Re: [mapserver-users] Mapserver images doesn't fit well on a tiling scheme???
On Tue, Mar 03, 2009 at 08:31:05AM -0800, Dan Little wrote: There are two steps to a tilecache... Step 1: Seeding it. Step 2: Querying from it. Metatile usefulness is best seen while seeding the tile cache. If you look at the attached graphic (a rough estimation of a 3x3 meta-tile setup) then you'll see as the tilecache seed iterates through the map, it oversamples the map and uses the center image to represent the tile (A). When moving onto the next tile (B), it performs the same over-sampling. Since the map is then never at the edge of the generation you do not see errors with off-map lines and labelling at the edges. This is incorrect. Instead, what happens, is that when you request, A, B, or C, the 3x3 grid centered around B is rendered. when you request tile D, E, or F, the 3x3 grid around E is rendered. In each case, a metaBuffer sized pixel boundary on all sides is created. So, a 3x3 metaTile is actually 768 (3*256) + 20 (2 * 10) - 788 pixels big. This way, things near the edges of tiles are still included, and you get fewer missed labels becasue the labels that san across the edges of A and B are included, where they wouldn't have been before. Regards, -- Christopher Schmidt MetaCarta ___ mapserver-users mailing list mapserver-users@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/mapserver-users
Re: [mapserver-users] Mapserver images doesn't fit well on a tiling scheme???
To summarize, here is the way to *completely* avoid truncated labels and edge artifacts: * use a 10 pixel metabuffer in your tilecache config (the number of metatiles is irrelevant, but as Chris points out, there'll be more labels included if you use a 3x3 (or more) metatiling scheme than a 1x1 one : metaTile=true metaSize=3,3 metaBuffer=10 * set a 10 pixel edge buffer in mapserver (so no labels are rendered in the 10 pixels on the edges of the image) : WEB METADATA labelcache_map_edge_buffer -10 END END * use PARTIALS FALSE in all your label blocks -- Thomas Bonfort CampToCamp ___ mapserver-users mailing list mapserver-users@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/mapserver-users
Re: [mapserver-users] Mapserver images doesn't fit well on a tiling scheme???
Thanks Chris and Thomas for clarifying... I think my thoughts were correct and my descriptions were not... go figure. MfG - Original Message From: thomas bonfort thomas.bonf...@gmail.com To: Christopher Schmidt crschm...@metacarta.com Cc: Dan Little danlit...@yahoo.com; mapserver-users@lists.osgeo.org Sent: Tuesday, March 3, 2009 12:01:45 PM Subject: Re: [mapserver-users] Mapserver images doesn't fit well on a tiling scheme??? To summarize, here is the way to *completely* avoid truncated labels and edge artifacts: * use a 10 pixel metabuffer in your tilecache config (the number of metatiles is irrelevant, but as Chris points out, there'll be more labels included if you use a 3x3 (or more) metatiling scheme than a 1x1 one : metaTile=true metaSize=3,3 metaBuffer=10 * set a 10 pixel edge buffer in mapserver (so no labels are rendered in the 10 pixels on the edges of the image) : WEB METADATA labelcache_map_edge_buffer -10 END END * use PARTIALS FALSE in all your label blocks -- Thomas Bonfort CampToCamp ___ mapserver-users mailing list mapserver-users@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/mapserver-users
