CGAL 6.1.1 - 2D Periodic Triangulations

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Periodic_2TriangulationTraits_2 Concept Reference
Reference Manual » Concepts

## Definition

The concept `Periodic_2TriangulationTraits_2` is the first template parameter of the classes `CGAL::Periodic_2_triangulation_2<Traits, Tds>`. This concept provides the types of the geometric primitives used in the triangulation and some function object types for the required predicates on those primitives.

It refines the concept `TriangulationTraits_2` from the CGAL 2D Triangulations package. It redefines the geometric objects, predicates and constructions to work with point-offset pairs. In most cases the offsets will be (0,0) and the predicates from `TriangulationTraits_2` can be used directly. For efficiency reasons we maintain for each functor the version without offsets.

Refines
  `TriangulationTraits_2`

In addition to the requirements described for the traits class `TriangulationTraits_2`, the geometric traits class of a Periodic triangulation must fulfill the following requirements:

Has models
  `CGAL::Periodic_2_triangulation_traits_2`

See also
  `TriangulationTraits_2`
  `CGAL::Periodic_2_triangulation_2<Traits,Tds>`

## Types
typedef unspecified_type | Point_2
| The point type.
typedef unspecified_type | Segment_2
| The segment type.
typedef unspecified_type | Vector_2
| The vector type.
typedef unspecified_type | Triangle_2
| The triangle type.
typedef unspecified_type | Iso_rectangle_2
| A type representing an axis-aligned rectangle.
typedef unspecified_type | Periodic_2_offset_2
| The offset type.

## Predicate types
typedef unspecified_type | Compare_x_2
| A predicate object that must provide the function operators.
typedef unspecified_type | Compare_y_2
| A predicate object that must provide the function operators.
typedef unspecified_type | Less_x_2
| Predicate object.
typedef unspecified_type | Less_y_2
| Predicate object.
typedef unspecified_type | Orientation_2
| A predicate object that must provide the function operators.

## Constructor types:
Note that the traits must provide exact constructions in order to guarantee exactness of the following construction functors.
typedef unspecified_type | Construct_point_2
| A constructor object for `Point_2`.
typedef unspecified_type | Construct_segment_2
| A constructor object for `Segment_2`.
typedef unspecified_type | Construct_triangle_2
| A constructor object for `Triangle_2`.

## Creation
| Periodic_2_triangulation_traits_2 ()
| Default constructor.
| Periodic_2_triangulation_traits_2 (const Periodic_2_triangulation_traits_2 &tr)
| Copy constructor.

## Predicate functions
The following functions give access to the predicate and constructor objects.
Compare_x_2 | compare_x_2_object ()
Compare_y_2 | compare_y_2_object ()
Less_x_2 | less_x_2_object ()
Less_y_2 | less_y_2_object ()
Orientation_2 | orientation_2_object ()
Construct_point_2 | construct_point_2_object ()
Construct_segment_2 | construct_segment_2_object ()
Construct_triangle_2 | construct_triangle_2_object ()

## Access Functions
void | set_domain (Iso_rectangle_2 domain)
| Sets the fundamental domain.
Iso_rectangle_2 | get_domain () const
| Returns the fundamental domain.

## Member Typedef Documentation

## ◆ Compare_x_2

typedef unspecified_type Periodic_2TriangulationTraits_2::Compare_x_2

A predicate object that must provide the function operators.

`Comparison_result operator()(Point_2 p, Point_2 q)`,

which returns `EQUAL` if the \( x\)-coordinates of the two points are equal and

`Comparison_result operator()(Point_2 p, Point_2 q, Periodic_2_offset_2 o_p, Periodic_2_offset_2 o_q)`,

which returns `EQUAL` if the \( x\)-coordinates and \( x\)-offsets of the two point-offset pairs are equal. Otherwise it must return a consistent order for any two points.

Precondition
  `p`, `q` lie inside the domain.

## ◆ Compare_y_2

typedef unspecified_type Periodic_2TriangulationTraits_2::Compare_y_2

A predicate object that must provide the function operators.

`Comparison_result operator()(Point_2 p, Point_2 q)`,

which returns `EQUAL` if the \( y\)-coordinates of the two points are equal and

`Comparison_result operator()(Point_2 p, Point_2 q, Periodic_2_offset_2 o_p, Periodic_2_offset_2 o_q)`,

which returns `EQUAL` if the \( y\)-coordinates and \( y\)-offsets of the two point-offset pairs are equal. Otherwise it must return a consistent order for any two points.

Precondition
  `p`, `q` lie inside the domain.

## ◆ Construct_point_2

typedef unspecified_type Periodic_2TriangulationTraits_2::Construct_point_2

A constructor object for `Point_2`.

