CGAL 6.1 - 2D and Surface Function Interpolation

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Functions
CGAL::regular_neighbor_coordinates_2()
Reference Manual » Natural Neighbor Coordinate Computation

##

The functions `regular_neighbor_coordinates_2()` compute natural neighbor coordinates, also called Sibson's coordinates, for weighted `2D` points provided a two-dimensional regular triangulation and a (weighted) query point inside the convex hull of the vertices of the triangulation.

We call these coordinates regular neighbor coordinates.

Implementation

This function computes the areas stolen from the power cells of points in the regular triangulation `rt` by the insertion of the query point `p`. The total area of the power cell of `p` is also computed and returned by the function.

Attention
  If `p` lies outside the convex hull, the coordinate values cannot be computed and the third value of the result triple is set to `false`.

Output Format

The return type is identical for all overloads of `CGAL::regular_neighbor_coordinates_2()`: it is `CGAL::Triple<CoordinateOutputIterator, Rt::Geom_traits::FT, bool >`

Regular neighbor coordinates are output in the first value of the triple, using an output iterator (see the concept `OutputIterator`). Internally, these coordinates are associated to some of the vertices of the triangulation, and a natural value type for the output iterator would thus be `std::pair<Rt::Vertex_handle, Rt::Geom_traits::FT>`. However, to allow flexibility in the format of the output, a functor passed as argument can be used to format the output as desired: this functor must have argument type `std::pair<Rt::Vertex_handle, Rt::Geom_traits::FT>` and its result type and the value type of the output iterator must be identical.

For example, we can use a functor of type CGAL::Identity<std::pair<Rt::Vertex_handle, Rt::Geom_traits::FT> > and an output iterator with value type `std::pair<Rt::Vertex_handle, Rt::Geom_traits::FT>` or we could extract the bare point and use a value type: `std::pair<Rt::Weighted_point, Rt::Geom_traits::FT>`, or simply the coordinates, etc.

This functor can be omitted and will default, for backward compatibility reasons, to a functor that extracts the point from the vertex, and the output iterator must then have value type `std::pair<Rt::Weighted_point, Rt::Geom_traits::FT>`.

See also
  `CGAL::natural_neighbor_coordinates_2()`
  `3D Surface Neighbor Coordinates Functions`
  `Interpolation Functions`

## Functions
template<class Rt , class CoordinateOutputIterator , class OutputFunctor >
CGAL::Triple< CoordinateOutputIterator, typename Rt::Geom_traits::FT, bool > | CGAL::regular_neighbor_coordinates_2 (const Rt &rt, const typename Rt::Weighted_point &p, CoordinateOutputIterator out, OutputFunctor fct, typename Rt::Face_handle start=typename Rt::Face_handle())
| Computes the regular neighbor coordinates for `p` with respect to the weighted points in the two-dimensional regular triangulation `rt`.
template<class Rt , class CoordinateOutputIterator , class OutputFunctor , class EdgeIterator , class VertexIterator >
CGAL::Triple< CoordinateOutputIterator, typename Traits::FT, bool > | CGAL::regular_neighbor_coordinates_2 (const Rt &rt, const typename Traits::Weighted_point &p, CoordinateOutputIterator out, OutputFunctor fct, EdgeIterator hole_begin, EdgeIterator hole_end, VertexIterator hidden_vertices_begin, VertexIterator hidden_vertices_end)
| Computes the regular neighbor coordinates for `p` with respect to the weighted points in the two-dimensional regular triangulation `rt`.
template<class Rt , class CoordinateOutputIterator , class OutputFunctor >
CGAL::Triple< CoordinateOutputIterator, typename Rt::Geom_traits::FT, bool > | CGAL::regular_neighbor_coordinates_2 (const Rt &rt, typename Rt::Vertex_handle vh, CoordinateOutputIterator out, OutputFunctor fct)
| Computes the regular neighbor coordinates of the point `vh->point()` with respect to the vertices of `rt` excluding `vh->point()`.

