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Bug on Rigid Body Simulation when an object is parented to another
Open, Waiting for Developer to ReproducePublic

Description

System Information
Operating system: Windows 10
Graphics card: GTX 1060 6G

Blender Version
2.80

Short description of error
Bug on Rigid Body Simulation when an object is parented to another

Exact steps for others to reproduce the error
Please check the video......

More, I have some questions on Rigid Body. I want to ask something, coding and algorithm, to the developers who work on it...
How can I reach them?

Thanks.

Details

Type
Bug

Event Timeline

Can confirm in Blender 2.8 and today daily build 2.81..
I think, the expected behavior should be child object will be effected by both Parent (transform) and rigid body.
In this case as parent object is still on it's place so child object can freely act as rigid body

Philipp Oeser (lichtwerk) triaged this task as Waiting for Developer to Reproduce priority.

In 2.80, I can see object jumping around, but for me, 2.81/master is stable (in that it ignores the sim completely)

Think this is expected behavior since there is a dependency circle:

Dependency cycle detected:
  SCScene/Transform Component/RIGIDBODY_SIM() depends on
  OBSphere/Transform Component/TRANSFORM_SIMULATION_INIT() via 'Object Transform -> Rigidbody Sim Eval'
  OBSphere/Transform Component/TRANSFORM_EVAL() via 'Transform Eval -> Simulation Init'
  OBSphere/Transform Component/TRANSFORM_PARENT() via 'Eval'
  OBSphere/Transform Component/TRANSFORM_LOCAL() via 'ObLocal -> ObParent'
  OBSphere/Transform Component/TRANSFORM_INIT() via 'Transform Init'
  OBCube/Transform Component/TRANSFORM_FINAL() via 'Parent'
  OBCube/Transform Component/RIGIDBODY_TRANSFORM_COPY() via 'Rigidbody Sync -> Transform Final'
  SCScene/Transform Component/RIGIDBODY_SIM() via 'Rigidbody Sim Eval -> RBO Sync'

2.79 magically behaved "better" in that it seemingly completely ignored the parent transform.

I think, the expected behavior should be child object will be effected by both Parent (transform) and rigid body.

Dont think this is possible with the current system (unless we somewhat translate parent transforms into bullet forces?)

CC @Sergey Sharybin (sergey), @Sergej Reich (sergof)

Afraid we have to close this?