CGAL 6.1 - 2D Regularized Boolean Set-Operations

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CGAL::General_polygon_set_2< Traits, Dcel > Class Template Reference
Reference Manual

`#include <CGAL/General_polygon_set_2.h>`

## Definition

template<typename Traits, typename Dcel>
class CGAL::General_polygon_set_2< Traits, Dcel >

An object of the `General_polygon_set_2` class-template represents a point set in the plane bounded by \( x\) monotone curves.

Points in the set lie on the boundary or on the positive side of the curves. This class template provides methods to apply regularized Boolean set-operations and few other utility methods. An `Arrangement_2` data structure is internally used to represent the point set. The arrangement is represented as a doubly-connected edge-list (DCEL).

The `Traits` template-parameter should be instantiated with a model of the concept `GeneralPolygonSetTraits_2`. The traits class defines the types of points, \( x\)-monotone curves, general polygons, and general polygons with holes, that is `Traits::Point_2`, `Traits::X_monotone_curve_2`, `Traits::Polygon_2`, and `Traits::Polygon_with_holes_2`, respectively. `Traits::Point_2` must be the type of the endpoints of `Traits::X_monotone_curve_2`, and `Traits::X_monotone_curve_2` must be the type of the curves that comprise the boundaries of the general polygons. The traits class supports geometric operations on the types above. We sometimes use the term polygon instead of general polygon for simplicity hereafter.

The template parameter `Dcel` should be instantiated with a model of the concept `GeneralPolygonSetDcel`. It is instantiated by default with the type `Gps_default_dcel<Traits>`. You can override this default, with a different DCEL class, typically an extension of the `Gps_default_dcel` class template. Overriding the default is necessary only if you intend to obtain the underlying internal arrangement and process it further.

The input and output of the Boolean set-operations methods consist of one or more general polygons, some of which may have holes. In particular, these methods operate on pairs of objects of type `General_polygon_set_2`, or directly on objects of type `Traits::Polygon_2` or `Traits::Polygon_with_holes_2`. An object of type `Traits::Polygon_2` is a valid operand, only if it is simple and its boundary is oriented counterclockwise. An object of type `Traits::Polygon_with_holes_2` is valid, only if its outer boundary bounds a relatively simple general polygon oriented counterclockwise, and each one of its holes is a simple polygon oriented clockwise. The holes are pairwise disjoint, except perhaps at the vertices, and are contained in the polygon bounded by the outer boundary. The outer boundary and the holes are also pairwise disjoint, except perhaps at the vertices.

See also
  `Arrangement_2`
  `AosXMonotoneTraits_2`
  `Nef_polyhedron_2`

Examples
  Boolean_set_operations_2/bezier_traits_adapter2.cpp, Boolean_set_operations_2/circle_segment.cpp, and Boolean_set_operations_2/dxf_union.cpp.

## Types
typedef unspecified_type | Traits_2
| the traits class in use.
typedef unspecified_type | Polygon_2
| the general polygon type.
typedef unspecified_type | Polygon_with_holes_2
| the general polygon with holes type.
typedef unspecified_type | Size
| number of polygons with holes size type.
typedef unspecified_type | Arrangement_2
| the arrangement type used internally.

## Creation
| General_polygon_set_2 ()
| default constructor; constructs an empty set of polygons `gps` represented by an empty arrangement.
| General_polygon_set_2 (const Self &other)
| copy constructor.
| General_polygon_set_2 (const Traits &traits)
| constructs an empty set of polygons that uses the given `traits` object for performing the geometric operations.
| General_polygon_set_2 (const Polygon_2 &pgn)
| constructs a set of polygons that consists of the single polygon `pgn`.
| General_polygon_set_2 (const Polygon_with_holes_2 &pgn_with_holes)
| constructs a set of polygons that consists of the single polygon with holes `pgn_with_holes`.
| General_polygon_set_2 (const Polygon_2 &pgn, const Traits &traits)
| constructs a set of polygons that uses the given traits object and consists of the single polygon `pgn`.
| General_polygon_set_2 (const Polygon_with_holes_2 &pgn_with_holes, const Traits &traits)
| constructs a set of polygons that uses the given traits object and consists of the single polygon with holes `pgn_with_holes`.

## Access Functions
template<class OutputIterator >
OutputIterator | polygons_with_holes (OutputIterator out)
| obtains the polygons with holes represented by `gps`.
Size | number_of_polygons_with_holes () const
| returns the total number of general polygons represented by `gps`.
bool | is_empty () const
| returns `true` if `gps` represents an empty set.
bool | is_plane () const
| returns `true` if `gps` represents the entire plane.
Traits & | traits () const
| obtains an instance of the traits.
const Arrangement_2 & | arrangement () const
| obtains the arrangement data structure that internally represents the general-polygon set.

