Single Sided Buffering gives undesireable output

[MShepherd]

This is possibly related to ticket#712.

Attempting to buffer a single side of a wavy line leads to chaotic output.

The attached image shows an attempted single side buffer of a coastline. The dark line shows the input, the blue area shows the attempted single sided buffering. A buffer size of 250000 was used.

Here is a the input: LINESTRING (-330000 7775580.27545528,-327124.603026804 7778363.07840546,-322646.558837081 7781868.88753221,-317433.043647011 7784688.27737948,-316303.203385341 7790968.44230594,-317442.143469762 7795751.14794915,-316863.906652886 7801677.2774448,-315913.30569277 7802924.06835483,-314537.40123425 7803861.47730282,-311744.141466252 7805672.38689663,-305851.078428029 7808929.40643811,-304225.017687078 7808227.43646823,-302182.883033831 7808050.1092118,-300837.489539075 7808309.99629711,-295964.386303115 7810615.19402131,-286917.531503575 7811709.67581166,-285784.240498585 7811630.91435707,-284509.123658347 7811158.98217569,-283285.545378713 7810662.45967257,-284406.256925248 7812239.92102531,-285338.757717091 7813074.21932283,-286580.725016533 7813793.3454897,-290562.738135843 7815738.14620312,-293108.523929261 7816001.89287396,-295866.893866139 7816780.72342721,-301699.247051365 7820331.71605258,-302692.71218015 7822575.94037292,-302307.038402448 7826957.45471089,-301514.47383015 7826678.10870587,-300723.359235454 7826094.98575103,-298923.364046851 7826394.66608802,-297586.418655574 7827008.29539278,-295525.566065385 7831517.48222906,-296359.824737537 7831846.80074167,-297230.741805492 7831615.815457,-298385.517235201 7830861.41057343,-300021.788771363 7829824.10596317,-301595.607265749 7830328.41682047,-304772.393211759 7831261.9697123,-306235.51816879 7833195.12484279,-305375.480278636 7837523.18967152,-304528.844013489 7840132.50457198,-303203.989857806 7844085.65160915,-302057.646776574 7846811.26012157,-296130.596253034 7853514.8912128,-295094.072764169 7852736.57659716,-292907.572738442 7850039.4435051,-290709.492152659 7847312.80075625,-285746.205755603 7840514.77816052,-280482.536308121 7833098.9635929,-277687.048453202 7829067.58653221,-272855.352341989 7820918.41328104,-272049.364283447 7819478.11404964,-270006.970268784 7814988.15790903,-268422.439296417 7810395.5062151,-267127.723668011 7805653.52122293,-266559.384135021 7803527.29837703,-266161.199654391 7800203.43344842,-262385.7113251 7783568.83316334,-260732.710429029 7771810.49130956,-259337.413896531 7761786.88588274,-258438.519346415 7756313.54858863,-257589.617699132 7753964.80948164,-255745.223426597 7750847.43222585,-255109.300469097 7749935.2713097,-250436.454772419 7741761.99538837,-244890.520991135 7731578.43369323,-244067.965065079 7728556.2122026,-238961.168664753 7720971.36709126,-238117.961601881 7720108.14071886,-236708.867743098 7718877.54355698,-236232.9723868 7718486.34885048,-234577.665219253 7716173.53455417,-233658.660710549 7715039.56590262,-231786.625659364 7713098.2216202,-230845.682143247 7712290.29781583,-229190.543466666 7711010.55068472,-218415.94435506 7704179.1421655,-213544.85626115 7700986.05016981,-211248.659460235 7703756.11219821,-211980.736797001 7707538.91723703,-211023.34533723 7710117.06389676,-204599.482650457 7707972.00399129,-202849.353939175 7707792.52550575,-201410.893966132 7708956.31826258,-200440.335895467 7711417.63992685,-199245.919402071 7715113.04001928,-200205.222756464 7717028.52202765,-213801.826923119 7716681.0821576,-216621.9928861 7715004.72774961,-220149.026434954 7713693.82773971,-218107.727027823 7719220.20761733,-214018.648960727 7723021.75978533,-212994.379712333 7723318.86375307,-207256.738456372 7721426.90372085,-200564.69055389 7719537.42107484,-202457.031516579 7721822.53775115,-203603.6830388 7722573.17351463,-205198.123642321 7724047.54506798,-210012.815338184 7736887.35329259,-207609.713659951 7742664.48918206,-195868.581748432 