Thanks for the info, ArtPearl!

In the meantime I have analysed your function tree and duplicated it here. Everything works fine.
And I learned a couple of new things by analysing your function, for example I have never used the Invert node before. The thing makes me more aware of the fact that there is math behind it. Your solution is really clever!

The only thing I have changed in your function is that I disconnected the Multiply node above the procedural terrain from the Constant Node. This way the procedural terrain can be scaled independently from the heightfield/area.

Yes the function looks complicated, but once a Meta node is created with the relevant parameters published it all becomes very simple. The picture below shows a possible parameter box of a "Heightfield Integrator" Metanode. The Metanode itself works perfectly.

http://www.eonmusic.ch http://www.artmatica.ch