Results 3 issues of jinjun1994

现在的实现是 osgb对应一个b3dm,能进行分割拆分吗

some mesh can't show. see : ![image](https://user-images.githubusercontent.com/21867818/168529928-c8f0128d-cedd-49d3-84bd-5f9c0f2f3631.png) in https://sandbox.babylonjs.com/, All meshes are normal. ![image](https://user-images.githubusercontent.com/21867818/168529678-67ea8837-00cf-46e6-812c-d54d8b7155f8.png)

bug

MSFT_lod.js: lod.addLevel(mesh, this._calculateDistance(nodeLevel, rootNodeDef)) Causes mesh removed from meshes

needs repro