I’ve got a building that is split into individual levels using OBJ files. Each OBJ file I load into prefab (into the same scene) generates new Materials despite all mtl files linking to the same image files. Obviously I would like each new loading OBJ file to reference existing Materials.

Also, when I name a container in the hierarchy pane, these names seem to change when I import another OBJ file. For example, if I’ve named a container Level1, it changes to Level2 on another import.

Prefab do not accept double ids, because Prefab is not where the party happends. For instance, what would happend if you would load two meshes, one being a cube, the other a sphere, both named “mycoolmesh”.
Now you export these and load into your project. How do you expect to know who’s who? In case of AS3 exports, having twice “new id” into code generates errors.

As about doubled/shared material, its the same problem. but you can in Prefab, reassign the material and share it. This brings an extra work but during exports, Prefab ensure that all that can be shared is shared. For instance, export only one map instead of two.

I have in the past (v1) tried to have unique prefab id’s while ignoring how meshes were named, sure it worked ok within Prefab, but as I couldn’t export these without altering the name to prevent conflicts, it was only moving the problem else where.
So I’ve decided to pick the most robust way.

Can you please refer any notes or something that can explain this in more detail. thanks. POS