7747695.46951301,-194992.135121821 7747608.12477142,-193436.009692121 7747067.01496242,-192194.274665979 7745899.99466843,-191174.65683265 7740047.62405241,-191068.991852394 7736277.20912907,-190266.159690681 7737237.47875582,-189160.893979236 7739014.1971642,-186591.422131367 7744019.56874312,-187807.575827446 7746213.88659277,-188839.194209644 7747805.71151419,-193553.661219894 7748328.25309177,-201961.349915637 7750061.85924604,-202658.070192692 7752855.83803161,-203098.157377153 7755598.04703112,-200834.728244343 7758923.89492514,-199686.053238401 7760180.05002752,-198396.312377972 7760087.34169595,-198390.322132114 7756614.94271672,-198880.043724802 7754166.40772904,-194777.385494895 7753435.86667339,-193636.127749891 7755800.15697602,-192502.34754999 7758877.92059913,-189370.977897518 7766259.9567503,-187201.531066824 7769054.66892442,-182013.209959018 7772064.40333259,-182854.887558681 7776390.46106273,-184028.701599322 7776888.13847125,-186316.938081218 7777007.65993206,-190302.164864217 7776678.63369297,-191708.860770666 7775887.16868382,-192607.750020295 7775064.52065522,-194309.863207631 7772803.73333907,-195517.580065094 7770363.8650097,-199257.703737691 7769603.58878602,-198222.844005642 7776957.62889123,-190673.841757512 7784560.4716956,-189807.651537892 7784833.43614977,-189352.977334319 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7772839.40521534,-170497.673055615 7769574.54754815,-170228.914048743 7757588.83550258,-171190.250326002 7755064.7781908,-172522.637001416 7752627.97351334,-173524.518178844 7750557.40663451,-173832.043741621 7743796.8270717,-172487.746907743 7742245.17458428,-168788.53114104 7740890.13698307,-166268.664769946 7740057.50954611,-165476.2273144 7740204.08556427,-163921.060080494 7742317.74875784,-162487.382495545 7743492.54812344,-157348.965917163 7742616.6181815,-156396.905832515 7740068.86505289,-157183.269514455 7736670.86012906,-163894.402468644 7727714.20819873,-165487.622303412 7723520.31447409,-166962.401247133 7722024.06869643,-169203.439600316 7720318.30847896,-171052.288217067 7718212.399079,-171815.325595969 7717147.40795928,-177243.225905937 7708019.08214255,-175874.360429684 7705042.43971118,-174790.985540933 7703968.89699978,-170169.018706367 7701928.41548901,-167751.067135541 7701386.41624881,-165999.391561191 7701170.99303456,-163751.220299314 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7729283.44105702,-34223.3393852479 7728168.73165259,-32089.1616103263 7726433.27896811,-30970.5540998093 7725240.49486343,-29597.7370979723 7723582.07868219,-28662.9454889426 7721710.98667943,-27335.1802313971 7719122.53487382,-26557.3800730052 7717855.84348102,-26472.8833794091 7717718.73123019,-24063.7851895414 7714811.49176184,-15421.2117609325 7705753.13487041,-10810.5574204371 7701763.88200424,-9102.96583461385 7700362.84803247,700.020671916506 7695108.64629651,2899.69049885707 7694474.58975993,14381.5678601113 7691927.77975866,21249.8004891459 7690584.45387939,26617.056722507 7690435.91400428,30391.5358212951 7689691.48978866,41871.9264446997 7685958.05162161,45555.4401785596 7685141.88406726,47474.275572454 7684263.70848249,51729.3525807039 7682151.26038332,53563.5636765536 7681035.94910429,56272.3762306781 7677417.28944434,57733.6661049849 7675111.43752765,59890.4370515388 7671986.58490454,61363.5217784856 7670534.31761979,62384.1031916628 7669971.10604897,65000 7668627.4112836)"

[strk]

Ticket retargeted after milestone closed

[strk]

Ticket retargeted after milestone closed

[mdavis]

See also ​this GISSE question for more examples of incorrect single-sided buffer output.

[strk]

Ticket retargeted after milestone closed

[strk]

This case would be fixed by ​https://github.com/libgeos/geos/pull/896#issuecomment-1538144558

[Sandro Santilli <strk@…>]

In 091f6d9/git:

Only keep biggest polygon from single-sided buffer

Closes GH-665
Closes #810
Closes #712

Includes unit test