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CGAL 6.1 - 2D Straight Skeleton and Polygon Offsetting
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CGAL 6.1 - 2D Straight Skeleton and Polygon Offsetting
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The concept StraightSkeletonBuilderTraits_2 describes the requirements for the geometric traits class required by the algorithm class CGAL::Straight_skeleton_builder_2.
CGAL::Straight_skeleton_builder_traits_2<K> Kernel Types | |
| typedef unspecified_type | Kernel |
A model of the Kernel concept. | |
| typedef unspecified_type | FT |
A model of the FieldWithSqrt concept provided by the kernel. | |
| typedef unspecified_type | Point_2 |
A model of the Kernel::Point_2 concept. | |
| typedef unspecified_type | Segment_2 |
A model of the Kernel::Segment_2 concept. | |
| typedef unspecified_type | Vector_2 |
A model of the Kernel::Vector_2 concept. | |
| typedef unspecified_type | Direction_2 |
A model of the Kernel::Direction_2 concept. | |
| typedef CGAL::Trisegment_2< Kernel > | Trisegment_2 |
| typedef CGAL::Trisegment_2_ptr< Trisegment_2 > | Trisegment_2_ptr |
Predicates and Constructors Types | |
| typedef unspecified_type | Do_ss_event_exist_2 |
| A predicate object type. | |
| typedef unspecified_type | Compare_ss_event_times_2 |
| A predicate object type. | |
| typedef unspecified_type | Are_ss_events_simultaneous_2 |
| A predicate object type. | |
| typedef unspecified_type | Construct_ss_event_time_and_point_2 |
| A construction object type. | |
| typedef unspecified_type | Construct_ss_trisegment_2 |
| A construction object type. | |
| typedef unspecified_type | Is_edge_facing_ss_node_2 |
| A predicate object type. | |
| typedef unspecified_type | Oriented_side_of_event_point_wrt_bisector_2 |
| A predicate object type. | |
Predicates and Constructors Functors | |
| Are_ss_events_simultaneous_2 | are_ss_events_simultaneous_2_object () const |
| Compare_ss_event_times_2 | compare_ss_event_times_2_object () const |
| Do_ss_event_exist_2 | do_ss_event_exist_2_object () const |
| Is_edge_facing_ss_node_2 | is_edge_facing_ss_node_2_object () const |
| Oriented_side_of_event_point_wrt_bisector_2 | oriented_side_of_event_point_wrt_bisector_2_object () const |
| Construct_ss_event_time_and_point_2 | construct_ss_event_time_and_point_2_object () const |
| Construct_ss_trisegment_2 | construct_ss_trisegment_2_object () const |
A predicate object type.
Must provide bool operator()( const Trisegment_2_ptr& l, const Trisegment_2_ptr& r),
which determines if the events given by l and r are coincident in time and space; that is, both triples of offset lines intersect at the same point and at the same Euclidean distance from their sources.
l and r must be edge-triples corresponding to events that actually exist (as determined by the predicate Do_ss_event_exist_2). A predicate object type.
Must provide
CGAL::Comparison_result operator()(const Trisegment_2_ptr& l, const Trisegment_2_ptr& r) const,
which compares the times for the events determined by the edge-triples l and r.
The time of an event given by an edge triple (which defines three oriented lines) is the Euclidean distance t at which the corresponding offset lines at t intersect in a single point.
l and r must be edge-triples corresponding to events that actually exist (as determined by the predicate Do_ss_event_exist_2). A construction object type.
Must provide
std::optional< std::tuple<FT, Point_2> > operator()( const Trisegment_2_ptr& e),
which returns the Euclidean distance t >= 0 and the intersection point at which the corresponding three offset lines at t intersect if they do.
If the values cannot be computed, not even approximately (because of overflow for instance), an empty optional must be returned.
A construction object type.
Must provide Trisegment_2_ptr operator()( const Segment_2& e0, const FT& w0, const Segment_2& e1, const FT& w1, const Segment_2& e2, const FT& w2 ) const,
which returns an intrusive pointer to an object containing the three oriented lines defined by the three input edges.
A predicate object type.
Must provide
bool operator()( const Trisegment_2_ptr& tri_segment, std::optional<FT> max_time ) const,
which determines if, given the three oriented lines defined by the three input edges, there exists a Euclidean distance t >= 0 and t <= max_time for which the corresponding three offset lines at t (parallel lines at a Euclidean distance of t) intersect in a single point.
A model of the FieldWithSqrt concept provided by the kernel.
This type is used to represent the event time stored in the skeleton nodes.
A predicate object type.
Must provide
bool operator()( const Point_2& contour_node, const Segment_2& opposite_edge ) const,
and
bool operator()( const Trisegment_2_ptr& skeleton_node, const Segment_2& opposite_edge ) const,
which return whether the point (either defined directly as a Point_2 if it is a contour node, or indirectly by its edge triple if it is a skeleton node) lies in the halfplane to the left of the directed edge opposite_edge.
skeleton_node must be an edge-triple corresponding to an event that actually exists (as determined by the predicate Do_ss_event_exist_2). | typedef unspecified_type StraightSkeletonBuilderTraits_2::Oriented_side_of_event_point_wrt_bisector_2 |
A predicate object type.
Must provide
CGAL::Oriented_side operator()( const Trisegment_2_ptr& e, const Segment_2& e0, const FT& w0, const Segment_2& e1, const FT& w1, const Trisegment_2_ptr& e01_event, bool e0_is_primary) const,
which returns the oriented side of the event point described by the edge triple e w.r.t. the (positive) bisector [e0,e1].
skeleton_node must be an edge-triple corresponding to an event that actually exists (as determined by the predicate Do_ss_event_exist_2). 
1.9.6