CGAL 6.1 - CGAL and the Boost Graph Library

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Functions
Selection Functions
Reference Manual

##

Several functions to enlarge or reduce a k-ring selection of vertices, edges, or faces.

## Functions
template<class FaceRange , class FaceGraph , class IsFaceSelectedPMap , class OutputIterator >
OutputIterator | CGAL::expand_face_selection (const FaceRange &selection, FaceGraph &fg, unsigned int k, IsFaceSelectedPMap is_selected, OutputIterator out)
| augments a selection with faces of `fg` that are adjacent to a face in `selection`.
template<class FaceRange , class FaceGraph , class IsFaceSelectedPMap , class OutputIterator >
OutputIterator | CGAL::reduce_face_selection (const FaceRange &selection, FaceGraph &fg, unsigned int k, IsFaceSelectedPMap is_selected, OutputIterator out)
| diminishes a selection of faces from faces adjacent to a non-selected face.
template<typename TriangleMesh , typename IsSelectedMap , typename NamedParameters = parameters::Default_named_parameters>
void | CGAL::regularize_face_selection_borders (TriangleMesh &mesh, IsSelectedMap is_selected, double weight, const NamedParameters &np=parameters::default_values())
| regularizes a selection in order to minimize the length of the border of the selection.
template<class HalfedgeRange , class FaceGraph , class OutputIterator >
OutputIterator | CGAL::select_incident_faces (const HalfedgeRange &hedges, FaceGraph &fg, OutputIterator out)
| Discovers and puts in `out` all faces incident to the target vertex of a halfedge in `hedges`.
template<class EdgeRange , class HalfedgeGraph , class IsEdgeSelectedPMap , class OutputIterator >
OutputIterator | CGAL::expand_edge_selection (const EdgeRange &selection, HalfedgeGraph &fg, unsigned int k, IsEdgeSelectedPMap is_selected, OutputIterator out)
| augments a selection with edges of `fg` that are adjacent to an edge in `selection`.
template<class EdgeRange , class HalfedgeGraph , class IsEdgeSelectedPMap , class OutputIterator >
OutputIterator | CGAL::reduce_edge_selection (const EdgeRange &selection, HalfedgeGraph &fg, unsigned int k, IsEdgeSelectedPMap is_selected, OutputIterator out)
| diminishes a selection of edges from edges adjacent to a non-selected edge.
template<class VertexRange , class HalfedgeGraph , class IsVertexSelectedPMap , class OutputIterator >
OutputIterator | CGAL::expand_vertex_selection (const VertexRange &selection, HalfedgeGraph &fg, unsigned int k, IsVertexSelectedPMap is_selected, OutputIterator out)
| augments a selection with vertices of `fg` that are adjacent to a vertex in `selection`.
template<class VertexRange , class HalfedgeGraph , class IsVertexSelectedPMap , class OutputIterator >
OutputIterator | CGAL::reduce_vertex_selection (const VertexRange &selection, HalfedgeGraph &fg, unsigned int k, IsVertexSelectedPMap is_selected, OutputIterator out)
| diminishes a selection of vertices from vertices adjacent to a non-selected vertex.
template<class TriangleMesh , class FaceRange , class IsSelectedMap >
void | CGAL::expand_face_selection_for_removal (const FaceRange &faces_to_be_deleted, TriangleMesh &tm, IsSelectedMap is_selected)
| Expands a selection of faces so that their removal does not create any non manifold vertex.

## Function Documentation

## ◆ expand_edge_selection()

template<class EdgeRange , class HalfedgeGraph , class IsEdgeSelectedPMap , class OutputIterator >

OutputIterator CGAL::expand_edge_selection | ( | const EdgeRange & | selection,
|  | HalfedgeGraph & | fg,
|  | unsigned int | k,
|  | IsEdgeSelectedPMap | is_selected,
|  | OutputIterator | out
| ) |  |

`#include <CGAL/boost/graph/selection.h>`

augments a selection with edges of `fg` that are adjacent to an edge in `selection`.

This process is applied `k` times considering all edges added in the previous steps. Two edges are said to be adjacent if they are incident to the same face or vertex. Each new edge added in the selection is added exactly once in `out`.

