I have just realised that the LWO micro exporter has a great functionality, not only for exporting terrain but also as a mean of visibilty analysis (see for eg.
http://edesignstudio.blogspot.com/2005/12/what-is-visual-impact-analysis.html ), because it exports the geometry that it sees from a selected camera.
If it would be possible to set the camera at 360 degree angle than the resulting terrain would be a surface that has polygons that you can only sees from a specific point.
There are many other GIS application that can do this but are usually quite slow and don't have a 3d viualization counterpart.
It may not be of everyone's interest but I wanted to share this with others and I hope that I could find some interesting application in the near future.
Please let me know if I am wrong
Nic