Re: [jts-dev] buffer(0) is dropping a polygon in a multipolygon

[Fernando González Cortés <fergonco@xxxxxxxxx>]

Hi Martin, thanks for the confirmation. Should have checked myself if I
could reproduce with current master.

Github issue is quite probably a problem of my corporate account.
Nowadays, I was expecting half the issue trackers to be closed to the
public due to AI.

GeometryFixer worked fine. I'll miss the buffer(0) arcane trick for the
reactions I got from my help-seeking colleages. It's not that fun
anymore, now that everyone can work with valid geometries... xD.


On Wed, Jun 10, 2026 at 11:44:40AM -0700, Martin Davis wrote:
> Hi, Fernando.  Glad that JTS is helpful for you.
>
> Thanks for the issue report.  Github is the best place to file issues, but
> since you can't for some reason this is the next best place.
>
> I can reproduce your problem in JTS 1.20.  This wasn't a problem in JTS
> 1.19.  And good news - it has been fixed in the current JTS code base.
> (I'm not sure which change fixed this - there were a number of fixes for
> the buffer code since the 1.20 release.,).
>
> By the way, the buffer(0) trick has be superseded by the GeometryFixer
> class, so you might want to try using that.
>
> cheers - Martin
>
>
>
>
> On Wed, Jun 10, 2026 at 2:13 AM Fernando González Cortés via jts-dev <
> jts-dev@xxxxxxxxxxx> wrote:
>
> > Hi all,
> >
> > First of all, I've been using JTS for around 25 years and I would like
> > to thank you for all the work these many years.
> >
> > Recently (JTS 1.20.0) I found a case where running buffer(0) is dropping
> > a polygon from a multipolygon. The input[1] consists of two polygons and
> > is valid. But running the buffer(0) operation just drops one of the
> > polygons.
> >
> > Is this a bug? It is at least worrying, buffer(0) being the way I try to
> > get out of trouble in JTS :S
> >
> > Wanted to open a github issue but couldn't. Please, let me know if this
> > is not the right channel.
> >
> >
> > [1]
> >
> > MULTIPOLYGON (((214830.95 6388204.12, 214829.08 6388209.43, 214827.77
> > 6388212.04, 214825.97 6388216.43, 214825.29 6388219.74, 214826.03
> > 6388223.43, 214829.03 6388227.85, 214829.46 6388227.95, 214832.86
> > 6388227.65, 214836.87 6388224.59, 214839.3 6388222.27, 214841.26
> > 6388220.79, 214842.22 6388219.75, 214843.21 6388218.2, 214844.34
> > 6388216.88, 214845.03 6388214.69, 214844.96 6388214.68, 214844.89
> > 6388214, 214844.69 6388213.34, 214844.37 6388212.74, 214843.94
> > 6388212.21, 214843.41 6388211.77, 214842.8 6388211.45, 214842.14
> > 6388211.25, 214841.46 6388211.18, 214841.39 6388210.5, 214841.19
> > 6388209.84, 214840.87 6388209.24, 214840.44 6388208.71, 214839.91
> > 6388208.27, 214839.3 6388207.95, 214838.64 6388207.75, 214837.96
> > 6388207.68, 214837.89 6388207, 214837.69 6388206.34, 214837.37
> > 6388205.74, 214836.94 6388205.21, 214836.41 6388204.77, 214835.8
> > 6388204.45, 214835.14 6388204.25, 214834.46 6388204.18, 214830.96
> > 6388204.18, 214830.95 6388204.12)), ((214921.96 6388211.29, 214921.96
> > 6388214.68, 214921.28 6388214.75, 214920.62 6388214.95, 214920.24
> > 6388215.15, 214920.63 6388216.43, 214921.67 6388218.48, 214923.17
> > 6388220.12, 214923.71 6388220.47, 214924.58 6388221.83, 214925.36
> > 6388222.63, 214928.95 6388225.36, 214930.71 6388226.22, 214933.07
> > 6388226.73, 214933.73 6388227.14, 214933.22 6388229.44, 214933.31
> > 6388230.43, 214931.8 6388232.27, 214929.54 6388236.26, 214928.23
> > 6388239.18, 214926.52 6388241.99, 214925.4 6388243.45, 214924
> > 6388244.92, 214920.72 6388246.61, 214919.89 6388246.82, 214917
> > 6388247.01, 214912.75 6388246.98, 214909.94 6388247.17, 214906.56
> > 6388246.65, 214901.85 6388244.56, 214897.33 6388241.25, 214896.83