## Function Documentation

## ◆ regular_neighbor_coordinates_2() [1/3]

template<class Rt , class CoordinateOutputIterator , class OutputFunctor >

CGAL::Triple< CoordinateOutputIterator, typename Rt::Geom_traits::FT, bool > CGAL::regular_neighbor_coordinates_2 | ( | const Rt & | rt,
|  | const typename Rt::Weighted_point & | p,
|  | CoordinateOutputIterator | out,
|  | OutputFunctor | fct,
|  | typename Rt::Face_handle | start = `typename Rt::Face_handle()`
| ) |  |

`#include <CGAL/regular_neighbor_coordinates_2.h>`

Computes the regular neighbor coordinates for `p` with respect to the weighted points in the two-dimensional regular triangulation `rt`.

Template Parameters

  Rt | must be a `Regular_triangulation_2<Traits, Tds>`. `Traits` must be a model of the concepts `RegularTriangulationTraits_2` and `PolygonTraits_2`.
  CoordinateOutputIterator | must be a model of `OutputIterator` and have the value type `OutputFunctor::result_type`. The output computed by the function is placed starting at `out`.
  OutputFunctor | must be a functor with argument type `std::pair<Rt::Vertex_handle, Rt::Geom_traits::FT>`.

See above for a detailed explanation on the usage of `OutputFunctor`.

Parameters

  rt | is the regular triangulation.
  p | is the query point.
  out | is an object of type `CoordinateOutputIterator`.
  fct | is an object of type `OutputFunctor`.
  start | is an optional argument that is used as a hint of where the locate process has to start its search.

Returns
  A triple consisting of:
  - a sequence of objects of types `OutputFunctor::result_type`, starting at `out`.
  - the normalization factor of the coordinates.
  - a Boolean value which is set to `true` if the coordinate computation was successful, and `false` otherwise.

Warning
  If the weight of `p` is so small that the point `p` would not have any power cell if it were inserted in the power diagram, then the resulting triple will be `(out, 0, true)` with no additional entry in `out` (compared to its state in input).

Examples
  Interpolation/rn_coordinates_2.cpp.

## ◆ regular_neighbor_coordinates_2() [2/3]

template<class Rt , class CoordinateOutputIterator , class OutputFunctor , class EdgeIterator , class VertexIterator >

CGAL::Triple< CoordinateOutputIterator, typename Traits::FT, bool > CGAL::regular_neighbor_coordinates_2 | ( | const Rt & | rt,
|  | const typename Traits::Weighted_point & | p,
|  | CoordinateOutputIterator | out,
|  | OutputFunctor | fct,
|  | EdgeIterator | hole_begin,
|  | EdgeIterator | hole_end,
|  | VertexIterator | hidden_vertices_begin,
|  | VertexIterator | hidden_vertices_end
| ) |  |

`#include <CGAL/regular_neighbor_coordinates_2.h>`

Computes the regular neighbor coordinates for `p` with respect to the weighted points in the two-dimensional regular triangulation `rt`.

The iterator range `[hole_begin, hole_end)` determines the boundary edges of the conflict zone of `p` in the triangulation `rt`. `rt.hidden_vertices_begin()` and `rt.hidden_vertices_end()` determines the iterator range over the hidden vertices of the conflict zone of `p` in`rt`. Those ranges can, for example, be computed using the function `rt.get_boundary_of_conflicts_and_hidden_vertices(p,std::back_inserter(hole), std::back_inserter(hidden_vertices), start)`.

Requirements
Same as above.

## ◆ regular_neighbor_coordinates_2() [3/3]

template<class Rt , class CoordinateOutputIterator , class OutputFunctor >

CGAL::Triple< CoordinateOutputIterator, typename Rt::Geom_traits::FT, bool > CGAL::regular_neighbor_coordinates_2 | ( | const Rt & | rt,
|  | typename Rt::Vertex_handle | vh,
|  | CoordinateOutputIterator | out,
|  | OutputFunctor | fct
| ) |  |

`#include <CGAL/regular_neighbor_coordinates_2.h>`

Computes the regular neighbor coordinates of the point `vh->point()` with respect to the vertices of `rt` excluding `vh->point()`.

Requirements
Same as above.