CGAL 6.1 - Polygon Mesh Processing

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Functions
Combinatorial Repair
Reference Manual

##

Functions to repair polygon soups and polygon meshes.

## Functions
template<typename PolygonMesh >
bool | CGAL::Polygon_mesh_processing::is_non_manifold_vertex (typename boost::graph_traits< PolygonMesh >::vertex_descriptor v, const PolygonMesh &pm)
| returns whether a vertex of a polygon mesh is non-manifold.
template<typename PolygonMesh , typename OutputIterator >
OutputIterator | CGAL::Polygon_mesh_processing::non_manifold_vertices (const PolygonMesh &pm, OutputIterator out)
| collects the non-manifold vertices (if any) present in the mesh.
template<typename PolygonMesh , typename NamedParameters = parameters::Default_named_parameters>
std::size_t | CGAL::Polygon_mesh_processing::duplicate_non_manifold_vertices (PolygonMesh &pm, const NamedParameters &np=parameters::default_values())
| duplicates all the non-manifold vertices of the input mesh.
template<class PolygonMesh , class NamedParameters = parameters::Default_named_parameters>
void | CGAL::Polygon_mesh_processing::merge_duplicated_vertices_in_boundary_cycle (typename boost::graph_traits< PolygonMesh >::halfedge_descriptor h, PolygonMesh &pm, const NamedParameters &np=parameters::default_values())
| merges identical vertices around a cycle of boundary edges.
template<class PolygonMesh , class NamedParameters = parameters::Default_named_parameters>
void | CGAL::Polygon_mesh_processing::merge_duplicated_vertices_in_boundary_cycles (PolygonMesh &pm, const NamedParameters &np=parameters::default_values())
| extracts boundary cycles and merges the duplicated vertices of each cycle.
template<typename PolygonMesh , typename PointRange , typename PolygonRange , typename NamedParameters = parameters::Default_named_parameters>
void | CGAL::Polygon_mesh_processing::polygon_mesh_to_polygon_soup (const PolygonMesh &mesh, PointRange &points, PolygonRange &polygons, const NamedParameters &np=parameters::default_values())
| adds the vertices and faces of a mesh into a (possibly non-empty) polygon soup.
template<typename PolygonRange >
bool | CGAL::Polygon_mesh_processing::is_polygon_soup_a_polygon_mesh (const PolygonRange &polygons)
| returns `true` if the soup of polygons defines a valid polygon mesh that can be handled by `CGAL::Polygon_mesh_processing::polygon_soup_to_polygon_mesh()`.
template<typename PolygonMesh , typename PointRange , typename PolygonRange , typename NamedParameters_PS = parameters::Default_named_parameters, typename NamedParameters_PM = parameters::Default_named_parameters>
void | CGAL::Polygon_mesh_processing::polygon_soup_to_polygon_mesh (const PointRange &points, const PolygonRange &polygons, PolygonMesh &out, const NamedParameters_PS &np_ps=parameters::default_values(), const NamedParameters_PM &np_pm=parameters::default_values())
| builds a polygon mesh from a soup of polygons.
template<typename PointRange , typename PolygonRange >
std::size_t | CGAL::Polygon_mesh_processing::remove_isolated_points_in_polygon_soup (PointRange &points, PolygonRange &polygons)
| removes the isolated points from a polygon soup.
template<typename PointRange , typename PolygonRange , typename NamedParameters = parameters::Default_named_parameters>
std::size_t | CGAL::Polygon_mesh_processing::merge_duplicate_points_in_polygon_soup (PointRange &points, PolygonRange &polygons, const NamedParameters &np=parameters::default_values())
| merges the duplicate points in a polygon soup.
template<typename PointRange , typename PolygonRange , typename NamedParameters = parameters::Default_named_parameters>
std::size_t | CGAL::Polygon_mesh_processing::merge_duplicate_polygons_in_polygon_soup (const PointRange &points, PolygonRange &polygons, const NamedParameters &np=parameters::default_values())
| merges the duplicate polygons in a polygon soup.
template<typename PointRange , typename PolygonRange , typename NamedParameters = parameters::Default_named_parameters>
void | CGAL::Polygon_mesh_processing::repair_polygon_soup (PointRange &points, PolygonRange &polygons, const NamedParameters &np=parameters::default_values())
| cleans a given polygon soup through various repairing operations.
template<typename PolygonMesh , typename NamedParameters = CGAL::parameters::Default_named_parameters>
std::size_t | CGAL::Polygon_mesh_processing::stitch_boundary_cycle (const typename boost::graph_traits< PolygonMesh >::halfedge_descriptor h, PolygonMesh &pmesh, const NamedParameters &np=parameters::default_values())
| stitches together, whenever possible, two halfedges belonging to the boundary cycle described by the halfedge `h`.
template<typename BorderHalfedgeRange , typename PolygonMesh , typename NamedParameters = CGAL::parameters::Default_named_parameters>
std::size_t | CGAL::Polygon_mesh_processing::stitch_boundary_cycles (const BorderHalfedgeRange &boundary_cycle_representatives, PolygonMesh &pmesh, const NamedParameters &np=parameters::default_values())
| stitches together, whenever possible, two halfedges belonging to the same boundary cycle.
template<typename PolygonMesh , typename HalfedgePairsRange , typename NamedParameters = CGAL::parameters::Default_named_parameters>
std::size_t | CGAL::Polygon_mesh_processing::stitch_borders (PolygonMesh &pmesh, const HalfedgePairsRange &hedge_pairs_to_stitch, const NamedParameters &np=parameters::default_values(), std::enable_if_t< boost::has_range_iterator< HalfedgePairsRange >::value > *=0)
| stitches together border halfedges in a polygon mesh.
template<typename PolygonMesh , typename NamedParameters = CGAL::parameters::Default_named_parameters>
std::size_t | CGAL::Polygon_mesh_processing::stitch_borders (PolygonMesh &pmesh, const NamedParameters &np=parameters::default_values())
| Same as the other overload, but the pairs of halfedges to be stitched are automatically found amongst all border halfedges.
template<typename BorderHalfedgeRange , typename PolygonMesh , typename NamedParameters = CGAL::parameters::Default_named_parameters>
std::size_t | CGAL::Polygon_mesh_processing::stitch_borders (const BorderHalfedgeRange &boundary_cycle_representatives, PolygonMesh &pmesh, const NamedParameters &np=parameters::default_values())
| Same as the other overload, but the pairs of halfedges to be stitched are automatically found amongst halfedges in cycles described by `boundary_cycle_representatives`.

