This is probably due to some sort of limitation with the mitring
algorithm. However, I notice that the 7th and 8th points of your
geometry are almost identical. If I remove one of these, the mitred
buffer looks fine. Can you clean the points of your geometries somehow
to avoid this situation?
Gabriel Reid wrote:
Hi,
I'm trying to create a negative mitred buffer on a (simple) polygon with
JTS 1.10, and I'm getting strange results very occasionally. For
example, the following code gives me an output geometry that actually
extends outside the original geometry (even though a negative buffer is
used).
WKTReader wktReader = new WKTReader();
String geom = "POLYGON ((588736.6028960398 4518922.914991864, "
+ "588736.1060708747 4518922.061957178,
588718.6830715544 "
+ "4518930.620699637, 588712.0102834741
4518933.8985304395, "
+ "588722.7612465625 4518964.956739423,
588755.2073151038 "
+ "4518948.2420851765, 588750.2892019567
4518938.490656119, "
+ "588750.2892047082 4518938.490654858,
588741.1098934844 "
+ "4518920.290260831, 588736.6028960398
4518922.914991864))";
Geometry inputGeometry = wktReader.read(geom);
BufferParameters bufferParameters = new BufferParameters();
bufferParameters.setJoinStyle(BufferParameters.JOIN_MITRE);
Geometry bufferedGeometry = BufferOp.bufferOp(
inputGeometry, -5.0,
bufferParameters);
I've tried using a few different strategies in investigating this, such
as reducing the coordinate precision, offsetting the x and/or y
coordinates by a constant offset, or iteratively buffering the geometry
(for example, buffering it five times by -1.0). All of these strategies
have had limited success, and none seem to work in all cases that I'm
encountering.
Does this situation spring out to anyone, or is there any advice on how
to get around this (or is this the expected behaviour for some reason?).
I would be happy to *attempt* to fix this in JTS if someone can point me
in the general direction of where the issue probably is.
Thanks in advance for any information,
Gabriel Reid
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--
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022
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