Geometry Boost List: Re: [geometry] Union clipping not working

Subject: Re: [geometry] Union clipping not working
From: Barend Gehrels (barend_at_[hidden])
Date: 2013-10-29 06:47:43

Hi Hunk,

> you are right
> 
> I registered my type only as Ring not as polygon.
> 
> It is possible to set my own polygon with my ring type? For environment ccw
> directed and for obstacles cw?
> 
> Is there an easy way to register my rings as polygon?

Yes. But not  macro. Because of the interior rings, this is more complex. See e.g.
http://www.boost.org/doc/libs/1_54_0/libs/geometry/doc/html/geometry/examples.html also recently discussed on this list.

> 
> I only want to know if the union polygon gets a hole or not

Why then not use boost::geometry::model::polygon, as output.

Another option ( trick) is doing an intersection too. If p and q are areas of input rings, and i and u are areas of intersection and union, u = p + q - i. If that does not hold, the union must have a hole.

Regards, Barend

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