Doxygen/html/Examples_2DataRepresentation_2Mesh_2MeshPolyLine_8cxx-example.html

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//  Software Guide : BeginLatex

//

//  This section illustrates how to represent a classical \emph{PolyLine}

//  structure using the \doxygen{Mesh}

//

//  \index{itk::Mesh!PolyLine}

//

//  Software Guide : EndLatex


//  Software Guide : BeginLatex

//

//  A PolyLine only involves zero and one dimensional cells, which are

//  represented by the \doxygen{VertexCell} and the \doxygen{LineCell}.

//

//  \index{itk::LineCell!header}

//  \index{itk::VertexCell!header}

//

//  Software Guide : EndLatex


// Software Guide : BeginCodeSnippet

#include "itkMesh.h"

#include "itkLineCell.h"

// Software Guide : EndCodeSnippet


int

main(int, char *[])

{

  //  Software Guide : BeginLatex

  //

  //  Then the PixelType is defined and the mesh type is instantiated with it.

  //  Note that the dimension of the space is two in this case.

  //

  //  \index{itk::Mesh!Instantiation}

  //  \index{itk::Mesh!PixelType}

  //

  //  Software Guide : EndLatex


  // Software Guide : BeginCodeSnippet

  using PixelType = float;

  using MeshType = itk::Mesh<PixelType, 2>;

  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex

  //

  //  The cell type can now be instantiated using the traits

  //  taken from the Mesh.

  //

  //  \index{itk::LineCell!Instantiation}

  //  \index{itk::VertexCell!Instantiation}

  //

  //  Software Guide : EndLatex


  // Software Guide : BeginCodeSnippet

  using CellType = MeshType::CellType;

  using VertexType = itk::VertexCell<CellType>;

  using LineType = itk::LineCell<CellType>;

  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex

  //

  //  The mesh is created and the points associated with the vertices are

  //  inserted.  Note that there is an important distinction between the

  //  points in the mesh and the \doxygen{VertexCell} concept. A VertexCell

  //  is a cell of dimension zero. Its main difference as compared to a point

  //  is that the cell can be aware of neighborhood relationships with other

  //  cells. Points are not aware of the existence of cells. In fact, from

  //  the pure topological point of view, the coordinates of points in the

  //  mesh are completely irrelevant.  They may as well be absent from the

  //  mesh structure altogether.  VertexCells on the other hand are necessary

  //  to represent the full set of neighborhood relationships on the

  //  Polyline.

  //

  //  In this example we create a polyline connecting the four vertices of a

  //  square by using three of the square sides.

  //

  //  \index{itk::Mesh!New()}

  //  \index{itk::Mesh!SetPoint()}

  //  \index{itk::Mesh!PointType}

  //  \index{itk::Mesh!Pointer}

  //

  //  Software Guide : EndLatex


  // Software Guide : BeginCodeSnippet

  auto mesh = MeshType::New();


  MeshType::PointType point0;

  MeshType::PointType point1;

  MeshType::PointType point2;

  MeshType::PointType point3;


  point0[0] = -1;

  point0[1] = -1;

  point1[0] = 1;

  point1[1] = -1;

  point2[0] = 1;

  point2[1] = 1;

  point3[0] = -1;

  point3[1] = 1;


  mesh->SetPoint(0, point0);

  mesh->SetPoint(1, point1);

  mesh->SetPoint(2, point2);

  mesh->SetPoint(3, point3);

  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex

  //

  //  We proceed now to create the cells, associate them with the points and

  //  insert them on the mesh.

  //

  //  \index{itk::AutoPointer!TakeOwnership()}

  //  \index{CellAutoPointer!TakeOwnership()}

  //  \index{CellType!creation}

  //  \index{itk::Mesh!SetCell()}

  //  \index{itk::LineCell!Instantiation}

  //  \index{itk::LineCell!SetPointId()}

  //

  //  Software Guide : EndLatex


  // Software Guide : BeginCodeSnippet

  CellType::CellAutoPointer cellpointer;


  cellpointer.TakeOwnership(new LineType);

  cellpointer->SetPointId(0, 0);

  cellpointer->SetPointId(1, 1);

  mesh->SetCell(0, cellpointer);


  cellpointer.TakeOwnership(new LineType);

  cellpointer->SetPointId(0, 1);

  cellpointer->SetPointId(1, 2);

  mesh->SetCell(1, cellpointer);


  cellpointer.TakeOwnership(new LineType);

  cellpointer->SetPointId(0, 2);

  cellpointer->SetPointId(1, 0);

  mesh->SetCell(2, cellpointer);

  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex

  //

  //  Finally the zero dimensional cells represented by the

  //  \doxygen{VertexCell} are created and inserted in the mesh.