## Function Documentation

## ◆ duplicate_non_manifold_vertices()

template<typename PolygonMesh , typename NamedParameters = parameters::Default_named_parameters>

std::size_t CGAL::Polygon_mesh_processing::duplicate_non_manifold_vertices | ( | PolygonMesh & | pm,
|  | const NamedParameters & | np = `parameters::default_values()`
| ) |  |

`#include <CGAL/Polygon_mesh_processing/manifoldness.h>`

duplicates all the non-manifold vertices of the input mesh.

Template Parameters

  PolygonMesh | a model of `HalfedgeListGraph` and `MutableHalfedgeGraph`
  NamedParameters | a sequence of Named Parameters

Parameters

  pm | the surface mesh to be repaired
  np | an optional sequence of Named Parameters among the ones listed below

Optional Named Parameters

  a property map associating points to the vertices of `pm` Type: a class model of `ReadWritePropertyMap` with `boost::graph_traits<PolygonMesh>::vertex_descriptor` as key type and `Point_3` as value type Default: `boost::get(CGAL::vertex_point, pm)` Extra: If this parameter is omitted, an internal property map for `CGAL::vertex_point_t` must be available in `PolygonMesh`. |
  a property map containing the constrained-or-not status of each vertex of `pm`. Type: a class model of `ReadWritePropertyMap` with `boost::graph_traits<PolygonMesh>::vertex_descriptor` as key type and `bool` as value type. It must be default constructible. Default: a default property map where no vertex is constrained Extra: `put(vcm, v, true)` will be called for each duplicated vertices, as well as the original non-manifold vertex in the input mesh. |
  an output iterator to collect the duplicated vertices Type: a model of `OutputIterator` with value type `std::vector<vertex_descriptor>` Default: unused Extra: The first vertex of each vector is a non-manifold vertex of the input mesh, followed by the new vertices that were created to fix the given non-manifold configuration. |

Returns
  the number of vertices created

See also
  `non_manifold_vertices()`

## ◆ is_non_manifold_vertex()

template<typename PolygonMesh >

bool CGAL::Polygon_mesh_processing::is_non_manifold_vertex | ( | typename boost::graph_traits< PolygonMesh >::vertex_descriptor | v,
|  | const PolygonMesh & | pm
| ) |  |

`#include <CGAL/Polygon_mesh_processing/manifoldness.h>`

returns whether a vertex of a polygon mesh is non-manifold.

Warning
  This function has linear runtime with respect to the size of the mesh. The function `non_manifold_vertices()` should be used when gathering all non manifold vertices.

Template Parameters

  PolygonMesh | a model of `HalfedgeListGraph`

Parameters

  v | a vertex of `pm`
  pm | a triangle mesh containing `v`

Returns
  `true` if the vertex is non-manifold, `false` otherwise

See also
  `duplicate_non_manifold_vertices()`

## ◆ is_polygon_soup_a_polygon_mesh()

template<typename PolygonRange >

bool CGAL::Polygon_mesh_processing::is_polygon_soup_a_polygon_mesh | ( | const PolygonRange & | polygons | ) |

`#include <CGAL/Polygon_mesh_processing/polygon_soup_to_polygon_mesh.h>`

returns `true` if the soup of polygons defines a valid polygon mesh that can be handled by `CGAL::Polygon_mesh_processing::polygon_soup_to_polygon_mesh()`.

It checks that each edge has at most two incident faces and such an edge is visited in opposite direction along the two face boundaries, no polygon has twice the same vertex, and the polygon soup describes a manifold surface. This function does not require a range of points as an argument since the check is purely topological. To each vertex of the mesh is associated an index that is used in the description of the boundaries of the polygons provided in `polygons`.

Template Parameters

  PolygonRange | a model of the concept `RandomAccessContainer` whose `value_type` is a model of the concept `RandomAccessContainer` whose `value_type` is `std::size_t`.

Parameters

  polygons | each element in the range describes a polygon using the indices of the vertices.

See also
  `CGAL::Polygon_mesh_processing::orient_polygon_soup()`

## ◆ merge_duplicate_points_in_polygon_soup()

template<typename PointRange , typename PolygonRange , typename NamedParameters = parameters::Default_named_parameters>

std::size_t CGAL::Polygon_mesh_processing::merge_duplicate_points_in_polygon_soup | ( | PointRange & | points,
|  | PolygonRange & | polygons,
|  | const NamedParameters & | np = `parameters::default_values()`
| ) |  |

`#include <CGAL/Polygon_mesh_processing/repair_polygon_soup.h>`

merges the duplicate points in a polygon soup.

Note that the index of a point that is merged with another point will thus change in all the polygons that the point appears in.

Template Parameters

  PointRange | a model of the concepts `SequenceContainer` and `Swappable` whose value type is the point type.
  PolygonRange | a model of the concept `RandomAccessContainer` whose `value_type` is itself a model of the concept `RandomAccessContainer` whose `value_type` is `std::size_t`.
  NamedParameters | a sequence of Named Parameters

Parameters

  points | points of the soup of polygons
  polygons | a vector of polygons. Each element in the vector describes a polygon using the indices of the points in `points`.
  np | an optional sequence of Named Parameters among the ones listed below

Optional Named Parameters

  an instance of a geometric traits class Type: The traits class must provide the nested functor `Less_xyz_3` to compare lexicographically two points a function `Less_xyz_3 less_xyz_3_object()`. Default: a CGAL Kernel deduced from the point type, using `CGAL::Kernel_traits` Extra: The geometric traits class must be compatible with the vertex point type. |

Returns
  the number of removed points

See also
  `repair_polygon_soup()`

## ◆ merge_duplicate_polygons_in_polygon_soup()

template<typename PointRange , typename PolygonRange , typename NamedParameters = parameters::Default_named_parameters>

std::size_t CGAL::Polygon_mesh_processing::merge_duplicate_polygons_in_polygon_soup | ( | const PointRange & | points,
|  | PolygonRange & | polygons,
|  | const NamedParameters & | np = `parameters::default_values()`
| ) |  |

`#include <CGAL/Polygon_mesh_processing/repair_polygon_soup.h>`

merges the duplicate polygons in a polygon soup.

Two polygons are duplicate if they share the same vertices in the same order. Note that the first vertex of the polygon does not matter, that is the triangle `0,1,2` is a duplicate of the triangle `2,0,1`.

Template Parameters

  PointRange | a model of the concept `RandomAccessContainer` whose value type is the point type.
  PolygonRange | a model of the concept `SequenceContainer` whose `value_type` is itself a model of the concepts `RandomAccessContainer` and `ReversibleContainer` whose `value_type` is `std::size_t`.
  NamedParameters | a sequence of Named Parameters

Parameters

  points | points of the soup of polygons
  polygons | a vector of polygons. Each element in the vector describes a polygon using the indices of the points in `points`.
  np | an optional sequence of Named Parameters among the ones listed below

Optional Named Parameters

  an instance of a geometric traits class Type: The traits class must provide the nested functor `Less_xyz_3` to compare lexicographically two points a function `Less_xyz_3 less_xyz_3_object()`. Default: a CGAL Kernel deduced from the point type, using `CGAL::Kernel_traits` Extra: The geometric traits class must be compatible with the vertex point type. |
  Parameter to indicate, when multiple polygons are duplicates, whether all the duplicate polygons should be removed or if one (arbitrarily chosen) face should be kept. Type: Boolean Default: `false` |
  Parameter to indicate if polygon orientation should be taken into account when determining whether two polygons are duplicates, that is, whether e.g. the triangles `0,1,2` and `0,2,1` are duplicates. Type: Boolean Default: `false` |

Returns
  the number of removed polygons

See also
  `repair_polygon_soup()`

## ◆ merge_duplicated_vertices_in_boundary_cycle()

template<class PolygonMesh , class NamedParameters = parameters::Default_named_parameters>

void CGAL::Polygon_mesh_processing::merge_duplicated_vertices_in_boundary_cycle | ( | typename boost::graph_traits< PolygonMesh >::halfedge_descriptor | h,
|  | PolygonMesh & | pm,
|  | const NamedParameters & | np = `parameters::default_values()`
| ) |  |

`#include <CGAL/Polygon_mesh_processing/merge_border_vertices.h>`

merges identical vertices around a cycle of boundary edges.

