.. role:: blue
   :class: blue

Mesh Iterators
==============
.. _Mesh_Iterators_:

.. kernel version: 118027

There are several types of iterators available for working with the mesh topology. They are located in the header files *halfedge_iterators.h* and *halfedge_range_iterators.h*:

1. :blue:`EdgeFanIterator` is the iterator for traversing the edges of the vertex fan in a counterclockwise direction (see Fig. 1). Example of use:

.. code-block:: cpp

   for( EdgeFanIterator it( halfedge, iEd ); !it.Done(); ++it )
       ;

   for( EdgeFanIterator it( halfedge, iVx, true ); !it.Done(); ++it ) {

       if( it.Edge() < SYS_MAX_T ) {
           ...
       }
       if( it.Twin() < SYS_MAX_T ) {
           ...
       }
   }

.. figure:: ../../pictures/P.2.2.1.png
   :width: 18cm
   :align: center

   Fig. 1

2. :blue:`EdgeFacetIterator` is the iterator for traversing facet edges, starting from the facet edge in a counterclockwise direction (see Fig. 2).

Example of use:

.. code-block:: cpp

   for( EdgeFacetIterator it( halfedge, iFacet ); !it.Done(); ++it ) {

       const MbHalfedgeEdge & ed = halfedge.Edge( it.Edge() );
   }

3. :blue:`EdgesAroundFacetBegEndPair` AllEdgesAroundFacet( *size_t* iFacet ) const;

Range based iterator for traversing facet edges, starting from the facet edge in a counterclockwise direction.

Example of use:

.. code-block:: cpp

   for( const MbHalfedgeEdge & ed : halfedge.AllEdgesAroundFacet( iFacet ) ) {
       ...
   }

.. figure:: ../../pictures/P.2.2.2.png
   :width: 15cm
   :align: center

   Fig. 2

4. :blue:`VerticesAroundFacetBegEndPair` AllVerticesAroundFacet( *size_t* iF ) const;

It is the iterator for traversing all vertices around the facet, starting from the vertex belonging to the edge defining the facet in a counterclockwise order (see Fig. 3).

Example of use:

.. code-block:: cpp

   for( const MbHalfedgeVertex & v : halfedge.AllVerticesAroundFacet( iFacet ) ) {
       ...
   }

.. figure:: ../../pictures/P.2.2.3.png
   :width: 15cm
   :align: center

   Fig. 3

5. :blue:`EdgesAroundVertexBegEndPair` AllEdgesAroundVertex( *size_t* iV ) const;

It is the iterator for traversing all edges (incoming and outgoing) adjacent to a given vertex, starting with the edge that defines the vertex (see Fig. 4). The traversal order is counterclockwise, alternating incoming and outgoing edges.

Example of use:

.. code-block:: cpp

   for( const MbHalfedgeEdge & ed : halfedge.AllEdgesAroundVertex( iVx ) ) {
       ...
   }

.. figure:: ../../pictures/P.2.2.4.png
   :width: 18cm
   :align: center

   Fig. 4

6. :blue:`VerticesAroundVertexBegEndPair` AllVerticesAroundVertex( *size_t* iV ) const;

It is the iterator for traversing all vertices adjacent to a given vertex (see Fig. 5). The order of traversal is counterclockwise, the first vertex is adjacent along the edge that defines the vertex.

Example of use:

.. code-block:: cpp

   for( const MbHalfedgeVertex & v : halfedge.AllVerticesAroundVertex( iVx ) ) {
       ...
   }

.. figure:: ../../pictures/P.2.2.5.png
   :width: 18cm
   :align: center

   Fig. 5

7. :blue:`FacetsAroundVertexBegEndPair` AllFacetsAroundVertex( *size_t* iV ) const;

It is the iterator for traversing all facets including the specified vertex (see Fig. 6). The traversal order is counterclockwise, the first facet includes the edge defining the vertex.

Example of use:

.. code-block:: cpp

   for( const MbHalfedgeFacet & f : halfedge.AllFacetsAroundVertex( iVx ) ) {
       ...
   }

.. figure:: ../../pictures/P.2.2.6.png
   :width: 18cm
   :align: center

   Fig. 6