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Undo unavailable for Remove Vertex Group in edit mode
Open, Needs Triage by DeveloperPublic


System Information
Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 391.01

Blender Version
Broken: version: 2.82 (sub 1), branch: master, commit date: 2019-11-27 03:54, hash: rB4fd99c949587

Bug description
After remove a vertex group from a mesh while in edit mode, the undo operator still works, but undo buffer does not seem to contain the remove vertex group operation, so using undo undoes whatever was done before the removal of vertex group. On entering object mode, using undo will undo the vertex group removal operation before any mesh editing, leading to confusing out-of-order undo operations

Repro steps:
Create new mesh
Create vertex group
Switch to edit mode
Move a vertex to make an obvious visible change
Remove vertex group
Move another vertex visibly
Switch to object mode
Use 'undo' operator multiple times
'undo' operator will undo vertex transforms, and appear to do nothing when it reaches the point in the undo buffer where it ought to undo 'remove vertex group'
Switch to object mode
Use 'undo' operator
Removed vertex group is back, and edit mode is active

I won't lay out all of the variations, but for more complicated failure modes with weirder out-of-order undo operations, try:

  • move vertex, remove group, move other vertex, switch to object mode, use undo function
  • create two vertex groups before entering edit mode, move vertex, delete first vertex group, move another vertex, delete second vertex group, move a third vertex. Enter object mode and use 'undo' operator



Event Timeline

Brace for incoming "this is a limitation of current undo system". Which exists for eons now :(

It wasn't present in 2.7x, if that helps. Has the undo system been redone?

It was present. You can't undo removal of vertex group in edit mode. In 2.7x and in 2.6x.

Well I'll be damned. I just checked, and I could have sworn it worked, but you are right. Well, still... I guess it is for devs to decide if it is a bug or not, but it certainly isn't as the user would expect.