## Modifiers
void | clear ()
| clears `gps`.
void | insert (Polygon_2 &pgn)
| inserts `pgn` into `gps`.
void | insert (Polygon_with_holes_2 &pgn_with_holes)
| inserts `pgn_with_holes` into `gps`.
template<class InputIterator >
void | insert (InputIterator begin, InputIterator end)
| inserts the range of polygons (or polygons with holes) into `gps`.
template<class InputIterator1 , class InputIterator2 >
void | insert (InputIterator1 pgn_begin, InputIterator1 pgn_end, InputIterator2 pgn_with_holes_begin, InputIterator2 pgn_with_holes_end)
| inserts the two ranges of polygons and polygons with holes into `gps`.
void | complement ()
| computes the complement of `gps`.
void | complement (const Polygon_set_2 &other)
| computes the complement of `other`.

## Univariate Operations
In the following univariate and bivariate methods the result is placed in `gps` after it is cleared.
void | intersection (const General_polygon_set_2 &other)
| computes the intersection of `gps` and `other`.
void | intersection (const Polygon_2 &pgn)
| computes the intersection of `gps` and `pgn`.
void | intersection (const Polygon_with_holes_2 &pgn)
| computes the intersection of `gps` and `pgn`.
template<class InputIterator >
void | intersection (InputIterator begin, InputIterator end)
| computes the intersection of a collection of point sets.
template<class InputIterator1 , class InputIterator2 >
void | intersection (InputIterator1 pgn_begin, InputIterator1 pgn_end, InputIterator2 pgn_with_holes_begin, InputIterator2 pgn_with_holes_end)
| computes the intersection of a collection of point sets.
void | join (const General_polygon_set_2 &other)
| computes the union of `gps` and `other`.
void | join (const Polygon_2 &pgn)
| computes the union of `gps` and `pgn`.
void | join (const Polygon_with_holes_2 &pgn)
| computes the union of `gps` and `pgn`.
template<class InputIterator >
void | join (InputIterator begin, InputIterator end)
| computes the union of the polygons (or polygons with holes) in the given range and the point set represented by `gps`.
template<class InputIterator1 , class InputIterator2 >
void | join (InputIterator1 pgn_begin, InputIterator1 pgn_end, InputIterator2 pgn_with_holes_begin, InputIterator2 pgn_with_holes_end)
| computes the union of the polygons and polygons with holes in the given two ranges and the point set represented by `gps`.
void | difference (const General_polygon_set_2 &other)
| computes the difference between `gps` and `other`.
void | difference (const Polygon_2 &pgn)
| computes the difference between `gps` and `pgn`.
void | difference (const Polygon_with_holes_2 &pgn)
| computes the difference between `gps` and `pgn`.
void | symmetric_difference (const General_polygon_set_2 &other)
| computes the symmetric difference between `gps` and `other`.
void | symmetric_difference (const Polygon_2 &pgn)
| computes the symmetric difference between `gps` and `pgn`.
void | symmetric_difference (const Polygon_with_holes_2 &pgn)
| computes the symmetric difference between `gps` and `pgn`.
template<class InputIterator >
void | symmetric_difference (InputIterator begin, InputIterator end)
| computes the symmetric difference (xor) of a collection of point sets.
template<class InputIterator1 , class InputIterator2 >
void | symmetric_difference (InputIterator1 pgn_begin, InputIterator1 pgn_end, InputIterator2 pgn_with_holes_begin, InputIterator2 pgn_with_holes_end)
| computes the symmetric difference (xor) of a collection of point sets.

## Bivariate Operations
The following bivariate function replace `gps` with the result.
void | intersection (const General_polygon_set_2 &gps1, const General_polygon_set_2 &gps2)
| computes the intersection of `gps1` and `gps2`.
void | join (const General_polygon_set_2 &gps1, const General_polygon_set_2 &gps2)
| computes the union of `gps1` and `gps2`.
void | difference (const General_polygon_set_2 &gps1, const General_polygon_set_2 &gps2)
| computes the difference between `gps1` and `gps2`.
void | symmetric_difference (const General_polygon_set_2 &gps1, const General_polygon_set_2 &gps2)
| computes the symmetric difference between `gps1` and `gps2`.

