CGAL 6.2 - 2D and Surface Function Interpolation

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Modules | Classes | Functions
Interpolation Functions
Reference Manual

##

## Modules
| Sibson Gradient Fitting Functions
| The first function implements Sibson's gradient estimation method based on natural neighbor coordinates [9].

## Classes
class | CGAL::Interpolation_gradient_fitting_traits_2< K >
| `Interpolation_gradient_fitting_traits_2` is a model for the concepts `InterpolationTraits` and `GradientFittingTraits`. More...
class | CGAL::Interpolation_traits_2< K >
| `Interpolation_traits_2` is a model for the concept `InterpolationTraits` and can be used to instantiate the geometric traits class of interpolation methods applied on a bivariate function over a two-dimensional domain. More...

## Functions
template<class CoordinateInputIterator , class ValueFunctor >
ValueFunctor::result_type::first_type | CGAL::linear_interpolation (CoordinateInputIterator first, CoordinateInputIterator beyond, const typename std::iterator_traits< CoordinateInputIterator >::value_type::second_type &norm, ValueFunctor value_function)
| The function `linear_interpolation()` computes the weighted sum of the function values which must be provided via a functor.
template<class CoordinateInputIterator , class ValueFunctor , class GradFunctor , class Traits , class Point >
ValueFunctor::result_type | CGAL::quadratic_interpolation (CoordinateInputIterator first, CoordinateInputIterator beyond, const typename std::iterator_traits< CoordinateInputIterator >::value_type::second_type &norm, const Point &p, ValueFunctor value_function, GradFunctor gradient_function, const Traits &traits)
| The function `quadratic_interpolation()` generates the interpolated function value as the weighted sum of the values plus a linear term in the gradient for each entity of the entity/coordinate pairs in the range `[first, beyond)`.
template<class CoordinateInputIterator , class ValueFunctor , class GradFunctor , class Traits , class Point >
std::pair< typename ValueFunctor::result_type, bool > | CGAL::sibson_c1_interpolation (CoordinateInputIterator first, CoordinateInputIterator beyond, const typename std::iterator_traits< CoordinateInputIterator >::value_type::second_type &norm, const Point &p, ValueFunctor value_function, GradFunctor gradient_function, const Traits &traits)
| The function `sibson_c1_interpolation()` generates the interpolated function value at the point `p`, using functors for the function values and the gradients, by applying Sibson's \( Z^1\) interpolant.
template<class CoordinateInputIterator , class ValueFunctor , class GradFunctor , class Traits , class Point >
ValueFunctor::result_type | CGAL::sibson_c1_interpolation_square (CoordinateInputIterator first, CoordinateInputIterator beyond, const typename std::iterator_traits< CoordinateInputIterator >::value_type::second_type &norm, const Point &p, ValueFunctor value_function, GradFunctor gradient_function, const Traits &traits)
| Same as `sibson_c1_interpolation()`, except that no square root operation is required for the number type `Traits::FT`.
template<class CoordinateInputIterator , class ValueFunctor , class GradFunctor , class Traits , class Point >
ValueFunctor::result_type | CGAL::farin_c1_interpolation (CoordinateInputIterator first, CoordinateInputIterator beyond, const typename std::iterator_traits< CoordinateInputIterator >::value_type::second_type &norm, const Point &p, ValueFunctor value_function, GradFunctor gradient_function, const Traits &traits)
| Generates the interpolated function value computed by Farin's interpolant.

## Function Documentation

## ◆ farin_c1_interpolation()

template<class CoordinateInputIterator , class ValueFunctor , class GradFunctor , class Traits , class Point >

ValueFunctor::result_type CGAL::farin_c1_interpolation | ( | CoordinateInputIterator | first,
|  | CoordinateInputIterator | beyond,
|  | const typename std::iterator_traits< CoordinateInputIterator >::value_type::second_type & | norm,
|  | const Point & | p,
|  | ValueFunctor | value_function,
|  | GradFunctor | gradient_function,
|  | const Traits & | traits
| ) |  |

`#include <CGAL/interpolation_functions.h>`

Generates the interpolated function value computed by Farin's interpolant.

