CGAL 6.1 - 2D Generalized Barycentric Coordinates

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Functions
Free Functions
Reference Manual

##

Free functions to compute barycentric weights and coordinates.

## Functions
template<typename PointRange , typename OutIterator , typename GeomTraits >
OutIterator | CGAL::Barycentric_coordinates::discrete_harmonic_weights_2 (const PointRange &polygon, const typename GeomTraits::Point_2 &query, OutIterator w_begin, const GeomTraits &traits, const Computation_policy_2 policy=Computation_policy_2::FAST_WITH_EDGE_CASES)
| computes 2D discrete harmonic weights.
template<typename PointRange , typename OutIterator , typename GeomTraits >
OutIterator | CGAL::Barycentric_coordinates::discrete_harmonic_coordinates_2 (const PointRange &polygon, const typename GeomTraits::Point_2 &query, OutIterator c_begin, const GeomTraits &traits, const Computation_policy_2 policy=Computation_policy_2::PRECISE_WITH_EDGE_CASES)
| computes 2D discrete harmonic coordinates.
template<typename PointRange , typename OutIterator , typename GeomTraits >
OutIterator | CGAL::Barycentric_coordinates::mean_value_weights_2 (const PointRange &polygon, const typename GeomTraits::Point_2 &query, OutIterator w_begin, const GeomTraits &traits, const Computation_policy_2 policy=Computation_policy_2::FAST_WITH_EDGE_CASES)
| computes 2D mean value weights.
template<typename PointRange , typename OutIterator , typename GeomTraits >
OutIterator | CGAL::Barycentric_coordinates::mean_value_coordinates_2 (const PointRange &polygon, const typename GeomTraits::Point_2 &query, OutIterator c_begin, const GeomTraits &traits, const Computation_policy_2 policy=Computation_policy_2::PRECISE_WITH_EDGE_CASES)
| computes 2D mean value coordinates.
template<typename PointRange , typename OutIterator , typename GeomTraits >
OutIterator | CGAL::Barycentric_coordinates::wachspress_weights_2 (const PointRange &polygon, const typename GeomTraits::Point_2 &query, OutIterator w_begin, const GeomTraits &traits, const Computation_policy_2 policy=Computation_policy_2::FAST_WITH_EDGE_CASES)
| computes 2D Wachspress weights.
template<typename PointRange , typename OutIterator , typename GeomTraits >
OutIterator | CGAL::Barycentric_coordinates::wachspress_coordinates_2 (const PointRange &polygon, const typename GeomTraits::Point_2 &query, OutIterator c_begin, const GeomTraits &traits, const Computation_policy_2 policy=Computation_policy_2::PRECISE_WITH_EDGE_CASES)
| computes 2D Wachspress coordinates.
template<typename VertexRange , typename OutIterator , typename GeomTraits , typename PointMap >
std::pair< OutIterator, bool > | CGAL::Barycentric_coordinates::boundary_coordinates_2 (const VertexRange &polygon, const typename GeomTraits::Point_2 &query, OutIterator c_begin, const GeomTraits &traits, const PointMap point_map)
| computes 2D boundary coordinates.
template<typename VertexRange , typename Query_2 , typename OutIterator , typename PointMap = CGAL::Identity_property_map<Query_2>>
std::pair< OutIterator, bool > | CGAL::Barycentric_coordinates::boundary_coordinates_2 (const VertexRange &polygon, const Query_2 &query, OutIterator c_begin, const PointMap point_map=PointMap())
| computes 2D boundary coordinates.
template<typename OutIterator , typename GeomTraits >
OutIterator | CGAL::Barycentric_coordinates::segment_coordinates_2 (const typename GeomTraits::Point_2 &p0, const typename GeomTraits::Point_2 &p1, const typename GeomTraits::Point_2 &query, OutIterator c_begin, const GeomTraits &traits)
| computes segment coordinates.
template<typename OutIterator , typename GeomTraits >
OutIterator | CGAL::Barycentric_coordinates::triangle_coordinates_2 (const typename GeomTraits::Point_2 &p0, const typename GeomTraits::Point_2 &p1, const typename GeomTraits::Point_2 &p2, const typename GeomTraits::Point_2 &query, OutIterator c_begin, const GeomTraits &traits)
| computes triangle coordinates.

