[geos-devel] OverlayOp JTS port

[Martin Davis]

The original plan for GEOS was that it would track JTS 100%.  This was 
to simplify porting new functionality as it is added to JTS.  However, 
at one point I think Sandro did some extra work on trying to improve 
GEOS robustness.  This is probably where the checkObviouslyWrongResult 
came from.  After this was done, JTS caught up - so this method may not 
be needed any more.



Obe, Regina wrote:
>
> I apologize for the barrage of questions.  As far as I can tell the
> OverlayOp.cpp is vintage JTS 1.7 (which I think is same as the JTS 1.9 
> for this class)
>
> except it has the additional calls of
>
> checkObviouslyWrongResult() - which most of that code looks like it 
> would never
> be called because of the #ifdefs except for the 
>
> assert(resultGeom);
> UNREFERENCED_PARAMETER(opCode); (have no clue what this does)
>
> and also a
> elevationMatrix->elevate(resultGeom);
>
> which looks like will get called since USE_ELEVATION_MATRIX 1.
>
> Is the elevationMatrix designed to deal with 3d geometries?  Didn't 
> realize
> Union actually works with those, but then I never tried it with 3d.
>
> So I'm a little puzzled why these 2 extra function calls since I 
> always thought
> GEOS was at best on par with JTS?
>
> Thanks,
> Regina
>
> -----Original Message-----
> From: geos-devel-bounces at lists.osgeo.org on behalf of Obe, Regina
> Sent: Wed 9/17/2008 9:26 AM
> To: GEOS Development List
> Subject: [geos-devel] OverlayOp JTS port
>
> I'm looking at the operation.overlay.OverlayOp in geos trunk
>
> In the header it says
> Last port: operation/overlay/OverlayOp.java rev. 1.23
>
> But I don't believe this to be right since when I compare the
> computeOverlay methods
> against 1.2 and 1.3 versions of JTS codebase, it has an additional
> EdgeNodingValidator check which wasn't introduced until later versions
> of JTS.
>
> So I'm wondering is the OverlayOp.cpp a mix of JTS versions or is the
> comment above just plain wrong.
>
> It also has a checkObviouslyWrongResult() check at the end of
> computerOverlay which I haven't figured out which version that was
> introduced in JTS (its not in 1.2,1.3, or 1.9).  Is this a GEOS specific
> check that has no JTS equivalent?
>
> Thanks,
> Regina
> -----------------------------------------
> The substance of this message, including any attachments, may be
> confidential, legally privileged and/or exempt from disclosure
> pursuant to Massachusetts law. It is intended
> solely for the addressee. If you received this in error, please
> contact the sender and delete the material from any computer.
>
> _______________________________________________
> geos-devel mailing list
> geos-devel at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/geos-devel
>
>
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> geos-devel mailing list
> geos-devel at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/geos-devel

-- 
Martin Davis
Senior Technical Architect
Refractions Research, Inc.
(250) 383-3022