Hi guys! I was hoping someone could help me with my FK/IK arms…
So I finished both arms, and they work fine, except that the IK arm bends in a weird way if the wrist is brought in towards the chest. The elbow snaps upward even with the pole vector in place, which is weird. I tried to fix it with ‘Set Preferred angle’, but then when I zero out the control the Mesh gets messed up (it twists because the rotation on the joint changed). I tried repainting/rebinding, but then when I bind the mesh on FK arms, it twists in IK mode (picture attached), and vice versa. How can I fix this? I realize it’s because the rotations on the FK bones and the IK bones are different for the elbow… but if I freeze transform the IK elbow after setting preferred angle, I still get wonky mesh.
If you have any suggestions on how to fix this, I would really appreciate it. Thank you!
What does the skeleton look like if you don’t freeze the transforms, but simply zero out the rotations on the elbow?
Do you have both joint orients and rotate axis set on the elbow before adding the IK control?
Did you build the left arm by hand or by mirroring from the right? Did the right work correctly?
Are you sure you have an IKRP solver and not an IKSC solver on the arm?
What is the rotate order on the elbow? Is it setup so the first euler term is the long axis of the bone?
You might want to try unbinding the skin and getting turning on the local axis display on your bones while you debug ('toggle -gl -la" in mel) so you can see that your local coords are right before you start weighting the skin.
FWIW, set preferred angle will only help the arm decide how to meet the IK solution. If you imagine the arm completely hyperextended so the upper and lower bones are parallel, it’s the preferred angle that tells the ik solver which way to bend the elbow when the target comes closer. For a simple setup like this it’s basically there to make sure the elbow bends in the plane of the thumb.
