this an idea of how to switch subpatches on/off according to its visiblity in renderer. Shoutbox talk by digitalwannbe.
On right side is some code, which is supposed to be in a subpatch and can be turned off. Its working by frustum culling, which is a dx method for checking visibility of meshes.
The drawback of this is, that its working for GPU only, because you need position of objects, which is calculated at CPU.
Anyway, its just a way. May be someone has some clues of how to extend it. Sorry for the messy patch.
subpatch_switch.v4p (39.0 kB)