Lightmap/UV overlapping in combined mesh

Hey Guys,

this is my first time posting and I am having trouble to wrap my head around it.
I have a huge Submarine that is imported with combined mesh so that I do not have to handle all the little parts and can easily move it around as one.
I have unwrapped all the little parts to have a unique UV map for the lightmap and I get the process. Problem is, when the mesh is combined I get overlapping errors, because he puts all of the uniquely unwrapped UVs of all the objects on top of each other :confused:
I do not know how to work around that. I dont want to have to have the submarine divided into all of the small parts and want to move it as one and assign materials as one. I also cannot make a UV of t he whole submarine since it is way too big.

Any ideas? What is the correct workflow for a huge object composed of multiple pieces?

Ok so, despite the UV page showing you overlapping UVs, they are in fact not (Well they are, but it wont affect it like that). To setup correctly, every UV’ed mesh needs its own named material in your 3d program. When you do this, You should get a new material channel for each UV set. The materials only affect the UVs of their mesh, so in practice they won’t be overlapping.

As for lightmapper, that will need a single UV for the entire submarine. The auto-unwrapper should have done it, but if not, I can tell you how I might do it. I would duplicate all my meshes in my 3D program, combine them, auto-arrange their UVs so they are all packed together non-overlapping. Then I would copy-paste the uv layout onto my indivudal meshes into their second uv channel. Paste it into all pieces then delete the duplicate. Lastly In unreal turn off “auto generate uv” and you have a uv channel that when combined, should all be laid out cleanly. If you were a clever scripter you could probably automate that copy-paste task.