## Function Documentation

## ◆ boundary_coordinates_2() [1/2]

template<typename VertexRange , typename Query_2 , typename OutIterator , typename PointMap = CGAL::Identity_property_map<Query_2>>

std::pair< OutIterator, bool > CGAL::Barycentric_coordinates::boundary_coordinates_2 | ( | const VertexRange & | polygon,
|  | const Query_2 & | query,
|  | OutIterator | c_begin,
|  | const PointMap | point_map = `PointMap()`
| ) |  |

`#include <CGAL/Barycentric_coordinates_2/boundary_coordinates_2.h>`

computes 2D boundary coordinates.

This is an overload of the function `boundary_coordinates_2`.

Template Parameters

  VertexRange | a model of `ConstRange` whose iterator type is `RandomAccessIterator`
  Query_2 | a model of `Kernel::Point_2`
  OutIterator | a model of `OutputIterator` that accepts values of type `GeomTraits::FT`
  PointMap | a model of `ReadablePropertyMap` whose key type is `VertexRange::value_type` and value type is `Query_2`. The default is `CGAL::Identity_property_map`.

Parameters

  polygon | an instance of `VertexRange` with 2D points, which form a simple polygon
  query | a query point
  c_begin | the beginning of the destination range with the computed coordinates
  point_map | an instance of `PointMap` that maps a vertex from `polygon` to `Query_2`; the default initialization is provided

Returns
  an output iterator to the element in the destination range, one past the last coordinate stored + the flag indicating whether the query point belongs to the polygon boundary

Precondition
  polygon.size() >= 3

## ◆ boundary_coordinates_2() [2/2]

template<typename VertexRange , typename OutIterator , typename GeomTraits , typename PointMap >

std::pair< OutIterator, bool > CGAL::Barycentric_coordinates::boundary_coordinates_2 | ( | const VertexRange & | polygon,
|  | const typename GeomTraits::Point_2 & | query,
|  | OutIterator | c_begin,
|  | const GeomTraits & | traits,
|  | const PointMap | point_map
| ) |  |

`#include <CGAL/Barycentric_coordinates_2/boundary_coordinates_2.h>`

computes 2D boundary coordinates.

This function computes boundary barycentric coordinates at a given `query` point with respect to the vertices of a simple `polygon`, that is one coordinate per vertex. The coordinates are stored in a destination range beginning at `c_begin`.

If `query` is at the vertex, the corresponding coordinate is set to one, while all other coordinates are zero. If `query` is on the edge, the two corresponding coordinates are segment coordinates, while all other coordinates are set to zero. If `query` is not on the boundary, all the coordinates are set to zero.

Internally, `segment_coordinates_2()` are used.

Template Parameters

  VertexRange | a model of `ConstRange` whose iterator type is `RandomAccessIterator`
  OutIterator | a model of `OutputIterator` that accepts values of type `GeomTraits::FT`
  GeomTraits | a model of `BarycentricTraits_2`
  PointMap | a model of `ReadablePropertyMap` whose key type is `VertexRange::value_type` and value type is `GeomTraits::Point_2`

Parameters

  polygon | an instance of `VertexRange` with 2D points, which form a simple polygon
  query | a query point
  c_begin | the beginning of the destination range with the computed coordinates
  traits | a traits class with geometric objects, predicates, and constructions; this parameter can be omitted if the traits class can be deduced from the point type
  point_map | an instance of `PointMap` that maps a vertex from `polygon` to `Point_2`

Returns
  an output iterator to the element in the destination range, one past the last coordinate stored + the flag indicating whether the query point belongs to the polygon boundary

Precondition
  polygon.size() >= 3

Examples
  Barycentric_coordinates_2/discrete_harmonic_coordinates.cpp.