Provides:

`Point_2 operator()(Point_2 p,Periodic_2_offset_2 p_o)`,

which constructs a point from a point-offset pair.

Precondition
  `p` lies inside the domain.

## ◆ Construct_segment_2

typedef unspecified_type Periodic_2TriangulationTraits_2::Construct_segment_2

A constructor object for `Segment_2`.

Provides:

`Segment_2 operator()(Point_2 p,Point_2 q)`,

which constructs a segment from two points and

`Segment_2 operator()(Point_2 p,Point_2 q, Periodic_2_offset_2 o_p, Periodic_2_offset_2 o_q)`,

which constructs a segment from the points `(p,o_p)` and `(q,o_q)`.

## ◆ Construct_triangle_2

typedef unspecified_type Periodic_2TriangulationTraits_2::Construct_triangle_2

A constructor object for `Triangle_2`.

Provides:

`Triangle_2 operator()(Point_2 p,Point_2 q,Point_2 r )`,

which constructs a triangle from three points and

`Triangle_2 operator()(Point_2 p,Point_2 q,Point_2 r, Periodic_2_offset_2 o_p, Periodic_2_offset_2 o_q, Periodic_2_offset_2 o_r)`,

which constructs a triangle from the three points `(p,o_p)`, `(q,o_q)` and `(r,o_r)`.

## ◆ Iso_rectangle_2

typedef unspecified_type Periodic_2TriangulationTraits_2::Iso_rectangle_2

A type representing an axis-aligned rectangle.

It must be a model of `Kernel::IsoRectangle_2`.

## ◆ Less_x_2

typedef unspecified_type Periodic_2TriangulationTraits_2::Less_x_2

Predicate object.

Provides the operators:

`bool operator()(Point p, Point q)` and

`bool operator()(Point p, Point q, Periodic_2_offset_2 o_p, Periodic_2_offset_2 o_q)`

which returns `true` if `p` is before `q` according to the \( x\)-ordering of points.

This predicate is only necessary if the insert function with a range of points (using Hilbert sorting) is used.

## ◆ Less_y_2

typedef unspecified_type Periodic_2TriangulationTraits_2::Less_y_2

Predicate object.

Provides the operators:

`bool operator()(Point p, Point q)` and

`bool operator()(Point p, Point q, Periodic_2_offset_2 o_p, Periodic_2_offset_2 o_q)`

which returns `true` if `p` is before `q` according to the \( y\)-ordering of points.

This predicate is only necessary if the insert function with a range of points (using Hilbert sorting) is used.

## ◆ Orientation_2

typedef unspecified_type Periodic_2TriangulationTraits_2::Orientation_2

A predicate object that must provide the function operators.

`Orientation operator()(Point_2 p, Point_2 q, Point_2 r)`,

which returns `LEFT_TURN`, `RIGHT_TURN` or `COLLINEAR` depending on \( r\) being, with respect to the oriented line `pq`, on the left side, on the right side or on the line. and

`Orientation operator()(Point_2 p, Point_2 q, Point_2 r, Periodic_2_offset_2 o_p, Periodic_2_offset_2 o_q, Periodic_2_offset_2 o_r)`,

which returns `LEFT_TURN`, `RIGHT_TURN` or `COLLINEAR` depending on `(r,o_r)` being, with respect to the oriented line defined by `(p,o_p)(q,o_q)` on the left side, on the right side or on the line.

## ◆ Periodic_2_offset_2

typedef unspecified_type Periodic_2TriangulationTraits_2::Periodic_2_offset_2

The offset type.

It must be a model of the concept `Periodic_2Offset_2`.

## ◆ Point_2

typedef unspecified_type Periodic_2TriangulationTraits_2::Point_2

The point type.

It must be a model of `Kernel::Point_2`.

## ◆ Segment_2

typedef unspecified_type Periodic_2TriangulationTraits_2::Segment_2

The segment type.

It must be a model of `Kernel::Segment_2`.

## ◆ Triangle_2

typedef unspecified_type Periodic_2TriangulationTraits_2::Triangle_2

The triangle type.

It must be a model of `Kernel::Triangle_2`.

## ◆ Vector_2

typedef unspecified_type Periodic_2TriangulationTraits_2::Vector_2

The vector type.

It must be a model of `Kernel::Vector_2`.

## Member Function Documentation

## ◆ set_domain()

void Periodic_2TriangulationTraits_2::set_domain | ( | Iso_rectangle_2 | domain | ) |

Sets the fundamental domain.

This is necessary to evaluate predicates correctly.

Precondition
  `domain` represents a square.