| Re: [jts-dev] singlesided buffer issue |
As Michael points out, the problem lies more in how to define a single-sided buffer and a flat buffer. (And given a definition, there might well be difficulties in computing it accurately!).Single-sided buffer also has well-known and obvious issues with lines that curve back on themselves. This has the same problem - what should be a useful and computable definition?Failing this, I'd settle for a ability to detect when a buffer curve fails to be "reasonable" - but at the moment that seems to be just as difficult.Does anyone have experience with other systems that offer flat and single-sided buffering, to describe how they react?On Sat, Aug 5, 2017 at 12:18 AM, Michaël Michaud <m.michael.michaud@xxxxxxxxx> wrote:Hi Andrea,
I get the same result and can get similar result with the following simpler line :
LINESTRING (-580 -420, -520 -340, -520 -320, 300 780)
Try to make a flat buffer of 1000.
I think the problem with flat buffer is that it is difficult to define a clear semantic.
One can give a clear definition of flat buffer for a single segment, but it seems
Round buffer is easier to define : set of points at a distance less than the buffer size
from original geometry.
But what would be the exact definition of a flat buffer ?
much more difficult for a complex linestring (at least for me).To understand what happens I suggest that you take the line hereabove.
Simplify it (create a segment from the first point to the last one).
Create a flat buffer of 1000 : this is what you intuitivelly want to get from your orginal line.Now extract segments from the line and create the flat buffer from each segment :
some parts of these buffers are out of the global buffer. This is where problems start.Michaël
But if you make the flat buffer of each segment of your line (or from the line hereabove),
you will start to see the problem.
Now you can do the flat buffer of the global line (simplified see that
some of these partial buffers are out of the flat buffer of the seg
If you offset the each segments of the line This later is generally build from the segments
Le 05/08/2017 à 08:31, Jody Garnett a écrit :
I just did the default - guess that is 10.
On Fri, Aug 4, 2017 at 10:53 PM andrea antonello <andrea.antonello@xxxxxxxxx> wrote:
Hi Jody,did you try to put a large buffer offset? Mine is -399. Yours seems much less.
Thanks,Andrea______________________________
On Aug 4, 2017 11:49 PM, "Jody Garnett" <jody.garnett@xxxxxxxxx> wrote:
I do not get the same result as you, using jts test builder 1.13.0.
--Jody Garnett
On 4 August 2017 at 01:37, andrea antonello <andrea.antonello@xxxxxxxxx> wrote:
Good morning,I have a question about a buffer operation that took me by surprise.
When I try to singleside buffer the line pasted at the end of this email, I get the result in the image, which is not what I expected.
I get the same strange effect if I try to do a flat "normal" buffer.
Also, if I try a buffercurve, I get the following:
I am a bit puzzeled and hoping I am doing something wrong, but I can't see what. The other option is that it is right and I don't understand why.
Anyone able to shed a light?
Thanks,Andrea
LINESTRING (0 0, -3.341025831596678 -9.511699104828482, -3.9173267613437486 -11.152389381205225, -4.655290460460725 -12.683277915214926, -5.277642344985547 -14.085978808571006, -5.8450433376336015 -15.55942962324408, -6.46790054334144 -17.104569134193817, -7.008530035310871 -18.554185870267396, -7.531869034054747 -20.04583560738692, -8.120789737822639 -21.551352935864642, -8.698730904143416 -23.044452484758644, -9.268085866264162 -24.56608615772882, -9.875280866517437 -26.023198736147304, -10.423107185458273 -27.59712683530244, -11.091249542383409 -29.21520237034225, -11.765651441379433 -30.745407227864206, -12.353220070771464 -32.24550017104774, -12.920986021518083 -33.8089472507946, -13.572871235594448 -35.40204450728231, -14.23106678217177 -36.92228474880561, -14.843044935425397 -38.4962039290467, -15.527325632514195 -40.07888460293741, -16.229679813779143 -41.66258135886821, -16.889453392999442 -43.24045246184633, -17.530737555000783 -44.82578344826224, -18.19367888131939 -46.430875386976226, -18.852821837540937 -47.98895638433618, -19.48209681524054 -49.544288209641536, -20.122954395364594 -51.10534369861354, -20.78041545065036 -52.680318712493076, -21.448417128589558 -54.22427532590544, -22.056262051593116 -55.78776912304601, -22.649504461742318 -57.36224417492353, -23.244812579225503 -58.90530255205503, -23.81554839018751 -60.457601843882244, -24.415263353382688 -62.00294899001487, -24.97616011282585 -63.49095070030995, -25.528530553849336 -64.92284081853725, -26.12470135752587 -66.49691253268317, -26.610363712695747 -67.964788586262, -27.163678941736737 -69.4630169492878, -27.72600153260169 -71.00992812463899, -28.283975527479953 -72.53606345230622, -28.83970121637123 -74.07732461287242, -29.38047290759914 -75.60776804795432, -29.92857536130531 -77.14736046330118, -30.44978115238645 -78.6767158803177, -30.98615014810916 -80.24376966316085, -31.55003751775271 -81.81829652196424, -32.1195367813246 -83.38387540441342, -32.70118442346179 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--Jody Garnett
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