Hi

I think Unity3D users PVS-based occlusion culling and Streaming of Assets and Terrains.

The thing I like about Unity3D is it's easy of use for things like adding lightmaps to models from most 3D Apps.

SEE following http://www.geartechgames.com/GearTech_Games/Unity_Tutorials/Unity_Tutorials.html

The above is modo to Unity3D - how easy is that..