[geos-devel] truncated buffer result

[Pierre GIRAUD]

Sorry there was a typo :

SELECT  astext(buffer(geometryfromtext('POLYGON((663194 1796327,663281
1796368,663226 1796300,663194 1796327.1,663194 1796327))'), 50));

The error was the first point didn't match the first one : missing "1"
( 796327 -> 1796327).

I also just tested in an upgraded postgis : POSTGIS="1.1.1"
GEOS="2.2.1" PROJ="Rel. 4.4.9, 29 Oct 2004" USE_STATS

Here is the response :

POLYGON((663193.969722321 1796327.06424776,663172.685114959
1796372.22914631,663259.685114959 1796413.22914631,663268.718916272
1796416.46828842,663278.205160608 1796417.92182762,663287.794368624
1796417.53621458,663297.133267731 1796415.32565554,663305.877806879
1796411.37158891,663313.705831622 1796405.81968506,663320.328952494
1796398.87447968,663325.503169464 1796390.79183862,663329.037861049
1796381.86953156,663330.802806939 1796372.43626205,663330.732985393
1796362.83955778,663328.830968681 1796353.43296753,663325.166828321
1796344.56303612,663319.875553601 1796336.55653753,663264.875553601
1796268.55653753,663257.885682593 1796261.48632391,663249.635099941
1796255.93888278,663240.4500212 1796252.13355155,663230.693610484
1796250.22078726,663220.751621512 1796250.27621773,663211.017145485
1796252.29765131,663201.875068854 1796256.20516358,663193.686855497
1796261.84425741,663161.686855497 1796288.94425741,663193.969722321
1796327.06424776))

I'll fill a bug.

On 3/9/06, Stephen Woodbridge <woodbri at swoodbridge.com> wrote:
> I just tried this on "POSTGIS="1.1.1" GEOS="2.2.1-CAPI-1.0.1" USE_STATS"
>
> and got "ERROR:  geometry contains non-closed rings"
>
> SELECT
> astext(buffer(geometryfromtext('POLYGON((663194 796327,663281
> 1796368,663226 1796300,663194 1796327.1,663194 1796327))'), 50));
>                                                 ^^^^^^^
>
> Notice the Y value of the last point has an extra leading "1", if I
> remove that I get:
>
> POLYGON((663144 796327,663144 1796327.1,663144.894659621
> 1796336.51623843,663147.54662185 1796345.59550374,663151.860982546
> 1796354.01288182,663157.683346337 1796361.46714516,663164.805351871
> 1796367.69153262,663172.972128319 1796372.46329587,663181.891416275
> 1796375.61167076,663191.244026668 1796377.02398833,663200.695263383
> 1796376.64970684,663209.906900826 1796374.50222048,663218.549287795
> 1796370.65838001,663218.736835661 1796370.52787101,663242.124446399
> 1796399.44346247,663248.737676265 1796406.19872337,663256.504198503
> 1796411.58848138,663265.146380576 1796415.42006697,663274.355287429
> 1796417.55651112,663283.801725107 1796417.92144165,663293.148008554
> 1796416.50181325,663302.060032965 1796413.34837386,663310.219217141
> 1796408.57385057,663317.333891921 1796402.34891989,663323.14972658
> 1796394.89610658,663327.45882048 1796386.4818289,663330.10713496
> 1796377.40687494,663330.999999811 1796367.99565018,663243.999999811
> 796326.995650178,663243.038468287 796317.241484331,663240.192519963
> 796307.862312066,663235.571516999 796299.218549815,663229.353032144
> 796291.642354176,663221.776025092 796285.424858027,663213.131659899
> 796280.804983066,663203.752116332 796277.960258697,663193.997825094
> 796277.000000047,663184.243617431 796277.96110728,663174.86432138
> 796280.806647624,663166.220358132 796285.427274594,663158.643892007
> 796291.645429891,663152.426066276 796299.222166486,663147.805815305
> 796307.866330715,663144.960682944 796317.245750531,663144
> 796326.999999991,663144 796327))
>
> Sorry no, pretty graphic, but the start and end points do match and they
> appear to be 50 units west of the start of the orginal polyline.
>
> Hope this helps,
>    -Steve
>
>
>
> Pierre GIRAUD wrote:
> > Hello,
> >
> > I probably found a tiny issue in the buffer computation on a POYGON shape.
> >
> > Using Mapserver geos implementation, I fell on a curious behaviour of
> > the buffer compuation (see attached image).
> > To reproduce the bug, I tried a similar request in PostGIS, and
> > obtained the same result. So I suppose this is a GEOS library issue.
> >
> > psql -d database -c "SELECT
> > astext(buffer(geometryfromtext('POLYGON((663194 796327,663281
> > 1796368,663226 1796300,663194 1796327.1,663194 1796327))'), 50));"
> >
> > Do I have to fill in a bug ?
> >
> > Regards
> >
> > Pierre GIRAUD
> >
> >
> > ------------------------------------------------------------------------
> >
> >
> > ------------------------------------------------------------------------
> >
> > _______________________________________________
> > 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
>