[mkgmap-dev] Internal Error Failed to render Multipolygon

Tue Dec 24 17:02:24 GMT 2024

Hi Gerd

niceSplitShift: OK. I presume that, for the multipolygon logic, it doesn't
matter that the area splitting division line isn't accurately representable at
lower resolutions.

missingOuter: I've never quite followed this part of MP processing but a
specific error relating to the input geometry, rather then "Internal Error',
must be much better.

checkAllOn: I think I'm missing something here and need to look at the code more
carefully. Will do this in a few days.

Happy Christmas
Ticker

On Tue, 2024-12-24 at 10:00 +0000, Gerd Petermann wrote:
> > > > Hi Ticker,
> > > > 
> > > > sorry for the late response. I think the main problem is the value for
> > > > niceSplitShift. I see much better results when I change that to 0 so
> > > > that
> > > > partitions are divided into equal halves.
> > > > I've also learned that the reported internal error is more often caused
> > > > by
> > > > invalid multipolygons where a ring with role inner is outside of the
> > > > bbox of
> > > > the outer ring.
> > > > Try e.g. https://files.mkgmap.org.uk/detail/566
> > > > 
> > > > I've attached a patch to address these two problems. One other problem
> > > > that
> > > > I
> > > > noticed is in method IsInUtil.checkAllOn()
> > > > Coord pTest = p1.destOnRhumbLine(EPS_OFF, p1.bearingTo(p2));
> > > > 
> > > > I noticed cases where this code calculates a point which is not on the
> > > > line
> > > > between p1 and p2, e.g. if the distance between these two points is
> > > > smaller
> > > > than EPS_OFF.
> > > > I introduced this line with r4499 which refers to your patch
> > > > isPointInShape_v3.patch. No idea why, I can't find the changes in that
> > > > patch.
> > > > Maybe I look at wrong file.
> > > > 
> > > > The partitioning is really a performance boost with very complex MPs
> > > > like
> > > > that
> > > > for lake Huron (relation 1205151). I see 10 secs instead of +130 secs
> > > > with
> > > > partitioning.
> > > > On the other hand it is more likely to hit edge cases where small
> > > > fragments
> > > > of
> > > > touching inner rings are reported as possibly wrong nested inners.
> > > > 
> > > > Gerd