CGAL 6.1 - dD Geometry Kernel

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CGAL::Hyperplane_d< Kernel > Class Template Reference
Reference Manual » Kernel Objects

`#include <CGAL/Kernel_d/Hyperplane_d.h>`

## Definition

template<typename Kernel>
class CGAL::Hyperplane_d< Kernel >

An instance of data type `Hyperplane_d` is an oriented hyperplane in \( d\) - dimensional space.

A hyperplane \( h\) is represented by coefficients \( (c_0,c_1,\ldots,c_d)\) of type `RT`. At least one of \( c_0\) to \( c_{ d - 1 }\) must be non-zero. The plane equation is \( \sum_{ 0 \le i < d } c_i x_i + c_d = 0\), where \( x_0\) to \( x_{d-1}\) are Cartesian point coordinates. For a particular \( x\) the sign of \( \sum_{ 0 \le i < d } c_i x_i + c_d\) determines the position of a point \( x\) with respect to the hyperplane (on the hyperplane, on the negative side, or on the positive side).

There are two equality predicates for hyperplanes. The (weak) equality predicate (`weak_equality`) declares two hyperplanes equal if they consist of the same set of points, the strong equality predicate (`operator==`) requires in addition that the negative halfspaces agree. In other words, two hyperplanes are strongly equal if their coefficient vectors are positive multiples of each other and they are (weakly) equal if their coefficient vectors are multiples of each other.

Implementation

Hyperplanes are implemented by arrays of integers as an item type. All operations like creation, initialization, tests, vector arithmetic, input and output on a hyperplane \( h\) take time \(O(h.dimension())\). coordinate access and `dimension()` take constant time. The space requirement is \(O(h.dimension())\).

## Related Functions
(Note that these are not member functions.)
bool | weak_equality (const Hyperplane_d< Kernel > &h1, const Hyperplane_d< Kernel > &h2)
| test for weak equality.

## Types
typedef unspecified_type | LA
| the linear algebra layer.
typedef unspecified_type | Coefficient_const_iterator
| a read-only iterator for the coefficients.

## Creation
| Hyperplane_d ()
| introduces a variable `h` of type `Hyperplane_d<Kernel>`.
template<class InputIterator >
| Hyperplane_d (int d, InputIterator first, InputIterator last, RT D)
| introduces a variable `h` of type `Hyperplane_d<Kernel>` initialized to the hyperplane with coefficients `set [first,last)` and `D`.
template<class InputIterator >
| Hyperplane_d (int d, InputIterator first, InputIterator last)
| introduces a variable `h` of type `Hyperplane_d<Kernel>` initialized to the hyperplane with coefficients `set [first,last)`.
template<class ForwardIterator >
| Hyperplane_d (ForwardIterator first, ForwardIterator last, Point_d< Kernel > o, Oriented_side side=ON_ORIENTED_BOUNDARY)
| constructs some hyperplane that passes through the points in `set [first,last)`.
| Hyperplane_d (Point_d< Kernel > p, Direction_d< Kernel > dir)
| constructs the hyperplane with normal direction `dir` that passes through \( p\).
| Hyperplane_d (RT a, RT b, RT c)
| introduces a variable `h` of type `Hyperplane_d<Kernel>` in \( 2\)-dimensional space with equation \( ax+by+c=0\).
| Hyperplane_d (RT a, RT b, RT c, RT d)
| introduces a variable `h` of type `Hyperplane_d<Kernel>` in \( 3\)-dimensional space with equation \( ax+by+cz+d=0\).

## Operations
int | dimension ()
| returns the dimension of `h`.
RT | operator[] (int i)
| returns the \( i\)-th coefficient of `h`.
RT | coefficient (int i)
| returns the \( i\)-th coefficient of `h`.
Coefficient_const_iterator | coefficients_begin ()
| returns an iterator pointing to the first coefficient.
Coefficient_const_iterator | coefficients_end ()
| returns an iterator pointing beyond the last coefficient.
Vector_d< Kernel > | orthogonal_vector ()
| returns the orthogonal vector of `h`.
Direction_d< Kernel > | orthogonal_direction ()
| returns the orthogonal direction of `h`.
Oriented_side | oriented_side (const Point_d< Kernel > &p)
| returns the side of the hyperplane `h` containing \( p\).
bool | has_on (const Point_d< Kernel > &p)
| returns true iff point `p` lies on the hyperplane `h`.
bool | has_on_boundary (const Point_d< Kernel > &p)
| returns true iff point `p` lies on the boundary of hyperplane `h`.
bool | has_on_positive_side (const Point_d< Kernel > &p)
| returns true iff point `p` lies on the positive side of hyperplane `h`.
bool | has_on_negative_side (const Point_d< Kernel > &p)
| returns true iff point `p` lies on the negative side of hyperplane `h`.
Hyperplane_d< Kernel > | transform (const Aff_transformation_d< Kernel > &t)
| returns \( t(h)\).

## Constructor & Destructor Documentation

## ◆ Hyperplane_d() [1/4]

template<typename Kernel >
template<class InputIterator >

CGAL::Hyperplane_d< Kernel >::Hyperplane_d | ( | int | d,
|  | InputIterator | first,
|  | InputIterator | last,
|  | RT | D
| ) |  |

introduces a variable `h` of type `Hyperplane_d<Kernel>` initialized to the hyperplane with coefficients `set [first,last)` and `D`.

