[geos-devel] Buffering Multipolygons

[Martin Davis]

Nope, I'm still here... for a couple more days.

In JTS buffer works on *everything*, including MultiPolygons.  So this
might be a bug in GEOS.

Martin Davis, Senior Technical Architect
Vivid Solutions Inc.      www.vividsolutions.com
Suite #1A-2328 Government Street Victoria, B.C. V8T 5G5
Phone: (250) 385 6040 - Local 308 Fax: (250) 385 6046


> -----Original Message-----
> From: geos-devel-bounces at geos.refractions.net 
> [mailto:geos-devel-bounces at geos.refractions.net] On Behalf Of 
> Chris Hodgson
> Sent: May 17, 2005 9:36 AM
> To: GEOS Development List
> Subject: Re: [geos-devel] Buffering Multipolygons
> 
> 
> I think Martin Davis is off on holidays, so I will offer this 
> tidbit - I 
> do recall that some JTS operations (union/intersection come 
> to mind) do 
> NOT work on multi-polygons. I wouldn't be surprised if buffer 
> was also 
> one of these operations.
> 
> The only convex hull algorithm I know works on a set of points, if a 
> similar one is used in JTS then it probably would work on any type of 
> shape, (even multi-*) because you would just break it down into the 
> constituent points.
> 
> My best bet is that you're code is right Steve - if you can buffer 
> regular polygons, and you can convex hull multi-polygons, 
> then it seems 
> more likely to me that buffering multi's just doesn't work than it is 
> that there is some special case not being handled in your code :)
> 
> Chris
> 
> 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
> > 
> > 
> > 
> ----------------------------------------------------------------------
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> > 
> > 
> > 
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> > 
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