[udig-devel] Tiling Renderer

[Jesse Eichar <jeichar@xxxxxxxxxxxxxxx>]

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