Doxygen/html/Examples_2DataRepresentation_2Mesh_2MeshCellVisitor2_8cxx-example.html

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//  Software Guide : BeginLatex

//

//  The following section illustrates a realistic example of the use of Cell

//  visitors on the \doxygen{Mesh}. A set of different visitors is defined

//  here, each visitor associated with a particular type of cell. All the

//  visitors are registered with a MultiVisitor class which is passed to the

//  mesh.

//

//  The first step is to include the \code{CellInterfaceVisitor} header file.

//

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

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

//  \index{CellVisitor}

//  \index{CellInterfaceVisitor}

//

//  Software Guide : EndLatex


#include "itkMesh.h"

#include "itkLineCell.h"

#include "itkTetrahedronCell.h"


// Software Guide : BeginCodeSnippet

#include "itkCellInterfaceVisitor.h"

// Software Guide : EndCodeSnippet


//  Software Guide : BeginLatex

//

//  The typical mesh types are now declared.

//

//  Software Guide : EndLatex


// Software Guide : BeginCodeSnippet

using PixelType = float;

using MeshType = itk::Mesh<PixelType, 3>;


using CellType = MeshType::CellType;


using VertexType = itk::VertexCell<CellType>;

using LineType = itk::LineCell<CellType>;

using TriangleType = itk::TriangleCell<CellType>;

using TetrahedronType = itk::TetrahedronCell<CellType>;

// Software Guide : EndCodeSnippet


//  Software Guide : BeginLatex

//

//  Then, custom CellVisitor classes should be declared. The only requirement

//  on the declaration of each visitor class is to provide a method named

//  \code{Visit()}. This method expects as arguments a cell identifier and a

//  pointer to the \emph{specific} cell type for which this visitor is

//  intended.

//

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

//  \index{CellInterfaceVisitor!requirements}

//  \index{CellInterfaceVisitor!Visit()}

//

//  Software Guide : EndLatex


//  Software Guide : BeginLatex

//

//  The following Vertex visitor simply prints out the identifier of the

//  point with which the cell is associated. Note that the cell uses the

//  method \code{GetPointId()} without any arguments. This method is only

//  defined on the VertexCell.

//

//  \index{itk::CellInterface!GetPointId()}

//  \index{GetPointId()}

//

//  Software Guide : EndLatex


// Software Guide : BeginCodeSnippet

class CustomVertexVisitor

{

public:

  void

  Visit(unsigned long cellId, VertexType * t)

  {

    std::cout << "cell " << cellId << " is a Vertex " << std::endl;

    std::cout << "    associated with point id = ";

    std::cout << t->GetPointId() << std::endl;

  }

  virtual ~CustomVertexVisitor() = default;

};

// Software Guide : EndCodeSnippet


//  Software Guide : BeginLatex

//

//  The following Line visitor computes the length of the line.  Note

//  that this visitor is slightly more complicated since it needs to get

//  access to the actual mesh in order to get point coordinates from the

//  point identifiers returned by the line cell. This is done by holding a

//  pointer to the mesh and querying the mesh each time point coordinates are

//  required. The mesh pointer is set up in this case with the

//  \code{SetMesh()} method.

//

//  Software Guide : EndLatex


// Software Guide : BeginCodeSnippet

class CustomLineVisitor

{

public:

  CustomLineVisitor()

    : m_Mesh(nullptr)

  {}

  virtual ~CustomLineVisitor() = default;


  void

  SetMesh(MeshType * mesh)

  {

    m_Mesh = mesh;

  }


  void

  Visit(unsigned long cellId, LineType * t)

  {

    std::cout << "cell " << cellId << " is a Line " << std::endl;

    LineType::PointIdIterator pit = t->PointIdsBegin();

    MeshType::PointType       p0;

    MeshType::PointType       p1;

    m_Mesh->GetPoint(*pit++, &p0);

    m_Mesh->GetPoint(*pit++, &p1);

    const double length = p0.EuclideanDistanceTo(p1);

    std::cout << " length = " << length << std::endl;

  }


private:

  MeshType::Pointer m_Mesh;

};

// Software Guide : EndCodeSnippet


//  Software Guide : BeginLatex

//

//  The Triangle visitor below prints out the identifiers of its points.

//  Note the use of the \code{PointIdIterator} and the \code{PointIdsBegin()}

//  and \code{PointIdsEnd()} methods.

//

//  \index{CellInterface!PointIdsBegin()}

//  \index{CellInterface!PointIdsEnd()}

//  \index{CellInterface!iterating points}

//  \index{PointIdsBegin()}

//  \index{PointIdsEnd()}

//

//  Software Guide : EndLatex


#ifndef CustomTriangleVisitorDefine

#  define CustomTriangleVisitorDefine

// Software Guide : BeginCodeSnippet

class CustomTriangleVisitor

{

public:

  void

  Visit(unsigned long cellId, TriangleType * t)

  {

    std::cout << "cell " << cellId << " is a Triangle " << std::endl;

    LineType::PointIdIterator pit = t->PointIdsBegin();

    LineType::PointIdIterator end = t->PointIdsEnd();

    while (pit != end)

    {

      std::cout << "  point id = " << *pit << std::endl;

      ++pit;

    }

  }

  virtual ~CustomTriangleVisitor() = default;

};

// Software Guide : EndCodeSnippet

#endif


//  Software Guide : BeginLatex

//

//  The TetrahedronVisitor below simply returns the number of faces on this

//  figure. Note that \code{GetNumberOfFaces()} is a method exclusive of 3D

//  cells.

