Modifying an IK constraint's "handle" position...

Hi all,

So I am fairly new to Blender, and I come from a large amount of experience from Maya originally.

I’m working on a human character rig and I have come across an issue that I cannot seem to wrap my brain around. It has to do with adjusting an IK constraint for an arm.

Here’s my arm:

I want to use an extra bone in my lower arm as a way to rotate the wrist. I believe this is somewhat of a common technique.

So Here is what I’m doing:

I’m duplicating the hand bone and calling it “L_ArmCtrl”. This bone will function as a way to position the hand (transformation and rotation only) and the idea is that the IK constraint will do all the work of bending the arm. The hand will never move from where it is placed but the arm will bend freely. (I would also add in an elbow control bone set back from the elbow and tell the IK constraint to point to it for elbow control.)

Next part:

So that solution didn’t work…

Then I tried this:

It is very important that I maintain the control position to be locked with the hand, but without breaking the lower arm.

Can anyone please give me some advice on how to set this up in the way that I have visioned?


In the bone properties for that bone in the IK panel you can lock that bone’s rotations in X and Z.

The approach to rigging in Blender is quite different than that of Maya (as you’ve likely guessed by now). I have a vague memory of putting two bones along the forearm and two more along the upper arm in Maya the one time I tried rigging something, but…

In Blender, that two-bone thing isn’t going to work without a lot of extra (and, frankly, unnecessary) work. No amount of locking, constraining, etc. will stop those bones from ‘breaking.’

The best introduction to rigging is Nathan Vegdahl’s Humane Rigging. All your questions will be answered in one place and it’ll teach you, from the ground up, how to approach rigging in Blender and help you by-pass all the Maya-specific things that don’t work. It’s well worth the money, I promise.

I actually discovered a work around after more tinkering:

Make a normal arm, (one upper arm bone and ONE lower arm bone) and make it sit directly on top of the original arm.

Then set up an IK constraint on the new arm

Next add a few copy rotation and position constraints to the original lower arm bone and voila, the originial arm will follow perfectly with the new controller arm.

I also set up a copy rotations constraint to the wrist roll bone on the original arm that copy’s only the y axis rotations of the hand. That way I get the nice transition of twisting the wrist as well as the IK control constraint for the arm!

There is an issue however,

The constraint system work around that I described before does not handle ANIMATION that well. The deformation bones that the IK bones are constrained to seem to have a dampening like effect, where they follow behind in a smooth unnatural looking way in playback time. So I guess this mish-mash of bone constraints is just simply not the solution.

Does anyone know of a way to move the IK constraint’s targeting “handle” position to the wrist so that I can keep my mid-forearm roll bone? I know I’m kind of using MAYA terms to describe my vision, but I really don’t know how else to explain exactly what it is I want to do.

Basically I’m trying to avoid this:

Can you upload file?