShrink;
  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.
  vtkNew<vtkLookupTable> categoricalLut;
  vtkSmartPointer<vtkLookupTable> originalLut =
      reader->GetOutput()->GetCellData()->GetScalars()->GetLookupTable();

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

  vtkNew<vtkDataSetMapper> geometryMapper;
  geometryMapper->SetInputConnection(geometryShrink->GetOutputPort());
  geometryMapper->SetScalarModeToUseCellData();
  geometryMapper->SetScalarRange(0, 11);

  vtkNew<vtkActor> geometryActor;
  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());
  }
  vtkNew<vtkCategoryLegend> legend;
  legend->SetScalarsToColors(categoricalLut);
  legend->SetValues(legendValues);
  legend->SetTitle("Cell Type");
  legend->GetBrush()->SetColor(colors->GetColor4ub("Silver").GetData());

  vtkNew<vtkContextTransform> placeLegend;
  placeLegend->AddItem(legend);
  placeLegend->Translate(640 - 20, 480 - 12 * 16);

  vtkNew<vtkContextView> contextView;
  contextView->GetScene()->AddItem(placeLegend);

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

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

  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
  renderWindowInteractor->SetRenderWindow(renderWindow);

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

  vtkNew<vtkCamera> aCamera;
  aCamera->Azimuth(-40.0);
  aCamera->Elevation(50.0);

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

  renderWindow->SetSize(640, 480);
  renderWindow->SetWindowName("ReadLegacyUnstructuredGrid");
  renderWindow->Render();

  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(ReadLegacyUnstructuredGrid)

find_package(VTK COMPONENTS 
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "ReadLegacyUnstructuredGrid: 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(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}
)

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.