CGAL 5.4.4 - 2D Straight Skeleton and Polygon Offsetting
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The concept PolygonOffsetBuilderTraits_2
describes the requirements for the geometric traits class required by the algorithm class CGAL::Polygon_offset_builder_2
.
CGAL::Polygon_offset_builder_2<Ss,Traits,Container>
Types | |
typedef unspecified_type | Compare_offset_against_event_time_2 |
A predicate object type. More... | |
typedef unspecified_type | Construct_offset_point_2 |
A construction object type. More... | |
Compare_offset_against_event_time_2 | compare_offset_against_event_time_2_object () const |
Construct_offset_point_2 | construct_offset_point_2_object () const |
A predicate object type.
Must provide Comparison_result operator()( FT d, const Trisegment_2_ptr& et) const
, which compares the Euclidean distance d
with the event time for et
. Such event time is the Euclidean distance at which the offset lines intersect in a single point. The source of such offset lines is given by the three oriented lines defined by the edge-triple et
.
et
must be an edge-triple corresponding to an event that actually exist (that is, there must exist an offset distance t > 0
at which the offset lines do intersect at a single point. A construction object type.
Must provide boost::optional<Point_2> operator()(const FT& t, const Segment_2& e0, Segment_2_with_ID const& e1, const Trisegment_2_ptr& et) const
, which constructs the point of intersection of the lines obtained by offsetting the oriented lines given by e0
and e0
an Euclidean distance t
.
If e0
and e1
are collinear, if seed
is not specified (nullptr
), then the midpoint should be returned, otherwise, the event point of et
should be returned.
If the point cannot be computed, not even approximately (because of overflow for instance), an empty optional must be returned.
et
must be an edge-triple corresponding to an event that actually exist (that is, there must exist an offset distance t > 0
at which the offset lines do intersect at a single point.