SphinxExamples/src/Core/QuadEdgeMesh/CutMesh/Code.cxx

/*=========================================================================
 *
 *  Copyright Insight Software Consortium
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0.txt
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *=========================================================================*/

#include "itkQuadEdgeMesh.h"
#include "itkQuadEdgeMeshPolygonCell.h"

#include "itkMeshFileReader.h"
#include "itkMeshFileWriter.h"

int main( int argc, char* argv[] )
{
  if( argc != 3 )
     {
     std::cerr << "Usage: "<< std::endl;
     std::cerr << argv[0];
     std::cerr << " <InputFileName> <OutputFileName>";
     std::cerr << std::endl;
     return EXIT_FAILURE;
     }

  const char * inputFileName = argv[1];
  const char * outputFileName = argv[2];

  constexpr unsigned int Dimension = 3;
  using CoordType = double;
  using MeshType = itk::QuadEdgeMesh< CoordType, Dimension >;
  using MeshPointer = MeshType::Pointer;
  using MeshPointsContainerPointer = MeshType::PointsContainerPointer;
  using MeshPointsContainerIterator = MeshType::PointsContainerIterator;
  using MeshPointType = MeshType::PointType;
  using MeshPointIdentifier = MeshType::PointIdentifier;
  using MeshCellIdentifier = MeshType::CellIdentifier;

  using ReaderType = itk::MeshFileReader< MeshType >;
  ReaderType::Pointer reader = ReaderType::New();
  reader->SetFileName( inputFileName );

  MeshPointer mesh = reader->GetOutput();

  MeshPointer output = MeshType::New();

  std::map< MeshPointIdentifier, MeshPointIdentifier > verticesMap;
  std::set< MeshCellIdentifier > facesSet;

  MeshPointsContainerPointer points = mesh->GetPoints();

  MeshPointsContainerIterator pIt   = points->Begin();
  MeshPointsContainerIterator pEnd  = points->End();

  while( pIt != pEnd )
  {
    MeshPointType p = pIt->Value();

    if( ( p[2] < 0. ) )
      {
      // here you do not want to use operator = to copy the coordinates from the
      // input mesh to the output one. Indeed the operator = does not only copy
      // the coordinates, but also the pointer to first QuadEdge of the 0-ring,
      // and it would be wrong.
      MeshPointType q;
      q.CastFrom( p );

      verticesMap[ pIt->Index() ] = output->AddPoint( q );

      // iterate on the 0-ring (vertex neighbors)
      MeshType::QEType* qe = p.GetEdge();
      MeshType::QEType* temp = qe;
      do
        {
        // insert the corresponding faces into std::set
        facesSet.insert( temp->GetLeft() );

        temp = temp->GetOnext();
        } while( qe != temp );
      }
    ++pIt;
  }

  MeshType::CellsContainerPointer cells = mesh->GetCells();

  using PolygonType = itk::QuadEdgeMeshPolygonCell< MeshType::CellType >;

  // iterate on the faces to be added into resulting mesh
  for( auto fIt : facesSet )
    {
    auto* face = dynamic_cast< PolygonType* >( cells->ElementAt( fIt ) );
    MeshType::PointIdentifier id[3];

    if( face )
      {
      MeshType::QEType *qe = face->GetEdgeRingEntry();
      MeshType::QEType *temp = qe;

      unsigned int k = 0;

      // iterate on the vertices of a given face
      do
        {
        // add the corresponding vertex into the output mesh if it has not been added yet
        if( verticesMap.find( temp->GetOrigin() ) == verticesMap.end() )
          {
          MeshType::PointType p = mesh->GetPoint( temp->GetOrigin() );

          MeshType::PointType q;
          q.CastFrom( p );

          verticesMap[ temp->GetOrigin() ] = output->AddPoint( q );
          }
        id[ k++ ] = verticesMap[ temp->GetOrigin() ];

        temp = temp->GetLnext();
        } while( qe != temp );

      // add the corresponding face into the output mesh
      output->AddFaceTriangle( id[0], id[1], id[2] );
      }
    }

  // save the corresponding mesh
  using MeshWriterType = itk::MeshFileWriter< MeshType >;
  MeshWriterType::Pointer writer = MeshWriterType::New();
  writer->SetInput( output );
  writer->SetFileName( outputFileName );

  try
    {
    writer->Update();
    }
  catch( itk::ExceptionObject& e )
    {
    std::cerr << "Error: " << e << std::endl;
    return EXIT_FAILURE;
    }

  return EXIT_SUCCESS;
}