Is it possible to set up pole targets and never have to use pole angle?

I watched a video tutorial that suggested to NOT use the pole angle parameter in an IK setup. The rationale was, the pole angle parameter only goes from -180 to 180 degrees, and you might want to use it in the future as a backup, and you’re unnecessarily limiting yourself by setting a pole angle when setting up your rig. (For example, if you set the pole angle to 90 degrees, if you later need to change this value further in the positive direction, you only have 90 additional degrees of wiggle room before you can’t go any further.)

The solution posed by the tutorial was to use the bone roll parameter to compensate instead. I understand how that worked in the context of the tutorial. But now I’m trying this out when creating my own rig and I’m wondering something…

Since I’m setting up a bone to point at an IK pole, it’s expected that the bone’s X axis needs to point toward the X axis of the IK pole. I’m trying to use the bone roll parameter to get the X axis to point at the IK pole (which is the heel in the screen capture below), but the bone roll just…rolls the bone around, and I can never point the X axis in the correct direction:

The X just goes around and around with the bone roll, when I need it to point back toward the heel. On the bone that I’m doing the bone roll on, I need the X axis to be pointing in the direction where the Y axis is.

Now, I can point the X axis in the correct direction if I use the pole angle parameter. And maybe that’s the correct thing to do in this particular situation. Or maybe I need to change something else in my rig so that I won’t run into this situation.

Thoughts? Suggestions? Tips?

Yeah, that sounds like a crazy tutorial. Can you believe Youtube lets just anybody post those? No verification of your Rigging Union identification number.

You don’t animate the pole target angle. You set it once, at the time that you rig the model. When you need the IK bone to bend in a different direction, you animate the pole target. You don’t need greater than 360 degrees total to describe any 2D angle like this, and because the pole target is a move bone, there is no discontinuity when rotating it through any number of rotations, although yes, you need at least three keyframes per full rotation to keep it working right. (Unless you want to parent it to an axis-angle bone or something I guess, then you can give that bone any number of rotations you want and the pole will follow.)

Past that: If you’re trying to adjust the angle for an IK leg, you’re adjusting the roll of the wrong bone. IAdjust the roll of the first bone in the chain. Your thigh bone, probably. If you instead have some weird foot IK setup, then you have picked the single worst place to put your pole, right at the singularity where it’ll always be screwing things up. Move it. But none of that matters, because it’s bad advice anyways.

If you want an exact pole target, that lines up with your bones perfectly, you don’t do it by adjusting roll to fit, because you need your roll to do other things, like establish axes for angle limits, or axes to help your animator out. (If you wanted to, though, you could give it a locked track constraint targeting the pole, lock Y, to +X. apply pose to rest pose, delete the constraint, and you’d have it.) Instead, to make an exact pole target, make it exact by using the right orientation to create your pole target. How? Change to normal orientation, duplicate your thigh bone, move in normal +x (any amount.) That duplicate bone is your pole target.

Thanks, @bandages! That’s really helpful information. :+1:

That’s too funny, where do I get mine ?

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