we are rendering our customized mapnik map with tilecache. For
performance reasons we are only able to provide a subset of the worlds
tiles. Nevertheless we want to provide tiles for the whole world and
are thinking to fall back to the osm tiles for this unrendered regions.
Thats why we want to change the code of tilecache to redirect calls to
openstreetmaps tile server. I would like to make this redirection
depending on the bounding box and the resolution. As the tilecache code
is very new for me I would like to ask you for some hints where and how
it is the best way to adjust the code.