Template Parameters

  EdgeRange | a range of edge descriptors, model of `Range`. Its iterator type is `InputIterator`.
  FaceGraph | a model of `FaceGraph`.
  IsEdgeSelectedPMap | a model of `ReadWritePropertyMap` with `boost::graph_traits<FaceGraph>::edge_descriptor` as key type and `bool` as value type.
  OutputIterator | an output iterator accepting edge descriptors.

Parameters

  selection | the initial selection of edges that will be expanded.
  fg | the graph containing the selected edges.
  k | the number of times the expansion procedure is iteratively applied.
  is_selected | indicates if an edge is part of the selection. It is updated by the function to accommodate new edges added to the selection.
  out | new edges added to the selection are added exactly once in `out`.

## ◆ expand_face_selection()

template<class FaceRange , class FaceGraph , class IsFaceSelectedPMap , class OutputIterator >

OutputIterator CGAL::expand_face_selection | ( | const FaceRange & | selection,
|  | FaceGraph & | fg,
|  | unsigned int | k,
|  | IsFaceSelectedPMap | is_selected,
|  | OutputIterator | out
| ) |  |

`#include <CGAL/boost/graph/selection.h>`

augments a selection with faces of `fg` that are adjacent to a face in `selection`.

This process is applied `k` times considering all faces added in the previous steps. Two faces are said to be adjacent if they share a vertex or an edge. Each new face added in the selection is added exactly once in `out`.

Template Parameters

  FaceRange | a range of face descriptors, model of `Range`. Its iterator type is `InputIterator`.
  FaceGraph | a model of `FaceGraph`.
  IsFaceSelectedPMap | a model of `ReadWritePropertyMap` with `boost::graph_traits<FaceGraph>::face_descriptor` as key type and `bool` as value type.
  OutputIterator | an output iterator accepting face descriptors.

Parameters

  selection | the initial selection of faces that will be expanded.
  fg | the graph containing the selected faces.
  k | the number of times the expansion procedure is iteratively applied.
  is_selected | indicates if a face is part of the selection. It is updated by the function to accommodate new faces added to the selection.
  out | new faces added to the selection are added exactly once in `out`.

## ◆ expand_face_selection_for_removal()

template<class TriangleMesh , class FaceRange , class IsSelectedMap >

void CGAL::expand_face_selection_for_removal | ( | const FaceRange & | faces_to_be_deleted,
|  | TriangleMesh & | tm,
|  | IsSelectedMap | is_selected
| ) |  |

`#include <CGAL/boost/graph/selection.h>`

Expands a selection of faces so that their removal does not create any non manifold vertex.

For each vertex that is incident to a selected face, we turn around that vertex and check if there is exactly one set of consecutive selected faces. If not, additional faces around that vertex are selected to match this condition.

Template Parameters

  TriangleMesh | a model of `FaceGraph` that is triangulated.
  FaceRange | a range of `boost::graph_traits<TriangleMesh>::face_descriptor`, with an iterator type model of `ForwardIterator`.
  IsSelectedMap | a model of `ReadWritePropertyMap` with `boost::graph_traits<TriangleMesh>::face_descriptor` as key and `bool` as value.

Parameters

  tm | the triangle mesh.
  faces_to_be_deleted | the range of selected faces.
  is_selected | a property map containing the selected-or-not status of each face of `tm`. It must associate `true` to each face of `faces_to_be_deleted` and `false` to any other face of `tm`. It will be modified if the face selection must be expanded.

## ◆ expand_vertex_selection()

template<class VertexRange , class HalfedgeGraph , class IsVertexSelectedPMap , class OutputIterator >

OutputIterator CGAL::expand_vertex_selection | ( | const VertexRange & | selection,
|  | HalfedgeGraph & | fg,
|  | unsigned int | k,
|  | IsVertexSelectedPMap | is_selected,
|  | OutputIterator | out
| ) |  |

`#include <CGAL/boost/graph/selection.h>`

augments a selection with vertices of `fg` that are adjacent to a vertex in `selection`.

This process is applied `k` times considering all vertices added in the previous steps. Two vertices are said to be adjacent if they are part of the same face. Each new vertex added in the selection is added exactly once in `out`.

