[udig-devel] Rendering pipeline: how CRS is used.

[Adrian Custer <acuster@xxxxxxxxx>]

Hey all,

Could someone explain the uses of CRS and transforms in the rendering
pipeline? I need a coarse overview of rendering as used by
uDig/streaming Renderer to understand:
 (1) how we go from shapefile data to screen data
 (2) what CRS's are stored in the rendering system
This is all prep work so I can compose an intro to CRS that will work as
background for a future, more complex discussion of CRS with features
and renderers.

What I really want is a pipeline, from a UTM shapefile (as an example)
to a displayed map on screen where we know what CRS's are in play and
where the transformations are performed. The initial start of the
operations are:

        10) Get Shapefile Metadata   => CRS used for
        geometryAttributeType
        20) Get Shapefile coordinates
        30) Build a geometry
        40) Build a feature
        ...
        ?) Create a Renderer (? with a crs?)
        ?) add the feature to the chain
        ...
        ?) transform to projected coordinates (if in lat/long?) ?
        ...
        ?) transform to image coordinates
        ...
        ?) transform to screen coordinates

If someone could flesh out the chain so I have a working idea of what's
going on, I would appreciate it.

thanks,
adrian