Precondition
  `size [first,last) == d`.

Template Parameters

  InputIterator | has `RT` as value type.

## ◆ Hyperplane_d() [2/4]

template<typename Kernel >
template<class InputIterator >

CGAL::Hyperplane_d< Kernel >::Hyperplane_d | ( | int | d,
|  | InputIterator | first,
|  | InputIterator | last
| ) |  |

introduces a variable `h` of type `Hyperplane_d<Kernel>` initialized to the hyperplane with coefficients `set [first,last)`.

Precondition
  `size [first,last) == d+1`.

Template Parameters

  InputIterator | has `RT` as value type.

## ◆ Hyperplane_d() [3/4]

template<typename Kernel >
template<class ForwardIterator >

CGAL::Hyperplane_d< Kernel >::Hyperplane_d | ( | ForwardIterator | first,
|  | ForwardIterator | last,
|  | Point_d< Kernel > | o,
|  | Oriented_side | side = `ON_ORIENTED_BOUNDARY`
| ) |  |

constructs some hyperplane that passes through the points in `set [first,last)`.

If `side` is `ON_POSITIVE_SIDE` or `ON_NEGATIVE_SIDE` then `o` is on that side of the constructed hyperplane.

Precondition
  A hyperplane with the stated properties must exist.

Template Parameters

  ForwardIterator | has `Point_d<Kernel>` as value type.

## ◆ Hyperplane_d() [4/4]

template<typename Kernel >

CGAL::Hyperplane_d< Kernel >::Hyperplane_d | ( | Point_d< Kernel > | p,
|  | Direction_d< Kernel > | dir
| ) |  |

constructs the hyperplane with normal direction `dir` that passes through \( p\).

The direction `dir` points into the positive side.

Precondition
  `p.dimension()==dir.dimension()` and `dir` is not degenerate.

## Member Function Documentation

## ◆ coefficient()

template<typename Kernel >

RT CGAL::Hyperplane_d< Kernel >::coefficient | ( | int | i | ) |

returns the \( i\)-th coefficient of `h`.

Precondition
  \( 0 \leq i \leq d\).

## ◆ has_on()

template<typename Kernel >

bool CGAL::Hyperplane_d< Kernel >::has_on | ( | const Point_d< Kernel > & | p | ) |

returns true iff point `p` lies on the hyperplane `h`.

Precondition
  `h.dimension() == p.dimension()`.

## ◆ has_on_boundary()

template<typename Kernel >

bool CGAL::Hyperplane_d< Kernel >::has_on_boundary | ( | const Point_d< Kernel > & | p | ) |

returns true iff point `p` lies on the boundary of hyperplane `h`.

Precondition
  `h.dimension() == p.dimension()`.

## ◆ has_on_negative_side()

template<typename Kernel >

bool CGAL::Hyperplane_d< Kernel >::has_on_negative_side | ( | const Point_d< Kernel > & | p | ) |

returns true iff point `p` lies on the negative side of hyperplane `h`.

Precondition
  `h.dimension() == p.dimension()`.

## ◆ has_on_positive_side()

template<typename Kernel >

bool CGAL::Hyperplane_d< Kernel >::has_on_positive_side | ( | const Point_d< Kernel > & | p | ) |

returns true iff point `p` lies on the positive side of hyperplane `h`.

Precondition
  `h.dimension() == p.dimension()`.

## ◆ operator[]()

template<typename Kernel >

RT CGAL::Hyperplane_d< Kernel >::operator[] | ( | int | i | ) |

returns the \( i\)-th coefficient of `h`.

Precondition
  \( 0 \leq i \leq d\).

## ◆ oriented_side()

template<typename Kernel >

Oriented_side CGAL::Hyperplane_d< Kernel >::oriented_side | ( | const Point_d< Kernel > & | p | ) |

returns the side of the hyperplane `h` containing \( p\).

Precondition
  `h.dimension() == p.dimension()`.

## ◆ orthogonal_direction()

template<typename Kernel >

Direction_d< Kernel > CGAL::Hyperplane_d< Kernel >::orthogonal_direction | ( |  | ) |

returns the orthogonal direction of `h`.

It points from the negative halfspace into the positive halfspace.

## ◆ orthogonal_vector()

template<typename Kernel >

Vector_d< Kernel > CGAL::Hyperplane_d< Kernel >::orthogonal_vector | ( |  | ) |

returns the orthogonal vector of `h`.

It points from the negative halfspace into the positive halfspace and its homogeneous coordinates are \( (c_0, \ldots, c_{d - 1},1)\).

## ◆ transform()

template<typename Kernel >

Hyperplane_d< Kernel > CGAL::Hyperplane_d< Kernel >::transform | ( | const Aff_transformation_d< Kernel > & | t | ) |

returns \( t(h)\).

Precondition
  `h.dimension() == t.dimension()`.

## Friends And Related Function Documentation

## ◆ weak_equality()

template<typename Kernel >

bool weak_equality | ( | const Hyperplane_d< Kernel > & | h1,
|  | const Hyperplane_d< Kernel > & | h2
| ) |  |
| related

test for weak equality.

Precondition
  `h1.dimension() == h2.dimension()`.