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I'd like this shoulder to spin only along the x axis whith the IK of the arm. The IK Lock axis switches aren't doing much though. I need everything to deform mechanically and rigidly adhering to those pivots in the models.

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This is the result when I shorten the IK chain to 2 excluding the shoulder bone.

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This is with the IK chain at 3 and ALL the axis locked on the shoulder bone.This doesn't make any sense to meh!

The right arm pivots behave correctly in FK. I'd like the IK elbow to move like it does in this animation.

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    $\begingroup$ Don't use a pole target, and lock the first bone in the 3-chain in all but Y axis. Further help, I'd need a file. $\endgroup$
    – Nathan
    Commented Jan 18 at 2:53
  • $\begingroup$ Perfect! That fixed the shoulder. Thank you! How would yolu control the direction of the elbow in this case? $\endgroup$
    – Zach Bowen
    Commented Jan 18 at 15:38
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    $\begingroup$ Try setting min and max rotation values for Arm.R and for Arm.R.001. so they don't overrotate while keeping axes locked. $\endgroup$
    – Tsybe
    Commented Jan 18 at 19:21
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    $\begingroup$ @ZachBowen Took a look at your new file. I'm afraid all that you can do to match your FK animation with IK involves some manual keyframing of at least one bone to get Blender to handle the angles right. The easiest bone to keyframe is Shoulder. Blender is just choking on a lot of these angles. It might be interesting to take a look at the structure in an earlier version-- I believe there were some recent, unmentioned changes to IK. $\endgroup$
    – Nathan
    Commented Jan 19 at 15:58
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    $\begingroup$ @ZachBowen Wait. To match that FK animation exactly with IK, all you have to do is rotate Arm.R -90 degrees in X axis. You can do this with a local space limit rotation constraint if you want. No guarantee this will work great with all other animations though. I would be tempted to add an extra Y axis bone (parent of shoulder) with +1 chain length to create "negative" stiffness in shoulder, as shoulder must rotate 180 degrees, without any other bones wanting to ever rotate >90 degrees, but not necessary for the anim you have. $\endgroup$
    – Nathan
    Commented Jan 20 at 14:18

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