"Child Of" Constraint corrupt animation process when switched off #81871

New Issue

Aleksandr · 2020-10-20T00:05:30+02:00

Aleksandr commented

2020-10-20 00:05:30 +02:00

System Information
Operating system: Linux-4.15.0-121-generic-x86_64-with-debian-buster-sid 64 Bits
Graphics card: GeForce RTX 2060/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 450.80.02

Blender Version
Broken: version: 2.90.1, branch: master, commit date: 2020-09-23 06:43, hash: 3e85bb34d0
Worked: (newest version of Blender that worked as expected)

Short description of error
Switched off constraints corrupt movement of bones and animation afterwards. Constraints which is switched off shouldn't influence the animation process. Animator need way to switch between different phases. For example, now I need my hand as a parent of weapon, later I need vice versa. But Blender making cycle dependency even when constraint is off.

Exact steps for others to reproduce the error
Open my blend file, select "IK" bone, Press G, drag it away, click Right Mouse Button, attention to weird behavior. After this delete constraint from "Weapon" bone and try again from the beginning.

Blender_ChildOf_BUG.blend
Screencast-2020-10-20_00.52.13.mp4

**System Information** Operating system: Linux-4.15.0-121-generic-x86_64-with-debian-buster-sid 64 Bits Graphics card: GeForce RTX 2060/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 450.80.02 **Blender Version** Broken: version: 2.90.1, branch: master, commit date: 2020-09-23 06:43, hash: `3e85bb34d0` Worked: (newest version of Blender that worked as expected) **Short description of error** Switched off constraints corrupt movement of bones and animation afterwards. Constraints which is switched off shouldn't influence the animation process. Animator need way to switch between different phases. For example, now I need my hand as a parent of weapon, later I need vice versa. But Blender making cycle dependency even when constraint is off. **Exact steps for others to reproduce the error** Open my blend file, select "IK" bone, Press G, drag it away, click Right Mouse Button, attention to weird behavior. After this delete constraint from "Weapon" bone and try again from the beginning. [Blender_ChildOf_BUG.blend](https://archive.blender.org/developer/F9018005/Blender_ChildOf_BUG.blend) [Screencast-2020-10-20_00.52.13.mp4](https://archive.blender.org/developer/F9018002/Screencast-2020-10-20_00.52.13.mp4)

Aleksandr commented

2020-10-20 00:05:30 +02:00

Added subscriber: @viadvena

Aleksandr commented

2020-10-20 00:12:56 +02:00

Screencast-2020-10-20_01.11.42.mp4

[Screencast-2020-10-20_01.11.42.mp4](https://archive.blender.org/developer/F9018061/Screencast-2020-10-20_01.11.42.mp4)

Germano Cavalcante commented

2020-10-20 23:04:20 +02:00

Added subscriber: @mano-wii

Germano Cavalcante commented

2020-10-20 23:04:20 +02:00

Changed status from 'Needs Triage' to: 'Archived'

Germano Cavalcante closed this issue

2020-10-20 23:04:20 +02:00

Germano Cavalcante self-assigned this 2020-10-20 23:04:20 +02:00

Germano Cavalcante commented

2020-10-20 23:04:20 +02:00

This is due to 2 dependency cycles between constraints.
See the console:

Read blend: C:\Users\GERMANO\Downloads\Blender_ChildOf_BUG.blend
Dependency cycle detected:
  OBArmature/Bone/POSE_IK_SOLVER() depends on
  OBArmature/IK/BONE_DONE() via 'IK'
  OBArmature/IK/BONE_READY() via 'Ready -> Done'
  OBArmature/IK/BONE_CONSTRAINTS() via 'Constraints -> Ready'
  OBArmature/WEAPON/BONE_DONE() via 'Child Of'
  OBArmature/WEAPON/BONE_READY() via 'Ready -> Done'
  OBArmature/WEAPON/BONE_CONSTRAINTS() via 'Constraints -> Ready'
  OBArmature/Hand/BONE_DONE() via 'Child Of'
  OBArmature/Hand/BONE_READY() via 'Ready -> Done'
  OBArmature/Hand/BONE_CONSTRAINTS() via 'Constraints -> Ready'
  OBArmature/Hand/BONE_POSE_PARENT() via 'Pose -> Constraints Stack'
  OBArmature/Bone.001/BONE_DONE() via 'Parent Bone -> Child Bone'
  OBArmature/Bone/POSE_IK_SOLVER() via 'IK Solver Result'
Dependency cycle detected:
  OBArmature/Hand/BONE_CONSTRAINTS() depends on
  OBArmature/IK/BONE_DONE() via 'Copy Rotation'
  OBArmature/IK/BONE_READY() via 'Ready -> Done'
  OBArmature/IK/BONE_CONSTRAINTS() via 'Constraints -> Ready'
  OBArmature/WEAPON/BONE_DONE() via 'Child Of'
  OBArmature/WEAPON/BONE_READY() via 'Ready -> Done'
  OBArmature/WEAPON/BONE_CONSTRAINTS() via 'Constraints -> Ready'
  OBArmature/Hand/BONE_DONE() via 'Child Of'
  OBArmature/Hand/BONE_READY() via 'Ready -> Done'
  OBArmature/Hand/BONE_CONSTRAINTS() via 'Constraints -> Ready'
Detected 2 dependency cycles

