[OSM-dev] New renderer... some thoughts on the way forward

nick at hogweed.org nick at hogweed.org
Wed May 31 00:32:24 BST 2006


Hello everyone,

A few thoughts on the renderer and how to deal with the current issues.

Firstly, yet another (!) compositer (but keep reading...)

http://nick.dev.openstreetmap.org/compositer.php

is a quick and dirty compositer I have written which will composit the 
Landsat, and the *PHP* versions of the OSM renderer and SRTM contour 
generator I wrote earlier in the year. As well as a bbox, width and height, 
it takes a layers parameter e.g.

http://nick.dev.openstreetmap.org/compositer.php?layers=landsat,osm,srtm&bbox=...

Allowed layers are: landsat, osm, srtm

Maybe in view of the problems with mod_ruby this could be used as a stopgap 
solution for putting the new renderer on the live server. Would certainly be 
good to see the IoW in glorious multicolour :-) Incidentally, just as the 
Ruby compositer (wmsmod.rbx) is unable to deal with the PHP-generated tiles, 
this PHP compositer is unable to deal properly with the Ruby-generated tiles, 
in that transparency is ignored....

Moving secondly onto the apparently most serious issue, the issue with the 
behaviour of mod_ruby. Are the problems I am experiencing with mod_ruby while 
attempting to develop the new renderer easily solvable? One solution someone 
mentioned was run Ruby as CGI, at least on the dev server.... Steve, are you 
able to do this without too much hassle? Presumably once it's been tested in 
a number of worldwide locations then it can be just transferred to the 
production server without problem.

The other issue is the question of ways. Experiments with grabbing ways from 
the dev server showed that the SQL is prohibitively slow, so ways could not 
be easily rendered with the current code. Again as a short term solution, 
until the SQL is optimised, is to parse the June planet.osm (the first with 
the IoW data) so that all segments which belong to ways are tagged with the 
tags of the parent way. This will allow both versions (PHP and Ruby) to show 
ways indirectly, and should lead to a good representation of the IoW 
(assuming ways have been tagged). Obviously this will need to be on the dev 
server.

So it appears that the short term solution is with the PHP version of the 
renderer on the dev server. Anyone got any thoughts on this.... solutions to 
the mod_ruby issue would be welcomed above everything else :-) as clearly, 
from the point of view of both aesthetics and code sharing/reuse, the 
Ruby/rmagick version is the long-term way forward.

Nick




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