Subject: Re: [geometry] difference algorithm produces invalid polygon?
From: Volker Schöch (vschoech_at_[hidden])
Date: 2012-07-17 04:20:00
Are there any news in this issue?
-- Volker Schöch | vschoech_at_[hidden] Senior Software Engineer think-cell Software GmbH | Chausseestr. 8/E | 10115 Berlin | Germany http://www.think-cell.com | phone +49 30 666473-10 | US phone +1 800 891 8091 Amtsgericht Berlin-Charlottenburg, HRB 85229 | European Union VAT Id DE813474306 Directors: Dr. Markus Hannebauer, Dr. Arno Schoedl -----Original Message----- From: geometry-bounces_at_[hidden] [mailto:geometry-bounces_at_[hidden]] On Behalf Of Barend Gehrels Sent: Dienstag, 6. März 2012 00:26 To: Boost.Geometry library mailing list Subject: Re: [geometry] difference algorithm produces invalid polygon? Hi Volker, On 29-2-2012 15:04, Volker Schöch wrote: >> Can you send a (WKT) sample of such a polygon? I think I understand but don't see how the x-constraint fit into this. > MULTIPOLYGON(((1716 1554,2076 2250,2436 2352,2796 1248,3156 2484,3516 > 2688,3516 2688,3156 2484,2796 1248,2436 2352,2076 2250, 1716 1554))) > > This seems to me like a more general form of the "spike only"-type polygon that I originally submitted. I merely mentioned the x-constraint to rule out any real self-intersections (and this constraint incidentially holds in my application, allowing to ensure correct order of points). > In the meantime I tried your polygon. The problem our library currently has with this polygon, actually with every spike (spike-only or a spikey feature) is that it does not know which way to go. As soon as the intersection point (two at a spot) is encountered, it decides going left or write, but because of the two it can make a wrong decision. The good news is I think this can be helped. Will study this later in more detail. Regards, Barend
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