Is there an example anywhere that you know of that shows how use use the results from the Polytope intersector?
I found the createPolytope function, however there only seems to be one result from the intersector. Note that I'm not using a Viewer anywhere, I'm just using osgEarth as a terrain database (using .earth files is a specific use case for the software).
I know that the ElevationSlice class does pretty much the same thing but with a PlaneIntersector.
If you are not running a viewer, there is a chance that only the first LOD of the terrain is getting built. The terrain only subdivides during the Cull traversal during the normal course of a frame loop.