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CellsInsideObject

vtk-examples/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 src/Testing/Data/cow.g.

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)

Question

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

Code

CellsInsideObject.cxx

#include <vtkActor.h>
#include <vtkCamera.h>
#include <vtkDataSetMapper.h>
#include <vtkMultiBlockDataSet.h>
#include <vtkMultiThreshold.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSelectEnclosedPoints.h>
#include <vtkSmartPointer.h>
#include <vtkTransform.h>
#include <vtkTransformPolyDataFilter.h>
#include <vtkUnstructuredGrid.h>

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

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

#include <algorithm> // For transform()
#include <cctype>    // For to_lower
#include <iostream>
#include <string> // For find_last_of()
#include <vector>

namespace {
vtkSmartPointer<vtkPolyData> ReadPolyData(std::string const& 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] : "");
  ;

  vtkSmartPointer<vtkPolyData> polyData2;
  vtkNew<vtkTransform> transform;
  vtkNew<vtkTransformPolyDataFilter> transformPD;
  // 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
  vtkNew<vtkSelectEnclosedPoints> select;
  select->SetInputData(polyData1);
  select->SetSurfaceData(polyData2);

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

  vtkNew<vtkMultiThreshold> threshold;
  // 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
  vtkNew<vtkNamedColors> colors;
  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
  vtkNew<vtkDataSetMapper> outsideMapper;
  outsideMapper->SetInputData(dynamic_cast<vtkUnstructuredGrid*>(
      vtkMultiBlockDataSet::SafeDownCast(
          threshold->GetOutput()->GetBlock(outsideId))
          ->GetBlock(0)));
  outsideMapper->ScalarVisibilityOff();

  vtkNew<vtkActor> outsideActor;
  outsideActor->SetMapper(outsideMapper);
  outsideActor->GetProperty()->SetDiffuseColor(outsideColor.GetData());
  outsideActor->GetProperty()->SetSpecular(.6);
  outsideActor->GetProperty()->SetSpecularPower(30);

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

  vtkNew<vtkActor> insideActor;
  insideActor->SetMapper(insideMapper);
  insideActor->GetProperty()->SetDiffuseColor(insideColor.GetData());
  insideActor->GetProperty()->SetSpecular(.6);
  insideActor->GetProperty()->SetSpecularPower(30);
  insideActor->GetProperty()->EdgeVisibilityOn();

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

  vtkNew<vtkActor> borderActor;
  borderActor->SetMapper(borderMapper);
  borderActor->GetProperty()->SetDiffuseColor(borderColor.GetData());
  borderActor->GetProperty()->SetSpecular(.6);
  borderActor->GetProperty()->SetSpecularPower(30);
  borderActor->GetProperty()->EdgeVisibilityOn();

  vtkNew<vtkDataSetMapper> surfaceMapper;
  surfaceMapper->SetInputData(polyData2);
  surfaceMapper->ScalarVisibilityOff();

  // Surface of object containing cell
  vtkNew<vtkActor> surfaceActor;
  surfaceActor->SetMapper(surfaceMapper);
  surfaceActor->GetProperty()->SetDiffuseColor(surfaceColor.GetData());
  surfaceActor->GetProperty()->SetOpacity(.1);

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

  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
  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(std::string const& fileName)
{
  vtkSmartPointer<vtkPolyData> polyData;
  std::string extension = "";
  if (fileName.find_last_of(".") != std::string::npos)
  {
    extension = fileName.substr(fileName.find_last_of("."));
  }
  // Make the extension lowercase
  std::transform(extension.begin(), extension.end(), extension.begin(),
                 ::tolower);
  if (extension == ".ply")
  {
    vtkNew<vtkPLYReader> reader;
    reader->SetFileName(fileName.c_str());
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".vtp")
  {
    vtkNew<vtkXMLPolyDataReader> reader;
    reader->SetFileName(fileName.c_str());
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".obj")
  {
    vtkNew<vtkOBJReader> reader;
    reader->SetFileName(fileName.c_str());
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".stl")
  {
    vtkNew<vtkSTLReader> reader;
    reader->SetFileName(fileName.c_str());
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".vtk")
  {
    vtkNew<vtkPolyDataReader> reader;
    reader->SetFileName(fileName.c_str());
    reader->Update();
    polyData = reader->GetOutput();
  }
  else if (extension == ".g")
  {
    vtkNew<vtkBYUReader> reader;
    reader->SetGeometryFileName(fileName.c_str());
    reader->Update();
    polyData = reader->GetOutput();
  }
  else
  {
    // Return a polydata sphere if the extension is unknown.
    vtkNew<vtkSphereSource> source;
    source->SetThetaResolution(20);
    source->SetPhiResolution(11);
    source->Update();
    polyData = source->GetOutput();
  }
  return polyData;
}
} // namespace

CMakeLists.txt

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(CellsInsideObject)

find_package(VTK COMPONENTS 
)

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

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.