## ◆ discrete_harmonic_coordinates_2()

template<typename PointRange , typename OutIterator , typename GeomTraits >

OutIterator CGAL::Barycentric_coordinates::discrete_harmonic_coordinates_2 | ( | const PointRange & | polygon,
|  | const typename GeomTraits::Point_2 & | query,
|  | OutIterator | c_begin,
|  | const GeomTraits & | traits,
|  | const Computation_policy_2 | policy = `Computation_policy_2::PRECISE_WITH_EDGE_CASES`
| ) |  |

`#include <CGAL/Barycentric_coordinates_2/Discrete_harmonic_coordinates_2.h>`

computes 2D discrete harmonic coordinates.

This function computes 2D discrete harmonic coordinates at a given `query` point with respect to the vertices of a strictly convex `polygon`, that is one coordinate per vertex. The coordinates are stored in a destination range beginning at `c_begin`.

Internally, the class `Discrete_harmonic_coordinates_2` is used. If one wants to process multiple query points, it is better to use that class. When using the free function, internal memory is allocated for each query point, while when using the class, it is allocated only once, which is much more efficient. However, for a few query points, it is easier to use this function. It can also be used when the processing time is not a concern.

Template Parameters

  PointRange | a model of `ConstRange` whose iterator type is `RandomAccessIterator` and value type is `GeomTraits::Point_2`
  OutIterator | a model of `OutputIterator` that accepts values of type `GeomTraits::FT`
  GeomTraits | a model of `BarycentricTraits_2`

Parameters

  polygon | an instance of `PointRange` with 2D points, which form a strictly convex polygon
  query | a query point
  c_begin | the beginning of the destination range with the computed coordinates
  traits | a traits class with geometric objects, predicates, and constructions; this parameter can be omitted if the traits class can be deduced from the point type
  policy | one of the `Computation_policy_2`; the default is `Computation_policy_2::PRECISE_WITH_EDGE_CASES`

Returns
  an output iterator to the element in the destination range, one past the last coordinate stored

Precondition
  polygon.size() >= 3
  polygon is simple
  polygon is strictly convex

## ◆ discrete_harmonic_weights_2()

template<typename PointRange , typename OutIterator , typename GeomTraits >

OutIterator CGAL::Barycentric_coordinates::discrete_harmonic_weights_2 | ( | const PointRange & | polygon,
|  | const typename GeomTraits::Point_2 & | query,
|  | OutIterator | w_begin,
|  | const GeomTraits & | traits,
|  | const Computation_policy_2 | policy = `Computation_policy_2::FAST_WITH_EDGE_CASES`
| ) |  |

`#include <CGAL/Barycentric_coordinates_2/Discrete_harmonic_coordinates_2.h>`

computes 2D discrete harmonic weights.

This function computes 2D discrete harmonic weights at a given `query` point with respect to the vertices of a strictly convex `polygon`, that is one weight per vertex. The weights are stored in a destination range beginning at `w_begin`.

Internally, the class `Discrete_harmonic_coordinates_2` is used. If one wants to process multiple query points, it is better to use that class. When using the free function, internal memory is allocated for each query point, while when using the class, it is allocated only once, which is much more efficient. However, for a few query points, it is easier to use this function. It can also be used when the processing time is not a concern.

Template Parameters

  PointRange | a model of `ConstRange` whose iterator type is `RandomAccessIterator` and value type is `GeomTraits::Point_2`
  OutIterator | a model of `OutputIterator` that accepts values of type `GeomTraits::FT`
  GeomTraits | a model of `BarycentricTraits_2`

Parameters

  polygon | an instance of `PointRange` with 2D points, which form a strictly convex polygon
  query | a query point
  w_begin | the beginning of the destination range with the computed weights
  traits | a traits class with geometric objects, predicates, and constructions; this parameter can be omitted if the traits class can be deduced from the point type
  policy | one of the `Computation_policy_2`; the default is `Computation_policy_2::FAST_WITH_EDGE_CASES`