  //

  //  Software Guide : EndLatex


  // Software Guide : BeginCodeSnippet

  cellpointer.TakeOwnership(new VertexType);

  cellpointer->SetPointId(0, 0);

  mesh->SetCell(3, cellpointer);


  cellpointer.TakeOwnership(new VertexType);

  cellpointer->SetPointId(0, 1);

  mesh->SetCell(4, cellpointer);


  cellpointer.TakeOwnership(new VertexType);

  cellpointer->SetPointId(0, 2);

  mesh->SetCell(5, cellpointer);


  cellpointer.TakeOwnership(new VertexType);

  cellpointer->SetPointId(0, 3);

  mesh->SetCell(6, cellpointer);

  // Software Guide : EndCodeSnippet


  // Print out the number of points and the number of cells.

  std::cout << "# Points= " << mesh->GetNumberOfPoints() << std::endl;

  std::cout << "# Cell  = " << mesh->GetNumberOfCells() << std::endl;


  //  Software Guide : BeginLatex

  //

  //  At this point the Mesh contains four points and three cells.  The

  //  points can be visited using PointContainer iterators.

  //

  // \index{itk::Mesh!PointsContainer}

  // \index{itk::Mesh!PointIterator}

  // \index{itk::Mesh!GetPoints()}

  // \index{PointsContainer!Begin()}

  // \index{PointsContainer!End()}

  //

  //  Software Guide : EndLatex


  // Software Guide : BeginCodeSnippet

  using PointIterator = MeshType::PointsContainer::ConstIterator;

  PointIterator       pointIterator = mesh->GetPoints()->Begin();

  const PointIterator pointEnd = mesh->GetPoints()->End();


  while (pointIterator != pointEnd)

  {

    std::cout << pointIterator.Value() << std::endl;

    ++pointIterator;

  }

  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex

  //

  //  The cells can be visited using CellsContainer iterators.

  //

  // \index{itk::Mesh!CellsContainer}

  // \index{itk::Mesh!CellIterator}

  // \index{itk::Mesh!GetCells()}

  // \index{CellsContainer!Begin()}

  // \index{CellsContainer!End()}

  //

  //  Software Guide : EndLatex


  // Software Guide : BeginCodeSnippet

  using CellIterator = MeshType::CellsContainer::ConstIterator;


  CellIterator cellIterator = mesh->GetCells()->Begin();

  CellIterator cellEnd = mesh->GetCells()->End();


  while (cellIterator != cellEnd)

  {

    CellType * cell = cellIterator.Value();

    std::cout << cell->GetNumberOfPoints() << std::endl;

    ++cellIterator;

  }

  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex

  //

  //  Note that cells are stored as pointer to a generic cell type that is the

  //  base class of all the specific cell classes. This means that at this

  //  level we can only have access to the virtual methods defined in the

  //  \code{CellType}.

  //

  //  The point identifiers to which the cells have been associated can be

  //  visited using iterators defined in the \code{CellType} trait. The

  //  following code illustrates the use of the PointIdIterator. The

  //  \code{PointIdsBegin()} method returns the iterator to the first

  //  point-identifier in the cell.  The \code{PointIdsEnd()} method returns

  //  the iterator to the past-end point-identifier in the cell.

  //

  //  \index{CellType!PointIdsBegin()}

  //  \index{CellType!PointIdsEnd()}

  //  \index{CellType!PointIdIterator}

  //  \index{PointIdIterator}

  //  \index{PointIdsBegin()}

  //  \index{PointIdsEnd()}

  //

  //  Software Guide : EndLatex


  cellIterator = mesh->GetCells()->Begin();

  cellEnd = mesh->GetCells()->End();


  while (cellIterator != cellEnd)

  {

    CellType * cell = cellIterator.Value();


    std::cout << "cell with " << cell->GetNumberOfPoints();

    std::cout << " points   " << std::endl;


    // Software Guide : BeginCodeSnippet

    using PointIdIterator = CellType::PointIdIterator;


    PointIdIterator pointIditer = cell->PointIdsBegin();

    PointIdIterator pointIdend = cell->PointIdsEnd();


    while (pointIditer != pointIdend)

    {

      std::cout << *pointIditer << std::endl;

      ++pointIditer;

    }

    // Software Guide : EndCodeSnippet


    ++cellIterator;

  }


  //  Software Guide : BeginLatex

  //

  //  Note that the point-identifier is obtained from the iterator using the

  //  more traditional \code{*iterator} notation instead the \code{Value()}

  //  notation used by cell-iterators.

  //

  //  Software Guide : EndLatex


  return EXIT_SUCCESS;

}