High detail and low detail tile sizes

I have a need for changing tile sizes in my hightmap world.
For large open deaserts, plains and sea bed, I can live with really large tiles because the terrain does not have much detail, but in the moutians, canyons, and populated areas I want to have small tiles so I can have more details in the my terrain.

Has anyone attempted this with any of the scene managers? The closest thing i've seen is that LOD changes can have a simular effect, but I want more control over it than that. (I also don't want my art guys spending hours and hours detailing the sea floor when I'd rather they be detailed the cities ).

Also when I am within a city, I want a flat terrain because most of my details will be in teh buildings and artifacts, I don't want to waste my polygon budget on a flat floor!


Anyone had success with this kind of thing? Is there an obvious feature I am missing?

Scorch.

check in wireframe mode.

Is there an obvious feature I am missing
Vertex compression, Current LOD and indices cache are optimal with regular Grid based tiles/page.
You won't achieve any of those with a different scheme.
Futur of GPUs will eventually even be optimized only for that kind of mesh (regular Grid based)

I don't want to waste my polygon budget on a flat floor!
You don't, as LOD scheme detect "roughness" of each tile and load indices buffer accordingly.