I plan to start animations in Blender soon and the above feature would make life much easier for me! if anybody has done this, your insight would be appreciated!
You might want to look at the spline ik system, it’s not exactly what you are looking for, but might be close enough for you.
It’s used mainly for tails or tentacles or ropes. Basically it’s a chain of bones that can be constrained to follow a curve. IDK if it will work on a closed loop curve, never tried that, and I think it has some issues if the curve’s length changes.
The deform bones that follow the curve must be a separate armature object, and since it’s a chain of bones, you need a vertex group for each bone in the deform chain.
Also of note is b-bones, or bezier bones, are bones that bend. You control how many segments the bones have and how the ends of the bone align up to the two other bones connected to it’s tail & tip.
Neither one is exactly what you are looking for, both methods require more than one vertex group.
Randy
This might be done better with Shapekeys - set a “Basis” key for the un-deforemd state and a second key with the vertices in their “rest” position at value 0 and in their deformed position at value 1. Then you can animate the Shapekey value by various methods, including drivers and keyframes.
It is difficult to tell exactly how the deformation is performed on your images, as in are they rotated about a fixed point, or pulled variously by the bones you have in place at the moment. What is the model? It would be good to see this mesh in its context.
Cheers, Clock.
PS Hi Randy - where have you been for so long my friend? 
Hi,
I second the method explained by revolt_randy, because contrary to the shapekeys approach (which apart from that has its own benefits) it allows you to connect an entire bone-based facial rig to it and not have surnumerary deformations (bone deforms and shapekeys on top of one another). Now, your facial rig can be entirely based on shapekeys as well, that is perfectly fine - but I wouldn’t mix the two for deformations of the same “order” - instead I’d let the shapekeys handle the smaller magnitude deformations, like wrinkles, small bulges, etc.
Wouldn’t the new twisty stretchy B Bone system work well for something like this ?
FWIW, I did try a splineIK chain controlled by a bezier circle, and the results were bad. Very bad…
I create a bezier circle and a chain of bones around the circle. Idea is to have the bezier circle control the chain of bones thru the splineIK constraint. And it just doesn’t work. See attached file…
When the splineIK constraint is applied, the chain rotates, which isn’t desirable…
And when control points of the circle are moved the chain rotates around the beizer circle. Which won’t work either.
For lip rigging, I’ve always just used regular bones.
I was looking at the docs to the new bendy bones, but haven’t a need to play with them, and don’t fully understand the new system…
Been a bit out of the loop so to speak…
Randy
@ clock PM sent your way
Attachments
splineik_lips.blend (404 KB)