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PointInsideObject2

vtk-examples/Cxx/PolyData/PointInsideObject2


Description

This example creates a volume (convex hull-ish) out of a mesh object. It then uses FindCell (which determines if a point is inside of a cell) to determine if a point is inside of any of the 3D cells created by Delaunay3D or not. This could potentially lead to false positives - that is, points that are outside the mesh but inside the convex hull.

Question

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

Code

PointInsideObject2.cxx

#include <vtkActor.h>
#include <vtkCellArray.h>
#include <vtkDelaunay3D.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPointSource.h>
#include <vtkPolyData.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSmoothPolyDataFilter.h>
#include <vtkSphereSource.h>
#include <vtkUnstructuredGrid.h>
#include <vtkVertexGlyphFilter.h>

int main(int, char*[])
{
  vtkNew<vtkNamedColors> colors;

  // Create a sphere
  vtkNew<vtkSphereSource> bigSphereSource;
  bigSphereSource->SetCenter(0.0, 0.0, 0.0);
  bigSphereSource->SetRadius(4);
  bigSphereSource->SetThetaResolution(20);
  bigSphereSource->SetPhiResolution(20);
  bigSphereSource->Update();

  vtkNew<vtkPolyDataMapper> bigSphereMapper;
  bigSphereMapper->SetInputConnection(bigSphereSource->GetOutputPort());

  vtkNew<vtkActor> bigSphereActor;
  bigSphereActor->SetMapper(bigSphereMapper);
  bigSphereActor->GetProperty()->SetOpacity(0.5);
  bigSphereActor->GetProperty()->SetColor(
      colors->GetColor3d("MistyRose").GetData());

  vtkNew<vtkSphereSource> smallSphereSource;
  smallSphereSource->SetCenter(1, 2, 1);
  smallSphereSource->SetRadius(2);
  smallSphereSource->SetThetaResolution(20);
  smallSphereSource->SetPhiResolution(20);
  smallSphereSource->Update();

  vtkNew<vtkPolyDataMapper> smallSphereMapper;
  smallSphereMapper->SetInputConnection(smallSphereSource->GetOutputPort());

  vtkNew<vtkActor> smallSphereActor;
  smallSphereActor->SetMapper(smallSphereMapper);
  smallSphereActor->GetProperty()->SetColor(
      colors->GetColor3d("Cornsilk").GetData());

  vtkNew<vtkPoints> pointsInside;
  vtkNew<vtkPolyData> polyDataInside;
  double point[3];

  // We generate points inside a spherical area defined by bigSphereSource.
  // Then we apply delaunay3D to it instead on  bigSphereSource.
  // This will avoid the "Unable to factor linear system" warnings cuused by
  //  degenerate points on the sphere.
  vtkNew<vtkPointSource> pointSource;
  pointSource->SetNumberOfPoints(400);
  // Slightly larger than the radius of the big sphere
  pointSource->SetRadius(4.2);

  vtkNew<vtkSmoothPolyDataFilter> smoothFilter;
  smoothFilter->SetInputConnection(0, bigSphereSource->GetOutputPort());
  smoothFilter->SetInputConnection(1, pointSource->GetOutputPort());

  vtkNew<vtkDelaunay3D> delaunay3D;
  // delaunay3D->SetInputConnection(bigSphereSource->GetOutputPort());
  delaunay3D->SetInputConnection(smoothFilter->GetOutputPort());
  delaunay3D->Update();

  for (vtkIdType i = 0; i < smallSphereSource->GetOutput()->GetNumberOfPoints();
       i++)
  {
    smallSphereSource->GetOutput()->GetPoint(i, point);

    double pcoords[3];
    // The number of weights >= max number of nodes in each cell
    double weights[4];
    int subId;
    vtkIdType cellId = delaunay3D->GetOutput()->FindCell(
        point, nullptr, 0, 0.1, subId, pcoords, weights);

    if (cellId >= 0)
    {
      std::cout << "In cell " << cellId << std::endl;
      std::cout << "inside" << std::endl;
      pointsInside->InsertNextPoint(point);
    }
    else
    {
      std::cout << "outside" << std::endl;
    }
  }

  polyDataInside->SetPoints(pointsInside);

  vtkNew<vtkVertexGlyphFilter> vertexGlyphFilter;
  vertexGlyphFilter->SetInputData(polyDataInside);
  vertexGlyphFilter->Update();

  // Mapper and actor for points inside
  vtkNew<vtkPolyDataMapper> pointsInsideMapper;
  pointsInsideMapper->SetInputConnection(vertexGlyphFilter->GetOutputPort());
  vtkNew<vtkActor> pointsInsideActor;
  pointsInsideActor->SetMapper(pointsInsideMapper);
  pointsInsideActor->GetProperty()->SetPointSize(6);
  pointsInsideActor->GetProperty()->SetColor(
      colors->GetColor3d("Magenta").GetData());

  vtkNew<vtkRenderer> renderer;
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->AddRenderer(renderer);
  renderWindow->SetWindowName("PointInsideObject2");

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

  renderer->AddActor(smallSphereActor);
  renderer->AddActor(bigSphereActor);
  renderer->AddActor(pointsInsideActor);
  renderer->SetBackground(colors->GetColor3d("DarkSlateGray").GetData());
  renderWindow->Render();
  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(PointInsideObject2)

find_package(VTK COMPONENTS 
  vtkCommonColor
  vtkCommonCore
  vtkCommonDataModel
  vtkFiltersCore
  vtkFiltersGeneral
  vtkFiltersSources
  vtkInteractionStyle
  vtkRenderingContextOpenGL2
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingGL2PSOpenGL2
  vtkRenderingOpenGL2
  QUIET
)

if (NOT VTK_FOUND)
  message("Skipping PointInsideObject2: ${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(PointInsideObject2 MACOSX_BUNDLE PointInsideObject2.cxx )
  target_link_libraries(PointInsideObject2 PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(PointInsideObject2 MACOSX_BUNDLE PointInsideObject2.cxx )
  target_link_libraries(PointInsideObject2 PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS PointInsideObject2
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build PointInsideObject2

Click here to download PointInsideObject2 and its CMakeLists.txt file. Once the tarball PointInsideObject2.tar has been downloaded and extracted,

cd PointInsideObject2/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:

./PointInsideObject2

WINDOWS USERS

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