A sloop is a great circle on a sphere. A shalfloop is an oriented sloop. It is always paired with a shalfloop whose supporting Sphere_circle is pointing in the opposite direction. The twin() member function returns this shalfloop of opposite orientation. Each Nef_polyhedron_S2 can only have one sloop (resp. two shalfloops).
The figure below depicts the relationship between a shalfloop and sfaces on a sphere map.
#include <CGAL/Nef_polyhedron_S2.h>
The following types are the same as in Nef_polyhedron_S2<Traits>.
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type of mark.
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sphere circle type stored in SHalfloop.
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const handle to SHalfloop.
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const handle to SFace.
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There is no need for a user to create a SHalfloop explicitly. The class Nef_polyhedron_S2<Traits> manages the needed shalfloops internally.
CGAL::Nef_polyhedron_S2<Traits>::SFace
CGAL::Nef_polyhedron_S2<Traits>::Sphere_circle