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Mirrored linked objects flip in Edit mode vs Object mode
Open, Confirmed, MediumPublic

Description

System Information
Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.60

Blender Version
Broken: version: 2.80 (sub 75), branch: master, commit date: 2019-07-29 14:47, hash: rBf6cb5f54494e
Worked: (optional)

Short description of error
When I Link Object data for multiple objects and apply a mirror modifier and link that modifier, while in object mode the model looks exactly how I'd like. However, when I rotate one of the linked & mirrored objects and go into edit mode, the objects flip sides and appear to be out of place.

Exact steps for others to reproduce the error
I follow these steps in Object mode:

  1. I remove the backside planks
  2. select all 4 of the front planks
  3. ctrl+l and link object data.
  4. I then select the top plank, and add a mirror modifier on the Y axis and it properly mirrors to the back side of the chest after I use the 'dropper' to choose the rim.
  5. I then hit ctrl+l to link the modifiers, and all planks appear on the backside (screenshot 1)
  6. I select the bottom plank (screenshot 2)
  7. I hit tab to enter Edit mode

Before:

After rotating a plank and then switching into Edit mode:

As you can see, for some reason while in Edit mode, the other 3 mirrored planks appear on the wrong side of the chest, but they appear in the correct place while in object mode. I reached out to the CG Cookie community to see if anyone else has experienced this, and they are able to recreate the issue in Blender 2.80 but cannot reproduce in Blender 2.79 which leads me to believe it's a 2.80 issue.

Details

Type
Bug

Event Timeline

Bastien Montagne (mont29) lowered the priority of this task from Needs Triage by Developer to Confirmed, Medium.

Confirmed, not sure what's happenning here, looks like in Edit mode the active object's transform is used for all modifiers evaluations...

Not sure what's happening here, generated coordinates from the modifier itself are 100% valid and identical in both Object and Edit mode.

@Clément Foucault (fclem), @Jeroen Bakker (jbakker) could it be some kind of optimization in Edit mode draw code, that would e.g. assume that when two objects share the same mesh, then they also share the same evaluated geometry?