One UV map destroyed when two objects joined #37182

%%%--- Windows 7 64 ---

- 2.69 RC2 and 3 ---


- When have two objects with separate UV maps. If you Cntrl J to join the objects. one of the objects looses it's UV map and all the uv verts default on top of each other into the lower left hand corner. The original object's UV Map remains intact. Behaviour does not occur in 2.68---


- Open the file, select the head, then select the body and Cntrl J to join them to one object. Go into edit mode and check out the UV map of the body. ---

%%%

Changed status to: 'Open'

%%%This is a new feature, all CD layers (UVmaps, vertex colors, vertex groups, etc.) are now merged by names. If you do not want that, just rename some of your uvmaps. Not a bug, closing.%%%

Changed status from 'Open' to: 'Archived'

%%%That is ridiculous. So if I want to join two objects together I've got to hunt through all the properties of the two objects and try and find out if somewhere they have the same names? Even though by default they are bound to unless they have been manually changed?

This will needlessly complicate just about every workflow out there. Supposed I've got a crowd scene with 30 characters in it. Each one will have a default 'uvmap' name. So now, if I want to join these into one object, I now have to go through all of these objects and rename the UV map to something unique? That is insane and seriously breaks workflow from previous versions. %%%

%%%@Tea: It's the other way around. If all the objects' uv maps have the same name (which they will unless you manually changed them) they will all be merged smoothly into a single UVMap layer.%%%

Added subscriber: @jonim8or

I suggest reopening this bug because I think there's a misunderstanding.
I encountered the bug described in the original post. (and to me the rest of the discussion seems to be missing the point of the original bug)
reproducing the bug is a bit tricky, which is why the attached file from tea_monster might not work.

I consistently get this bug when I do the following steps:
0) open blender in an empty scene

create a cube (or any other mesh primitive)
go to edit mode and unwrap the cube (for this bug the kind of unwrapping does not really matter)
go back to object mode and duplicate the cube (using shift-d)
go to edit mode, and unwrap the second cube in a different way (so it has different uvs)
go back to object mode, Shift-select the first cube, and press Ctrl+J
in edit mode, the uvs of one of the two cubes appear as expected, the uvs of the other have gone to the lower-left corner of the uv layer. There is still only one UV layer, called "UVMap" (as it was in each of the two cubes before joining)

When I ctrl-Z until just before the join, and then join again, it works as expected (both cubes keep their UV layout). So there is something weird and buggy and inconsistent going on.

Added subscriber: @MaleneThyssen

Yep i get this one too.

Trying to join two different meshes - but keeping their individual materials and uvmaps - blender joins the meshes on ctrl + j

But one mesh looses its UVmap. It just collapses to a point in the lower left corner.
The material carries over though
I cant get it to work if i try do the ctrl + z trick suggested over here.
All meshes, materials and textures have unique names.
I tried renaming all the uvmaps to unique names too - but with no change in the problem
The objects that shows this behavior has been copied from another mesh now deleted in the scene.

Its a pain in the *** having to unwrap everything again - and making the textures again too just because i want to join meshes. Are you sure this really is intended behavior and not a bug?

@jonim8or You did not revive the right bug… :P

Will merge this one into #37577.

Changed status from 'Archived' to: 'Duplicate'

✘ Merged into #37577.

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One UV map destroyed when two objects joined #37182