osgEarth is a scalable terrain rendering toolkit for OpenSceneGraph. Just create a simple XML file, point it at your imagery, elevation, and vector data, load it into your favorite OSG application, and go! osgEarth supports all kinds of data and comes with lots of examples to help you get up and running quickly and easily.
But osgEarth does more than just render terrain:
* Drape vector (GIS) data on the terrain
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http://wush.net/trac/osggis/
osgGIS is software that enables you to visualize, query, and manipulate GIS data from within an OpenSceneGraph application. In short, you can generate spatially accurate 3D geometry from GIS data layers while maintaining connectivity to the GIS data sources.
screens from openGIS: (links:)
http://wush.net/trac/osggis/browser/ima ... light1.jpg
http://wush.net/trac/osggis/browser/ima ... 172207.jpg
How difficult would it be to implement it in FG??