Make a spline IK the child of a bone?

I am attempting to rig and animate a vehicle and its rider, using bones to animate the wheel turning. I had hoped to drive the movement of the arms based on the wheel rotation. A technique I thought would be ideal for the arms of the rider would be to rig them using spline IKs and make the ends of the spline IKs a child of each main bone in the steering wheel. However, when I do this and test rotate the wheel, the hand moves in the opposite direction of the wheel rotation and the character’s shoulder slides out of its socket.

The green lines in the above image illustrate the location of the spline IKs. The red circles are where the parent bones in the wheel are located.

Does anyone know how I could resolve this?

Get rid of the spline IK and just use a regular IK setup instead. Spline Ik really has nothing to offer you here, it’s more useful for rigging up cables, wires, hoses, tentacles, etc, things that can bend. In fact, I’m wondering if you might have messed up terminology here, as a spline IK is a bit of work to set up. To set up a proper spline IK, you have to create a curve object, at it’s control points you add in bone hooks, then create an entirely separate armature object which is a chain of bones along the curve. The hook bones control the curve, which controls the chain of bones following the curve…Totally not needed here.

You can duplicate the hand bone and make it a child of a steering wheel bone. Ad an Inverse Kinematics constraint to the lower arm bone, chain length set to 2 and use the duplicated hand bone as the target. Now the lower arm and upper arm should always move to stay in touch with the duplicated hand bone. You should set up an elbow poll target for the constraint as well, that way you can vary the elbow position, to keep the elbows from digging into the body.

Have the hand bone copy the rotation of the duplicate hand bone, and use the duplicate hand bone as the hand controller.

If this isn’t clear, or you have problems, please post up a .blend file.


(NVM, got it now)


Nevermind, I figured it out. Guess I had to rearrange the orientation of the IK target empties as well so the rotation worked properly. Thanks for the help!