Aware of this, and indeed IK is how I was getting the FK positions to keyframe. The point of all this was to try to get this to FK-only, but I've solved it now in any case. I see that my post said that "use of FK" wasn't a valid answer, but it should have said "IK".
I'm sure there are FK uses I'm not thinking of. I'm so attached to IK that I'd rather find a way to use that instead (like a Child Of constraint to let the IK target be parented to the calf on some frames, for instance). But about engine support, you bake the transform of bones into FK keyframes (you sample the bone…
In my tiny experience doing animations, FK is quicker to work with for certain limb movements as it works with complete predictability. Sometimes IK doesn't interpolate the way you want. Also when you move part of an IK system, everything attached comes with it. In order to just tweak one part, you gotta locked off all the…
I guess this is more of a question for the animation forum, but why is FK still a thing? There's not one movement you can't do with an IK limb, whereas using FK makes some movements (like the one you're talking about, keeping a bone steady while its parent moves) very annoying to do.
I'm trying to animate a leg swing with quaternion bone FK. There are two frames in particular (denoted 6 and 12 in the bottom of the gif below) where the resulting motion of the left (front) leg is not as desired: the limb chain overshoots in a small arc. The culprit seems to be the contribution of the thigh. All the…