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ClipUnstructuredGridWithPlane

vtk-examples/Cxx/UnstructuredGrid/ClipUnstructuredGridWithPlane

Description

The example uses vtkTableBasedClipDataSet to clip a vtkUnstructuredGrid. The resulting output and clipped output are presented in yellow and red respectively. To illustrate the clipped interfaces, the example uses a vtkTransform to rotate each output about their centers.

Note that unlike other clipping filters (except for vtkClipPolyData), vtkTableBasedClipDataSet retains the original cells if they are not clipped.

After exiting, the example reports the number of each cell type for each output:

The inside dataset contains a
  [vtkUnstructuredGrid](https://www.vtk.org/doc/nightly/html/classvtkUnstructuredGrid.html#details) that has 26116 cells
    Cell type [vtkTetra](https://www.vtk.org/doc/nightly/html/classvtkTetra.html#details) occurs 3751 times.
    Cell type [vtkHexahedron](https://www.vtk.org/doc/nightly/html/classvtkHexahedron.html#details) occurs 17361 times.
    Cell type [vtkWedge](https://www.vtk.org/doc/nightly/html/classvtkWedge.html#details) occurs 628 times.
    Cell type [vtkPyramid](https://www.vtk.org/doc/nightly/html/classvtkPyramid.html#details) occurs 4376 times.
The clipped dataset contains a 
  [vtkUnstructuredGrid](https://www.vtk.org/doc/nightly/html/classvtkUnstructuredGrid.html#details) that has 25655 cells
    Cell type [vtkTetra](https://www.vtk.org/doc/nightly/html/classvtkTetra.html#details) occurs 3715 times.
    Cell type [vtkHexahedron](https://www.vtk.org/doc/nightly/html/classvtkHexahedron.html#details) occurs 16984 times.
    Cell type [vtkWedge](https://www.vtk.org/doc/nightly/html/classvtkWedge.html#details) occurs 616 times.
    Cell type [vtkPyramid](https://www.vtk.org/doc/nightly/html/classvtkPyramid.html#details) occurs 4340 times.

Compare these results with ClipUnstructuredGridWithPlane2 (C++), ClipUnstructuredGridWithPlane2 (Python). Also, the resulting vtkUnstructuredGrid's has 1/4 the number of cells.

usage

ClipUnstructuredGridWithPlane treemesh.vtk

thanks

Thanks to Bane Sullivan for sharing the treemesh.vtk unstructured grid dataset.

Other languages

See (Python)

Question

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

Code

ClipUnstructuredGridWithPlane.cxx

#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkCellTypes.h>
#include <vtkDataSetMapper.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPlane.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkTableBasedClipDataSet.h>
#include <vtkTransform.h>
#include <vtkUnstructuredGrid.h>
#include <vtkUnstructuredGridReader.h>

#include <iostream>
#include <string>

int main(int argc, char* argv[])
{
  if (argc < 2)
  {
    std::cout << "Usage: " << argv[0] << " filename.vtk e.g. treemesh.vtk"
              << std::endl;
    return EXIT_FAILURE;
  }
  // 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();

  double bounds[6];
  reader->GetOutput()->GetBounds(bounds);
  double center[3];
  reader->GetOutput()->GetCenter(center);

  vtkNew<vtkNamedColors> colors;
  vtkNew<vtkRenderer> renderer;
  renderer->SetBackground(colors->GetColor3d("Wheat").GetData());
  renderer->UseHiddenLineRemovalOn();

  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->AddRenderer(renderer);
  renderWindow->SetSize(640, 480);

