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I have a question about the mesh management in Blender.

In this question 55 woo shares a file. If I take a look into the Outliner I'll find 3 objects. But if I select an object and go into the Object Data panel, in the top dropdown menu I can find a lot of other meshes, even though they are not marked with the F of Fake User:

enter image description here

I can also find these meshes in the Outliner if I choose to display the Orphan Data. It will display a series of greyed objects that don't exist anymore, and if I unfold one of them it will show its mesh, which is supposed to have 1 user, but it doesn't as the object is not here:

enter image description here

So of course I can purge these meshes with the Purge button of the Outliner, or File > Clean Up > Unused Data-Blocks. But why are these meshes even here when they are not used and are not even marked as fake users, why are they not managed like any other data like materials or actions, which disappear when the file is closed, and how did this happen?

I can't reproduce the problem from scratch, if I create an object, delete it, close and reopen the file, the mesh of this object isn't available anymore.

Thanks in advance.

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1 Answer 1

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These meshes are not in the Orphan Data because they have objects which are deleted but still in the file.

A normal object looks like this:

[Blend] ← [Scene] ← [Object] ← [Object Data] ← [Material] ← [Texture] ← [Image file]

Then you delete an object from the scene, it is not deleted actually, it is unlinked from the scene, so it becomes like this:

... [Object] ← [Object Data] ← [Material] ← [Texture] ← [Image file]

So now as you see, only the object is orphan, object data, material, textures etc. have actually a parent.

Then you remove orphan data you will remove only the object while object data becomes orphaned:

... -removed- ... [Object Data] ← [Material] ← [Texture] ← [Image file]

So to remove all the data linked to the removed objects, you have to run this recursive, or File → Clean Up → Recursive Remove Unused Datablocks.

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  • $\begingroup$ thanks Crantisz, still a bit messy for me but it will get clearer ;) $\endgroup$
    – moonboots
    Commented Jun 1, 2022 at 9:50
  • $\begingroup$ weird that when you open a file, the data are still here, then when you save, re-open, now they are gone because they have no "parent", but it was actually already the case when you first saved. So from what I understand it will get rid of the data if its parent is not here when you open the file $\endgroup$
    – moonboots
    Commented Jun 1, 2022 at 9:55
  • $\begingroup$ Yes, Unused data blocks are removed on save and open. But only one "layer" $\endgroup$
    – Crantisz
    Commented Jun 1, 2022 at 10:01
  • $\begingroup$ ok I think I get it, thanks a lot ;) $\endgroup$
    – moonboots
    Commented Jun 1, 2022 at 10:02

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