Hi @digman
First of all, I think I got it! Thank you sooooooooo much. I can´t thank you enough, because this solves a lot of problems for me.
To answer your question, the model was created in Sketchup 2017 and uploaded to 3DCoat.
My fault was, that I did the changes in the modeling room, than I baked with "Updated Painting Mesh with Retopo Mesh", so my model looked good in "Paint room". When I entered the "UV room", first of all I did not use "Upd. Islands" and then I used "Unwrap" instead of "PackUV2", this crashed my texture.
So the following may be interesting for some other users, this is my current and I hope correct sequence now.
In the "Modeling room", update the mesh by "Take mesh from the Painting room"
Do the model modifications.
Bake mesh by "Update Painting mesh with Retopo mesh", you may save it or not. (Up to you)
Change into "Paint room", model looks good.
Change into "UV room".
Press "Upd. Islands", then "PackUV2"
Change into "Paint room", model and texture is still fine.
Up to now I only did minor modifications in the "Modeling room", like deleting one or two faces, adding a seam or face here or changing soft seam to hard seam.
Dear @digman you deserve your title as "Reputable Contributor" and everyone who gets help from you can be happy!
Thank you again and best regards
Walter
PS: The problem of the different UV sets in UV room and Paint room came for sure from my misuse of the software.
The popup window of the command "PackUV2", for me was misleading. It says that it is just rearranging the islands, so I had no idea that the command would have anything to do with modifications on the model.
Just as an idea; wouldn´t it be great if you change your model in the "Modeling room" and when leaving and baking by "Update Painting mesh with Retopo mesh" that the UV islands are automatically updated and packed by PachUV2, so UV set in UV room and paint room are the same!? Just to make things simple.
