[mkgmap-dev] Proof of concept for better sea in overview map

Mon Jun 7 20:02:08 BST 2021

I guess that is a time for a full Norway map based on default style - so
that is quite okay. Not a sea only Norway map... Well I hope that Thorsten
Kukuk can adapt his sea files in the near future then...

On Mon, 7 Jun 2021 at 19:37, Gerd Petermann <gpetermann_muenchen at hotmail.com>
wrote:

> OK, I think found a good solution. Speed is quite OK, I see  9 min 48 secs
> for map of norway and instead of 8 min 44 secs with  r4756, and I consider
> Norway to be a worst case.
>
> See https://www.mkgmap.org.uk/websvn/revision.php?repname=mkgmap&rev=4761
> for the details.
>
> Gerd
>
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von
> Gerd Petermann <gpetermann_muenchen at hotmail.com>
> Gesendet: Montag, 7. Juni 2021 12:11
> An: Development list for mkgmap
> Betreff: Re: [mkgmap-dev] Proof of concept for better sea in overview map
>
> With the provided patch the speed is very poor for areas like Norway,
> probably twice the time.
> It is much slower because it does the complex multipolygon cutting for
> each level in the overview map. Probably too slow for complex coastal areas.
> This time will be the same for precomp-sea unless we can store sea
> polygons for each resolution.
>
> Performance will be no problem if I find a way to use Douglas-Peucker or
> similar before cutting. That was my original idea but DP produces self
> intersecting polygons and the MultipolygonCutter cannot cope with that.
>
> Gerd
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von
> Felix Hartmann <extremecarver at gmail.com>
> Gesendet: Montag, 7. Juni 2021 11:55
> An: Development list for mkgmap
> Betreff: Re: [mkgmap-dev] Proof of concept for better sea in overview map
>
> Is it only much slower because of not using precomp sea? Or will it be
> much slower in general? And what is much slower for say Europe continent
> map? If a modern 4core/8thread processor needs 30 minutes more I would
> prefer the old way knowing it is worse (if the time difference is
> negligible with precomp-sea then that would be great).
>
> On Mon, 7 Jun 2021 at 12:26, Ticker Berkin <rwb-mkgmap at jagit.co.uk<mailto:
> rwb-mkgmap at jagit.co.uk>> wrote:
> Hi Gerd
>
> This is going to take some studying to work out the implications. Can't
> do much for the next few days however, but will look carefully at the
> end of the week.
>
> Ticker
>
> On Sun, 2021-06-06 at 14:02 +0000, Gerd Petermann wrote:
> > Hi,
> >
> > the attached patch improves the overview map, but so far only when
> > precomp-sea is NOT used.
> > I tested it with --generate-sea=multipolygon,floodblocker  so that
> > mkgmap really has a multipolygon with the natual=sea data.
> >
> > For each level in the overview map it uses the original multipolygon
> > data to compute the rings which will might visible at the given
> > resolution. This requires more time compared to the current code but
> > the result is much better and some fine tuning is possible.
> >
> > To be able to use this also with --precomp-sea we need some changes
> > in the code which generates sea.zip so that one multipolygon relation
> > for each tile is stored.
> >
> > I've uploaded the results here:
> > https://files.mkgmap.org.uk/download/511/compare.7z
> > What do you think?
> >
> > Gerd
> >
> >
> > _______________________________________________
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>
> --
> Felix Hartman - Openmtbmap.org & VeloMap.org
>
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-- 
Felix Hartman - Openmtbmap.org & VeloMap.org
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