CGAL 6.2 - 2D Envelopes

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Modules | Classes | Functions
Reference Manual

##

Ron Wein
This package consists of functions that computes the lower (or upper) envelope of a set of arbitrary curves in 2D. The output is represented as an envelope diagram, namely a subdivision of the \( x\)-axis into intervals, such that the identity of the curves that induce the envelope on each interval is unique.
Introduced in: CGAL 3.3
Depends on: 2D Arrangements
BibTeX: cgal:w-e2-26a
License: GPL

This package consists of functions that compute the lower (or upper) envelope of a set of arbitrary curves in 2D. The output is represented as an envelope diagram, namely a subdivision of the \( x\)-axis into intervals, such that the identity of the curves that induce the envelope over each interval is unique.

## Classified Reference Pages

## Functions

- `CGAL::lower_envelope_2`
- `CGAL::upper_envelope_2`
- `CGAL::lower_envelope_x_monotone_2`
- `CGAL::upper_envelope_x_monotone_2`

## Concepts

- `EnvelopeDiagram_1`
- `EnvelopeDiagramVertex`
- `EnvelopeDiagramEdge`

## Classes

- `CGAL::Envelope_diagram_1<Traits>`

## Modules
| Concepts

## Classes
class | CGAL::Envelope_diagram_1< Traits >
| This class is the default envelope-diagram class used by envelope functions to represent the minimization or the maximization diagram of a set of curves. More...

## Functions
template<class InputIterator , class EnvelopeDiagram >
void | CGAL::lower_envelope_2 (InputIterator begin, InputIterator end, EnvelopeDiagram &diag)
| Computes the lower envelope of a set of curves in \( \mathbb{R}^2\), as given by the range `[begin, end)`.
template<class InputIterator , class EnvelopeDiagram >
void | CGAL::lower_envelope_x_monotone_2 (InputIterator begin, InputIterator end, EnvelopeDiagram &diag)
| Computes the lower envelope of a set of \( x\)-monotone curves in \( \mathbb{R}^2\), as given by the range `[begin, end)`.
template<class InputIterator , class EnvelopeDiagram , class Traits >
void | CGAL::lower_envelope_x_monotone_2 (InputIterator begin, InputIterator end, EnvelopeDiagram &diag, const Traits &traits)
| Computes the lower envelope of a set of \( x\)-monotone curves in \( \mathbb{R}^2\), as given by the range `[begin, end)` with the help of the arrangement traits object `traits` responsible for their creation.
template<class InputIterator , class EnvelopeDiagram >
void | CGAL::upper_envelope_2 (InputIterator begin, InputIterator end, EnvelopeDiagram &diag)
| Computes the upper envelope of a set of curves in \( \mathbb{R}^2\), as given by the range `[begin, end)`.
template<class InputIterator , class EnvelopeDiagram >
void | CGAL::upper_envelope_x_monotone_2 (InputIterator begin, InputIterator end, EnvelopeDiagram &diag)
| Computes the upper envelope of a set of \( x\)-monotone curves in \( \mathbb{R}^2\), as given by the range `[begin, end)`.
template<class InputIterator , class EnvelopeDiagram , class Traits >
void | CGAL::upper_envelope_x_monotone_2 (InputIterator begin, InputIterator end, EnvelopeDiagram &diag, const Traits &traits)
| Computes the upper envelope of a set of \( x\)-monotone curves in \( \mathbb{R}^2\), as given by the range `[begin, end)` with the help of the arrangement traits object `traits` responsible for their creation.

## Function Documentation

## ◆ lower_envelope_2()

template<class InputIterator , class EnvelopeDiagram >

void CGAL::lower_envelope_2 | ( | InputIterator | begin,
|  | InputIterator | end,
|  | EnvelopeDiagram & | diag
| ) |  |

`#include <CGAL/envelope_2.h>`

Computes the lower envelope of a set of curves in \( \mathbb{R}^2\), as given by the range `[begin, end)`.

The lower envelope is represented using the output minimization diagram `diag`.

Template Parameters

  InputIterator | must be an input iterator with value type `EnvelopeDiagram::Traits_2::Curve_2`.
  EnvelopeDiagram | must be a model of the concept `EnvelopeDiagram_1`.

## ◆ lower_envelope_x_monotone_2() [1/2]

template<class InputIterator , class EnvelopeDiagram >

void CGAL::lower_envelope_x_monotone_2 | ( | InputIterator | begin,
|  | InputIterator | end,
|  | EnvelopeDiagram & | diag
| ) |  |

`#include <CGAL/envelope_2.h>`

Computes the lower envelope of a set of \( x\)-monotone curves in \( \mathbb{R}^2\), as given by the range `[begin, end)`.

The lower envelope is represented using the output minimization diagram `diag`.

Template Parameters

  InputIterator | must be an input iterator with value type `EnvelopeDiagram::X_monotone_curve_2`.
  EnvelopeDiagram | must be a model of the concept `EnvelopeDiagram_1`.

## ◆ lower_envelope_x_monotone_2() [2/2]

template<class InputIterator , class EnvelopeDiagram , class Traits >

void CGAL::lower_envelope_x_monotone_2 | ( | InputIterator | begin,
|  | InputIterator | end,
|  | EnvelopeDiagram & | diag,
|  | const Traits & | traits
| ) |  |

`#include <CGAL/envelope_2.h>`

Computes the lower envelope of a set of \( x\)-monotone curves in \( \mathbb{R}^2\), as given by the range `[begin, end)` with the help of the arrangement traits object `traits` responsible for their creation.

Reusing the same traits object improves speed if the traits class caches data. The lower envelope is represented using the output minimization diagram `diag`.

Template Parameters

  InputIterator | must be an input iterator with value type `EnvelopeDiagram::X_monotone_curve_2`.
  EnvelopeDiagram | must be a model of the concept `EnvelopeDiagram_1`.
  Traits | must be a model of the concept `AosXMonotoneTraits_2`.

## ◆ upper_envelope_2()

template<class InputIterator , class EnvelopeDiagram >

void CGAL::upper_envelope_2 | ( | InputIterator | begin,
|  | InputIterator | end,
|  | EnvelopeDiagram & | diag
| ) |  |

`#include <CGAL/envelope_2.h>`

Computes the upper envelope of a set of curves in \( \mathbb{R}^2\), as given by the range `[begin, end)`.

The upper envelope is represented using the output maximization diagram `diag`.

Template Parameters

  InputIterator | must be an input iterator with value type `EnvelopeDiagram::Traits_2::Curve_2`.
  EnvelopeDiagram | must be a model of the concept `EnvelopeDiagram_1`.

## ◆ upper_envelope_x_monotone_2() [1/2]

template<class InputIterator , class EnvelopeDiagram >

void CGAL::upper_envelope_x_monotone_2 | ( | InputIterator | begin,
|  | InputIterator | end,
|  | EnvelopeDiagram & | diag
| ) |  |

`#include <CGAL/envelope_2.h>`

Computes the upper envelope of a set of \( x\)-monotone curves in \( \mathbb{R}^2\), as given by the range `[begin, end)`.

The upper envelope is represented using the output maximization diagram `diag`.

Template Parameters

  InputIterator | must be an input iterator with value type `EnvelopeDiagram::X_monotone_curve_2`.
  EnvelopeDiagram | must be a model of the concept `EnvelopeDiagram_1`.

## ◆ upper_envelope_x_monotone_2() [2/2]

template<class InputIterator , class EnvelopeDiagram , class Traits >

void CGAL::upper_envelope_x_monotone_2 | ( | InputIterator | begin,
|  | InputIterator | end,
|  | EnvelopeDiagram & | diag,
|  | const Traits & | traits
| ) |  |

`#include <CGAL/envelope_2.h>`

Computes the upper envelope of a set of \( x\)-monotone curves in \( \mathbb{R}^2\), as given by the range `[begin, end)` with the help of the arrangement traits object `traits` responsible for their creation.

Reusing the same traits object improves speed if the traits class caches data. The upper envelope is represented using the output maximization diagram `diag`.

Template Parameters

  InputIterator | must be an input iterator with value type `EnvelopeDiagram::X_monotone_curve_2`.
  EnvelopeDiagram | must be a model of the concept `EnvelopeDiagram_1`.
  Traits | must be a model of the concept `AosXMonotoneTraits_2`.