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/** \page tutorial_07b Deleting geometry elements

This small example shows how to remove faces and vertices from a mesh.

We basically use the geometry created in \ref tutorial_01.

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If we want our mesh class to be able to remove vertices, faces or edges
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we have to extend the default traits for our mesh class.
Vertices, faces and (half-)edges need the OpenMesh::Attributes::Status attribute
which is used to hold the flag "deleted" if an element is deleted.

The struct which defines the mesh traits then looks like this:

\dontinclude delete_geometry.cc
\skipline struct
\until };

After having created the geometry of the cube one can delete faces and vertices
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by simply calling delete_vertices() (delete_faces() or delete_edges() respectively).
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Note that there is actually no way to directly delete halfedges since they are automatically
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affected when the parent edge is marked as deleted!

The status whether an element is marked as deleted can be requested by

\code
mesh.status(handle).deleted();  // true if element handle is marked as deleted
                                // false otherwise
\endcode

where handle is either a vertex-, edge- or face-handle.

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In this example we delete all faces except one and the corresponding vertices.
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The code looks like this

\dontinclude delete_geometry.cc
\skipline // Delete face 0
\until mesh.delete_vertex(vhandle[3], false);

Now the deleted faces and vertices are marked as "deleted" internally.
Call garbage_collection() to definitely remove them from memory.

\dontinclude delete_geometry.cc
\skipline // Delete all
\until mesh.garbage_collection();

The full source code of the example:

\include delete_geometry.cc

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**/