I want to rotate hand bone when I rotate IK bone as well. So I decided to using Copy Rotation constraint. Here's how looks like:

enter image description here

Nothing special, important thing is that Hand Bone has Copy Rotation to IK Bone. I set the Target Space and Onwer Space both Local Space.

But when I rotate IK bone, hand rotates totally wrong axis:

enter image description here enter image description here

I think this happens because Copy rotation just copy the rotation values literally, my guess.

How do I make hand rotates properly? I think it needs to be change the rotation based on current rotation, but there's no option for that in Copy Rotation constraint.

Any advice will very appreciate it.

  • $\begingroup$ There is a constraint called Transformation that, I think, could allow you to copy a rotation from an axis to another axis, but is there a reason why the hand is not child of the controller? That's what I usually do so when I move the controller it moves both the hand and the lower arm $\endgroup$ – moonboots Aug 28 '18 at 9:09
  • $\begingroup$ @moonboots Because of Unity Humanoid type, it forces me to keep parenting each connected bones. I generally do parenting hand to IK bone in first person animation, but full human rig couldn't do that. I already tried with Transformation constraint but it didn't worked. $\endgroup$ – modernator Aug 28 '18 at 9:38

Copy hand bone,make it a little larger or a little smaller then the hand bone, so it'll be easy to select, parent it only to Root bone and make it an IK target. That's the easiest way to avoid Copy rotation problems and have clean, easy to work with rig.

  • $\begingroup$ IK bones are already parented to Root bone. $\endgroup$ – modernator Aug 28 '18 at 14:49
  • $\begingroup$ That's not the main point. The main point is to have IK targets at exactly the same starting location and rotation as hand bones, then you'll have no troubles. $\endgroup$ – Mzidare Aug 28 '18 at 14:56
  • $\begingroup$ You may want to check the axis of the bones themselves the bone roll I think, some time that gets messed up. $\endgroup$ – Jarrett Vann Dec 12 '19 at 5:46

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