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CGAL 4.4 - 2D Arrangements
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ArrangementVerticalRayShoot_2 Concept Reference
Concepts

Definition

A model of the ArrangementVerticalRayShoot_2 concept can answer vertical ray-shooting queries on an arrangement attached to it. Namely, given a Arrangement_2::Point_2 object, representing a point in the plane, it returns the arrangement feature (edge or vertex) that lies strictly above it (or below it). By "strictly" we mean that if the query point lies on an arrangement edge (or on an arrangement vertex) this edge will not be the query result, but the feature lying above or below it. (An exception to this rule is the degenerate case where the query point lies in the interior of a vertical edge.) Note that it may happen that the query point lies above the upper envelope (or below the lower envelope) of the arrangement, and the vertical ray emanating from the query point goes to infinity without hitting any arrangement feature on its way. In this case the unbounded face is returned.

A Note on Backwards Compatibility
The ray_shoot_up and ray_shoot_down member functions used to return CGAL::Object up to CGAL version 4.2. Starting with CGAL version 4.3 the return type is determined by a metafunction. To preserve backwards compatibility CGAL::Object can be constructed from the new return types implicitly, but switching to the new style is recommended. To enable the old style without any overhead, the macro CGAL_ARR_POINT_LOCATION_VERSION can be defined to 1 before any CGAL header is included.

Has Models:

CGAL::Arr_naive_point_location<Arrangement>

CGAL::Arr_walk_along_line_point_location<Arrangement>

CGAL::Arr_trapezoid_ric_point_location<Arrangement>

CGAL::Arr_landmarks_point_location<Arrangement,Generator>

See Also
CGAL::Arr_naive_point_location<Arrangement>
CGAL::Arr_walk_along_line_point_location<Arrangement>
CGAL::Arr_trapezoid_ric_point_location<Arrangement>
CGAL::Arr_landmarks_point_location<Arrangement,Generator>
CGAL::Arr_point_location_result<Arrangement>
CGAL_ARR_POINT_LOCATION_VERSION

Types

typedef unspecified_type Arrangement_2
 the associated arrangement type.
 
typedef unspecified_type Point_2
 equivalent to Arrangement_2::Point_2.
 

Creation

 ArrangementVerticalRayShoot_2 ()
 default constructor.
 
 ArrangementVerticalRayShoot_2 (const Arrangement_2 &arr)
 constructs a ray-shooting object rs attached to the given arrangement arr.
 

Query Functions

Arr_point_location_result
< Arrangement_2 >::Type 		ray_shoot_up (const Point_2 &q) const
 locates the arrangement feature that is first hit by an upward-directed vertical ray emanating from the query point q, and returns a handle for this feature. More...
 
Arr_point_location_result
< Arrangement_2 >::Type 		ray_shoot_down (const Point_2 &q) const
 locates the arrangement feature that is first hit by a downward-directed vertical ray emanating from the query point q, and returns a handle for this feature. More...
 

Operations

void attach (const Arrangement_2 &arr)
 attaches rs to the given arrangement arr.
 
void detach ()
 detaches rs from the arrangement it is currently attached to.
 

Member Function Documentation

Arr_point_location_result<Arrangement_2>::Type ArrangementVerticalRayShoot_2::ray_shoot_down ( const Point_2 &  q) const

locates the arrangement feature that is first hit by a downward-directed vertical ray emanating from the query point q, and returns a handle for this feature.

The function returns a discriminated union container of the following bounded types:

  • Arrangement_2::Halfedge_const_handle, in case the vertical ray hits an arrangement edge;
  • Arrangement_2::Vertex_const_handle, in case the vertical ray hits an arrangement vertex.
  • Arrangement_2::Face_const_handle for the unbounded arrangement face, in case q lies below the lower envelope of the arrangement.
Precondition
rs is attached to a valid arrangement instance.
Arr_point_location_result<Arrangement_2>::Type ArrangementVerticalRayShoot_2::ray_shoot_up ( const Point_2 &  q) const

locates the arrangement feature that is first hit by an upward-directed vertical ray emanating from the query point q, and returns a handle for this feature.

The function returns a discriminated union container of the following bounded types:

  • Arrangement_2::Halfedge_const_handle, in case the vertical ray hits an arrangement edge;
  • Arrangement_2::Vertex_const_handle, in case the vertical ray hits an arrangement vertex.
  • Arrangement_2::Face_const_handle for the unbounded arrangement face, in case q lies above the upper envelope of the arrangement.
Precondition
rs is attached to a valid arrangement instance.