[Algorithms] Special cases of Weiler-Atherton

[Andrzej Borucki]

I am writing Weiler-Atherton algorithm. I can't find full description of
this.
My source trial is on bitbucket on aborucki/weileratherton, this is unclear
of brute_force_intersections() function because I am moving form
brute-force to Bentley-Ottmann sweep line intersections.
I have two main rountines:
brute_force_intersections(): inserting points of intersections
unionWalk - walk over lists and make union two polygons.
In unionWalk are special cases: vertex of one polygon touch vertex second
polygon etc
Where can I find detail description of this algorithm?

[p***@free.fr]

Hi,

I tried this almost 10 years ago :-)
The algorithm was Ok if I remember well but then I should have worked some float precision issues which I didn't do ;-(

May be this can help
http://pierloic.free.fr/clip/clip.html
--
pl


----- Mail original -----
De: "Andrzej Borucki" <***@gmail.com>
À: gdalgorithms-***@lists.sourceforge.net
Envoyé: Dimanche 23 Novembre 2014 13:30:55
Objet: [Algorithms] Special cases of Weiler-Atherton



I am writing Weiler-Atherton algorithm. I can't find full description of this.
My source trial is on bitbucket on aborucki/weileratherton, this is unclear of brute_force_intersections() function because I am moving form brute-force to Bentley-Ottmann sweep line intersections.
I have two main rountines:
brute_force_intersections(): inserting points of intersections

unionWalk - walk over lists and make union two polygons.

In unionWalk are special cases: vertex of one polygon touch vertex second polygon etc
Where can I find detail description of this algorithm?


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[Andrzej Borucki]

Yes, I saw this.
And algorithm Greiner-Hormann is similar to this. In base version not
handles special cases, but is extension to special case by Foster and
Overleft. This extension requires computing if point is inside or outside
neighbor polygon. Fortunately is not need computing it for all vertices,
only for first, and vertices which meet intersections points
I don't know which if faster - Greiner-Hormann with special cases or Vatti?