[Tilesathome] lowzoom tile generation

[Robert (Jamie) Munro]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Dirk-Lüder Kreie wrote:
> Robert (Jamie) Munro schrieb:
>>> Raphael Studer wrote:
>>>
>>>> On this, or another, list, i've read about the idea to create special
>>>> 12z tiles where only main routes (highway=primary) and some other
>>>> important things like big lakes/rivers/cities where rendered.
>>> They could be uploaded at size 128*128.
> 
> yes.
> 
>>> I think that lowzoom itself should be run on the T at H server. The upload
>>> stuff should mark which z12 tiles are new since the last time lowzoom
>>> was run. Then lowzoom could generate all the z11 tiles that have those
>>> z12 tiles in them, and work it's way up to z1.
> 
> Then it would constantly re-render the z0-z5 tiles.

Good. Then they would constantly be up to date. But as it is working
it's way up to there, it would probably very rarely make it - it would
require a fairly long period of no uploads before it could re-render
everything.

> Besides lowzoom being quite RAM and IO intensive, which is a kind of
> load we should not put on dev at this time.

It could be made to run only when the upload queue is empty.

I haven't looked at the script, but it should require only 192k of RAM
per uncompressed 256*256 tile - less than 1Mb for 4 tiles + the one its
making. RAM could be optimised further by only storing 1 incoming tile
at a time.

Robert (Jamie) Munro
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.6 (Darwin)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQFGwMrEz+aYVHdncI0RAuybAJ97C5O1Rbeu7KmEu2vMhz4nISddIgCdGCHG
l3n3i4Eu2OvR3/NQDOmfa1A=
=iQw3
-----END PGP SIGNATURE-----