[mapguide-users] RE: MapGuide Automated Tiling Engine

[Jason Birch]

Hi Kori,
 
Currently, the tile service code only renders a tile if it does not exist, otherwise it just streams back the existing tile.  Look around line 172+ in ServerTileService.cpp:
 
<http://trac.osgeo.org/mapguide/browser/branches/1.2.x/MgDev/Server/src/Services/Tile/ServerTileService.cpp <http://trac.osgeo.org/mapguide/browser/branches/1.2.x/MgDev/Server/src/Services/Tile/ServerTileService.cpp> >
 
I guess it would be convenient for tile generators to have a Create() function that only returns a result code... no point in shipping image bytestreams around for this.  You'd likely want to have a filter argument to this function where you could restrict creation to things like "if not exists" or "if older than".
 
You could hack a file existence check before trying to generate the tile, but please be aware that the directory structure for cached tiles has changed considerably in MapGuide OS 1.2, and the ability to specify tile size on a per-server basis has been added, so any calculations made based on a fixed tile size or tile group size may be invalid.  Because of this, you'll have to account for the server version number in any such test.  Personally, I wouldn't risk this, as the tile structure is an undocumented feature, and is liable to change.  Stick with the APIs to reduce your risk and maintenance overhead.
 
More information on these settings and changes can be see in the serverconfig.ini file in SVN (look for [TileServiceProperties]) :
 
<http://trac.osgeo.org/mapguide/browser/branches/1.2.x/MgDev/Server/src/Core/serverconfig.ini <http://trac.osgeo.org/mapguide/browser/branches/1.2.x/MgDev/Server/src/Core/serverconfig.ini> >
 
in this email thread:
 
<http://lists.osgeo.org/pipermail/mapguide-internals/2007-January/000509.html <http://lists.osgeo.org/pipermail/mapguide-internals/2007-January/000509.html> >
 
and in this RFC:
 
<http://trac.osgeo.org/mapguide/wiki/MapGuideRfc13 <http://trac.osgeo.org/mapguide/wiki/MapGuideRfc13> >
 
Additionally, there should be considerable speed improvements for tile generation with MapGuide OS 1.2:

 
<http://trac.osgeo.org/mapguide/wiki/MapGuideRfc11 <http://trac.osgeo.org/mapguide/wiki/MapGuideRfc11> >
 
Jason

________________________________

From: Kori Maleski
Subject: RE: [mapguide-users] RE: MapGuide Automated Tiling Engine

The MapGuide TileService function that retrieves tiles is the same one that
does a check to see if it exists, so there isn't a handy way to skip the
process.

I may be able to speed the requests if they do already exist.

-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/ms-tnef
Size: 6522 bytes
Desc: not available
Url : http://lists.osgeo.org/pipermail/mapguide-users/attachments/20070507/03eab4c5/attachment.bin