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

New Issue

Alexander · 2021-03-21T16:07:27+01:00

Alexander commented

2021-03-21 16:07:27 +01:00

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

Open attached .blend
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.

Alexander commented

2021-03-21 16:07:27 +01:00

Added subscriber: @alexander.ossur

Omar Emara commented

2022-03-22 08:56:15 +01:00

Added subscriber: @OmarEmaraDev

Omar Emara commented

2022-03-22 08:56:15 +01:00

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

Omar Emara commented

2022-03-22 08:56:15 +01:00

I can replicate the sudden jumps in the pole target, which is most apparent in the X location graph.

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)

Alexander Gavrilov commented

2022-07-11 18:06:30 +02:00

Added subscriber: @angavrilov

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

Alexander Gavrilov commented

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