## Query Functions
bool | do_intersect (const General_polygon_set_2 &other)
| returns `true` if `gps` and `other` intersect in their interior, and `false` otherwise.
bool | do_intersect (const Polygon_2 &pgn)
| returns `true` if `gps` and `pgn` intersect in their interior, and `false` otherwise.
bool | do_intersect (const Polygon_with_holes_2 &pgn)
| returns `true` if `gps` and `pgn` intersect in their interior, and `false` otherwise.
template<class InputIterator >
void | do_intersect (InputIterator begin, InputIterator end)
| returns `true` if the interior of the point sets in a collection intersect, and `false` otherwise.
template<class InputIterator1 , class InputIterator2 >
void | do_intersect (InputIterator1 pgn_begin, InputIterator1 pgn_end, InputIterator2 pgn_with_holes_begin, InputIterator2 pgn_with_holes_end)
| returns `true` if the interior of the point sets in a collection intersect, and `false` otherwise.
bool | locate (const Point_2 &p, Polygon_with_holes_2 &pgn)
| obtains a polygon with holes that contains the query point `p`, if exists, through `pgn`, and returns `true`.
Oriented_side | oriented_side (const Point_2 &q)
| returns either the constant `ON_ORIENTED_BOUNDARY`, `ON_POSITIVE_SIDE`, or `ON_NEGATIVE_SIDE`, iff `p` lies on the boundary, properly on the positive side, or properly on the negative side of `gps` respectively.
Oriented_side | oriented_side (const General_polygon_set_2 &other)
| returns either the constant `ON_NEGATIVE_SIDE`, `ON_ORIENTED_BOUNDARY`, or `ON_POSITIVE_SIDE`, iff `other` and `gps` are completely disjoint, in contact, or intersect in their interior, respectively.
Oriented_side | oriented_side (const Polygon_2 &pgn)
| returns either the constant `ON_NEGATIVE_SIDE`, `ON_ORIENTED_BOUNDARY`, or `ON_POSITIVE_SIDE`, iff `pgn` and `gps` are completely disjoint, in contact, or intersect in their interior, respectively.
Oriented_side | oriented_side (const Polygon_with_holes_2 &pgn)
| returns either the constant `ON_NEGATIVE_SIDE`, `ON_ORIENTED_BOUNDARY`, or `ON_POSITIVE_SIDE`, iff `pgn` and `gps` are completely disjoint, in contact, or intersect in their interior, respectively.

## Miscellaneous
bool | is_valid () const
| returns `true` if `gps` represents a valid point set.

## Member Typedef Documentation

## ◆ Polygon_2

template<typename Traits , typename Dcel >

typedef unspecified_type CGAL::General_polygon_set_2< Traits, Dcel >::Polygon_2

the general polygon type.

Must model the `GpsTraitsGeneralPolygon_2` concept.

## ◆ Polygon_with_holes_2

template<typename Traits , typename Dcel >

typedef unspecified_type CGAL::General_polygon_set_2< Traits, Dcel >::Polygon_with_holes_2

the general polygon with holes type.

Must model the `GpsTraitsGeneralPolygonWithHoles_2` concept.

## Member Function Documentation

## ◆ complement()

template<typename Traits , typename Dcel >

void CGAL::General_polygon_set_2< Traits, Dcel >::complement | ( | const Polygon_set_2 & | other | ) |

computes the complement of `other`.

`gps` is overridden by the result.

## ◆ do_intersect() [1/2]

template<typename Traits , typename Dcel >
template<class InputIterator >

void CGAL::General_polygon_set_2< Traits, Dcel >::do_intersect | ( | InputIterator | begin,
|  | InputIterator | end
| ) |  |

returns `true` if the interior of the point sets in a collection intersect, and `false` otherwise.

The collection consists of the polygons (or polygons with holes) in the given range and the point set represented by `gps`. (The value type of the input iterator is used to distinguish between the two options.)

## ◆ do_intersect() [2/2]

template<typename Traits , typename Dcel >
template<class InputIterator1 , class InputIterator2 >

void CGAL::General_polygon_set_2< Traits, Dcel >::do_intersect | ( | InputIterator1 | pgn_begin,
|  | InputIterator1 | pgn_end,
|  | InputIterator2 | pgn_with_holes_begin,
|  | InputIterator2 | pgn_with_holes_end
| ) |  |

returns `true` if the interior of the point sets in a collection intersect, and `false` otherwise.

The collection consists of the polygons and polygons with holes in the given two ranges and the point set represented by `gps`.

## ◆ insert() [1/4]

template<typename Traits , typename Dcel >
template<class InputIterator >

void CGAL::General_polygon_set_2< Traits, Dcel >::insert | ( | InputIterator | begin,
|  | InputIterator | end
| ) |  |

inserts the range of polygons (or polygons with holes) into `gps`.

(The value type of the input iterator is used to distinguish between the two.)

Precondition
  If the given range contains objects of type `Polygon_with_holes_2`, then these polygons and the point set represented by `gps` are pairwise disjoint, except maybe at the vertices. If the given range contains objects of type `Polygon_2`, then these polygons and the point set represented by `gps` are pairwise disjoint without any exceptions.