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

  double xnorm[3] = {-1.0, -1.0, 1.0};

  vtkNew<vtkPlane> clipPlane;
  clipPlane->SetOrigin(reader->GetOutput()->GetCenter());
  clipPlane->SetNormal(xnorm);

  vtkNew<vtkTableBasedClipDataSet> clipper;
  clipper->SetClipFunction(clipPlane);
  clipper->SetInputData(reader->GetOutput());
  clipper->SetValue(0.0);
  clipper->GenerateClippedOutputOn();
  clipper->Update();

  vtkNew<vtkDataSetMapper> insideMapper;
  insideMapper->SetInputData(clipper->GetOutput());
  insideMapper->ScalarVisibilityOff();

  vtkNew<vtkActor> insideActor;
  insideActor->SetMapper(insideMapper);
  insideActor->GetProperty()->SetDiffuseColor(
      colors->GetColor3d("Banana").GetData());
  insideActor->GetProperty()->SetAmbient(.3);
  insideActor->GetProperty()->EdgeVisibilityOn();

  vtkNew<vtkDataSetMapper> clippedMapper;
  clippedMapper->SetInputData(clipper->GetClippedOutput());
  clippedMapper->ScalarVisibilityOff();

  vtkNew<vtkActor> clippedActor;
  clippedActor->SetMapper(clippedMapper);
  clippedActor->GetProperty()->SetDiffuseColor(
      colors->GetColor3d("Tomato").GetData());
  insideActor->GetProperty()->SetAmbient(.3);
  clippedActor->GetProperty()->EdgeVisibilityOn();

  // Create transforms to make a better visualization
  vtkNew<vtkTransform> insideTransform;
  insideTransform->Translate(-(bounds[1] - bounds[0]) * .75, 0, 0);
  insideTransform->Translate(center[0], center[1], center[2]);
  insideTransform->RotateY(-120.0);
  insideTransform->Translate(-center[0], -center[1], -center[2]);
  insideActor->SetUserTransform(insideTransform);

  vtkNew<vtkTransform> clippedTransform;
  clippedTransform->Translate((bounds[1] - bounds[0]) * .75, 0, 0);
  clippedTransform->Translate(center[0], center[1], center[2]);
  clippedTransform->RotateY(60.0);
  clippedTransform->Translate(-center[0], -center[1], -center[2]);
  clippedActor->SetUserTransform(clippedTransform);

  renderer->AddViewProp(clippedActor);
  renderer->AddViewProp(insideActor);

  renderer->ResetCamera();
  renderer->GetActiveCamera()->Dolly(1.4);
  renderer->ResetCameraClippingRange();
  renderWindow->Render();
  renderWindow->SetWindowName("ClipUnstructuredGridWithPlane");
  renderWindow->Render();

  interactor->Start();

  // Generate a report
  vtkIdType numberOfCells = clipper->GetOutput()->GetNumberOfCells();
  std::cout << "------------------------" << std::endl;
  std::cout << "The inside dataset contains a " << std::endl
            << clipper->GetOutput()->GetClassName() << " that has "
            << numberOfCells << " cells" << std::endl;
  typedef std::map<int, int> CellContainer;
  CellContainer cellMap;
  for (vtkIdType i = 0; i < numberOfCells; i++)
  {
    cellMap[clipper->GetOutput()->GetCellType(i)]++;
  }

  for (auto c : cellMap)
  {
    std::cout << "\tCell type " << vtkCellTypes::GetClassNameFromTypeId(c.first)
              << " occurs " << c.second << " times." << std::endl;
  }

  numberOfCells = clipper->GetClippedOutput()->GetNumberOfCells();
  std::cout << "------------------------" << std::endl;
  std::cout << "The clipped dataset contains a " << std::endl
            << clipper->GetClippedOutput()->GetClassName() << " that has "
            << numberOfCells << " cells" << std::endl;
  typedef std::map<int, int> OutsideCellContainer;
  CellContainer outsideCellMap;
  for (vtkIdType i = 0; i < numberOfCells; i++)
  {
    outsideCellMap[clipper->GetClippedOutput()->GetCellType(i)]++;
  }

  for (auto c : outsideCellMap)
  {
    std::cout << "\tCell type " << vtkCellTypes::GetClassNameFromTypeId(c.first)
              << " occurs " << c.second << " times." << std::endl;
  }
  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(ClipUnstructuredGridWithPlane)

find_package(VTK COMPONENTS 
)

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

Download and Build ClipUnstructuredGridWithPlane

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

cd ClipUnstructuredGridWithPlane/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:

./ClipUnstructuredGridWithPlane

WINDOWS USERS

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