Irrlicht Engine

I know this function have been added to irrlicht. How to use it?

I tried this code with an mesh(size:100k) and rendered it for 100 times,but the speed is lower than the default method,I dont't kown the reason.

I recently write an dll, which need inherit CSceneManager. Unfortunately, I got a lot of link error. Lots of methods in C*** classes are regarded as unresolved external symbols(LNK 2001). the Irrlicht.lib had been linked in the program. What's wrong?
I checked Irrlicht, I can't find how Irrlicht ...