Hi Frank, Thanks for the reply. It might be worth keeping the option to control layer ordering somehow in a mosaic. The reason I'm exploring this is to see if it's possible to emulate the ArcGIS 10 "closest to center" behavior. I'm thinking that if I dynamically write the VRT, I can control how images are overlapped in response to the BBOX extents specified in a WMS request.
Roger -- On Tue, Jun 22, 2010 at 8:16 AM, Frank Warmerdam <warmer...@pobox.com>wrote: > Roger André wrote: > >> Hi All, >> >> I'd like to control the order in which overlapping images are displayed in >> a mosaic. Is it possible to do that by using a VRT, and altering the order >> in which the files are defined in it? >> >> The online doc for gdalbuildvrt states, "If there is some amount of >> spatial overlapping between files, the order may depend on the order they >> are inserted in the VRT file, but this behaviour should not be relied on." >> >> Not sure if this disclaimer is for the gdalbuildvrt utility, or describes >> the generic behavior of a raster VRT. >> > > Roger, > > I believe the statement applies to the VRT format itself. I have looked > at the code, and it always applies them linearly based on the order they > appear in the .VRT list of sources. I think you could depend on it "for > now" > though in a future version we might do something more fancy that would > result in alternate ordering. > > Best regards, > -- > > ---------------------------------------+-------------------------------------- > I set the clouds in motion - turn up | Frank Warmerdam, > warmer...@pobox.com > light and sound - activate the windows | > http://pobox.com/~warmerdam<http://pobox.com/%7Ewarmerdam> > and watch the world go round - Rush | Geospatial Programmer for Rent > >
_______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev