At the end of today's Live Q&A I attempted to post a query related to spline controlled animation.
I hadn't set up the model very well so there wasn't much to see at the time... translation: it barely worked.
After the session I modified the character and inner rig a little more while it was fresh in my mind.
I'll be glad to share the setup (minimal man charcter and rig) but it's still barely at the stage of being presentable.
The attached video does demonstrate a little of the setup and hopefully demonstrate where I'd like to go with the idea.
I mentioned during the session that I'd probably need to set up some use cases to properly demonstrate but the basic premise is to be able to animate (characters or objects) without directly manipulating any bones (only Nulls and CPs).
Most of the animation (in this test) is made via 5 control points on a single (curcular) spline. To move the mass of the object inside that spline there are three Nulls. This to provide better means to move the model in depth and to aid in control of squash and stretch. This is a form of 'control cage' in that the model would have a basic or even complex rig but the animator doesn't have to work with any of that unless necessary (or for final polishing). A complex rig would likely contain levels of similar 5 cp splines that control specific areas of a model (i.e. outer facial... inner facial... eyes... mouth... each might have a spline ring of its own.
Use cases? Well, I dunno. There are probably as many as we can take the time to think of.
Because the CPs and Nulls are minimal confusion with what bones to move and animate is reduced.
Heads up displays and 'pickers' could be produced based on Pose sliders that mirror the structure (or actually use) the model. Ideally (I believe) these interfaces would be copies of the model (or controller) because that allows for one to one selection. You'd know you have the right Controller because *it is* the same control just in a different setting/view.
This type of thing is considerably harder to setup (IMO) with bones.
Additonal prospects are at hand although a few would need fine tuning from Steffen ala a feature request. An example of this would be to either allow single CPs to exist (rather unlikely) or mode were splines do not show; resulting in the same basic effect as if the CPs were floating on screen or on a surface as if there on their own. Some refresh issues also exist when animating individual CPs. I use the space bar to refresh the screen often while animating with these 5 CPs and 3 Nulls.
There are no IK/FK and other fancy things in this setup but someone knowledgeable of such could certainly take the approach to the next level.
But... enough with the words...
Here's a (very) rough walkthrough of my test with Minimal Man who consists of about 10 bones, 3 nulls and one 5 CP spline controller.: