Rigify: "Snap the IK chain keyframes to FK" does not give a consistent result #86792

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opened 2021-03-21 16:07:27 +01:00 by Alexander · 6 comments

System Information
Operating system: Windows 10
Graphics card: GTX 1080ti

Blender Version
Broken: 2.92

Short description of error
When working with animation, snapping IK to FK is not accurate

Exact steps for others to reproduce the error

  1. Open attached .blend
  2. Select Left Leg FK and click "Action"button under"IK->FK (foot.L)"3. SelectPole Targetand check Keyframes in theGraph Editor.

Result: You will see how Pole Target is "jumping" from one place to another, which is completely wrong. You will see IK does not accurately follow FK, because Pole Target location is also not accurate.
FK2IK-problem.blend
Expected result: IK should accurately follow FK.

**System Information** Operating system: Windows 10 Graphics card: GTX 1080ti **Blender Version** Broken: 2.92 **Short description of error** When working with animation, snapping IK to FK is not accurate **Exact steps for others to reproduce the error** 1. Open attached .blend 2. Select **Left Leg FK** and click **"Action"**button under**"IK->FK (foot.L)"**3. Select**Pole Target**and check Keyframes in the**Graph Editor**. Result: You will see how **Pole Target is "jumping" from one place to another**, which is completely wrong. You will see **IK does not accurately follow FK**, because Pole Target location is also not accurate. [FK2IK-problem.blend](https://archive.blender.org/developer/F9902514/FK2IK-problem.blend) Expected result: IK should accurately follow FK.
Author

Added subscriber: @alexander.ossur

Added subscriber: @alexander.ossur
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Added subscriber: @OmarEmaraDev

Added subscriber: @OmarEmaraDev
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Changed status from 'Needs Triage' to: 'Confirmed'

Changed status from 'Needs Triage' to: 'Confirmed'
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I can replicate the sudden jumps in the pole target, which is most apparent in the X location graph.

20220322-095454.png

I can replicate the sudden jumps in the pole target, which is most apparent in the X location graph. ![20220322-095454.png](https://archive.blender.org/developer/F12939539/20220322-095454.png)

Added subscriber: @angavrilov

Added subscriber: @angavrilov
Alexander Gavrilov self-assigned this 2022-07-11 18:06:30 +02:00

Can confirm something is broken. Additional info: only the pole target mode is broken, and it seems to be related to 'strange' rotations of the FK (i.e. it's impossible to reproduce it with IK exactly because shin_fk has non-X rotation), as the "FK -> IK non-pole -> FK -> IK pole" process works.

Can confirm something is broken. Additional info: only the pole target mode is broken, and it seems to be related to 'strange' rotations of the FK (i.e. it's impossible to reproduce it with IK exactly because `shin_fk` has non-X rotation), as the "FK -> IK non-pole -> FK -> IK pole" process works.
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Reference: blender/blender-addons#86792
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