Given a WMS request for a 256x256 map tile and vector data stored in Oracle Spatial, I am trying to understand how GeoTools crops the image. Judging by some database tracing, GeoTools does not appear to use the sdo_intersection function. Instead it simply queries all polygons that have any interaction with the bounding box of the map tile (via the sdo_relate operator). This will result in a lot of vertices outside the bounding box of the map tile. How does GeoTools transform this into just the vertices present on the map tile and/or where in the source code does this happen?
The reason I ask, is because I am trying to implement a high throughput map tiler to transform some very large polygons into smaller polygons of the right size for a map tile. I have tried to do this by using sdo_intersection to compute the intersection of the large polygons with the bounding box of the map tile, but it is very very slow. I have seen a single intersection of a tile bounding box and a 40,000 vertex polygon take 11 seconds. Since I have to perform over 100,000 of these operations, I need to find something faster. I know its possible to do this faster, because GeoTools creates map tiles in less than 11 seconds on the same data. But so far I have not been able to find the magic code in the source I downloaded. Any help would be greatly appreciated. ------------------------------------------------------------------------- Sponsored by: SourceForge.net Community Choice Awards: VOTE NOW! Studies have shown that voting for your favorite open source project, along with a healthy diet, reduces your potential for chronic lameness and boredom. Vote Now at http://www.sourceforge.net/community/cca08 _______________________________________________ Geotools-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/geotools-devel
