Unfortunately there's no rule or metric about which operations will fail on
invalid geometry. It all comes down to the details of the algorithm. For
instance, overlay ops are likely to fail, whereas buffer is relatively
robust (although with the caveat that for an invalid geometry the result
may not be what is "expected"). In some cases this is noted in the Javadoc.
The bottom line is that geometry passed to any non-trivial JTS operation
should be known to be valid. There is a performance hit for doing this, for
sure. Perhaps an even bigger issue is: what do you do with an invalid
geometry? (Of course there are various heuristic ways of cleaning it up,
but in general this is context-dependent). Generally it's best to ensure
validity as early as possible in the system, so that subsequent processing
can proceed robustly. That's why JTS leaves the question of when to do
validity checking to the client, since only they can know when it is
appropriate and efficient to do it.
On Wed, May 21, 2014 at 8:00 AM, Rob Emanuele <[email protected]> wrote:
> Thanks Martin. We were doing isValid checks other places in the code
> (inside the wrapped geometry initializations), and I assumed that was
> happening for MultiPolygon too, which it wasn't. And I haven't quite
> internalized what vector data is invalid and what's valid.
>
> Is it the case that most operations will throw a TopologyException for
> invalid geometries? I've been debating not putting the isValid check inside
> the wrapped Geometry class initializers, since this article:
> http://www.vividsolutions.com/jts/caseStudy_largePolyValidation.htmworries me
> about the potential performance hit of validating each geometry
> on creation. But if most operations you would do with an invalid polygon
> would throw TopologyExceptions, it might be worth it to eat the performance
> hit and make sure everything is valid before letting the user start working
> with the geometry, for the scala wrapper.
>
>
>
> On Tue, May 20, 2014 at 5:30 PM, Martin Davis <[email protected]> wrote:
>
>> The TopologyException occurs because the MultiPolygon is not valid. The
>> two components overlap (precisely, the first polygon contains the second).
>>
>>
>> On Tue, May 20, 2014 at 2:17 PM, Rob Emanuele <[email protected]>wrote:
>>
>>> Hello,
>>>
>>> I was wondering if I could get some insight on why this would be
>>> throwing a TopologyException. I've been looking through the JTS source, and
>>> trying different variations on the MultiPolygon, but I can't seem to nail
>>> down what about this is causing the issue (sorry for the scala code, I did
>>> this example in the interpreter, but I think it should be clear):
>>>
>>> import com.vividsolutions.jts.geom._
>>>
>>> val f = new GeometryFactory()
>>> val l = f.createLineString(Array(new Coordinate(0,0), new
>>> Coordinate(2,2)))
>>>
>>> val exterior1 = f.createLinearRing(Array(new Coordinate(0,0), new
>>> Coordinate(0,2), new Coordinate(2,2), new Coordinate(2,0), new
>>> Coordinate(0,0)))
>>>
>>> val exterior2 = f.createLinearRing(Array(new Coordinate(0,0), new
>>> Coordinate(0,1), new Coordinate(2,1), new Coordinate(2,0), new
>>> Coordinate(0,0)))
>>>
>>>
>>> val p1 = f.createPolygon(exterior1, Array())
>>>
>>> val p2 = f.createPolygon(exterior2, Array())
>>>
>>>
>>> val mp = f.createMultiPolygon(Array(p1, p2))
>>>
>>> mp.union(l)
>>>
>>> Here is the exception thrown in the interpreter:
>>> com.vividsolutions.jts.geom.TopologyException: side location conflict [
>>> (0.0, 1.0, NaN) ]
>>> at
>>> com.vividsolutions.jts.geomgraph.EdgeEndStar.propagateSideLabels(EdgeEndStar.java:300)
>>> at
>>> com.vividsolutions.jts.geomgraph.EdgeEndStar.computeLabelling(EdgeEndStar.java:136)
>>> at
>>> com.vividsolutions.jts.geomgraph.DirectedEdgeStar.computeLabelling(DirectedEdgeStar.java:127)
>>> at
>>> com.vividsolutions.jts.operation.overlay.OverlayOp.computeLabelling(OverlayOp.java:373)
>>> at
>>> com.vividsolutions.jts.operation.overlay.OverlayOp.computeOverlay(OverlayOp.java:173)
>>> at
>>> com.vividsolutions.jts.operation.overlay.OverlayOp.getResultGeometry(OverlayOp.java:127)
>>> at
>>> com.vividsolutions.jts.operation.overlay.OverlayOp.overlayOp(OverlayOp.java:66)
>>> at
>>> com.vividsolutions.jts.operation.overlay.snap.SnapIfNeededOverlayOp.getResultGeometry(SnapIfNeededOverlayOp.java:96)
>>> at
>>> com.vividsolutions.jts.operation.overlay.snap.SnapIfNeededOverlayOp.overlayOp(SnapIfNeededOverlayOp.java:58)
>>> at com.vividsolutions.jts.geom.Geometry.union(Geometry.java:1395)
>>> at .<init>(<console>:18)
>>> at .<clinit>(<console>)
>>> at .<init>(<console>:7)
>>> at .<clinit>(<console>)
>>> at $print(<console>)
>>> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>>> at
>>> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
>>> at
>>> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
>>> at java.lang.reflect.Method.invoke(Method.java:606)
>>> at
>>> scala.tools.nsc.interpreter.IMain$ReadEvalPrint.call(IMain.scala:734)
>>> at
>>> scala.tools.nsc.interpreter.IMain$Request.loadAndRun(IMain.scala:983)
>>> at
>>> scala.tools.nsc.interpreter.IMain.loadAndRunReq$1(IMain.scala:573)
>>> at scala.tools.nsc.interpreter.IMain.interpret(IMain.scala:604)
>>> at scala.tools.nsc.interpreter.IMain.interpret(IMain.scala:568)
>>> at
>>> scala.tools.nsc.interpreter.ILoop.reallyInterpret$1(ILoop.scala:756)
>>> at
>>> scala.tools.nsc.interpreter.ILoop.interpretStartingWith(ILoop.scala:801)
>>> at scala.tools.nsc.interpreter.ILoop.command(ILoop.scala:713)
>>> at
>>> scala.tools.nsc.interpreter.ILoop.processLine$1(ILoop.scala:577)
>>> at scala.tools.nsc.interpreter.ILoop.innerLoop$1(ILoop.scala:584)
>>> at scala.tools.nsc.interpreter.ILoop.loop(ILoop.scala:587)
>>> at
>>> scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply$mcZ$sp(ILoop.scala:878)
>>> at
>>> scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply(ILoop.scala:833)
>>> at
>>> scala.tools.nsc.interpreter.ILoop$$anonfun$process$1.apply(ILoop.scala:833)
>>> at
>>> scala.tools.nsc.util.ScalaClassLoader$.savingContextLoader(ScalaClassLoader.scala:135)
>>> at scala.tools.nsc.interpreter.ILoop.process(ILoop.scala:833)
>>> at scala.tools.nsc.interpreter.ILoop.main(ILoop.scala:900)
>>> at xsbt.ConsoleInterface.run(ConsoleInterface.scala:57)
>>> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
>>> at
>>> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
>>> at
>>> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
>>> at java.lang.reflect.Method.invoke(Method.java:606)
>>> at
>>> sbt.compiler.AnalyzingCompiler.call(AnalyzingCompiler.scala:73)
>>> at
>>> sbt.compiler.AnalyzingCompiler.console(AnalyzingCompiler.scala:64)
>>> at sbt.Console.console0$1(Console.scala:23)
>>> at
>>> sbt.Console$$anonfun$apply$2$$anonfun$apply$1.apply$mcV$sp(Console.scala:24)
>>> at sbt.TrapExit$.executeMain$1(TrapExit.scala:33)
>>> at sbt.TrapExit$$anon$1.run(TrapExit.scala:42)
>>>
>>> Any insights on why this simple example is throwing?
>>>
>>> Thanks,
>>> Rob
>>>
>>>
>>>
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>>>
>>
>
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Instantly run your Selenium tests across 300+ browser/OS combos.
Get unparalleled scalability from the best Selenium testing platform available
Simple to use. Nothing to install. Get started now for free."
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