Template Parameters

  PolygonMesh | a model of `FaceListGraph` and `MutableFaceGraph`.
  NamedParameters | a sequence of Named Parameters.

Parameters

  h | a halfedge that belongs to a boundary cycle.
  pm | the polygon mesh which contains the boundary cycle.
  np | an optional sequence of Named Parameters among the ones listed below

Optional Named Parameters

  a property map associating points to the vertices of `pm` Type: a class model of `ReadWritePropertyMap` with `boost::graph_traits<PolygonMesh>::vertex_descriptor` as key type and `Point_3` as value type Default: `boost::get(CGAL::vertex_point, pm)` |

See also
  `merge_duplicated_vertices_in_boundary_cycles()`

## ◆ merge_duplicated_vertices_in_boundary_cycles()

template<class PolygonMesh , class NamedParameters = parameters::Default_named_parameters>

void CGAL::Polygon_mesh_processing::merge_duplicated_vertices_in_boundary_cycles | ( | PolygonMesh & | pm,
|  | const NamedParameters & | np = `parameters::default_values()`
| ) |  |

`#include <CGAL/Polygon_mesh_processing/merge_border_vertices.h>`

extracts boundary cycles and merges the duplicated vertices of each cycle.

Template Parameters

  PolygonMesh | a model of `FaceListGraph` and `MutableFaceGraph`.
  NamedParameters | a sequence of Named Parameters.

Parameters

  pm | the polygon mesh which contains the cycles.
  np | an optional sequence of Named Parameters among the ones listed below

Optional Named Parameters

  a property map associating points to the vertices of `pm` Type: a class model of `ReadWritePropertyMap` with `boost::graph_traits<PolygonMesh>::vertex_descriptor` as key type and `Point_3` as value type Default: `boost::get(CGAL::vertex_point, pm)` |

See also
  `merge_duplicated_vertices_in_boundary_cycle()`

## ◆ non_manifold_vertices()

template<typename PolygonMesh , typename OutputIterator >

OutputIterator CGAL::Polygon_mesh_processing::non_manifold_vertices | ( | const PolygonMesh & | pm,
|  | OutputIterator | out
| ) |  |

`#include <CGAL/Polygon_mesh_processing/manifoldness.h>`

collects the non-manifold vertices (if any) present in the mesh.

A non-manifold vertex `v` is returned via one incident halfedge `h` such that `target(h, pm) = v` for all the umbrellas that `v` appears in (an umbrella being the set of faces incident to all the halfedges reachable by walking around `v` using `hnext = prev(opposite(h, pm), pm)`, starting from `h`).

Template Parameters

  PolygonMesh | a model of `HalfedgeListGraph`
  OutputIterator | a model of `OutputIterator` holding objects of type `boost::graph_traits<PolygonMesh>::halfedge_descriptor`

Parameters

  pm | a triangle mesh
  out | the output iterator that collects halfedges incident to `v`

Returns
  the output iterator

See also
  `is_non_manifold_vertex()`
  `duplicate_non_manifold_vertices()`

## ◆ polygon_mesh_to_polygon_soup()

template<typename PolygonMesh , typename PointRange , typename PolygonRange , typename NamedParameters = parameters::Default_named_parameters>

void CGAL::Polygon_mesh_processing::polygon_mesh_to_polygon_soup | ( | const PolygonMesh & | mesh,
|  | PointRange & | points,
|  | PolygonRange & | polygons,
|  | const NamedParameters & | np = `parameters::default_values()`
| ) |  |

`#include <CGAL/Polygon_mesh_processing/polygon_mesh_to_polygon_soup.h>`

adds the vertices and faces of a mesh into a (possibly non-empty) polygon soup.

Template Parameters

  PolygonMesh | a model of `FaceListGraph`
  PointRange | a model of the concepts `RandomAccessContainer` and `BackInsertionSequence` whose value type can be constructed from the point type of the polygon mesh
  PolygonRange | a model of the concepts `RandomAccessContainer` and `BackInsertionSequence` whose value type is itself a model of the concepts `RandomAccessContainer` and `BackInsertionSequence` whose value type is `std::size_t`
  NamedParameters | a sequence of Named Parameters

Parameters

  mesh | the mesh whose faces are being put in the polygon soup
  points | points making the polygons of the soup
  polygons | each element in the vector describes a polygon using the indices of the points in `points`
  np | an optional sequence of Named Parameters among the ones listed below

Optional Named Parameters

  a property map associating points to the vertices of `mesh` Type: a class model of `ReadablePropertyMap` with `boost::graph_traits<PolygonMesh>::vertex_descriptor` as key type and `Point_3` as value type Default: `boost::get(CGAL::vertex_point, mesh)` |

Advanced

`PolygonRange` can also be a model of the concepts `RandomAccessContainer` and `BackInsertionSequence` whose value type is an array, but it is the user's responsibility to ensure that all faces have the same number of vertices, and that this number is equal to the size of the array.

