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vertex group list doesnt update on all clones - vertex groups are shared, but vertex group names do not get updated on all instances
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Description

System Information
Manjaro Linux, Ati mobility radeon 4650,

Blender Version
Broken: 2.73- hash 53ec177, also in 2.72 stable

Short description of error
Basically if you create a clone of an object (alt+d), the clone will share the original object's data. If you add a vertex color, all the clones inherit the new vertex color - both as a new entry in the list and the actual data. If you add a shape key, all the clones inherit the shape keys.

If you add a new vertex group and assign some vertices to it, only the currently edited clone will acquire the new vertex group list entry in the vertex groups list. It will share the data of that vertex group, but it will not be added as a new entry to the vertex group lists of the clones.

To reproduce this bug:

  1. create a monkey head
  2. Clone it
  3. Add a new vertex group to the original and assign some verts to it
  4. Edit the clone - its vertex group list is empty!

<adding a new vertex group does not get added to all the instances, only the currently edited one>

  1. Add a new vertex group to the clone and click "select", it will select the vertex group of the original.

<however the instances still share vertex group data among each other, this opens an opportunity for a colossal error of the user- to overwrite a vertex group by mistake!>
6.Rename the clone's vertex group to something

  1. Go back to the original - the name you gave to the vertex group of the clone is not the same as the name of the vertex group in the original
  2. Create some more clones and add a bunch of vertex groups to each one- name them differently.
  3. Now assign some verts

Data is consistent between clones, but the names of vertex groups are completely inconsistent

So as a result, the user might overwrite their vertex group, by adding a new vertex group to a clone and editing it. Little do they know, they are writing over another vertex group that is just not yet listed and named.

Exact steps for others to reproduce the error
Based on a (as simple as possible) attached .blend file with minimum amount of steps

Details

Type
Bug

Event Timeline

Todor Imreorov (blurymind) created this task.
Todor Imreorov (blurymind) raised the priority of this task from to Needs Triage by Developer.
Bastien Montagne (mont29) claimed this task.

Thanks for the report, but this is a very old known TODO/limitation of current vgroups. Unfortunately, getting rid of it would mean a major redesign, so this is not considered a bug…

perhaps adding an ID number to the names of vertex groups automatically would make things a little bit more bearable :)