[geos-devel] Buffering Multipolygons

[strk at refractions.net]

On Tue, May 17, 2005 at 11:33:27PM -0500, Stephen Lime wrote:
> Sorry, not a regular  PostGIS user I'm afraid to say. Here's a simple 
> WKT mutipolygon though: 
> 
>   MULTIPOLYGON(((10 10, 10 20, 20 20, 20 15, 10 10)), ((60 60, 70 7, 80 
> 60, 60 60 ))) 
> 
> Steve 

=# select astext(buffer('MULTIPOLYGON(((10 10, 10 20, 20 20, 20 15, 10 10)), ((60 60, 70 7, 80 60, 60 60 )))', 0));
              astext
-----------------------------------
 POLYGON((60 60,80 60,70 7,60 60))
(1 row)

=# select postgis_geos_version();
 postgis_geos_version
----------------------
 3.0.0
(1 row)

Is the result correct ?
3.0.0 is the CVS version (next release).

--strk;

> 
> On May 17, 2005, at 2:47 PM, strk at refractions.net wrote: 
> 
> 
> > On Tue, May 17, 2005 at 06:05:50PM +0200, strk at refractions.net 
> > wrote: 
> > 
> > > On Tue, May 17, 2005 at 08:19:06AM -0500, Steve Lime wrote: 
> > > 
> > > > What flavor of script or test data? Do you really want a 
> > > > perl/mapscript 
> > > > script? 
> > > > 
> > >  
> > > No, just an .sql script containing table creation, data load (WKT 
> > > geoms) 
> > > and the failing call to GeomUnion(). The dataset should be the 
> > > smallest possible reproducing the problem. 
> > > 
> >  
> > Err.. sorry, the call is to buffer() not to GeomUnion, 
> > so a single command should be able to show the problem and let us 
> > test it on other versions. 
> > Something like: 
> >  select buffer('MULTIPOLYGON...', #); 
> > 
> > --strk; 
> > 
> > 
> > >  
> > > --strk; 
> > > 
> > > 
> > > >  
> > > > 
> > > > > 
> > > > > > 
> > > > > > > strk at refractions.net 05/17/05 1:33 AM >>> 
> > > > > > > 
> > > > > > 
> > > > > 
> > > > If you send a small script we can test it. 
> > > > --strk; 
> > > > 
> > > > On Tue, May 17, 2005 at 01:02:58AM -0500, Steve Lime wrote: 
> > > > 
> > > > > Hi All: I'm wondering if someone can confirm that buffering a 
> > > > > multipolygon works with GEOS 2.1.1. I'm testing my conversion 
> > > > > code and 
> > > > > am having problems with just this case: simple polgons 
> > > > > with/without 
> > > > > holes work fine, anything with multiple outer rings does not 
> > > > > (bus 
> > > > > 
> > > > error 
> > > > 
> > > > > on Mac OS). The conversion code must be close because 
> > > > > computing a 
> > > > > 
> > > > convex 
> > > > 
> > > > > hull on the same test shape works fine. 
> > > > > 
> > > > > I've attached a small graphic that shows the multipolygon 
> > > > > (with GEOS 
> > > > > computed convext hull)... 
> > > > > 
> > > > > Steve 
> > > > > 
> > > >  
> > > > 
> > > > 
> > > > > _______________________________________________ 
> > > > > geos-devel mailing list 
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> > > > > 
> > > >  
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> > 
> 
> 

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