I've been looking to moving my rigging set up over to KineFX, but there's still a couple of things that seem strangely counter-intuitive. One of them is parenting the roots of IK chains.

In most any other programs, if you parents the roots of your IK chains (your L and R hip, for instance) to your pelvis, then move your pelvis up and down, the hips will move, the feet will say planted and everything in between will be driven by the IK chain. In KineFX, parenting the roots just moves the entire chain up and down, like in an FK rig.

You can get something like the usual pelvis behavior with the center of mass control in the full body IK, but it's not as precise as the traditional set-up. Ideally you'd have both in your rig.

I'm sure I could rig up a VOP with some offsets to drive the foot IK control counter to the movement of the pelvis, but I'm wondering if I'm missing something obvious.

Here's a few examples showing the basics, and ramping up to a usable(ish) workflow. Would love to hear if there's a better way! The lazy method is just to use FBIK of course, but that's cheating.

Thanks Matt! Much simpler approach. I was trying something with a counter off-set in a rig VOP. It works similar to your 4th set up, just a lot more complicated

A couple questions:

-- Generally I think your 4th set up makes more sense as part of a complete rig. You'd have the hips posed as part of the main FK chain, and you'd side chain off the IK controls and blend between them as needed. However, this set up (like the one I was working on) works for position and rotation around the z-axis, but if you rotate the hips around x or y the feet go wonky. But why? Seems like it should work for everything.

-- In my set-up, I was doing a counter offset based on the hip movement. I thought I should have been able to do it directly from the transform matrix and the rest_transfer, but neither worked the way I thought they would unless I extracted the transforms. Shouldn't there be a simpler way of doing this? Aside from whether this is the best way to set up the rig (trying to better understand matrix math). I don't quite understand how you'd do the same thing with the transform matrix: compare the rest transform matrix with the animated matrix, take the difference and apply the inverse to the IK drivers.

-- Finally, your last set up works the best along all axes, but I think you'd still want to split out the hip controls as a separate rig pose (like I said above, to me it makes more sense to have a single hip control upstream as part of the FK chain. But then I think I can see how you'd just skeleton blend that into the chain you've built here.

Thanks again!

Yep, as these setups get more fancy you'd probably have separate rig poses for FK and IK, I was trying to keep this as clean as possible. I know folk are hiding a lot of the complexities of these switching setups under HDA's, but I haven't got to that level of fancy yet.

Made a few more notes on the wiki btw: https://www.tokeru.com/cgwiki/index.php?title=HoudiniKinefx#IK_Chain_Legs_Setup [www.tokeru.com]