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Rigid Body Constraints break when copying its empty object
Confirmed, NormalPublicKNOWN ISSUE


System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce RTX 2080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 446.14

Blender Version
Broken: version: 2.90.0 Alpha, branch: master, commit date: 2020-07-08 20:30, hash: rB31bc76ea4e4b

Short description of error
Copying a rigid body constraint via CTRL+C / CTRL+V breaks it permanently (you have to remove and re-add the constraint to make it work again).

Exact steps for others to reproduce the error

  • Create a simple rigid body constraint setup. You can use this file to start:
  • Select all objects
  • CTRL+C to copy
  • CTRL+V to paste
  • Move the new objects a bit to avoid clipping, and play the animation - the active object just falls down
  • Fixed by removing and manually re-creating the constraint on the Empty.001 object

This does not happen when using SHIFT+D to duplicate.

Seems like the dependency graph loses the connections between the constraint and the rigid body objects after copying.

Working (before copy):

Broken (after copy):

Event Timeline

RedMser (RedMser) renamed this task from Rigid Body Constraints can not be copied (only duplicated) to Rigid Body Constraints break when copying its empty object.Jul 15 2020, 5:25 PM
RedMser (RedMser) created this task.
Richard Antalik (ISS) changed the task status from Needs Triage to Confirmed.Jul 16 2020, 12:50 AM

I figured out that this is caused by the empty not correctly being added back to the RigidBodyConstraints collection.

A similar bug I found which is related to this (please let me know if I should open a new issue for it):

When *appending* the objects from the example blend file, the RigidBodyConstraints collection is not created at all, breaking the constraints until manually fixed.

Bastien Montagne (mont29) changed the subtype of this task from "Report" to "Known Issue".Aug 3 2020, 5:27 PM
Bastien Montagne (mont29) moved this task from Backlog to Long-Term on the Nodes & Physics board.

Would consider this a known issue for now, this is probably rather tricky to solve...

Indeed copy internally uses append mechanism, so both issues are actually the same.