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[mkgmap-dev] tile takes very long time to generate

From Dave dfjkman at gmail.com on Thu Mar 18 11:02:39 GMT 2021

Hi Gerd,

Nested polygons may not be as rare as you think, it was a situation I was thinking about when this discussion started. Zambia has a number of large wetlands where there are islands with wetland within the island, particularly as these wetlands are seasonal and the islands will be inundated during the rains with the low points of the island staying wet once the water recedes. This is similar to your forest with a lake that contains a forest.


	  Original Message  	

From: gpetermann_muenchen at hotmail.com
Sent: 18 March 2021 12:21
To: mkgmap-dev at lists.mkgmap.org.uk
Reply to: mkgmap-dev at lists.mkgmap.org.uk
Subject: Re: [mkgmap-dev] tile takes very long time to generate

Hi all,

I still struggle with the unit test because it's hard to say what we want to get in special cases.
The current code doesn't really work in the way that I expected. I always thought that roles like "inner" and "outer" are completely ignored and that mkgmap calculates and uses the correct roles. This is only partly true. See attached file with MP were a forest contains a lake that contains a forest.
For a nested polygon where the innermost ring has wrong role "inner" this doesn't work as expected. The forest  in the lake is ignored. With the correct role "outer" it is not ignored. No idea if this is intended or an error. Fortunately nested MP are very rare.


Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Ticker Berkin <rwb-mkgmap at jagit.co.uk>
Gesendet: Montag, 15. März 2021 17:15
An: Development list for mkgmap
Betreff: Re: [mkgmap-dev] tile takes very long time to generate

Hi Gerd

You might consider the some of the ideas here as improvements to the
initial parts of MP processing.

This is a patch based on trunk rather than the new branch. It isn't
structured as for final usage, rather for minimising the spread of
changes, working in parallel with the existing code so I could see if
found the same MP problems as the existing code and having clearly
identifiable diagnostics in the log file.


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