your tech has come a long way since you started the project, good to see irrlicht getting used for ambitious projects like this.
out of curiosity, which version of irrlicht are you using?
This new Gekkeiju is finally using 1.7.2. The current version, which already had the same kind of terrain, used 1.2. The difference in rendering speed is really huge so I'm glad that I finally had time to upgrade the engine.