I’ve looked, but there doesn’t seem to be any documentations out there or anyone who is asking the same thing.
I have some scenes that is lit in the Unity 4 and I need to bring it to Unity 5, for all sorts of reasons other than lighting. The issue at hand is Unity doesn’t attach my old lightmaps when it upgrades a project nor does it does it create lightmap slots to browse for old maps.
I don’t know of any way to create lightmap slots other than to finish a bake. However, even with no setting change it generates new lightmaps and atlas the UVs differently thus breaking the old lightsmaps.
Can you reattach old lightmaps and without breaking the old atlas UVs?