[postgis-devel] Problem in st_StriaghtSkeleton - Hangs!

Stephen Mather mather.stephen at gmail.com
Wed Jan 17 18:25:20 PST 2018


For sure you can get a much less expensive result than the SFCGAL approach by using voronoi on a densified version of your geometry. It’s a few orders of magnitude faster that SFCGAL.

Stephen V. Mather 
+1 (216) 339-6347 (Signal, Telegram, Cell, and WhatsApp)

> On Jan 18, 2018, at 02:12, Regina Obe <lr at pcorp.us> wrote:
> 
> Well it certainly takes longer than I care to wait and not cancellable.  But CPU on my end is not spiking.
> 
> But I'm running a 1.3 branch (dated in September 7, 2017), but unfortunately.
> 
> I know the 1.2.2 version had tons of issues with things including ST_StraightSkeleton, so I suspect ST_StraightSkeleton is pretty unusable in the 1.2 versions.
> 
> The rest of issues I see are with the output
> 
> https://github.com/Oslandia/SFCGAL/issues
> 
> I'm going to try to build against latests head (my last head build seems to have failed).
> 
> I thought Stephen Mathers had written one that doesn't require SFCGAL, though I could be mistaken.
> 
> Steve - if you are on list can you respond?
> 
> Thanks,
> Regina
> 
> 
> 
> 
> -----Original Message-----
> From: postgis-devel [mailto:postgis-devel-bounces at lists.osgeo.org] On Behalf Of Stephen Woodbridge
> Sent: Wednesday, January 17, 2018 2:47 PM
> To: PostGIS Development Discussion <postgis-devel at lists.osgeo.org>
> Subject: [postgis-devel] Problem in st_StriaghtSkeleton - Hangs!
> 
> Hi all,
> 
> I have run into a problem using st_StraightSkelton() where it appears to hang at 100 cpu. Maybe an endless loop?
> 
> select st_straightskeleton('POLYGON((256 760,518 760,518 630,674 630,674
> 239,673 239,127 239,127 240,126 240,126 513,127 513,127 514,126 514,126
> 630,255 630,256 630,256 760),(128 629,128 423,270 423,270 422,271
> 422,271 240,672 240,672 629,128 629),(258 759,258 631,516 631,516
> 759,258 759),(128 421,128 240,269 240,269 421,128 421))'::geometry);
> 
> POSTGIS="2.3.3 r15473" GEOS="3.5.1-CAPI-1.9.1 r4246" SFCGAL="1.2.2" 
> PROJ="Rel. 4.9.2, 08 September 2015" GDAL="GDAL 1.11.3, released 2015/09/16" LIBXML="2.9.3" LIBJSON="0.11.99" RASTER
> 
> Can anyone reproduce this?
> Any idea how to work around it?
> 
> Is there a non-CGAL version of skeleton?
> 
> Thanks,
>   -Steve
> 
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