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I have several meshes all using the same material, UV mapped and ready. When I join some of them, one of them loses its UV map entirely.

I checked that all meshes joined doesn't have any modifiers and that scale and rotation has been reset.

Any ideas of how to fix this?

Blender 2.76b

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    $\begingroup$ Do the UV maps of those separate meshes have the same name before joining objects ? You can check that in Object data > UV maps rollout in Properties editor. $\endgroup$ – Mr Zak Jan 6 '16 at 20:06
  • $\begingroup$ Ahh, thank you! The UV map names where different and when I renamed them it worked! Please write an answer so I can select it as the solution. $\endgroup$ – Max Kielland Jan 6 '16 at 23:05
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When joining already uwrapped objects, you have 2 options:

UV maps before joining objects were called equally

The default name for UV map after it's created is "UVMap". If it wasn't changed or if both objects have this map renamed so objects still has UV map called the same, after joining it will become one UV map:

enter image description here

All the islands of both objects will be added on this UV map as they were in original maps. So most likely they will overlap and it may be desired to pack and / or organize them in some way.

UV maps before joining objects were called differently

Resulting object will have as many UV maps as there were ones with different names (in example below 2).

enter image description here

All the islands are on their original maps and there isn't any overlapping. This may be desirable in some cases (e.g. baking). Note though that one object may have no more than 8 UV maps.

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Just to clarify the answer: the UV map names of the two meshes that you want to join must have the same name before joining in order for the meshes to keep their own UV mapping after joining. You can find these names in the Properties editor/panel > Data > UV Maps and you can change the names by simply double clicking on the name itself.

In my case that had me googling this very same question, I used Bezier curves to create part of my model which uses curve data for UV mapping. So instead of the default name "UVMap", it was instead by default named "Orco". When I wanted to combine my curve based mesh to my sculpted mesh, I had to change the name "Orco" to "UVMap". I tested it vice versa as well, changing the name "UVMap" of the sculpted mesh to "Orco" before joining the meshes which also worked and my two meshes kept their UV mapping after joining them into one.

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