Template Parameters

  VertexRange | a range of vertex descriptors, model of `Range`. Its iterator type is `InputIterator`.
  FaceGraph | a model of `FaceGraph`.
  IsVertexSelectedPMap | a model of `ReadWritePropertyMap` with `boost::graph_traits<FaceGraph>::vertex_descriptor` as key type and `bool` as value type.
  OutputIterator | an output iterator accepting vertex descriptors.

Parameters

  selection | the initial selection of vertices that will be expanded.
  fg | the graph containing the selected vertices.
  k | the number of times the expansion procedure is iteratively applied.
  is_selected | indicates if a vertex is part of the selection. It is updated by the function to accommodate new vertices added to the selection.
  out | new vertices added to the selection are added exactly once in `out`.

## ◆ reduce_edge_selection()

template<class EdgeRange , class HalfedgeGraph , class IsEdgeSelectedPMap , class OutputIterator >

OutputIterator CGAL::reduce_edge_selection | ( | const EdgeRange & | selection,
|  | HalfedgeGraph & | fg,
|  | unsigned int | k,
|  | IsEdgeSelectedPMap | is_selected,
|  | OutputIterator | out
| ) |  |

`#include <CGAL/boost/graph/selection.h>`

diminishes a selection of edges from edges adjacent to a non-selected edge.

This process is applied `k` times considering all edges removed in the previous steps. Two edges are said to be adjacent if they are incident to the same face or vertex. Each edge removed from the selection is added exactly once in `out`.

Template Parameters

  EdgeRange | a range of edge descriptors, model of `Range`. Its iterator type is `InputIterator`.
  FaceGraph | a model of `FaceGraph`.
  IsEdgeSelectedPMap | a model of `ReadWritePropertyMap` with `boost::graph_traits<FaceGraph>::edge_descriptor` as key type and `bool` as value type.
  OutputIterator | an output iterator accepting edge descriptors.

Parameters

  selection | the initial selection of edges that will be reduced.
  fg | the graph containing the selected edges.
  k | the number of times the reduction procedure is iteratively applied.
  is_selected | indicates if an edge is part of the selection. It is updated by the function to accommodate edges removed from the selection.
  out | edges removed from the selection are added exactly once in `out`.

## ◆ reduce_face_selection()

template<class FaceRange , class FaceGraph , class IsFaceSelectedPMap , class OutputIterator >

OutputIterator CGAL::reduce_face_selection | ( | const FaceRange & | selection,
|  | FaceGraph & | fg,
|  | unsigned int | k,
|  | IsFaceSelectedPMap | is_selected,
|  | OutputIterator | out
| ) |  |

`#include <CGAL/boost/graph/selection.h>`

diminishes a selection of faces from faces adjacent to a non-selected face.

This process is applied `k` times considering all faces removed in the previous steps. Two faces are said to be adjacent if they share a vertex or an edge. Each face removed from the selection is added exactly once in `out`.

Template Parameters

  FaceRange | a range of face descriptors, model of `Range`. Its iterator type is `InputIterator`.
  FaceGraph | a model of `FaceGraph`.
  IsFaceSelectedPMap | a model of `ReadWritePropertyMap` with `boost::graph_traits<FaceGraph>::face_descriptor` as key type and `bool` as value type.
  OutputIterator | an output iterator accepting face descriptors.

Parameters

  selection | the initial selection of faces that will be expanded.
  fg | the graph containing the selected faces.
  k | the number of times the reduction procedure is iteratively applied.
  is_selected | indicates if a face is part of the selection. It is updated by the function to accommodate faces removed from the selection.
  out | faces removed from the selection are added exactly once in `out`.

update is-selected attribute and output iterator

## ◆ reduce_vertex_selection()

template<class VertexRange , class HalfedgeGraph , class IsVertexSelectedPMap , class OutputIterator >

OutputIterator CGAL::reduce_vertex_selection | ( | const VertexRange & | selection,
|  | HalfedgeGraph & | fg,
|  | unsigned int | k,
|  | IsVertexSelectedPMap | is_selected,
|  | OutputIterator | out
| ) |  |

`#include <CGAL/boost/graph/selection.h>`

diminishes a selection of vertices from vertices adjacent to a non-selected vertex.

This process is applied `k` times considering all vertices removed in the previous steps. Two vertices are said to be adjacent if they are part of the same face. Each vertex removed from the selection is added exactly once in `out`.