Undefined behavior of rig when it has dependency cycle is not a bug.
There is chance it is fake/avoidable dependency cycle, but for investigation we need a simple rig, which only includes relevant parts, with as few bones as possible.

You'd need to find a way to rig your model without introducing such cycles.

This is due to 2 dependency cycles between constraints. See the console: ``` Read blend: C:\Users\GERMANO\Downloads\Blender_ChildOf_BUG.blend Dependency cycle detected: OBArmature/Bone/POSE_IK_SOLVER() depends on OBArmature/IK/BONE_DONE() via 'IK' OBArmature/IK/BONE_READY() via 'Ready -> Done' OBArmature/IK/BONE_CONSTRAINTS() via 'Constraints -> Ready' OBArmature/WEAPON/BONE_DONE() via 'Child Of' OBArmature/WEAPON/BONE_READY() via 'Ready -> Done' OBArmature/WEAPON/BONE_CONSTRAINTS() via 'Constraints -> Ready' OBArmature/Hand/BONE_DONE() via 'Child Of' OBArmature/Hand/BONE_READY() via 'Ready -> Done' OBArmature/Hand/BONE_CONSTRAINTS() via 'Constraints -> Ready' OBArmature/Hand/BONE_POSE_PARENT() via 'Pose -> Constraints Stack' OBArmature/Bone.001/BONE_DONE() via 'Parent Bone -> Child Bone' OBArmature/Bone/POSE_IK_SOLVER() via 'IK Solver Result' Dependency cycle detected: OBArmature/Hand/BONE_CONSTRAINTS() depends on OBArmature/IK/BONE_DONE() via 'Copy Rotation' OBArmature/IK/BONE_READY() via 'Ready -> Done' OBArmature/IK/BONE_CONSTRAINTS() via 'Constraints -> Ready' OBArmature/WEAPON/BONE_DONE() via 'Child Of' OBArmature/WEAPON/BONE_READY() via 'Ready -> Done' OBArmature/WEAPON/BONE_CONSTRAINTS() via 'Constraints -> Ready' OBArmature/Hand/BONE_DONE() via 'Child Of' OBArmature/Hand/BONE_READY() via 'Ready -> Done' OBArmature/Hand/BONE_CONSTRAINTS() via 'Constraints -> Ready' Detected 2 dependency cycles ``` Undefined behavior of rig when it has dependency cycle is not a bug. There is chance it is fake/avoidable dependency cycle, but for investigation we need a simple rig, which only includes relevant parts, with as few bones as possible. You'd need to find a way to rig your model without introducing such cycles.

Aleksandr commented

2020-10-21 11:28:16 +02:00

I hopped it's possible to change behavior of blender working with off constraints. Because logic tell the user that switched off constraint shouldn't influence on rig and there is shouldn't be dependency till it on. May be Blender use ancient constraints system... At least Blender should have "Switcher" constraint or dynamic parent like in Maya.

Aleksandr commented

2020-10-21 11:34:20 +02:00

I knew at the start there is dependency cycle, I wrote about it at the start. My point is "if we take off the wheel it shouldn't push the car"))

Germano Cavalcante commented

2020-10-21 13:38:51 +02:00

Changed status from 'Archived' to: 'Needs Triage'

Germano Cavalcante reopened this issue

2020-10-21 13:38:51 +02:00

Germano Cavalcante removed their assignment 2020-10-21 13:38:51 +02:00

Richard Antalik commented

2020-10-22 19:13:21 +02:00

Added subscriber: @iss

Richard Antalik commented

2020-10-22 19:13:21 +02:00

I think this is same issue as #73199 (Editing an object that is referenced in a disabled modifier (of another object) forces the other modifiers on the same stack to update)
So dependency graph will start evaluate and stop as soon as it encounters dependency cycle.

I think this is same issue as #73199 (Editing an object that is referenced in a disabled modifier (of another object) forces the other modifiers on the same stack to update) So dependency graph will start evaluate and stop as soon as it encounters dependency cycle.

Richard Antalik commented

2020-10-22 19:13:37 +02:00

Closed as duplicate of #73199

Richard Antalik closed this issue

2020-10-22 19:13:37 +02:00

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"Child Of" Constraint corrupt animation process when switched off #81871