Requirements

Same requirements as the function `sibson_c1_interpolation()`, but the input iterator must provide random access (be a model of `RandomAccessIterator`) and `Traits::FT` does not need to provide the square root operation.

Precondition
  The range `[first, beyond)` contains either one or more than three elements. The function `farin_c1_interpolation()` interpolates the function values and the gradients that are provided by functors using the method described in [4].

See also
  `CGAL::sibson_c1_interpolation()`

Examples
  Interpolation/interpolation_2.cpp.

## ◆ linear_interpolation()

template<class CoordinateInputIterator , class ValueFunctor >

ValueFunctor::result_type::first_type CGAL::linear_interpolation | ( | CoordinateInputIterator | first,
|  | CoordinateInputIterator | beyond,
|  | const typename std::iterator_traits< CoordinateInputIterator >::value_type::second_type & | norm,
|  | ValueFunctor | value_function
| ) |  |

`#include <CGAL/interpolation_functions.h>`

The function `linear_interpolation()` computes the weighted sum of the function values which must be provided via a functor.

Template Parameters

  CoordinateInputIterator | must be a model of `ForwardIterator` and must have as value type a pair associating an entity, e.g. the `Vertex_handle` or `Point` types of a triangulation, to a (non-normalized) barycentric coordinate.
  ValueFunctor | must be a functor where `ValueFunctor::argument_type` must be equivalent to `std::iterator_traits<CoordinateInputIterator>::value_type::first_type` and `ValueFunctor::result_type` is a pair of the function value type and a Boolean. The function value type `VT` must provide an addition operator, and a multiplication operator with the type `Traits::FT`.

A model of the functor `ValueFunctor` is provided by the struct `CGAL::Data_access` instantiated with an associative container (e.g. `std::map`) and having:

- `std::iterator_traits<CoordinateInputIterator>::value_type::first_type` (the entity type) as `key_type`
- `std::iterator_traits<CoordinateInputIterator>::value_type::second_type` (the coordinate type) as `mapped_type`.

The two template parameters must satisfy the following conditions:

- `std::iterator_traits<CoordinateInputIterator>::value_type::first_type` (the entity type) is equivalent to a `ValueFunctor::argument_type`.
- `std::iterator_traits<CoordinateInputIterator>::value_type::second_type` (the coordinate type) is a field number type that is equivalent to `ValueFunctor::result_type::first_type`.

For example, if `CoordinateInputIterator` is an iterator with value type `std::pair<Vertex_handle, double>`, then the `ValueFunctor` must have argument type `Vertex_handle` (or convertible to) and return type `std::pair<double, bool>`.

Parameters

  first,beyond | is the iterator range for the coordinates.
  norm | is the normalization factor.
  value_function | is a functor of type `ValueFunctor` that allows to access a pair of a function value and a Boolean at a given entity. The Boolean indicates whether the function value could be retrieved correctly. This function generates the interpolated function value as the weighted sum of the values corresponding to each entry of the entity/coordinate pairs in the range `[first, beyond)`.

Precondition
  `norm` \( \neq0\).
  `first != beyond`.
  `value_function(p.first).second == true` for all pairs `p` in the range `[first, beyond)`.

See also
  `CGAL::quadratic_interpolation()`
  `CGAL::natural_neighbor_coordinates_2()`
  `CGAL::regular_neighbor_coordinates_2()`
  `3D Surface Neighbor Coordinates Functions`

Examples
  Interpolation/interpolation_2.cpp, Interpolation/linear_interpolation_2.cpp, and Interpolation/linear_interpolation_of_vector_3.cpp.

## ◆ quadratic_interpolation()

template<class CoordinateInputIterator , class ValueFunctor , class GradFunctor , class Traits , class Point >

ValueFunctor::result_type CGAL::quadratic_interpolation | ( | CoordinateInputIterator | first,
|  | CoordinateInputIterator | beyond,
|  | const typename std::iterator_traits< CoordinateInputIterator >::value_type::second_type & | norm,
|  | const Point & | p,
|  | ValueFunctor | value_function,
|  | GradFunctor | gradient_function,
|  | const Traits & | traits
| ) |  |

`#include <CGAL/interpolation_functions.h>`

The function `quadratic_interpolation()` generates the interpolated function value as the weighted sum of the values plus a linear term in the gradient for each entity of the entity/coordinate pairs in the range `[first, beyond)`.

Returns
  If the interpolation was successful, the pair contains the interpolated function value as first and `true` as second value. Otherwise, the second value will be `false`.

Template Parameters

  Traits | must be a model of `InterpolationTraits`. Note that, contrary to some other interpolation methods, the number type `FT` provided by `Traits` does not need to provide the square root operation.
  CoordinateInputIterator | must be a model of `ForwardIterator` and must have as value type a pair associating an entity to a (non-normalized) barycentric coordinate. More precisely, `std::iterator_traits<CoordinateInputIterator>::value_type::first_type` can be of the following types: a type equivalent to `Traits::Point_d` or `Traits::Weighted_point_d` an iterator type providing a `point()` function returning a type equivalent to `Traits::Point_d` or `Traits::Weighted_point_d`; and `std::iterator_traits<CoordinateInputIterator>::value_type::second_type` must be equivalent to `Traits::FT`.
  ValueFunctor | must be a functor where `ValueFunctor::argument_type` must be equivalent to `std::iterator_traits<CoordinateInputIterator>::value_type::first_type` and `ValueFunctor::result_type` is a pair of the function value type and a Boolean. The function value type must provide a multiplication and addition operation with the type `Traits::FT` as well as a constructor with argument `0`.
  GradFunctor | must be a functor where `GradFunctor::argument_type` must be equivalent to `std::iterator_traits<CoordinateInputIterator>::value_type::first_type` and `Functor::result_type` is a pair of the function's gradient type and a Boolean. The function gradient type must provide a multiplication operation with `Traits::Vector_d`.
  Point | must be equivalent to `Traits::Point_d` or `Traits::Weighted_point_d`.

A model of the functor types `ValueFunctor` (resp. `GradFunctor`) is provided by the struct `CGAL::Data_access`. It must be instantiated accordingly with an associative container (e.g. `std::map`) having `std::iterator_traits<CoordinateInputIterator>::value_type::first_type` as `key_type` and the function value type (resp. the function gradient type) as `mapped_type`.

Parameters

  first,beyond | is the iterator range of the barycentric coordinates for the query point `p`.
  norm | is the normalization factor.
  p | is the point at which the interpolated function value is computed.
  value_function | is a functor that allows to access values of the interpolated function.
  gradient_function | is a functor that allows to access the function gradients. If the functor `gradient_function` cannot supply the gradient of a point, the function returns a pair where the Boolean is set to `false`.
  traits | is an instance of the traits class.

Precondition
  `norm` \( \neq0\).
  `first != beyond`.
  `value_function(p.first).second == true` for pairs `p` in the range `[first, beyond)`

See also
  `CGAL::linear_interpolation()`
  `CGAL::Interpolation_traits_2<K>`
  `CGAL::natural_neighbor_coordinates_2()`
  `CGAL::regular_neighbor_coordinates_2()`
  `3D Surface Neighbor Coordinates Functions`

Examples
  Interpolation/interpolation_2.cpp.

## ◆ sibson_c1_interpolation()

template<class CoordinateInputIterator , class ValueFunctor , class GradFunctor , class Traits , class Point >

std::pair< typename ValueFunctor::result_type, bool > CGAL::sibson_c1_interpolation | ( | CoordinateInputIterator | first,
|  | CoordinateInputIterator | beyond,
|  | const typename std::iterator_traits< CoordinateInputIterator >::value_type::second_type & | norm,
|  | const Point & | p,
|  | ValueFunctor | value_function,
|  | GradFunctor | gradient_function,
|  | const Traits & | traits
| ) |  |

`#include <CGAL/interpolation_functions.h>`

The function `sibson_c1_interpolation()` generates the interpolated function value at the point `p`, using functors for the function values and the gradients, by applying Sibson's \( Z^1\) interpolant.

Returns
  If the interpolation was successful, the pair contains the interpolated function value as first and `true` as second value. Otherwise, `false` is returned as second value.

Template Parameters

  Traits | must be a model of `InterpolationTraits`. The number type `FT` provided by `Traits` must support the square root operation `sqrt()`.
  CoordinateInputIterator | must be a model of `ForwardIterator` and must have as value type a pair associating an entity to a (non-normalized) barycentric coordinate. More precisely, `std::iterator_traits<CoordinateInputIterator>::value_type::first_type` can be of the following types: a type equivalent to `Traits::Point_d` or `Traits::Weighted_point_d` an iterator type providing a `point()` function returning a type equivalent to `Traits::Point_d` or `Traits::Weighted_point_d`; and `std::iterator_traits<CoordinateInputIterator>::value_type::second_type` must be equivalent to `Traits::FT`.
  ValueFunctor | must be a functor where `ValueFunctor::argument_type` must be equivalent to `std::iterator_traits<CoordinateInputIterator>::value_type::first_type` and `ValueFunctor::result_type` is a pair of the function value type and a Boolean. The function value type must provide a multiplication and addition operation with the type `Traits::FT` as well as a constructor with argument `0`.
  GradFunctor | must be a functor where `GradFunctor::argument_type` must be equivalent to `std::iterator_traits<CoordinatetCoordinateInputIteratorIterator>::value_type::first_type` and `Functor::result_type` is a pair of the function's gradient type and a Boolean. The function gradient type must provide a multiplication operation with `Traits::Vector_d`.
  Point | must be equivalent to `Traits::Point_d` or `Traits::Weighted_point_d`.

A model of the functor types `ValueFunctor` (resp. `GradFunctor`) is provided by the struct `CGAL::Data_access`. It must be instantiated accordingly with an associative container (e.g. `std::map`) having `std::iterator_traits<CoordinateInputIterator>::value_type::first_type` as `key_type` and the function value type (resp. the function gradient type) as `mapped_type`.

Parameters

  first,beyond | is the iterator range of the barycentric coordinates for the query point `p`.
  norm | is the normalization factor.
  p | is the point at which the interpolated function value is computed.
  value_function | is a functor that allows to access values of the interpolated function.
  gradient_function | is a functor that allows to access the function gradients. If the functor `gradient_function` cannot supply the gradient of a point, the function returns a pair where the Boolean is set to `false`.
  traits | is an instance of the traits class.

Precondition
  `norm` \( \neq0\).
  `first != beyond`.
  `value_function(q).second == true` for all points `q` of the point/coordinate pairs in the range `[first, beyond)`

See also
  `CGAL::Interpolation_traits_2<K>`
  `CGAL::sibson_c1_interpolation_square()`
  `CGAL::natural_neighbor_coordinates_2()`
  `CGAL::regular_neighbor_coordinates_2()`
  3D Surface Neighbor Coordinates Functions

Examples
  Interpolation/interpolation_2.cpp.

## ◆ sibson_c1_interpolation_square()

template<class CoordinateInputIterator , class ValueFunctor , class GradFunctor , class Traits , class Point >

ValueFunctor::result_type CGAL::sibson_c1_interpolation_square | ( | CoordinateInputIterator | first,
|  | CoordinateInputIterator | beyond,
|  | const typename std::iterator_traits< CoordinateInputIterator >::value_type::second_type & | norm,
|  | const Point & | p,
|  | ValueFunctor | value_function,
|  | GradFunctor | gradient_function,
|  | const Traits & | traits
| ) |  |

`#include <CGAL/interpolation_functions.h>`

Same as `sibson_c1_interpolation()`, except that no square root operation is required for the number type `Traits::FT`.

See also
  `CGAL::sibson_c1_interpolation()`

Examples
  Interpolation/interpolation_2.cpp, Interpolation/sibson_interpolation_2.cpp, and Interpolation/sibson_interpolation_vertex_with_info_2.cpp.