CGAL users discussion list

[Efi Fogel <>]

Robert Bryce wrote:
> Hi all,
>
> I’m looking at the polygon set operations (union, intersection, 
> difference).
>
> How does CGAL handle self-intersecting polygons in these operations?
>
> Thanks,
>
> --Rob
An input polygon must be strictly simple and its vertices must be 
oriented counterclockwise.

An input polygon with holes is represented by at most one simple polygon 
oriented counterclockwise that defines the outer boundary of the 
polygon, and for each hole a strictly simple polygon, whose vertices are 
oriented clockwise around the interior of the hole.

A finite number of vertices on the outer boundary of a polygon with 
holes may appear more than once, but self intersections or overlapping 
are not allowed.

The General_polygon_set_2 class has an un-documented experimental member 
function that simplifies an input polygon and converts it into a valid 
polygon with holes.

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