Template Parameters

  VertexRange | a range of vertex descriptors, model of `Range`. Its iterator type is `InputIterator`.
  FaceGraph | a model of `FaceGraph`.
  IsVertexSelectedPMap | a model of `ReadWritePropertyMap` with `boost::graph_traits<FaceGraph>::vertex_descriptor` as key type and `bool` as value type.
  OutputIterator | an output iterator accepting vertex descriptors.

Parameters

  selection | the initial selection of vertices that will be reduced.
  fg | the graph containing the selected vertices.
  k | the number of times the reduction procedure is iteratively applied.
  is_selected | indicates if a vertex is part of the selection. It is updated by the function to accommodate vertices removed from the selection.
  out | vertices removed from the selection are added exactly once in `out`.

## ◆ regularize_face_selection_borders()

template<typename TriangleMesh , typename IsSelectedMap , typename NamedParameters = parameters::Default_named_parameters>

void CGAL::regularize_face_selection_borders | ( | TriangleMesh & | mesh,
|  | IsSelectedMap | is_selected,
|  | double | weight,
|  | const NamedParameters & | np = `parameters::default_values()`
| ) |  |

`#include <CGAL/boost/graph/selection.h>`

regularizes a selection in order to minimize the length of the border of the selection.

The alpha expansion algorithm is used (see `CGAL::alpha_expansion_graphcut()`) using the length of the edge between two faces as the edge cost and the initial selected/unselected property of a face as the face cost.

If `prevent_unselection` is set to `true`, the cost of unselecting a face is set to infinity, which forces the regularization to only select new faces and ensures that the regularization keeps all selected faces.

Template Parameters

  TriangleMesh | a model of `FaceGraph`
  IsSelectedMap | a model of `ReadWritePropertyMap` with `boost::graph_traits<TriangleMesh>::face_descriptor` as key type and `bool` as value type
  NamedParameters | a sequence of named parameters

Parameters

  mesh | the mesh containing the selected faces.
  is_selected | indicates if a face is part of the selection. It is updated by the function to accommodate faces added or removed from the selection.
  weight | sets the tradeoff between data fidelity and regularity, ranging from 0 (no regularization at all, selection is left unaltered) to 1 (maximum regularization, usually selects or unselects everything so that the length of the border of the selection is 0)
  np | an optional sequence of Named Parameters among the ones listed below

Optional Named Parameters

  a property map associating points to the vertices of `tm` Type: a class model of `ReadWritePropertyMap` with `boost::graph_traits<TriangleMesh>::vertex_descriptor` as key type and `Point_3` as value type Default: `boost::get(CGAL::vertex_point, tm)` Extra: If this parameter is omitted, an internal property map for `CGAL::vertex_point_t` must be available in `TriangleMesh`. |
  a property map associating to each face of `tm` a unique index between `0` and `num_faces(tm) - 1` Type: a class model of `ReadablePropertyMap` with `boost::graph_traits<TriangleMesh>::face_descriptor` as key type and `std::size_t` as value type Default: an automatically indexed internal map |
  Boolean used to indicate if selection can be only expanded or if it can also be shrunk. Type: `bool` Default: `false` Extra: The geometric traits class must be compatible with the vertex point type. |
  an instance of a geometric traits class Type: a class model of `Kernel` 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. |

Examples
  BGL_graphcut/face_selection_borders_regularization_example.cpp.

## ◆ select_incident_faces()

template<class HalfedgeRange , class FaceGraph , class OutputIterator >

OutputIterator CGAL::select_incident_faces | ( | const HalfedgeRange & | hedges,
|  | FaceGraph & | fg,
|  | OutputIterator | out
| ) |  |

`#include <CGAL/boost/graph/selection.h>`

Discovers and puts in `out` all faces incident to the target vertex of a halfedge in `hedges`.

Faces are put exactly once in `out`.

Template Parameters

  HalfedgeRange | a range of halfedge descriptors, model of `Range`. Its iterator type is `InputIterator`.
  HalfedgeGraph | a model of `HalfedgeGraph`.
  OutputIterator | an output iterator accepting face descriptors.

Parameters

  hedges | the range a halfedge descriptors consider during the face selection.
  fg | the graph containing the input halfedges.
  out | faces added to the selection are added exactly once in `out`.