[geos-devel] Buffering Multipolygons

[strk at refractions.net]

Martin, inspecting this problem I found out a comment
of you:

                // <FIX> - handle negative depths

Actually, there's a negative depth in the 'non-working' case:

  BufferSubgraph::findResultEdges got 2 edges
   dirEdge 0: depth:-1
   dirEdge 1: depth:0
  PolygonBuilder::buildMaximalEdgeRings got 2 dirEdges
    dirEdge 0 inResult:0 isArea:1
    dirEdge 1 inResult:0 isArea:1
    returning 0 maxEdgeRings

While non negative depts are in the 'working' case:

  BufferSubgraph::findResultEdges got 2 edges
   dirEdge 0: depth:0
   dirEdge 1: depth:1
     in result
  PolygonBuilder::buildMaximalEdgeRings got 2 dirEdges
    dirEdge 0 inResult:0 isArea:1
    dirEdge 1 inResult:1 isArea:1
    returning 1 maxEdgeRings

I checked JTS and the notice is still there (your comment).
Anyway Dave reports it is working with JTS. Do you have
any hint on how to proceed ?

--strk;



On Thu, May 19, 2005 at 08:48:13AM +0200, strk at refractions.net wrote:
> 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;
> > _______________________________________________
> > geos-devel mailing list
> > geos-devel at geos.refractions.net
> > http://geos.refractions.net/mailman/listinfo/geos-devel
> _______________________________________________
> geos-devel mailing list
> geos-devel at geos.refractions.net
> http://geos.refractions.net/mailman/listinfo/geos-devel