Driven shape keys update problem

Support Basics & Interface
1

I have a human armature with deform, FK and IK bones, and Copy Rotation constraints on the deform bones. I want to have corrective shape keys driven by bone rotations, and the obvious idea is to use the deform bones as drivers. However, when I rotate an FK bone (say), the deform bone moves in the viewport (due to the constraints), but the rotation value in the interface panel does not update. More importantly, the rotations in the shapekey drivers are not updated neither, so the corrective shape keys never kick in.

It is straightforward to evade this problem for the FK rig; just use the FK bone as a driver instead. But this does not work for the IK rig. When I move the end effector, the rotation of the IK bones do not update, even if they move in the viewport.

The problems persists in animation. AFAIU the driver is an F-Curve, and typically the bones in an IK chain have no keyframes, but only the end effectors.

Is there some way to make driven shape keys work. I think it was possible in 2.49.

2

So after reading your problem, I got to looking at a character I’m working on. I have 2 sets of bones - FK & IK for the arms, FK are also the deformers. While the character deforms well without aid of shape keys, it’s shirt needed the aid of shape keys for the shoulders. I set the driver up for the shape key to work based on rotation of a FK arm bone. Yes, I had the same problem, when switching to IK the FK bones copy rotation of IK bones and the driver didn’t work. So I poked around the driver’s area of the f-curve editor.

In the variable panel, it was setup to work based on the rotation of a bone and the ‘Local Space’ box was checked. Removing the ‘Local Space’ check mark fixed the driver so it would work when the copy rotation constraint was on and the rig was set to IK. I haven’t fully tested this, but I’ll reply if I discover anything.

Randy