At the moment I'm thinking of a traditional height map stored in a texture, using the vertex shader to displace the mesh vertices and calculate normals. Combine this with some clever texturing and it might result in rather nice looking stuff. No idea how expensive it is to send a new texture to the card every frame though. Experiments will show how good an idea this is.
The thing about this is how I represent it logically. Probably in much the same way. How I manipulate it should be interesting...
As an aside, writing all this stuff down really helps you find the holes in things. At the beginning of writing this post I had planned on writing about a VERY different idea, but it turned out to be just silly.
I would really hope to have more screens soon. And a name. It's not a game if it doesn't have a name. [smile]