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Multiples targetless IKs in a chain gives weird behaviour (known as FakeIK for FK posing)
Closed, ResolvedPublicBUG


System Information
Operating system: Windows 10
Graphics card: GTX 1070

Blender Version
Broken: 2.80RC2
Worked: ≤ 2.79

Short description of error
Translating the last bone in the chain everything works well (it actually rotates all the bones in the targtless IK chain). The problem is to Translate other targetless IK bone in the middle of the chain, causing the last bone not to update in realtime, but applies correctly at the confirmation.

Exact steps for others to reproduce the error
Press G to move the hand bone from the blend file. It'll work correctly. Select the lowerArm bone and repeat the process, pressing G to translate it. The hand won't update until you confirm the action.

Probable related issue: T61621

Event Timeline

Sebastian Parborg (zeddb) lowered the priority of this task from 90 to 50.

There is no such thing as "Fake IK". This is obviously some kind of weird bug that for some reason triggers what is actually called the "Auto IK" feature. If you simply enable the "Auto IK" option without using any weird hacks, it works as expected.

Yes, you are right. Some artists calls it to differ from the AutoIK option, since it has an IK constrain in a limited chain and it still is FK but moves like IK to pose. That is why the "FakeIK" term among some artists.
Terms aside, here is the problem:

It gets really ugly in a character:

As additional (and probably not useful) information about AutoIK: As an animator this is one of the most important feature that makes posing in FK easy and faster. It is so natural versus the awkward 'rotating each bone from chain'. So, thanks for this feature!

Sybren A. Stüvel (sybren) reopened this task as Confirmed.Feb 24 2020, 3:27 PM

@Germano Cavalcante (mano-wii) This is not the same issue as T73051.

Worked: >= 2.79

Well that's solved then, because 2.82 >= 2.79. I guess this has to be "Worked: ≤ 2.79"

Aaron Carlisle (Blendify) changed the subtype of this task from "Report" to "Bug".Feb 25 2020, 3:19 AM

I'm unassigning myself, so that someone with more experience with the IK code can pick it up.