Skip to content

ClipUnstructuredGridWithPlane2

vtk-examples/Cxx/UnstructuredGrid/ClipUnstructuredGridWithPlane2

Description

The example uses vtkClipDataSet 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 this clipping filter does not retain 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 that has 110084 cells
    Cell type vtkTetra occurs 106934 times.
    Cell type vtkWedge occurs 3150 times.
------------------------
The clipped dataset contains a 
vtkUnstructuredGrid that has 111733 cells
    Cell type vtkTetra occurs 107401 times.
    Cell type vtkWedge occurs 4332 times.

Compare these results with ClipUnstructuredGridWithPlane. Notice that in this example, the original vtkHexahedron in the unclipped regions are converted to vtkTetra. Also, the resulting vtkUnstructuredGrid's have more than 4 times the number of cells.

usage

ClipUnstructuredGridWithPlane2 treemesh.vtk

thanks

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

Other languages

See (Python), (PythonicAPI)

Question

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

Code

ClipUnstructuredGridWithPlane2.cxx

#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkCellTypes.h>
#include <vtkClipDataSet.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 <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;
  }

  // If false, output using the original code.
  auto correctOutput = true;

  // 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<vtkClipDataSet> clipper;
  vtkNew<vtkClipDataSet> clipper1;

  if (correctOutput)
  {
    clipper->SetClipFunction(clipPlane);
    clipper->SetInputData(reader->GetOutput());
    clipper->SetValue(0.0);
    clipper->GenerateClippedOutputOn();
    clipper->Update();

    // Set inside out, generate the clipped output and
    //  use the clipped output for the clipped mapper.
    // If this is done a similar image to
    //  ClipUnstructuredGridWithPlane is created.
    clipper1->SetClipFunction(clipPlane);
    clipper1->SetInputData(reader->GetOutput());
    clipper1->SetValue(0.0);
    clipper1->InsideOutOn();
    clipper1->GenerateClippedOutputOn();
    clipper1->Update();
  }
  else
  {
    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(0.3);
  insideActor->GetProperty()->EdgeVisibilityOn();

  vtkNew<vtkDataSetMapper> clippedMapper;
  if (correctOutput)
  {
    clippedMapper->SetInputData(clipper1->GetClippedOutput());
  }
  else
  {
    clippedMapper->SetInputData(clipper->GetClippedOutput());
  }
  clippedMapper->ScalarVisibilityOff();

  vtkNew<vtkActor> clippedActor;
  clippedActor->SetMapper(clippedMapper);
  clippedActor->GetProperty()->SetDiffuseColor(
      colors->GetColor3d("Tomato").GetData());
  insideActor->GetProperty()->SetAmbient(0.3);
  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]);
  if (correctOutput)
  {
    clippedTransform->RotateY(60.0);
  }
  else
  {
    clippedTransform->RotateY(-120.0);
  }
  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("ClipUnstructuredGridWithPlane2");
  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;
  }

  std::cout << "------------------------" << std::endl;
  CellContainer outsideCellMap;
  if (correctOutput)
  {
    numberOfCells = clipper1->GetClippedOutput()->GetNumberOfCells();
    std::cout << "The clipped dataset contains a " << std::endl
              << clipper1->GetClippedOutput()->GetClassName() << " that has "
              << numberOfCells << " cells" << std::endl;
    for (vtkIdType i = 0; i < numberOfCells; i++)
    {
      outsideCellMap[clipper1->GetClippedOutput()->GetCellType(i)]++;
    }
  }
  else
  {
    numberOfCells = clipper->GetClippedOutput()->GetNumberOfCells();
    std::cout << "The clipped dataset contains a " << std::endl
              << clipper->GetClippedOutput()->GetClassName() << " that has "
              << numberOfCells << " cells" << std::endl;
    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(ClipUnstructuredGridWithPlane2)

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

if (NOT VTK_FOUND)
  message(FATAL_ERROR "ClipUnstructuredGridWithPlane2: 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(ClipUnstructuredGridWithPlane2 MACOSX_BUNDLE ClipUnstructuredGridWithPlane2.cxx )
  target_link_libraries(ClipUnstructuredGridWithPlane2 PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS ClipUnstructuredGridWithPlane2
  MODULES ${VTK_LIBRARIES}
)

Download and Build ClipUnstructuredGridWithPlane2

Click here to download ClipUnstructuredGridWithPlane2 and its CMakeLists.txt file. Once the tarball ClipUnstructuredGridWithPlane2.tar has been downloaded and extracted,

cd ClipUnstructuredGridWithPlane2/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:

./ClipUnstructuredGridWithPlane2

WINDOWS USERS

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