what about having the different level of details with the distances of the switch between lods like now, but with the engine that switch not all the model but only the parts of the model that are too far?
you have your planet, from space, at big distances, you see the low detail model, it is flat and the details are only textures
you approach the surface, you see the high detail lod with landscape modeled, mountains, buildings and so over, but only in a close range of view, outside this range of view you see only the medium level of detail, and for the parts of the model more far, the parts that you can't see o that are very far, again the low level of detail
i don't know if it would be possible to have the engine to switch the from one lod to another to render different parts of the same object...and there will be probably the problm of an enormous pof to be loaded at the begnning
an alternative may be to have the details as single objects and to set the distances of the switch for any single elment of the landscape....true pain in the ass.....and with some probs: you will have too targettable elements
second alternative may be like the first one, but instead of having different pofs for any details, the details will be subobjects of a single pof, but you must be able to set "switching distance" for any single subobjects .. in this way you don't have too things targettable
obviuosly i don't mean to model all the landscape of all the surface of a planet...eh;)
just the areas where the action will be....
imagine you have to approach the surface of a planet form space... not all the trajectoris (its the right word?) will be safe... only certain...you can set waypoints to be reached in order to enter the atmosphere, or you will explode, so you can create a situation wher a player can reach only specific areas of a planet, the areas you will have to model