Today I found that meshes, which I exported as .FBX files have different UV than in Blender 2.8. Previously there was no such issue. I made some tests and found that if you will use .OBJ format instead, UV exported correctly. Also, I tested models, which I previously exported correctly in older versions of Blender 2.8 and they also have issues with UV now. Anybody else has such issues? How to solve this or I have to wait an unknown amount of time until this will be fixed? Can’t use OBJ only because meshes have rigs/armature.
I did more research and found the following details:
If I repack UV and try to export it, I will get same results in FBX, like with old layout - looks like some old UV existed somewhere in .blend file and it exports instead of those, which shows in Blender 2.8.
I also tried to use Blender 2.79 and append problematic object in it - appended object also had the wrong UV, like in FBX export. Making UV unwrap again also didn’t help - old UV still exported somehow. Applying modifiers manually also didn’t help.
Finally found the issue. For some reason, some objects have multiple UV Maps (I didn’t create them manually, so I didn’t know that they existed, maybe some addon created them) and on some objects, not the first UV Map was selected. And when I exported such objects, I got first UV Map selected, which contained the wrong UV (because I did it for others). I removed all unnecessary UV Maps and it fixed an issue.
yeh as of now there is no manual way to re-arrange blender UV maps. In UE4 if you import as .fbx (grouped) it will only pick the first 2 UV maps, if non-grouped it will keep all the UV maps but your objects will be seperate (usually you want to use .fbx to pack multiple .obj’s into 1 and keep their respective UV maps).
There is an add-on called “Asset Creation Toolset for 2.8” which, has many cool tools, allows you to change the UV name/order: https://gumroad.com/mrven?recommended_by=library#