[Tilesathome] Memory requirement of T at H

[Gert Gremmen]

Hi All,

I have been looking at the SVG files of the
tiles around Rotterdam, and they can be as big
as 27 MB .
Does anyone know if the inkscape memory problems
are caused by the size if the input data (27MB) of
by the actual rendering ? I have tried to open the files
on several platforms and most do not have the problem that inkscape has.
I have viewed these
large files with photoshop, and with 


Before the problem can be tackled, I think'we should give others the
opportunity to understand the
perl script. While perl is not that difficult, being the
implementation of regular expressions the most difficult part to read, I
have most problems just to understand the script in what is happening.
There is no document of actually what the sript is doing, and in what
order.

There is a bit of comment , but no overall view.

Let's start with seeking the support of the community and create a wiki
page with a full description of the
current method, the list of modules and their function, and a list of
procedures and functions with their arguments and a description. And a
list
a commented variables and constants.

I believe that many of our
list members may be able to help if they were
given the opportunity....





Regards,

Gert Gremmen

Hi Maciek,

This is known as the T at H Unrenderability theorem:

For any given computer system, there exists a set of tiles that are too
complex for that system to render in real time.

There are a couple of approaches to this problem:

1. I have working with Dodi on reducing the size of the SVG files
generated. The files are bloated out with a lot of extra stuff that is
outside of the render box and so never get's rendered. It get's pulled
in along with the place names to handle generation of names accross tile
borders. The use of the smart-linecaps feature for nearly every single
line generated also blows out the size and complexity by a factor of at
least 2, especially in the lowzoom processing. If we can reduce the size
of the generated SVG, then Inkscape will be better able to process it.
Dodi seems to be tied up at the moment, so this work has stalled.

2. I have added the option to use Batik instead of Inkscape to render
tiles. You may have better luck with Batik in extreme situations.
Unfortunately, there is a bug in Osmarender that causes Batik to fail
occasionally. Still working on this one also.

3. A more general solution is to use Osmosis to cut the dowloaded OSM
file into smaller strips for processing the higher zoom levels. This
will result in smalled SVG's. Since the higher zoom levels process the
SVG's in strips anyway, nothing is lost. This requires a mod to Osmosis
and much work on tilesgen.pl and I just haven't had a chance to work on
it.


Hopefully, after Christmas, we can get something happening. Options 1
and 2 are in hand. Any assistance offered with option 3 would be
appreciated.


Regards,
Brent.



*********** REPLY SEPARATOR  ***********

On 19/12/2007 at 1:13 AM mkalkal  wrote:

>Hi,
>
>   My computer has 1GB of RAM and 3GB of swap,but  when I was given to 
>render such tiles :
>Doing tileset 1171,1547 (zoom 12)
>Doing tileset 2103,1347 (zoom 12)
>inkscape was  killed with out of memory message. My current system is 
>Debian lenny and i686 kernel.
>I wonder if I should to switch to amd64 kernel in order to give
inkscape 
>more virtual space ?
>Simply adding more swap may not work.
>What do you think ?
>
>
>Maciek Kaliszewski
>
>
>
>----------------------------------------------------------------------

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____________________________________________________________
Brent Easton                       
Analyst/Programmer                               
University of Western Sydney                                   
Email: b.easton at uws.edu.au


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