Returns
  an output iterator to the element in the destination range, one past the last weight stored

Precondition
  polygon.size() >= 3
  polygon is simple
  polygon is strictly convex

## ◆ mean_value_coordinates_2()

template<typename PointRange , typename OutIterator , typename GeomTraits >

OutIterator CGAL::Barycentric_coordinates::mean_value_coordinates_2 | ( | const PointRange & | polygon,
|  | const typename GeomTraits::Point_2 & | query,
|  | OutIterator | c_begin,
|  | const GeomTraits & | traits,
|  | const Computation_policy_2 | policy = `Computation_policy_2::PRECISE_WITH_EDGE_CASES`
| ) |  |

`#include <CGAL/Barycentric_coordinates_2/Mean_value_coordinates_2.h>`

computes 2D mean value coordinates.

This function computes 2D mean value coordinates at a given `query` point with respect to the vertices of a simple `polygon`, that is one coordinate per vertex. The coordinates are stored in a destination range beginning at `c_begin`.

Internally, the class `Mean_value_coordinates_2` is used. If one wants to process multiple query points, it is better to use that class. When using the free function, internal memory is allocated for each query point, while when using the class, it is allocated only once, which is much more efficient. However, for a few query points, it is easier to use this function. It can also be used when the processing time is not a concern.

Template Parameters

  PointRange | a model of `ConstRange` whose iterator type is `RandomAccessIterator` and value type is `GeomTraits::Point_2`
  OutIterator | a model of `OutputIterator` that accepts values of type `GeomTraits::FT`
  GeomTraits | a model of `BarycentricTraits_2`

Parameters

  polygon | an instance of `PointRange` with 2D points, which form a simple polygon
  query | a query point
  c_begin | the beginning of the destination range with the computed coordinates
  traits | a traits class with geometric objects, predicates, and constructions; this parameter can be omitted if the traits class can be deduced from the point type
  policy | one of the `Computation_policy_2`; the default is `Computation_policy_2::PRECISE_WITH_EDGE_CASES`

Returns
  an output iterator to the element in the destination range, one past the last coordinate stored

Precondition
  polygon.size() >= 3
  polygon is simple

Examples
  Barycentric_coordinates_2/mean_value_coordinates.cpp.

## ◆ mean_value_weights_2()

template<typename PointRange , typename OutIterator , typename GeomTraits >

OutIterator CGAL::Barycentric_coordinates::mean_value_weights_2 | ( | const PointRange & | polygon,
|  | const typename GeomTraits::Point_2 & | query,
|  | OutIterator | w_begin,
|  | const GeomTraits & | traits,
|  | const Computation_policy_2 | policy = `Computation_policy_2::FAST_WITH_EDGE_CASES`
| ) |  |

`#include <CGAL/Barycentric_coordinates_2/Mean_value_coordinates_2.h>`

computes 2D mean value weights.

This function computes 2D mean value weights at a given `query` point with respect to the vertices of a simple `polygon`, that is one weight per vertex. The weights are stored in a destination range beginning at `w_begin`.

Internally, the class `Mean_value_coordinates_2` is used. If one wants to process multiple query points, it is better to use that class. When using the free function, internal memory is allocated for each query point, while when using the class, it is allocated only once, which is much more efficient. However, for a few query points, it is easier to use this function. It can also be used when the processing time is not a concern.

