Check out the latest Staff Blog update that talks about what's changed, what's new, and what's up with these "Pixels".
A screen shot of the new swamp graphics.
The "flat" heightmap (gently rolling flat lands) is used to draw the ground as usual at an average altitude of y=0.0f.
Then a huge water mesh is draw at y=0.0f.
Z buffering does the rest.
Add the usual vegetation coverage (woods, jungle, grass, etc), and you're done!
Drawing the entire ground twice is a perfomance hit, but not too bad.
The game's framerate is limited to a speed that can be maintained under worst case conditions. Despite swamp's performance hit, the game is still able to meet and exceed this target framerate. But just like the first version of the game, swamp will still be the most graphically intensive terrain type to draw.