## ◆ insert() [2/4]

template<typename Traits , typename Dcel >
template<class InputIterator1 , class InputIterator2 >

void CGAL::General_polygon_set_2< Traits, Dcel >::insert | ( | InputIterator1 | pgn_begin,
|  | InputIterator1 | pgn_end,
|  | InputIterator2 | pgn_with_holes_begin,
|  | InputIterator2 | pgn_with_holes_end
| ) |  |

inserts the two ranges of polygons and polygons with holes into `gps`.

Precondition
  All polygons in the first range, all polygon with holes in the second range, and the point set represented by `gps` are pairwise disjoint, except maybe at the vertices

## ◆ insert() [3/4]

template<typename Traits , typename Dcel >

void CGAL::General_polygon_set_2< Traits, Dcel >::insert | ( | Polygon_2 & | pgn | ) |

inserts `pgn` into `gps`.

Precondition
  `pgn` and the point set represented by `gps` are disjoint. This precondition enables the use of very efficient insertion methods. Use the respective overloaded method that inserts a polygon of type `Polygon_with_holes_2`, if only a relaxed precondition can be guaranteed. If even the relaxed precondition cannot be guaranteed, use the `join` method.

## ◆ insert() [4/4]

template<typename Traits , typename Dcel >

void CGAL::General_polygon_set_2< Traits, Dcel >::insert | ( | Polygon_with_holes_2 & | pgn_with_holes | ) |

inserts `pgn_with_holes` into `gps`.

Precondition
  `pgn_with_holes` does not intersect with the point set represented by `gps`, except maybe at the vertices. If this relaxed precondition cannot be guaranteed, use the `join` method.

## ◆ intersection() [1/2]

template<typename Traits , typename Dcel >
template<class InputIterator >

void CGAL::General_polygon_set_2< Traits, Dcel >::intersection | ( | InputIterator | begin,
|  | InputIterator | end
| ) |  |

computes the intersection of a collection of point sets.

The collection consists of the polygons (or polygons with holes) in the given range and the point set represented by `gps`. (The value type of the input iterator is used to distinguish between the two options.)

## ◆ intersection() [2/2]

template<typename Traits , typename Dcel >
template<class InputIterator1 , class InputIterator2 >

void CGAL::General_polygon_set_2< Traits, Dcel >::intersection | ( | InputIterator1 | pgn_begin,
|  | InputIterator1 | pgn_end,
|  | InputIterator2 | pgn_with_holes_begin,
|  | InputIterator2 | pgn_with_holes_end
| ) |  |

computes the intersection of a collection of point sets.

The collection consists of the polygons and polygons with holes in the given two ranges and the point set represented by `gps`.

## ◆ join()

template<typename Traits , typename Dcel >
template<class InputIterator >

void CGAL::General_polygon_set_2< Traits, Dcel >::join | ( | InputIterator | begin,
|  | InputIterator | end
| ) |  |

computes the union of the polygons (or polygons with holes) in the given range and the point set represented by `gps`.

(The value type of the input iterator is used to distinguish between the two options.)

## ◆ locate()

template<typename Traits , typename Dcel >

bool CGAL::General_polygon_set_2< Traits, Dcel >::locate | ( | const Point_2 & | p,
|  | Polygon_with_holes_2 & | pgn
| ) |  |

obtains a polygon with holes that contains the query point `p`, if exists, through `pgn`, and returns `true`.

Otherwise, returns `false`.

## ◆ symmetric_difference() [1/2]

template<typename Traits , typename Dcel >
template<class InputIterator >

void CGAL::General_polygon_set_2< Traits, Dcel >::symmetric_difference | ( | InputIterator | begin,
|  | InputIterator | end
| ) |  |

computes the symmetric difference (xor) of a collection of point sets.

The collection consists of the polygons (or polygons with holes) in the given range and the point set represented by `gps`. (The value type of the input iterator is used to distinguish between the two options.)

## ◆ symmetric_difference() [2/2]

template<typename Traits , typename Dcel >
template<class InputIterator1 , class InputIterator2 >

void CGAL::General_polygon_set_2< Traits, Dcel >::symmetric_difference | ( | InputIterator1 | pgn_begin,
|  | InputIterator1 | pgn_end,
|  | InputIterator2 | pgn_with_holes_begin,
|  | InputIterator2 | pgn_with_holes_end
| ) |  |

computes the symmetric difference (xor) of a collection of point sets.

The collection consists of the polygons and polygons with holes in the given two ranges and the point set represented by `gps`.

## ◆ traits()

template<typename Traits , typename Dcel >

Traits & CGAL::General_polygon_set_2< Traits, Dcel >::traits | ( |  | ) | const

obtains an instance of the traits.

If the traits was passed as a parameter to the constructor of `gps`, it is returned. Otherwise, a newly created instance is returned.