Hi, I'm forwarding Ticket reported to the MapGuide Trac system:
http://trac.osgeo.org/mapguide/ticket/172#comment:6 It's also related to GEOS and may be interesting. Shortly, one of datasource supported by MapGuide is OGR. OGR uses GEOS, so MapGuide indirectly uses GEOS capabilities for various geometric operations. I believe it's worth to check the whole ticket, but below I pasted most interesting comment: ############################################################################ #172: Bug in Selection polygon from PostGiS (PostgreSql) ------------------------------------------+--------------------------------- Reporter: [EMAIL PROTECTED] | Owner: Type: defect | Status: new Priority: high | Milestone: Component: General | Version: 1.2.0 Severity: major | Resolution: Keywords: | External_id: 939561 ------------------------------------------+--------------------------------- Comment (by ksgeograf): I have been examining the problem, using a custom build of the OGR provider. It is true that without GEOS support in OGR, the Intersect only does a BBOX check. However, merely enabling GEOS will not work, as the viewer sends a square that is orthogonal to the axes (like a BBOX). The GEOS library will interpret this as another BBOX, and only perform the BBOX check anyway. When I change the polgyon sent from the viewer to a triangle, it takes 22 seconds to calculate the Intersects result with a polygon with 8000 linesegments. I have a 2+ GHz machine. It seems that GEOS always builds a full intersection matrix, before returning the result. This is obviously not optimal for a simple hit test. Even with this knowledge, I still don't see how it can take 22 seconds to calculate 8000 * 3 intersections. Can someone explain this, or how to fix it? ############################################################################ Cheers -- Mateusz Loskot http://mateusz.loskot.net _______________________________________________ geos-devel mailing list geos-devel@geos.refractions.net http://geos.refractions.net/mailman/listinfo/geos-devel