Template Parameters

  PointRange | a model of `ConstRange` whose iterator type is `RandomAccessIterator` and value type is `GeomTraits::Point_2`
  OutIterator | a model of `OutputIterator` that accepts values of type `GeomTraits::FT`
  GeomTraits | a model of `BarycentricTraits_2`

Parameters

  polygon | an instance of `PointRange` with 2D points, which form a simple polygon
  query | a query point
  w_begin | the beginning of the destination range with the computed weights
  traits | a traits class with geometric objects, predicates, and constructions; this parameter can be omitted if the traits class can be deduced from the point type
  policy | one of the `Computation_policy_2`; the default is `Computation_policy_2::FAST_WITH_EDGE_CASES`

Returns
  an output iterator to the element in the destination range, one past the last weight stored

Precondition
  polygon.size() >= 3
  polygon is simple

## ◆ segment_coordinates_2()

template<typename OutIterator , typename GeomTraits >

OutIterator CGAL::Barycentric_coordinates::segment_coordinates_2 | ( | const typename GeomTraits::Point_2 & | p0,
|  | const typename GeomTraits::Point_2 & | p1,
|  | const typename GeomTraits::Point_2 & | query,
|  | OutIterator | c_begin,
|  | const GeomTraits & | traits
| ) |  |

`#include <CGAL/Barycentric_coordinates_2/segment_coordinates_2.h>`

computes segment coordinates.

This function computes barycentric coordinates at a given `query` point with respect to the end points `p0` and `p1` of a segment that is one coordinate per end point. The coordinates are stored in a destination range beginning at `c_begin`.

After the coordinates \(b_0\) and \(b_1\) are computed, the query point \(q\) can be obtained as \(q = b_0p_0 + b_1p_1\). If \(q\) does not belong to the line through \(p_0\) and \(p_1\), it is projected onto this line, and only then the coordinates are computed. See more details in the user manual here.

Template Parameters

  OutIterator | a model of `OutputIterator` that accepts values of type `GeomTraits::FT`
  GeomTraits | a model of `BarycentricTraits_2`

Parameters

  p0 | the first vertex of a segment
  p1 | the second vertex of a segment
  query | a query point
  c_begin | the beginning of the destination range with the computed coordinates
  traits | a traits class with geometric objects, predicates, and constructions; this parameter can be omitted if the traits class can be deduced from the point type

Returns
  an output iterator to the element in the destination range, one past the last coordinate stored

Precondition
  p0 != p1

Examples
  Barycentric_coordinates_2/segment_coordinates.cpp.

## ◆ triangle_coordinates_2()

template<typename OutIterator , typename GeomTraits >

OutIterator CGAL::Barycentric_coordinates::triangle_coordinates_2 | ( | const typename GeomTraits::Point_2 & | p0,
|  | const typename GeomTraits::Point_2 & | p1,
|  | const typename GeomTraits::Point_2 & | p2,
|  | const typename GeomTraits::Point_2 & | query,
|  | OutIterator | c_begin,
|  | const GeomTraits & | traits
| ) |  |

`#include <CGAL/Barycentric_coordinates_2/triangle_coordinates_2.h>`

computes triangle coordinates.

This function computes barycentric coordinates at a given `query` point with respect to the points `p0`, `p1`, and `p2`, which form a triangle, that is one coordinate per point. The coordinates are stored in a destination range beginning at `c_begin`.

After the coordinates \(b_0\), \(b_1\), and \(b_2\) are computed, the query point \(q\) can be obtained as \(q = b_0p_0 + b_1p_1 + b_2p_2\). See more details in the user manual here.

Template Parameters

  OutIterator | a model of `OutputIterator` that accepts values of type `GeomTraits::FT`
  GeomTraits | a model of `BarycentricTraits_2`

Parameters

  p0 | the first vertex of a triangle
  p1 | the second vertex of a triangle
  p2 | the third vertex of a triangle
  query | a query point
  c_begin | the beginning of the destination range with the computed coordinates
  traits | a traits class with geometric objects, predicates, and constructions; this parameter can be omitted if the traits class can be deduced from the point type

Returns
  an output iterator to the element in the destination range, one past the last coordinate stored

Precondition
  area_2(p0, p1, p2) != 0

Examples
  Barycentric_coordinates_2/triangle_coordinates.cpp.

## ◆ wachspress_coordinates_2()

template<typename PointRange , typename OutIterator , typename GeomTraits >

OutIterator CGAL::Barycentric_coordinates::wachspress_coordinates_2 | ( | const PointRange & | polygon,
|  | const typename GeomTraits::Point_2 & | query,
|  | OutIterator | c_begin,
|  | const GeomTraits & | traits,
|  | const Computation_policy_2 | policy = `Computation_policy_2::PRECISE_WITH_EDGE_CASES`
| ) |  |

`#include <CGAL/Barycentric_coordinates_2/Wachspress_coordinates_2.h>`

computes 2D Wachspress coordinates.

This function computes 2D Wachspress coordinates at a given `query` point with respect to the vertices of a strictly convex `polygon`, that is one coordinate per vertex. The coordinates are stored in a destination range beginning at `c_begin`.

Internally, the class `Wachspress_coordinates_2` is used. If one wants to process multiple query points, it is better to use that class. When using the free function, internal memory is allocated for each query point, while when using the class, it is allocated only once, which is much more efficient. However, for a few query points, it is easier to use this function. It can also be used when the processing time is not a concern.

Template Parameters

  PointRange | a model of `ConstRange` whose iterator type is `RandomAccessIterator` and value type is `GeomTraits::Point_2`
  OutIterator | a model of `OutputIterator` that accepts values of type `GeomTraits::FT`
  GeomTraits | a model of `BarycentricTraits_2`

Parameters

  polygon | an instance of `PointRange` with 2D points, which form a strictly convex polygon
  query | a query point
  c_begin | the beginning of the destination range with the computed coordinates
  traits | a traits class with geometric objects, predicates, and constructions; this parameter can be omitted if the traits class can be deduced from the point type
  policy | one of the `Computation_policy_2`; the default is `Computation_policy_2::PRECISE_WITH_EDGE_CASES`

Returns
  an output iterator to the element in the destination range, one past the last coordinate stored

Precondition
  polygon.size() >= 3
  polygon is simple
  polygon is strictly convex

Examples
  Barycentric_coordinates_2/wachspress_coordinates.cpp.

## ◆ wachspress_weights_2()

template<typename PointRange , typename OutIterator , typename GeomTraits >

OutIterator CGAL::Barycentric_coordinates::wachspress_weights_2 | ( | const PointRange & | polygon,
|  | const typename GeomTraits::Point_2 & | query,
|  | OutIterator | w_begin,
|  | const GeomTraits & | traits,
|  | const Computation_policy_2 | policy = `Computation_policy_2::FAST_WITH_EDGE_CASES`
| ) |  |

`#include <CGAL/Barycentric_coordinates_2/Wachspress_coordinates_2.h>`

computes 2D Wachspress weights.

This function computes 2D Wachspress weights at a given `query` point with respect to the vertices of a strictly convex `polygon`, that is one weight per vertex. The weights are stored in a destination range beginning at `w_begin`.

Internally, the class `Wachspress_coordinates_2` is used. If one wants to process multiple query points, it is better to use that class. When using the free function, internal memory is allocated for each query point, while when using the class, it is allocated only once, which is much more efficient. However, for a few query points, it is easier to use this function. It can also be used when the processing time is not a concern.

Template Parameters

  PointRange | a model of `ConstRange` whose iterator type is `RandomAccessIterator` and value type is `GeomTraits::Point_2`
  OutIterator | a model of `OutputIterator` that accepts values of type `GeomTraits::FT`
  GeomTraits | a model of `BarycentricTraits_2`

Parameters

  polygon | an instance of `PointRange` with 2D points, which form a strictly convex polygon
  query | a query point
  w_begin | the beginning of the destination range with the computed weights
  traits | a traits class with geometric objects, predicates, and constructions; this parameter can be omitted if the traits class can be deduced from the point type
  policy | one of the `Computation_policy_2`; the default is `Computation_policy_2::FAST_WITH_EDGE_CASES`

Returns
  an output iterator to the element in the destination range, one past the last weight stored

Precondition
  polygon.size() >= 3
  polygon is simple
  polygon is strictly convex