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[udig-devel] Tiling Renderer

Hi Cole,

I saw the reference to writing a Tiling WMS Renderer so I'm going to spill a bunch of my ideas. I was starting work on a TilingRenderer that works for any renderer. Basically the design follows the Decorator pattern. A tiling Renderer wraps around a child renderer and handles image caching, tile creation and management. I've started a prototype that you can find in the code base. It doesn't work as yet and I'm starting with the simplest case. I've layed out the work flow for a full fledged Tiling renderer in it but at the moment I am concentrating on just getting it to reuse the previous image when pans occur.

The final renderer I envision will cache, mostly on disk, tiles for different zoom levels and areas. Spatial indexes will have to be maintained for fast look up. When panning or zooming the available tiles will be used and the missing tiles will be approximated from the existing tiles at different zoom levels.

You know what REALLY needs to be done? WMS Renderer currently ignores the Envelope object that is passed in in its render() method. For tiling to work in the general case, the WMS renderer needs to behave correctly. Otherwise it will re-render for every tile and the Servers are going to hate us.

Just some thoughts that you might want to consider,

Jesse


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