[mkgmap-dev] [PATCH v3] - provide alternative sea drawing mechanism

Thu Dec 31 07:34:46 GMT 2009

Thanks!  My archipelago is now OK.

In my style file I added this:
natural=land [0x27 resolution 10]

in the typ file draw priority:
0x32 = 1
0x27 = 2
all others = 3 and up

I compiled the map using the --generate-sea=no-mp switch and all my
problem islands (not sure if everything is OK) appears.
Compilation took 2 minutes compared to the usual 118 min :)

On Thu, Dec 31, 2009 at 6:02 AM, Mark Burton <markb at ordern.com> wrote:
>
> v3 - generate land poly even if tile doesn't contain any sea (when
> --generate-sea=no-mp is specified) so that GPS units that ignore the
> colour of the background poly (0x4b) don't the wrong background colour.
>
> ---------
>
> v2 - avoid generating sea poly when unclipped tile contains coastline
> but the clipped tile contains no coastline.
>
> ---------
>
> Firstly, I would like to thank everyone who responded to my
> "Understanding the sea" post. From those posts and my own study, I
> finally worked out what it does. And yes, it works pretty well inasmuch
> that it generates some useful polygons. The "sea sector" heuristic
> doesn't work for me so I have been disabling it.
>
> The problem is, the end result is "butt ugly". Our MP implementation
> really can't do a good job on zillions of little islands.
>
> After frigging around for a couple of days trying to improve the
> visual quality, I tried the obvious alternative technique of not using
> a MP but, instead, just having a sea background and then put the land
> on top using plain polygons. Guess what? It works very nicely as the
> attached pics show. I now have a splendid map of the Baltic area (OK
> it's weird at the edges but that's not a problem for now).
>
> Here's the (future) commit comment for this patch:
>
>    Provide an alternative to using a multipolygon when generating the
>    sea.
>    The --generate-sea option can now take a comma separated list of
>    values:
>    no-mp - don't generate the sea using a multipolygon - instead,
>    generate a background sea polygon and then individual land polygons
>    with tag natural=land. This requires a suitable land polygon type
>    to be defined in the style file (suggested type is 0x010100) and
>    the polygon must be defined in the TYP file as having a higher
>    drawing level than the sea polygon type.
>
>    no-sea-sectors - disable the generation of "sea sectors" when the
>    coastline fails to reach the tile's boundary.
>
>    With no values specified, the --generate-sea option should work as
>    before.
>
> Oh yes, this patch doesn't include it, but I am also disabling the DP
> code for polygons as it makes them weird.
>
> Cheers and thanks again for the helpful postings.
>
> Mark
>
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>

-- 
cheers,
maning
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