CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Looking here:
http://doc.cgal.org/latest/Straight_skeleton_2/index.html

I can read:
"This CGAL package requires the input polygon (with holes) to be 
non-degenerate, strictly-simple, and oriented counter-clockwise."

Sebastien.


On 05/16/2014 10:22 PM, Hyungon Kim wrote:
> Hi,
>
> I am using 3.6 CGAL 2D straight skeleton and polygon offsetting to glow 2D
> polygon.
> I found out that the order of points is critical to enter_contour function
> even if the points represent the same polygon.
> I means that the contour in some case is empty if I use the points following
> reverse_orientation of polygon.
>
>    for (vit = boundary.vertices_begin(); vit != boundary.vertices_end();
> vit++) {
>          points.push_back(*vit);
>    }
>    ssb.enter_contour(points.rbegin(),points.rend());
>    => after offset, return the correct contour
>
>
>    boundary.reverse_orientation();
>    ssb.enter_contour(boundary.vertices_begin(),boundary.vertices_end());
>    => after offset, return empty contour
>
>
> I didn't find the statement to mention it from the manual or examples.
> Is it an error in skeleton or an usage error?
>
> Attached you will find the simple example code.
>
> Thanks,
> Hyungon Kim
> exam_glow.cpp
> <http://cgal-discuss.949826.n4.nabble.com/file/n4659326/exam_glow.cpp>
>
>
>
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