See also
  `CGAL::Polygon_mesh_processing::orient_polygon_soup()`
  `CGAL::Polygon_mesh_processing::is_polygon_soup_a_polygon_mesh()`
  `CGAL::Polygon_mesh_processing::polygon_soup_to_polygon_mesh()`

## ◆ polygon_soup_to_polygon_mesh()

template<typename PolygonMesh , typename PointRange , typename PolygonRange , typename NamedParameters_PS = parameters::Default_named_parameters, typename NamedParameters_PM = parameters::Default_named_parameters>

void CGAL::Polygon_mesh_processing::polygon_soup_to_polygon_mesh | ( | const PointRange & | points,
|  | const PolygonRange & | polygons,
|  | PolygonMesh & | out,
|  | const NamedParameters_PS & | np_ps = `parameters::default_values()`,
|  | const NamedParameters_PM & | np_pm = `parameters::default_values()`
| ) |  |

`#include <CGAL/Polygon_mesh_processing/polygon_soup_to_polygon_mesh.h>`

builds a polygon mesh from a soup of polygons.

Precondition
  the input polygon soup describes a consistently oriented polygon mesh. This can be checked using the function `CGAL::Polygon_mesh_processing::is_polygon_soup_a_polygon_mesh(polygons)` .

Template Parameters

  PolygonMesh | a model of `MutableFaceGraph`
  PointRange | a model of the concept `RandomAccessContainer` whose value type is the point type
  PolygonRange | a model of the concept `RandomAccessContainer` whose value type is a model of the concept `RandomAccessContainer` whose value type is `std::size_t`
  NamedParameters_PS | a sequence of Named Parameters
  NamedParameters_PM | a sequence of Named Parameters

Parameters

  points | points of the soup of polygons
  polygons | each element in the range describes a polygon using the indices of the points in `points`
  out | the polygon mesh to be built
  np_ps | an optional sequence of Named Parameters among the ones listed below

Optional Named Parameters

  a property map associating points to the elements of the range `points` Type: a model of `ReadablePropertyMap` whose value type is a point type convertible to the point type of the vertex point map associated to the polygon mesh Default: `CGAL::Identity_property_map` |
  an `OutputIterator` containing the pairs source-vertex-index from `points`, target-vertex. Type: a class model of `OutputIterator` accepting `std::pair<int, boost::graph_traits<PolygonMesh>::vertex_descriptor>` Default: `Emptyset_iterator` |
  an `OutputIterator` containing the pairs polygon-index from `polygons`, target-face. Type: a class model of `OutputIterator` accepting `std::pair<int, boost::graph_traits<PolygonMesh>::face_descriptor>` Default: `Emptyset_iterator` |
  a property map associating each soup point of `points` to a vertex of `out`. Type: a class model of `ReadablePropertyMap` with an integer type as key type and `boost::graph_traits<PolygonMesh>::vertex_descriptor` as value type. Default: unused |
  a property map associating each soup polygon of `polygons` to a face of `out` Type: a class model of `ReadablePropertyMap` with an integer type as key type and `boost::graph_traits<PolygonMesh>::face_descriptor` as value type. Default: unused |

Parameters

  np_pm | an optional sequence of Named Parameters among the ones listed below

Optional Named Parameters

  a property map associating points to the vertices of `out` Type: a class model of `ReadWritePropertyMap` with `boost::graph_traits<PolygonMesh>::vertex_descriptor` as key type and `Point_3` as value type Default: `boost::get(CGAL::vertex_point, out)` Extra: If this parameter is omitted, an internal property map for `CGAL::vertex_point_t` must be available in `PolygonMesh`. |

See also
  `CGAL::Polygon_mesh_processing::orient_polygon_soup()`
  `CGAL::Polygon_mesh_processing::is_polygon_soup_a_polygon_mesh()`
  `CGAL::Polygon_mesh_processing::polygon_mesh_to_polygon_soup()`

Examples
  Polygon_mesh_processing/orient_polygon_soup_example.cpp.

## ◆ remove_isolated_points_in_polygon_soup()

template<typename PointRange , typename PolygonRange >

std::size_t CGAL::Polygon_mesh_processing::remove_isolated_points_in_polygon_soup | ( | PointRange & | points,
|  | PolygonRange & | polygons
| ) |  |

`#include <CGAL/Polygon_mesh_processing/repair_polygon_soup.h>`

removes the isolated points from a polygon soup.

