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[mkgmap-dev] Sea generation

From Charlie Ferrero charlie at cferrero.net on Mon Nov 15 05:29:44 GMT 2010

On 15/11/2010 01:11, Adrian wrote:
> On 14/11/2010, Charlie Ferrero wrote:
>> 3. Compiled with mkgmap r1728 with your patch, using:
>> generate-sea:multipolygon,extend-sea-sectors,close-gaps=1000
>> No sea, entire map is land
> Have you put the drawing order of sea after land in your .TYP file?
> Otherwise the land polygon will cover the sea.
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You were right, I had the draw order wrong.  That was the problem.

However now I see what the patch is doing, maybe I'm missing the point. 
  The problem with the polygons version of generate-sea is that it 
underlays the entire tile with a sea polygon, then plots land polygons 
on top as required.  This results in quite a slow map to pan around on.

Your patch does the reverse (draws a land polygon everywhere, then plots 
sea on top as required) but has the same problematic effect of slow 
panning.  Is there some other improvement in the multipolygons version 
of generate-sea that makes it preferable to use it over the simpler (and 
quicker to compile) polygons version?

I don't mean to sound ungrateful - I'm just trying to understand the 
difference in the two ways of generating sea.  In my mind, the best 
solution would be a multipolygon one where sea and land polygons do not 
overlap at all - thus you should get much less redraw slowness on panning.


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