//

//  \index{GetNumberOfFaces()!TetrahedronCell}

//  \index{TetrahedronCell!GetNumberOfFaces()}

//

//  Software Guide : EndLatex


// Software Guide : BeginCodeSnippet

class CustomTetrahedronVisitor

{

public:

  void

  Visit(unsigned long cellId, TetrahedronType * t)

  {

    std::cout << "cell " << cellId << " is a Tetrahedron " << std::endl;

    std::cout << "  number of faces = ";

    std::cout << t->GetNumberOfFaces() << std::endl;

  }

  virtual ~CustomTetrahedronVisitor() = default;

};

// Software Guide : EndCodeSnippet


int

main(int, char *[])

{

  auto mesh = MeshType::New();


  // Creating the points and inserting them in the mesh

  //

  MeshType::PointType point0;

  MeshType::PointType point1;

  MeshType::PointType point2;

  MeshType::PointType point3;


  point0[0] = -1;

  point0[1] = -1;

  point0[2] = -1;

  point1[0] = 1;

  point1[1] = 1;

  point1[2] = -1;

  point2[0] = 1;

  point2[1] = -1;

  point2[2] = 1;

  point3[0] = -1;

  point3[1] = 1;

  point3[2] = 1;


  mesh->SetPoint(0, point0);

  mesh->SetPoint(1, point1);

  mesh->SetPoint(2, point2);

  mesh->SetPoint(3, point3);


  // Creating and associating the Tetrahedron

  //

  CellType::CellAutoPointer cellpointer;


  cellpointer.TakeOwnership(new TetrahedronType);

  cellpointer->SetPointId(0, 0);

  cellpointer->SetPointId(1, 1);

  cellpointer->SetPointId(2, 2);

  cellpointer->SetPointId(3, 3);

  mesh->SetCell(0, cellpointer);


  // Creating and associating the Triangles

  //

  cellpointer.TakeOwnership(new TriangleType);

  cellpointer->SetPointId(0, 0);

  cellpointer->SetPointId(1, 1);

  cellpointer->SetPointId(2, 2);

  mesh->SetCell(1, cellpointer);


  cellpointer.TakeOwnership(new TriangleType);

  cellpointer->SetPointId(0, 0);

  cellpointer->SetPointId(1, 2);

  cellpointer->SetPointId(2, 3);

  mesh->SetCell(2, cellpointer);


  cellpointer.TakeOwnership(new TriangleType);

  cellpointer->SetPointId(0, 0);

  cellpointer->SetPointId(1, 3);

  cellpointer->SetPointId(2, 1);

  mesh->SetCell(3, cellpointer);


  cellpointer.TakeOwnership(new TriangleType);

  cellpointer->SetPointId(0, 3);

  cellpointer->SetPointId(1, 2);

  cellpointer->SetPointId(2, 1);

  mesh->SetCell(4, cellpointer);


  // Creating and associating the Edges

  //

  cellpointer.TakeOwnership(new LineType);

  cellpointer->SetPointId(0, 0);

  cellpointer->SetPointId(1, 1);

  mesh->SetCell(5, cellpointer);


  cellpointer.TakeOwnership(new LineType);

  cellpointer->SetPointId(0, 1);

  cellpointer->SetPointId(1, 2);

  mesh->SetCell(6, cellpointer);


  cellpointer.TakeOwnership(new LineType);

  cellpointer->SetPointId(0, 2);

  cellpointer->SetPointId(1, 0);

  mesh->SetCell(7, cellpointer);


  cellpointer.TakeOwnership(new LineType);

  cellpointer->SetPointId(0, 1);

  cellpointer->SetPointId(1, 3);

  mesh->SetCell(8, cellpointer);


  cellpointer.TakeOwnership(new LineType);

  cellpointer->SetPointId(0, 3);

  cellpointer->SetPointId(1, 2);

  mesh->SetCell(9, cellpointer);


  cellpointer.TakeOwnership(new LineType);

  cellpointer->SetPointId(0, 3);

  cellpointer->SetPointId(1, 0);

  mesh->SetCell(10, cellpointer);


  // Creating and associating the Vertices

  //

  cellpointer.TakeOwnership(new VertexType);

  cellpointer->SetPointId(0, 0);

  mesh->SetCell(11, cellpointer);


  cellpointer.TakeOwnership(new VertexType);

  cellpointer->SetPointId(0, 1);

  mesh->SetCell(12, cellpointer);


  cellpointer.TakeOwnership(new VertexType);

  cellpointer->SetPointId(0, 2);

  mesh->SetCell(13, cellpointer);


  cellpointer.TakeOwnership(new VertexType);

  cellpointer->SetPointId(0, 3);

  mesh->SetCell(14, cellpointer);


  // Simple verification of the number of points and cells inserted

  //

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

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


  //  Software Guide : BeginLatex

  //

  // \index{itk::Mesh!Cell\-Interface\-Visitor\-Implementation}

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

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

  // \index{CellVisitor}

  //

  //  With the cell visitors we proceed now to instantiate CellVisitor

  //  implementations. The visitor classes defined above are used as template

  //  arguments of the cell visitor implementation.

