[geos-devel] Buffering Multipolygons

[strk at refractions.net]

Found out that geos-2.0.0 already has this bug.

It seems related to vertex order. If you swap vertex order
of second shell result is correct:

  <a>
MULTIPOLYGON (((10 10, 10 20, 20 20, 20 15, 10 10)),
	((60 60, 80 60, 70 7, 60 60)))
  </a>

Martin, where should vertex order be enforced ?

--strk;


On Wed, May 18, 2005 at 07:52:09PM +0200, strk at refractions.net wrote:
> On Wed, May 18, 2005 at 09:08:23AM -0400, dblasby at openplans.org wrote:
> > buffering this in JUMP (using JTS), works fine.
> > 
> > -->
> > MULTIPOLYGON (((10 10, 10 20, 20 20, 20 15, 10 10)),
> >   ((60 60, 70 7, 80 60, 60 60)))
> > 
> > strk; your result is not correct.  You've lost the 1st polygon!
> 
> You're right! I've verified geos-1.0.0 not having this problem.
> I'll check out 2.0.0 and up and see what broke this.
> I'll add a test in testLeaksBig.xml for this as well.
> Following is the XML test (parametrized buffer argument will only work
> with GEOS CVS, other versions will use 10 as argument instead of arg3):
> 
> <run>
>   <precisionModel type="FLOATING"/>
> 
> 
> <case>
>   <desc>Multipolygon buffering</desc>
>   <a>MULTIPOLYGON (((10 10, 10 20, 20 20, 20 15, 10 10)), ((60 60, 70 7, 80 60, 60 60)))</a>
> <test>
>   <op name="buffer" arg1="a" arg3="0">
>   	MULTIPOLYGON (((10 10, 10 20, 20 20, 20 15, 10 10)), ((60 60, 70 7, 80 60, 60 60)))
>   </op>
> </test>
> </case>
> 
> 
> </run>
> 
> 
> --strk;
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