A point is considered isolated if it does not appear in any polygon of the soup.

Template Parameters

  PointRange | a model of the concept `SequenceContainer` whose value type is the point type.
  PolygonRange | a model of the concept `RandomAccessContainer` whose `value_type` is itself a model of the concept `RandomAccessContainer` whose `value_type` is `std::size_t`.

Parameters

  points | points of the soup of polygons
  polygons | a vector of polygons. Each element in the vector describes a polygon using the indices of the points in `points`.

Returns
  the number of removed isolated points

See also
  `repair_polygon_soup()`

## ◆ repair_polygon_soup()

template<typename PointRange , typename PolygonRange , typename NamedParameters = parameters::Default_named_parameters>

void CGAL::Polygon_mesh_processing::repair_polygon_soup | ( | PointRange & | points,
|  | PolygonRange & | polygons,
|  | const NamedParameters & | np = `parameters::default_values()`
| ) |  |

`#include <CGAL/Polygon_mesh_processing/repair_polygon_soup.h>`

cleans a given polygon soup through various repairing operations.

More precisely, this function carries out the following tasks, in the same order as they are listed:

- merging of duplicate points, using the function `CGAL::Polygon_mesh_processing::merge_duplicate_points_in_polygon_soup()`;
- simplification of polygons to remove geometrically identical consecutive vertices;
- splitting of "pinched" polygons, that is polygons in which a geometric position appears more than once. The splitting process results in multiple non-pinched polygons;
- removal of invalid polygons, that is polygons with fewer than 2 vertices;
- removal of duplicate polygons, using the function `CGAL::Polygon_mesh_processing::merge_duplicate_polygons_in_polygon_soup()`;
- removal of isolated points, using the function `CGAL::Polygon_mesh_processing::remove_isolated_points_in_polygon_soup()`.

Note that the point and polygon containers will be modified by the repairing operations, and thus the indexing of the polygons will also be changed.

Template Parameters

  PointRange | a model of the concepts `SequenceContainer` and `Swappable` and whose value type is the point type.
  PolygonRange | a model of the concept `SequenceContainer` whose `value_type` is itself a model of the concepts `SequenceContainer`, `Swappable`, and `ReversibleContainer` whose `value_type` is `std::size_t`.
  NamedParameters | a sequence of Named Parameters

Parameters

  points | points of the soup of polygons
  polygons | a vector of polygons. Each element in the vector describes a polygon using the indices of the points in `points`.
  np | an optional sequence of Named Parameters among the ones listed below

Optional Named Parameters

  an instance of a geometric traits class Type: The traits class must provide the nested functors `Less_xyz_3` and `Equal_3` to respectivelycompare lexicographically two points and to check if two points are identical. For each functor `Foo`, a function `Foo foo_object()` must be provided. Default: a CGAL Kernel deduced from the point type, using `CGAL::Kernel_traits` Extra: The geometric traits class must be compatible with the vertex point type. |
  Parameter to indicate, when multiple polygons are duplicates, whether all the duplicate polygons should be removed or if one (arbitrarily chosen) face should be kept. Type: Boolean Default: `false` |
  Parameter to indicate if polygon orientation should be taken into account when determining whether two polygons are duplicates, that is, whether e.g. the triangles `0,1,2` and `0,2,1` are duplicates. Type: Boolean Default: `false` |

## ◆ stitch_borders() [1/3]

template<typename BorderHalfedgeRange , typename PolygonMesh , typename NamedParameters = CGAL::parameters::Default_named_parameters>

std::size_t CGAL::Polygon_mesh_processing::stitch_borders | ( | const BorderHalfedgeRange & | boundary_cycle_representatives,
|  | PolygonMesh & | pmesh,
|  | const NamedParameters & | np = `parameters::default_values()`
| ) |  |

`#include <CGAL/Polygon_mesh_processing/stitch_borders.h>`

Same as the other overload, but the pairs of halfedges to be stitched are automatically found amongst halfedges in cycles described by `boundary_cycle_representatives`.

Two border halfedges `h1` and `h2` are set to be stitched if the points associated to the source and target vertices of `h1` are the same as those of the target and source vertices of `h2`, respectively.

