CGAL 4.7 - 2D and 3D Linear Geometry Kernel
CGAL::Point_3< Kernel > Class Template Reference

#include <CGAL/Point_3.h>

## Definition

An object of the class Point_3 is a point in the three-dimensional Euclidean space $$\E^3$$.

Remember that Kernel::RT and Kernel::FT denote a RingNumberType and a FieldNumberType, respectively. For the kernel model Cartesian<T>, the two types are the same. For the kernel model Homogeneous<T>, Kernel::RT is equal to T, and Kernel::FT is equal to Quotient<T>.

Operators

The following operations can be applied on points:

See Also
Kernel::Point_3

## Related Functions

(Note that these are not member functions.)

bool operator< (const Point_3< Kernel > &p, const Point_3< Kernel > &q)
returns true iff p is lexicographically smaller than q (the lexicographical order being defined on the Cartesian coordinates).

bool operator> (const Point_3< Kernel > &p, const Point_3< Kernel > &q)
returns true iff p is lexicographically greater than q.

bool operator<= (const Point_3< Kernel > &p, const Point_3< Kernel > &q)
returns true iff p is lexicographically smaller or equal to q.

bool operator>= (const Point_3< Kernel > &p, const Point_3< Kernel > &q)
returns true iff p is lexicographically greater or equal to q.

Vector_3< Kerneloperator- (const Point_3< Kernel > &p, const Point_3< Kernel > &q)
returns the difference vector between q and p. More...

Point_3< Kerneloperator+ (const Point_3< Kernel > &p, const Vector_3< Kernel > &v)
returns the point obtained by translating p by the vector v.

Point_3< Kerneloperator- (const Point_3< Kernel > &p, const Vector_3< Kernel > &v)
returns the point obtained by translating p by the vector -v.

## Types

typedef unspecified_type Cartesian_const_iterator
An iterator for enumerating the Cartesian coordinates of a point.

## Creation

Point_3 (const Origin &ORIGIN)
introduces a point with Cartesian coordinates $$(0,0,0)$$.

Point_3 (int x, int y, int z)
introduces a point p initialized to (x,y,z).

Point_3 (double x, double y, double z)
introduces a point p initialized to (x,y,z) provided RT supports it.

Point_3 (const Kernel::RT &hx, const Kernel::RT &hy, const Kernel::RT &hz, const Kernel::RT &hw=RT(1))
introduces a point p initialized to (hx/hw,hy/hw, hz/hw). More...

Point_3 (const Kernel::FT &x, const Kernel::FT &y, const Kernel::FT &z)
introduces a point p initialized to (x,y,z).

## Operations

bool operator== (const Point_3< Kernel > &q) const
Test for equality: Two points are equal, iff their $$x$$, $$y$$ and $$z$$ coordinates are equal.

bool operator!= (const Point_3< Kernel > &q) const
Test for inequality.

## Coordinate Access

There are two sets of coordinate access functions, namely to the homogeneous and to the Cartesian coordinates.

They can be used independently from the chosen kernel model. Note that you do not loose information with the homogeneous representation, because the FieldNumberType is a quotient.

Kernel::RT hx () const
returns the homogeneous $$x$$ coordinate.

Kernel::RT hy () const
returns the homogeneous $$y$$ coordinate.

Kernel::RT hz () const
returns the homogeneous $$z$$ coordinate.

Kernel::RT hw () const
returns the homogenizing coordinate.

Kernel::FT x () const
returns the Cartesian $$x$$ coordinate, that is hx()/hw().

Kernel::FT y () const
returns the Cartesian $$y$$ coordinate, that is hy()/hw().

Kernel::FT z () const
returns the Cartesian $$z$$ coordinate, that is hz()/hw().

## Convenience Operators

The following operations are for convenience and for compatibility with code for higher dimensional points.

Again they come in a Cartesian and in a homogeneous flavor.

Kernel::RT homogeneous (int i) const
returns the i'th homogeneous coordinate of p, starting with 0. More...

Kernel::FT cartesian (int i) const
returns the i'th Cartesian coordinate of p, starting with 0. More...

Kernel::FT operator[] (int i) const
returns cartesian(i). More...

Cartesian_const_iterator cartesian_begin () const
returns an iterator to the Cartesian coordinates of p, starting with the 0th coordinate.

Cartesian_const_iterator cartesian_end () const
returns an off the end iterator to the Cartesian coordinates of p.

int dimension () const
returns the dimension (the constant 3).

Bbox_3 bbox () const
returns a bounding box containing p.

Point_3< Kerneltransform (const Aff_transformation_3< Kernel > &t) const
returns the point obtained by applying t on p.

## Constructor & Destructor Documentation

template<typename Kernel >
 CGAL::Point_3< Kernel >::Point_3 ( const Kernel::RT & hx, const Kernel::RT & hy, const Kernel::RT & hz, const Kernel::RT & hw = RT(1) )

introduces a point p initialized to (hx/hw,hy/hw, hz/hw).

Precondition
hw $$\neq$$ 0.

## Member Function Documentation

template<typename Kernel >
 Kernel::FT CGAL::Point_3< Kernel >::cartesian ( int i) const

returns the i'th Cartesian coordinate of p, starting with 0.

Precondition
$$0\leq i \leq2$$.
template<typename Kernel >
 Kernel::RT CGAL::Point_3< Kernel >::homogeneous ( int i) const

returns the i'th homogeneous coordinate of p, starting with 0.

Precondition
$$0\leq i \leq3$$.
template<typename Kernel >
 Kernel::FT CGAL::Point_3< Kernel >::operator[] ( int i) const

returns cartesian(i).

Precondition
$$0\leq i \leq2$$.

## Friends And Related Function Documentation

template<typename Kernel >
 Vector_3< Kernel > operator- ( const Point_3< Kernel > & p, const Point_3< Kernel > & q )
related

returns the difference vector between q and p.

You can substitute ORIGIN for either p or q, but not for both.