Christian Müller ha scritto: > Do we have something like pyramids for for vector data ? > > What I mean is having a FeatureSource (say, the boundary of Europe having > 100 000 vertices) and drawing the boundary on a 640x480 image. > I really do not need 100 000 points and therefore I make some > generalizations, each as its own feature source, minimizing io traffic and > cpu usage. > > It would be nice to have a (read only) FeatureSource as a Wrapper for all > the generalizations (best design pattern would be a composite), which > selects the proper generalization (depending on world and pixel size) and > returns a much smaller number of vertices. > > It is the same concept as we have for image pyramids (I think, > AbstractGridCoverageReader has the logic built in). > > Opinions ?
Are you talking WMS or WFS? WMS already does on the fly generalization before rendering. And if you want to use pre-generalized data, you can, just store multiple geometric columns in your database, and use scale dependent rules to decide which geometry to use. This effectively allows for using pre-decimated geometries, thought of course it would be nicer if the datastore hid the extra columns and could decide which one to pick automatically based on a generalization hint. WFS wise, we're thinking to work on something like that as well. WFS 1.1 specification allows to return not only attributes, but also functions over attributes. At the moment they are not supported, but we are looking into what amount of work it would take to support them. Once that is working, we could have a generalize(geom, distance) function that does generalization, and also plays fully by the WFS rules. Opinions? Cheers Andrea -- Andrea Aime OpenGeo - http://opengeo.org Expert service straight from the developers. ------------------------------------------------------------------------------ Apps built with the Adobe(R) Flex(R) framework and Flex Builder(TM) are powering Web 2.0 with engaging, cross-platform capabilities. Quickly and easily build your RIAs with Flex Builder, the Eclipse(TM)based development software that enables intelligent coding and step-through debugging. Download the free 60 day trial. http://p.sf.net/sfu/www-adobe-com _______________________________________________ Geotools-devel mailing list Geotools-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/geotools-devel
