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irregular scaling breaks IK (if no inherit ticked)

Rahel

When I scale the parent irregularly the IK of the child (without inherit) gets offset. (2)

The IK stays stable if I add a bone between them which does not inherit scale. (1) If this bug is easy to fix it would be cool to keep the number of bones low.

Rahel

Nate

This should be fixed in v3, which also allows scaling and translating the parent and child IK bones.

Pharan

@Rahel what version were you using?

Rahel

This issue happened in v3... :/

Nate

You said "if I add a bone between them which does not inherit scale", but in v3 it is not possible to have bones between the child and parent. Also you say "without inherit", without inherit what? Scale, rotation, both? Which bone is not inheriting? I'm afraid your image is also not clear what is going on. Maybe just post a project showing the problem.

Rahel

Okay... B is a child of A and the bug happens on image 2.
image 1 : original position.
image 2 : B does not inherit scale from A. I scaled A and that's where the offset happens.
image 3 : B inherits scale from A. I scaled A and everything looks good.

The bone i mentioned I could add between to avoid the bug would be between A and B in this case.

I hope it's more clear now.. 🙂
I added an example.

Nate

Thanks, it makes sense now. Unfortunately disabling inherit scale for the parent bone in a 2 bone IK chain makes the IK math more complex. I'm not sure this is going to work. It would be better to support it and we'll work on that, but if it isn't possible we may have to disable it in a future release.

BinaryCats

im far to hungover for all this reading malarkey. but could it be this: I wish there was more going on in this forum

Nate

Not sure what you mean from that thread, BCats? IK works correctly with any scaling of any bones. It's just that disable inherit scale (and obviously disable inherit rotation, since IK is setting rotation) screws up IK, depending on what bone is scaled. It might be fixable, I'm not sure. If you're hungover, you should read through the IK math. :nerd:

BinaryCats

We replied at the same time, I was pointing the thread to OP. I just remembered you saying some particular setup breaking the IK from a while back and thought that OP might be experiencing that 🙂

and thanks :tmi: