Hi Martin, The union operation is implemented by buffering the union of the input, rather than the union of the input buffered, if you see the distinction. I was hoping JTS had already optimized this, but from what you are saying, I would guess not.
Larry On 8/31/07, Martin Davis <[EMAIL PROTECTED]> wrote: > Cool... > > I think that one way around the "slow union" problem is to develop a > "Cascading Union" function. This will build up a union of multiple > geometries by forming them into a tree, and recursively unioning the > branches of the tree from the leaves to the root. In theory this > should provide a fairly optimal balance between performance and memory use. > > A nice way to form the tree would be to add the input geometries to a > JTS Quadtree or STRtree and then traverse the tree in depth-first > order. Unfortunately currently the implementations don't support the > ability to traverse the tree in any order - this wouldn't be too hard to > add, though. > > Thoughts? Anyone keen on trying this out? > > Martin > > > > Larry Becker wrote: > > I have committed the improved buffer plugin. Three sample screens are > > attached in english, french, and german. It now supports buffering > > the selection. It provides a convenience union option. The sidebar > > picture now previews the current options. It copies attributes by > > default, even from selections on multiple layers, but this can be > > turned off. It supports setting the number of segments in a quarter > > circle. > > > > Be careful with the union operation. With large selections, it can > > take a long time. For instance using Uwe's GeoCity project, I tried > > to buffer everything by 1000 meters. Without union it completed in > > about 20 seconds, and with union I finally killed it after 5 minutes. > > > > regards, > > Larry Becker > > > > > > ------------------------------------------------------------------------ > > > > > > ------------------------------------------------------------------------ > > > > > > ------------------------------------------------------------------------ > > > > ------------------------------------------------------------------------ > > > > ------------------------------------------------------------------------- > > This SF.net email is sponsored by: Splunk Inc. > > Still grepping through log files to find problems? Stop. > > Now Search log events and configuration files using AJAX and a browser. > > Download your FREE copy of Splunk now >> http://get.splunk.com/ > > ------------------------------------------------------------------------ > > > > _______________________________________________ > > Jump-pilot-devel mailing list > > Jump-pilot-devel@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > > > > -- > Martin Davis > Senior Technical Architect > Refractions Research, Inc. > (250) 383-3022 > > > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Splunk Inc. > Still grepping through log files to find problems? Stop. > Now Search log events and configuration files using AJAX and a browser. > Download your FREE copy of Splunk now >> http://get.splunk.com/ > _______________________________________________ > Jump-pilot-devel mailing list > Jump-pilot-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel > -- http://amusingprogrammer.blogspot.com/ ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Jump-pilot-devel mailing list Jump-pilot-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jump-pilot-devel
