Today I converted all Region-placed objects in MMORPG Tycoon 2 to render via the region’s octree. This includes buildings, roads, monsters, player characters, and AI developers. This basically means that any objects which aren’t at least vaguely in front of the camera won’t use up time being drawn by the graphics card.
The player himself, his GraveShip, and his mouse cursor are not constrained within a single region, and so are still not rendering via an octree. The terrain itself also is not covered by the octree; it has its own system for accomplishing a similar task.
Tomorrow I should be able to try out a forest, and see what performance on it is going to be like. Crossing fingers!