How are they doing this?????????????

Look at it:
-Dynamic shadows at realtime on terrain and casted from objects
-Very improved multitexturing
-Several shaders (I'm not sure whether they have a depth of field in background, then several normalmapping, and for sure there is something on the grass)
-Hundrets of objects (look at the grass and the stones, ok there are probably several per object but it's still a lot)
-And all syncronised on several pcs and if the video really shows the editiors inerface at realtime and isn't only a cut, they have three views on screen.

How do they manage to get all this working in an acceptable performance????