  //

  //  Software Guide : EndLatex


  // Software Guide : BeginCodeSnippet

  using VertexVisitorInterfaceType =

    itk::CellInterfaceVisitorImplementation<PixelType,

                                            MeshType::CellTraits,

                                            VertexType,

                                            CustomVertexVisitor>;


  using LineVisitorInterfaceType =

    itk::CellInterfaceVisitorImplementation<PixelType,

                                            MeshType::CellTraits,

                                            LineType,

                                            CustomLineVisitor>;


  using TriangleVisitorInterfaceType =

    itk::CellInterfaceVisitorImplementation<PixelType,

                                            MeshType::CellTraits,

                                            TriangleType,

                                            CustomTriangleVisitor>;


  using TetrahedronVisitorInterfaceType =

    itk::CellInterfaceVisitorImplementation<PixelType,

                                            MeshType::CellTraits,

                                            TetrahedronType,

                                            CustomTetrahedronVisitor>;

  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex

  //

  //  Note that the actual \code{CellInterfaceVisitorImplementation} is

  //  templated over the PixelType, the CellTraits, the CellType to be visited

  //  and the Visitor class defining what to do with the cell.

  //

  //  A visitor implementation class can now be created using the normal

  //  invocation to its \code{New()} method and assigning the result to a

  //  \doxygen{SmartPointer}.

  //

  //  Software Guide : EndLatex


  // Software Guide : BeginCodeSnippet

  auto vertexVisitor = VertexVisitorInterfaceType::New();


  auto lineVisitor = LineVisitorInterfaceType::New();


  auto triangleVisitor = TriangleVisitorInterfaceType::New();


  auto tetrahedronVisitor = TetrahedronVisitorInterfaceType::New();

  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex

  //

  //  Remember that the LineVisitor requires the pointer to the mesh object

  //  since it needs to get access to actual point coordinates. This is done

  //  by invoking the \code{SetMesh()} method defined above.

  //

  //  Software Guide : EndLatex


  // Software Guide : BeginCodeSnippet

  lineVisitor->SetMesh(mesh);

  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex

  //

  // Looking carefully you will notice that the \code{SetMesh()} method is

  // declared in \code{CustomLineVisitor} but we are invoking it on

  // \code{LineVisitorInterfaceType}. This is possible thanks to the way in

  // which the VisitorInterfaceImplementation is defined. This class derives

  // from the visitor type provided by the user as the fourth template

  // parameter. \code{LineVisitorInterfaceType} is then a derived class of

  // \code{CustomLineVisitor}.

  //

  //  Software Guide : EndLatex


  //  Software Guide : BeginLatex

  //

  //  The set of visitors should now be registered with the MultiVisitor class

  //  that will walk through the cells and delegate action to every registered

  //  visitor when the appropriate cell type is encountered. The following

  //  lines create a MultiVisitor object.

  //

  //  \index{CellMultiVisitorType}

  //  \index{MultiVisitor}

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

  //

  //  Software Guide : EndLatex


  // Software Guide : BeginCodeSnippet

  using CellMultiVisitorType = CellType::MultiVisitor;

  auto multiVisitor = CellMultiVisitorType::New();

  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex

  //

  //  Every visitor implementation is registered with the Mesh using the

  //  \code{AddVisitor()} method.

  //

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

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

  //

  //  Software Guide : EndLatex


  // Software Guide : BeginCodeSnippet

  multiVisitor->AddVisitor(vertexVisitor);

  multiVisitor->AddVisitor(lineVisitor);

  multiVisitor->AddVisitor(triangleVisitor);

  multiVisitor->AddVisitor(tetrahedronVisitor);

  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex

  //

  //  Finally, the iteration over the cells is triggered by calling the method

  //  \code{Accept()} on the Mesh class.

  //

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

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

  //

  //  Software Guide : EndLatex


  // Software Guide : BeginCodeSnippet

  mesh->Accept(multiVisitor);

  // Software Guide : EndCodeSnippet


  //  Software Guide : BeginLatex

  //

  //  The \code{Accept()} method will iterate over all the cells and for each

  //  one will invite the MultiVisitor to attempt an action on the cell. If no

  //  visitor is interested on the current cell type, the cell is just ignored

  //  and skipped.

  //

  //  Software Guide : EndLatex


  return EXIT_SUCCESS;

}