Template Parameters

  BorderHalfedgeRange | a model of `Range` with value type `boost::graph_traits<PolygonMesh>::halfedge_descriptor`
  PolygonMesh | a model of `FaceListGraph` and `MutableFaceGraph`
  NamedParameters | a sequence of Named Parameters

Parameters

  boundary_cycle_representatives | a range of border halfedges, each describing a boundary cycle whose halfedges will be considered for stitching
  pmesh | the polygon mesh to be modified by the stitching procedure
  np | optional sequence of Named Parameters among the ones listed below

Optional Named Parameters

  specifies if the borders should only be stitched only within their own connected component. Type: Boolean Default: `false` |
  a property map associating to each face of `pmesh` a unique index between `0` and `num_faces(pmesh) - 1` Type: a class model of `ReadablePropertyMap` with `boost::graph_traits<PolygonMesh>::face_descriptor` as key type and `std::size_t` as value type Default: an automatically indexed internal map |
  a property map associating points to the vertices of `pmesh` Type: a class model of `ReadWritePropertyMap` with `boost::graph_traits<PolygonMesh>::vertex_descriptor` as key type and `Point_3` as value type Default: `boost::get(CGAL::vertex_point, pmesh)` Extra: If this parameter is omitted, an internal property map for `CGAL::vertex_point_t` must be available in `PolygonMesh`. |
  an instance of a geometric traits class Type: The traits class must provide the nested type `Point_3`, and the nested functors: `Less_xyz_3` to compare lexicographically two points `Equal_3` to check whether two points are identical. For each functor `Foo`, a function `Foo foo_object()` must be provided. Default: a CGAL Kernel deduced from the point type, using `CGAL::Kernel_traits` Extra: The geometric traits class must be compatible with the vertex point type. |

Returns
  the number of pairs of halfedges that were stitched.

See also
  `stitch_boundary_cycle()`
  `stitch_boundary_cycles()`

## ◆ stitch_borders() [2/3]

template<typename PolygonMesh , typename HalfedgePairsRange , typename NamedParameters = CGAL::parameters::Default_named_parameters>

std::size_t CGAL::Polygon_mesh_processing::stitch_borders | ( | PolygonMesh & | pmesh,
|  | const HalfedgePairsRange & | hedge_pairs_to_stitch,
|  | const NamedParameters & | np = `parameters::default_values()`,
|  | std::enable_if_t< boost::has_range_iterator< HalfedgePairsRange >::value > * | = `0`
| ) |  |

`#include <CGAL/Polygon_mesh_processing/stitch_borders.h>`

stitches together border halfedges in a polygon mesh.

The halfedges to be stitched are provided in `hedge_pairs_to_stitch`. For each pair `p` in this vector, `p.second` and its opposite will be removed from `pmesh`.

Template Parameters

  PolygonMesh | a model of `MutableFaceGraph`
  HalfedgePairsRange | a range of `std::pair<boost::graph_traits<PolygonMesh>::halfedge_descriptor, boost::graph_traits<PolygonMesh>::halfedge_descriptor>`, model of `Range`. Its iterator type is `InputIterator`.

Parameters

  pmesh | the polygon mesh to be modified by stitching
  hedge_pairs_to_stitch | a range of `std::pair` of halfedges to be stitched together
  np | an optional sequence of Named Parameters among the ones listed below

Optional Named Parameters

  a property map associating points to the vertices of `pm` Type: a class model of `ReadWritePropertyMap` with `boost::graph_traits<PolygonMesh>::vertex_descriptor` as key type and `Point_3` as value type Default: `boost::get(CGAL::vertex_point, pmesh)` Extra: If this parameter is omitted, an internal property map for `CGAL::vertex_point_t` must be available in `PolygonMesh`. |

Returns
  the number of pairs of halfedges that were stitched.

See also
  `stitch_boundary_cycle()`
  `stitch_boundary_cycles()`

## ◆ stitch_borders() [3/3]

template<typename PolygonMesh , typename NamedParameters = CGAL::parameters::Default_named_parameters>

std::size_t CGAL::Polygon_mesh_processing::stitch_borders | ( | PolygonMesh & | pmesh,
|  | const NamedParameters & | np = `parameters::default_values()`
| ) |  |

`#include <CGAL/Polygon_mesh_processing/stitch_borders.h>`

Same as the other overload, but the pairs of halfedges to be stitched are automatically found amongst all border halfedges.

Two border halfedges `h1` and `h2` are set to be stitched if the points associated to the source and target vertices of `h1` are the same as those of the target and source vertices of `h2`, respectively.

Template Parameters

  BorderHalfedgeRange | a model of `Range` with value type `boost::graph_traits<PolygonMesh>::halfedge_descriptor`
  PolygonMesh | a model of `FaceListGraph` and `MutableFaceGraph`
  NamedParameters | a sequence of Named Parameters

Parameters

  pmesh | the polygon mesh to be modified by the stitching procedure
  np | optional sequence of Named Parameters among the ones listed below

Optional Named Parameters

  a property map associating points to the vertices of `pmesh` Type: a class model of `ReadWritePropertyMap` with `boost::graph_traits<PolygonMesh>::vertex_descriptor` as key type and `Point_3` as value type Default: `boost::get(CGAL::vertex_point, pmesh)` Extra: If this parameter is omitted, an internal property map for `CGAL::vertex_point_t` must be available in `PolygonMesh`. |
  specifies if the borders should only be stitched only within their own connected component. Type: Boolean Default: `false` |
  a property map associating to each face of `pmesh` a unique index between `0` and `num_faces(pmesh) - 1` Type: a class model of `ReadablePropertyMap` with `boost::graph_traits<PolygonMesh>::face_descriptor` as key type and `std::size_t` as value type Default: an automatically indexed internal map |

Returns
  the number of pairs of halfedges that were stitched.

