CellsInsideObject

VTKExamples/Cxx/PolyData/CellsInsideObject

Description¶

This example illustrates how to extract the cells that exist inside a closed surface. It uses vtkSelectEnclosedPoints to mark points that are inside and outside the surface. vtkMultiThreshold is used to extract the three meshes into three vtkMultiBlockDataSet's. The cells completely outside are shown in crimson, completely inside are yellow and border cells are green. A translucent copy of the closed surface helps illustrate the selection process.

If two polydata datasets are provided, the example uses the second as the closed surface. If only one dataset is provided, the closed surface is generated by rotating the first dataset by 90 degrees around its Y axis.

Info

The example is run with the cow.g data.

Warning

The surface that contains cells must be closed and manifold. The example does not check for this. Run ClosedSurface (C++) or (Python) to check your surface.

Other Languages

See (Python)

Code¶

CellsInsideObject.cxx

#include <string>
#include <vector>
#include <iostream>

#include <vtkSmartPointer.h>
#include <vtkSelectEnclosedPoints.h>
#include <vtkMultiThreshold.h>
#include <vtkMultiBlockDataSet.h>
#include <vtkUnstructuredGrid.h>
#include <vtkTransformPolyDataFilter.h>
#include <vtkTransform.h>

#include <vtkBYUReader.h>
#include <vtkOBJReader.h>
#include <vtkPLYReader.h>
#include <vtkPolyDataReader.h>
#include <vtkSTLReader.h>
#include <vtkXMLPolyDataReader.h>
#include <vtkSphereSource.h>

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

#include <vtkNamedColors.h>
#include <vtksys/SystemTools.hxx>

namespace
{
vtkSmartPointer<vtkPolyData> ReadPolyData(const char *fileName);
}

int main (int argc, char *argv[])
{
  // Read the polyData's
  auto polyData1 =
    ReadPolyData(argc > 1 ? argv[1] : "");;
  auto polyData =
    ReadPolyData(argc > 2 ? argv[2] : "");;

  auto polyData2 = vtkSmartPointer<vtkPolyData>::New();
  auto transform = vtkSmartPointer<vtkTransform>::New();
  auto transformPD = vtkSmartPointer<vtkTransformPolyDataFilter>::New();
  // If only one polydata is present, generate a second polydata by
  // rotating the orginal about its center.
  if (argc < 3)
  {
    std::cout << "Generating modified polyData1" << std::endl;
    double center[3];
    polyData1->GetCenter(center);
    transform->Translate(center[0], center[1], center[2]);
    transform->RotateY(90.0);
    transform->Translate(-center[0], -center[1], -center[2]);
    transformPD->SetTransform(transform);
    transformPD->SetInputData(polyData1);
    transformPD->Update();
    polyData2 = transformPD->GetOutput();
  }
  else
  {
    polyData2 = polyData;
  }
  // Mark points inside with 1 and outside with a 0
  auto select =
    vtkSmartPointer<vtkSelectEnclosedPoints>::New();
  select->SetInputData(polyData1);
  select->SetSurfaceData(polyData2);

  // Extract three meshes, one completely inside, one completely
  // outside and on the border between the inside and outside.

  auto threshold =
    vtkSmartPointer<vtkMultiThreshold>::New();
  // Outside points have a 0 value in ALL points of a cell
  int outsideId = threshold->AddBandpassIntervalSet(
    0, 0,
    vtkDataObject::FIELD_ASSOCIATION_POINTS, "SelectedPoints",
    0, 1);
  // Inside points have a 1 value in ALL points of a cell
  int insideId = threshold->AddBandpassIntervalSet(
    1, 1,
    vtkDataObject::FIELD_ASSOCIATION_POINTS, "SelectedPoints",
    0, 1);
  // Border points have a 0 or a 1 in at least one point of a cell
  int borderId = threshold->AddIntervalSet(
    0, 1,
    vtkMultiThreshold::OPEN, vtkMultiThreshold::OPEN,
    vtkDataObject::FIELD_ASSOCIATION_POINTS, "SelectedPoints",
    0, 0);

  threshold->SetInputConnection(select->GetOutputPort());

  // Select the intervals to be output
  threshold->OutputSet(outsideId);
  threshold->OutputSet(insideId);
  threshold->OutputSet(borderId);
  threshold->Update();

  // Visualize
  auto colors =
    vtkSmartPointer<vtkNamedColors>::New();
  vtkColor3d outsideColor    = colors->GetColor3d("Crimson");
  vtkColor3d insideColor     = colors->GetColor3d("Banana");
  vtkColor3d borderColor     = colors->GetColor3d("Mint");
  vtkColor3d surfaceColor    = colors->GetColor3d("Peacock");
  vtkColor3d backgroundColor = colors->GetColor3d("Silver");

  // Outside
  auto outsideMapper =
    vtkSmartPointer<vtkDataSetMapper>::New();
  outsideMapper->SetInputData(
    dynamic_cast<vtkUnstructuredGrid*>(vtkMultiBlockDataSet::SafeDownCast(threshold->GetOutput()->GetBlock(outsideId))->GetBlock(0)));
  outsideMapper->ScalarVisibilityOff();

  auto outsideActor =
    vtkSmartPointer<vtkActor>::New();
  outsideActor->SetMapper(outsideMapper);
  outsideActor->GetProperty()->SetDiffuseColor(outsideColor.GetData());
  outsideActor->GetProperty()->SetSpecular(.6);
  outsideActor->GetProperty()->SetSpecularPower(30);

