Hi,
First of all, thank you for sharing this code with me.
Yes, I still can't subscribe, but since I got in contact with you, it isn't
that big of a problem.
I tested all four versions but if I understand correctly EarClip and
EarClipperO are the older ones. EarClipper is working much faster - don't
see any more performance issues.
(In my app I am triangulating some polygons each screen refresh to draw
them)
However after some time running my java app started Not Responding.
After investigating my input I found out that when app generate incorrect
(self-intersecting) polygon like these:
POLYGON ((5670 4363, 6465 2509, 6458 2500, 5670 4364, 5670 4363))
POLYGON ((8235 3680, 7868 3610, 7454 3890, 7360 4381, 7640 4795, 7763 4818,
7821 4679, 7821 4680, 7535 4213, 7891 3796, 8144 3901, 8235 3680))
through some robustness issue in previously used intersection() - it
happens randomly,
EarClipper hangs app. I've done ThreadDump and found specific line:
"LWJGL Application" #15 prio=5 os_prio=0 tid=0x000000001911a800 nid=0x1be0
runnable [0x000000001d73e000]
java.lang.Thread.State: RUNNABLE
at
com.vividsolutions.jts.polytriangulate.EarClipper.computeEars(EarClipper.java:116)
at
com.vividsolutions.jts.polytriangulate.EarClipper.triangulate(EarClipper.java:80)...
I suppose I haven't done proper stress testing because I usually have from
5 to 30 points in polygon. Can you make a fix to ear clip algorithm or
should I do an extra check for my polygons? If so how would you recommend
fixing them using jts?
Thanks
On Sun, Jan 24, 2016 at 12:30 AM Martin Davis <[email protected]> wrote:
> Have a look at this - this is the code that is intended to wind up in JTS
> at some point. Feedback welcome.
>
> https://github.com/dhtong/jts/tree/master/src/polytriangulate
>
> Not sure about the subscribe issue - is it still happening?
>
> On Sat, Jan 23, 2016 at 5:37 AM, Stanisław Góra <[email protected]>
> wrote:
>
>> Hi,
>>
>> I am looking for a best way to triangulate polygons using JTS. Since it
>> does not have Constrained Delaunay implementation (which would really help
>> me) i looked at using Conforming Delaunay and setting constraints. Then i
>> needed to get rid of the triangles that lie outside (concave) polygons and
>> inside their holes. Testing each triangle with disjoint() and covers()
>> functions takes much longer than triangulation itself and doesn't even
>> produce reliable results because of some robustness issue. (triangles
>> around added Steiner points lying on constrained segments return incorrect
>> inside/outside polygon result).
>> Then I found this thread
>> http://sourceforge.net/p/jts-topo-suite/mailman/jts-topo-suite-user/thread/[email protected]/
>> and
>> tried Michael's Ear Clipping code. It does great job at triangulating
>> polygons but is a lot slower (92% time is spent on covers() function) and
>> is killing performance on a android device even more than delaunay.
>>
>> In this article
>> http://lin-ear-th-inking.blogspot.com/2011/04/polygon-triangulation-via-ear-clipping.html
>> Martin
>> Davis said that the Ear Clipping code will get added to JTS in the next
>> release, and while it didn't maybe it was further optimized.
>> Also, are there any plans to implement Constrained Delaunay? I realized I
>> can't use Conforming Delaunay for yet another reason: I have some very long
>> rectangle-like polygons to triangulate, which forces delaunay property to
>> generate countless small triangles and produces "Too many splitting
>> iterations" error.
>> Otherwise can You point me to a fastest (runtime) way of triangulating
>> polygons using either Conforming Delaunay or Ear Clipping given my problems?
>>
>> Thank You very much,
>> Stanisław Góra
>>
>> PS. It seems I'm unable to subscribe jts user list - getting "Bug in
>> Mailman version 2.1.9"
>>
>>
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