See also
  `stitch_boundary_cycle()`
  `stitch_boundary_cycles()`

## ◆ stitch_boundary_cycle()

template<typename PolygonMesh , typename NamedParameters = CGAL::parameters::Default_named_parameters>

std::size_t CGAL::Polygon_mesh_processing::stitch_boundary_cycle | ( | const typename boost::graph_traits< PolygonMesh >::halfedge_descriptor | h,
|  | PolygonMesh & | pmesh,
|  | const NamedParameters & | np = `parameters::default_values()`
| ) |  |

`#include <CGAL/Polygon_mesh_processing/stitch_borders.h>`

stitches together, whenever possible, two halfedges belonging to the boundary cycle described by the halfedge `h`.

Two border halfedges `h1` and `h2` can be stitched if the points associated to the source and target vertices of `h1` are the same as those of the target and source vertices of `h2`, respectively.

Template Parameters

  PolygonMesh | a model of `MutableFaceGraph`
  NamedParameters | a sequence of Named Parameters

Parameters

  h | a border halfedge of the polygon mesh `pmesh`
  pmesh | the polygon mesh to be stitched
  np | an optional sequence of Named Parameters among the ones listed below

Optional Named Parameters

  a property map associating points to the vertices of `pm` Type: a class model of `ReadWritePropertyMap` with `boost::graph_traits<PolygonMesh>::vertex_descriptor` as key type and `Point_3` as value type Default: `boost::get(CGAL::vertex_point, pmesh)` Extra: If this parameter is omitted, an internal property map for `CGAL::vertex_point_t` must be available in `PolygonMesh`. |
  an instance of a geometric traits class Type: The traits class must provide the nested type `Point_3`, and the nested functors: `Less_xyz_3` to compare lexicographically two points `Equal_3` to check whether two points are identical. For each functor `Foo`, a function `Foo foo_object()` must be provided. Default: a CGAL Kernel deduced from the point type, using `CGAL::Kernel_traits` Extra: The geometric traits class must be compatible with the vertex point type. |

Returns
  the number of pairs of halfedges that were stitched.

See also
  `stitch_boundary_cycles()`
  `stitch_borders()`

## ◆ stitch_boundary_cycles()

template<typename BorderHalfedgeRange , typename PolygonMesh , typename NamedParameters = CGAL::parameters::Default_named_parameters>

std::size_t CGAL::Polygon_mesh_processing::stitch_boundary_cycles | ( | const BorderHalfedgeRange & | boundary_cycle_representatives,
|  | PolygonMesh & | pmesh,
|  | const NamedParameters & | np = `parameters::default_values()`
| ) |  |

`#include <CGAL/Polygon_mesh_processing/stitch_borders.h>`

stitches together, whenever possible, two halfedges belonging to the same boundary cycle.

Two border halfedges `h1` and `h2` can be stitched if the points associated to the source and target vertices of `h1` are the same as those of the target and source vertices of `h2`, respectively.

Template Parameters

  BorderHalfedgeRange | a model of `Range` with value type `boost::graph_traits<PolygonMesh>::halfedge_descriptor`
  PolygonMesh | a model of `MutableFaceGraph`
  NamedParameters | a sequence of Named Parameters

Parameters

  boundary_cycle_representatives | a range of border halfedges, each describing a boundary cycle of the mesh `pmesh`
  pmesh | the polygon mesh to be modified by stitching
  np | an optional sequence of Named Parameters among the ones listed below

Optional Named Parameters

  a property map associating points to the vertices of `pm` Type: a class model of `ReadWritePropertyMap` with `boost::graph_traits<PolygonMesh>::vertex_descriptor` as key type and `Point_3` as value type Default: `boost::get(CGAL::vertex_point, pmesh)` Extra: If this parameter is omitted, an internal property map for `CGAL::vertex_point_t` must be available in `PolygonMesh`. |
  an instance of a geometric traits class Type: The traits class must provide the nested type `Point_3`, and the nested functors: `Less_xyz_3` to compare lexicographically two points `Equal_3` to check whether two points are identical. For each functor `Foo`, a function `Foo foo_object()` must be provided. Default: a CGAL Kernel deduced from the point type, using `CGAL::Kernel_traits` Extra: The geometric traits class must be compatible with the vertex point type. |

Returns
  the number of pairs of halfedges that were stitched.

See also
  `stitch_boundary_cycle()`
  `stitch_borders()`