Examples/DataRepresentation/Mesh/Mesh1.cxx

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//  Software Guide : BeginLatex
//
//  The \doxygen{Mesh} class is intended to represent shapes in space.  It
//  derives from the \doxygen{PointSet} class and hence inherits all the
//  functionality related to points and access to the pixel-data associated
//  with the points.  The mesh class is also $N$-dimensional which
//  allows a great flexibility in its use.
//
//  In practice a \code{Mesh} class can be seen as a \code{PointSet} to
//  which cells (also known as elements) of many different dimensions and
//  shapes have been added. Cells in the mesh are defined in terms of the
//  existing points using their point-identifiers.
//
//  As with \code{PointSet}, a \code{Mesh} object may be \emph{static}
//  or \emph{dynamic}. The first is used when the number of
//  points in the set is known in advance and not expected
//  to change as a consequence of the manipulations performed on the
//  set. The dynamic style, on the other hand, is intended to support
//  insertion and removal of points in an efficient manner. In addition
//  to point management, the distinction facilitates optimization of
//  performance and memory management of cells.
//
//  \index{itk::Mesh}
//  \index{itk::Mesh!Static}
//  \index{itk::Mesh!Dynamic}
//  \index{itk::Mesh!Header file}
//
//  In order to use the Mesh class, its header file should be included.
//
//  Software Guide : EndLatex
 
// Software Guide : BeginCodeSnippet
#include "itkMesh.h"
// Software Guide : EndCodeSnippet
 
int
main(int, char *[])
{
 
  //  Software Guide : BeginLatex
  //
  //  Then, the type associated with the points must be selected and used for
  //  instantiating the Mesh type.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using PixelType = float;
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  The \code{Mesh} type extensively uses the capabilities provided by
  //  \href{https://www.boost.org/more/generic_programming.html}{Generic
  //  Programming}. In particular, the \code{Mesh} class is parameterized over
  //  \code{PixelType}, spatial dimension, and (optionally) a parameter set
  //  called \code{MeshTraits}.  \code{PixelType} is the type of the
  //  value associated with each point (just as is done with \code{PointSet}).
  //  The following illustrates a typical instantiation of \code{Mesh}.
  //
  //  \index{itk::Mesh!Instantiation}
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  constexpr unsigned int Dimension = 3;
  using MeshType = itk::Mesh<PixelType, Dimension>;
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  Meshes typically require large amounts of memory. For this reason, they
  //  are reference counted objects, managed using \doxygen{SmartPointers}.
  //  The following line illustrates how a mesh is created by invoking the
  //  \code{New()} method on \code{MeshType} and assigning the result to a
  //  \code{SmartPointer}.
  //
  //  \index{itk::Mesh!New()}
  //  \index{itk::Mesh!Pointer()}
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  auto mesh = MeshType::New();
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  Management of points in a \code{Mesh} is identical to that in a
  //  \code{PointSet}. The type of point associated with the mesh can be
  //  obtained through the \code{PointType} trait. The following code shows
  //  the creation of points compatible with the mesh type defined above and
  //  the assignment of values to its coordinates.
  //
  //  \index{itk::Mesh!PointType}
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  MeshType::PointType p0;
  MeshType::PointType p1;
  MeshType::PointType p2;
  MeshType::PointType p3;
 
  p0[0] = -1.0;
  p0[1] = -1.0;
  p0[2] = 0.0; // first  point ( -1, -1, 0 )
  p1[0] = 1.0;
  p1[1] = -1.0;
  p1[2] = 0.0; // second point (  1, -1, 0 )
  p2[0] = 1.0;
  p2[1] = 1.0;
  p2[2] = 0.0; // third  point (  1,  1, 0 )
  p3[0] = -1.0;
  p3[1] = 1.0;
  p3[2] = 0.0; // fourth point ( -1,  1, 0 )
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  The points can now be inserted into the \code{Mesh} using the
  //  \code{SetPoint()} method. Note that points are copied into the mesh
  //  structure, meaning that the local instances of the points can now be
  //  modified without affecting the Mesh content.
  //
  //  \index{itk::Mesh!SetPoint()}
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  mesh->SetPoint(0, p0);
  mesh->SetPoint(1, p1);
  mesh->SetPoint(2, p2);
  mesh->SetPoint(3, p3);
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  The current number of points in a mesh can be queried with the
  //  \code{GetNumberOfPoints()} method.
  //
  //  \index{itk::Mesh!GetNumberOfPoints()}
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  std::cout << "Points = " << mesh->GetNumberOfPoints() << std::endl;
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  The points can now be efficiently accessed using the Iterator to the
  //  \code{PointsContainer} as was done in the previous section for the
  //  PointSet.
  //
  //  \index{PointsContainer!Iterator}
  //  \index{itk::Mesh!GetPoints()}
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using PointsIterator = MeshType::PointsContainer::Iterator;
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  A point iterator is initialized to the first point with the
  //  \code{Begin()} method of the \code{PointsContainer}.
  //
  //  \index{PointsContainer!Begin()}
  //  \index{itk::Mesh!GetPoints()}
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  PointsIterator pointIterator = mesh->GetPoints()->Begin();
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  The \code{++} operator is used to advance the iterator from one
  //  point to the next. The value associated with the \code{Point} to which
  //  the iterator is pointing is obtained with the \code{Value()} method.
  //  The loop for walking through all the points is controlled by comparing
  //  the current iterator with the iterator returned by the \code{End()}
  //  method of the \code{PointsContainer}. The following illustrates the
  //  typical loop for walking through the points of a mesh.
  //
  //  \index{PointsContainer!End()}
  //  \index{PointsContainer!Iterator}
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  const PointsIterator end = mesh->GetPoints()->End();
  while (pointIterator != end)
  {
    const MeshType::PointType p = pointIterator.Value(); // access the point
    std::cout << p << std::endl;                         // print the point
    ++pointIterator; // advance to next point
  }
  // Software Guide : EndCodeSnippet
 
  return EXIT_SUCCESS;
}