  // Inside
  auto insideMapper =
    vtkSmartPointer<vtkDataSetMapper>::New();
  insideMapper->SetInputData(
    dynamic_cast<vtkUnstructuredGrid*>(vtkMultiBlockDataSet::SafeDownCast(threshold->GetOutput()->GetBlock(insideId))->GetBlock(0)));
  insideMapper->ScalarVisibilityOff();

  auto insideActor =
    vtkSmartPointer<vtkActor>::New();
  insideActor->SetMapper(insideMapper);
  insideActor->GetProperty()->SetDiffuseColor(insideColor.GetData());
  insideActor->GetProperty()->SetSpecular(.6);
  insideActor->GetProperty()->SetSpecularPower(30);
  insideActor->GetProperty()->EdgeVisibilityOn();

  // Border
  auto borderMapper =
    vtkSmartPointer<vtkDataSetMapper>::New();
  borderMapper->SetInputData(
    dynamic_cast<vtkUnstructuredGrid*>(vtkMultiBlockDataSet::SafeDownCast(threshold->GetOutput()->GetBlock(borderId))->GetBlock(0)));
  borderMapper->ScalarVisibilityOff();

  auto borderActor =
    vtkSmartPointer<vtkActor>::New();
  borderActor->SetMapper(borderMapper);
  borderActor->GetProperty()->SetDiffuseColor(borderColor.GetData());
  borderActor->GetProperty()->SetSpecular(.6);
  borderActor->GetProperty()->SetSpecularPower(30);
  borderActor->GetProperty()->EdgeVisibilityOn();

  auto surfaceMapper =
    vtkSmartPointer<vtkDataSetMapper>::New();
  surfaceMapper->SetInputData(polyData2);
  surfaceMapper->ScalarVisibilityOff();

  // Surface of object containing cell
  auto surfaceActor =
    vtkSmartPointer<vtkActor>::New();
  surfaceActor->SetMapper(surfaceMapper);
  surfaceActor->GetProperty()->SetDiffuseColor(surfaceColor.GetData());
  surfaceActor->GetProperty()->SetOpacity(.1);

  auto renderer =
    vtkSmartPointer<vtkRenderer>::New();
  auto renderWindow =
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->AddRenderer(renderer);
  renderWindow->SetSize(640, 480);

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

  renderer->SetBackground(backgroundColor.GetData());
  renderer->UseHiddenLineRemovalOn();

  renderer->AddActor(surfaceActor);
  renderer->AddActor(outsideActor);
  renderer->AddActor(insideActor);
  renderer->AddActor(borderActor);

  renderWindow->SetWindowName("CellsInsideObject");
  renderWindow->Render();
  renderer->GetActiveCamera()->Azimuth(30);
  renderer->GetActiveCamera()->Elevation(30);
  renderer->GetActiveCamera()->Dolly(1.25);
  renderWindow->Render();

  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

namespace
{
vtkSmartPointer<vtkPolyData> ReadPolyData(const char *fileName)
{
  vtkSmartPointer<vtkPolyData> polyData;
  std::string extension = vtksys::SystemTools::GetFilenameLastExtension(std::string(fileName));
  if (extension == ".ply")
  {
    auto reader =
      vtkSmartPointer<vtkPLYReader>::New();
    reader->SetFileName (fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".vtp")
  {
    auto reader =
      vtkSmartPointer<vtkXMLPolyDataReader>::New();
    reader->SetFileName (fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".obj")
  {
    auto reader =
      vtkSmartPointer<vtkOBJReader>::New();
    reader->SetFileName (fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".stl")
  {
    auto reader =
      vtkSmartPointer<vtkSTLReader>::New();
    reader->SetFileName (fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".vtk")
  {
    auto reader =
      vtkSmartPointer<vtkPolyDataReader>::New();
    reader->SetFileName (fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".g")
  {
    auto reader =
      vtkSmartPointer<vtkBYUReader>::New();
    reader->SetGeometryFileName (fileName);
    reader->Update();
    polyData = reader->GetOutput();
  }
  else
  {
    auto source =
      vtkSmartPointer<vtkSphereSource>::New();
    source->Update();
    polyData = source->GetOutput();
  }
  return polyData;
}
}

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(CellsInsideObject)

find_package(VTK COMPONENTS 
  vtkCommonColor
  vtkCommonCore
  vtkCommonDataModel
  vtkCommonTransforms
  vtkFiltersGeneral
  vtkFiltersModeling
  vtkFiltersSources
  vtkIOGeometry
  vtkIOLegacy
  vtkIOPLY
  vtkIOXML
  vtkInteractionStyle
  vtkRenderingContextOpenGL2
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingGL2PSOpenGL2
  vtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
  message("Skipping CellsInsideObject: ${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(CellsInsideObject MACOSX_BUNDLE CellsInsideObject.cxx )
  target_link_libraries(CellsInsideObject PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(CellsInsideObject MACOSX_BUNDLE CellsInsideObject.cxx )
  target_link_libraries(CellsInsideObject PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS CellsInsideObject
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build CellsInsideObject¶

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

cd CellsInsideObject/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:

./CellsInsideObject

WINDOWS USERS

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