Hello
I saw Level of detail option in scenecomposer.
When i click that: 
How to configure that? Is it even work in game?
I tried set different values but nothing happen.
See this post for explanations
http://hub.jmonkeyengine.org/forum/topic/brand-new-lod-generator/#post-232404
To have it to work in game you have to add a LodControl on the geometry and it will switch lod levels according to camera distance.