> > 6388240.71, 214896.58 6388240.06, 214895.71 6388238.91, 214894.99
> > 6388237.43, 214892.43 6388230.66, 214892.09 6388228.78, 214891.76
> > 6388225.18, 214890.46 6388225.18, 214889.78 6388225.25, 214889.12
> > 6388225.45, 214888.52 6388225.77, 214888.08 6388226.13, 214888.89
> > 6388230.43, 214889.82 6388233.66, 214891.62 6388237.43, 214894.09
> > 6388241.52, 214895.71 6388243.21, 214897.27 6388244.43, 214903.53
> > 6388247.81, 214906.21 6388250.24, 214908.67 6388251.19, 214909.71
> > 6388251.89, 214916.14 6388250.58, 214919.87 6388250.2, 214922.06
> > 6388249.78, 214924.64 6388248.87, 214925.62 6388247.93, 214926.68
> > 6388247.4, 214927.21 6388246.65, 214928.56 6388245.78, 214929.14
> > 6388244.43, 214929.9 6388243.62, 214930.68 6388240.96, 214931.78
> > 6388239.21, 214932.14 6388238.36, 214932.32 6388237.43, 214934.15
> > 6388233.88, 214941.21 6388227.22, 214942.6 6388224.82, 214943.72
> > 6388223.43, 214944.01 6388222.73, 214944.71 6388222, 214945.4 6388220.1,
> > 214945.65 6388216.7, 214944.81 6388209.43, 214945.52 6388206.4, 214946.7
> > 6388205.08, 214947.59 6388204.35, 214948.7 6388204.08, 214952.07
> > 6388204.36, 214955.21 6388206.1, 214956.79 6388207.23, 214958.84
> > 6388209.31, 214961.01 6388212.09, 214961.67 6388213.06, 214962.21
> > 6388214.43, 214964.87 6388216.72, 214965.5 6388218.19, 214965.71
> > 6388218.33, 214966.16 6388218.05, 214966.57 6388217.29, 214966.66
> > 6388216.66, 214967.09 6388216.06, 214968.88 6388214.58, 214970.23
> > 6388213.09, 214971.14 6388212.5, 214973.13 6388211.65, 214976.21
> > 6388211.08, 214980.51 6388210.66, 214983.33 6388209.55, 214984.56
> > 6388208.65, 214987.25 6388206.12, 214988.91 6388204.04, 214991.5
> > 6388199.72, 214992.66 6388197.25, 214992.64 6388197.25, 214991.96
> > 6388197.18, 214991.89 6388196.5, 214991.69 6388195.84, 214991.37
> > 6388195.24, 214990.94 6388194.71, 214990.41 6388194.27, 214989.8
> > 6388193.95, 214989.14 6388193.75, 214988.46 6388193.68, 214985.93
> > 6388193.68, 214984.92 6388198.93, 214983.61 6388202.28, 214980.81
> > 6388206.13, 214979.33 6388206.97, 214972.71 6388208.9, 214971.91
> > 6388209.43, 214967.42 6388211.45, 214966.08 6388212.24, 214965.71
> > 6388212.29, 214965.33 6388212.22, 214962.03 6388210.42, 214960.61
> > 6388208.33, 214958.14 6388205.93, 214956.92 6388204.22, 214955.21
> > 6388202.76, 214954.49 6388202.43, 214953.58 6388200.56, 214952.36
> > 6388198.93, 214953.27 6388192.35, 214953.38 6388190.18, 214944.71
> > 6388190.18, 214945.3 6388191.55, 214946.2 6388195.06, 214946.21
> > 6388195.81, 214945.56 6388198.69, 214945.36 6388199.05, 214944.77
> > 6388199.35, 214944.45 6388199.92, 214943.34 6388202.43, 214942.56
> > 6388203.78, 214941.75 6388206.08, 214941.91 6388213.26, 214941.39
> > 6388214.87, 214941.21 6388214.98, 214941.06 6388214.82, 214940.72
> > 6388213.42, 214940.17 6388212.93, 214939.62 6388211.74, 214939.28
> > 6388211.36, 214938.88 6388211.11, 214938.14 6388210.98, 214937.52
> > 6388210.57, 214936.06 6388207.59, 214934.21 6388205.81, 214932.76
> > 6388203.89, 214930.86 6388202.01, 214928.96 6388200.81, 214928.96
> > 6388203.94, 214930.71 6388204.86, 214931.4 6388205.54, 214932.74
> > 6388207.4, 214934.03 6388209.61, 214935.59 6388211.56, 214937.45
> > 6388214.66, 214938.68 6388216.04, 214939.34 6388219.93, 214939.18
> > 6388220.87, 214938.67 6388221.6, 214937.23 6388222.96, 214934.86
> > 6388224.43, 214933.96 6388224.45, 214930.5 6388223.64, 214928.01
> > 6388222.02, 214926.1 6388220.35, 214924.79 6388218.17, 214921.96
> > 6388211.29)))
> >
> > _______________________________________________
> > jts-dev mailing list
> > jts-dev@xxxxxxxxxxx
> > To unsubscribe from this list, visit
> > https://dev.eclipse.org/mailman/listinfo/jts-dev
> >