Spine Setups

Rigging
#1

I’m sorry if this will come across somewhat newbish or maybe over discussed, but from my research there really hasn’t been much discussion on the issues that I see.

I’ve been playing with all sorts of spines. nspine, awesome spine, divine spine, fk spine, ik spine, ribbon spine, flexiplane and the spine Jason created in the AFR videos. None of them however have an all in one sort of functionality.

Functionalities
over rotate 180 degrees without flipping (for extreme twisting)
squashing and stretching to preserve volume (preferably without relying on pow)
allow fk and Ik control (as an option or an option integrated in simultatneously (like in the AFR videos)).

The ribbon spine is nice, but i don’t like that it doesn’t bend naturally like an fk spine, you have to counter animate the mid section. Same with the “flexiplane”. In animation you only want to really stretch the character to give exaggeration. Having Fk control is ideal so that you always have the same range of motion, and any stretching can be done separately to help exaggerate the range of motion.

Aaron Holly altered the ribbon spine setup to allow for over twisting. He combined a bunch of utilities nodes to spread out the average between each joint, but personally I don’t like the result. The divine spine is nice, it allows for the over rotation as well as the squashing and stretching but it doesn’t allow for a robust ik system. You can’t just grab the top ik control and animate as you wish expecting the rest of the spine to deform the way a spine “should”. Many spine setups have one or more missing capabilities.

My personal preference is the fk/ik setup Jason has setup in the AFR videos. The only thing it lacks is the ability to rotate over 180 degrees without flipping and the fk controls fall behind if you animate with the ik controls.

Obviously, with so many different spines and different uses for those spine setups you’ll have to really pick and choose depending on the job. Is there, however, a stronger preference from an animators perspective? Also, is there a spine setup that actually has all the functionalities listed above integrated into one?

I figured that this was at least worth a discussion.

#2

One option to improve the fk/ik setup you mentioned might be to just add another layer of bones on top of the existing bones. These could be twisted using a slider, but would otherwise follow the original bones. This way, you can use the pelvis/ribcage controllers for all of the normal motion, and in the very rare occasion that you need to twist it past 180 then the slider can be used. Most of the time it’s a good idea to allow the animator to manually twist each spine bone anyway- they like to do their own little rotation offsets to add overlapping action etc.

#3

The choice between FK and IK is pretty basic to rigging design. It’s very hard to describe the coordinated motion of multiple bones through space in a way that is not either driven by successive rotations or driven by ik. It’s pretty much a mathematical necessity – at least in the current state of rigging math – so it’s something we have to live with for the forseeable future.

Of course, it’s a math necessity that is made far more complex by animator tastes and the needs of different scenes - there’s often not much you can do to convince animators to change from their preferred styles, even when those styles are based more on ‘what’s familiar’ than ‘what’s best for the task at hand?’.

You can try to tweak out some of the difference using blends between IK and FK controls, switches that allow for different parent and child spaces, or fixup operations using constrants and expressions. However the ‘all-in-one’ design can easily turn into something which suits no purpose particularly well because it tries to suit them all - if the animator has to coordinate the movement of 10 different sliders to get the right behavior, it can be hard to see the benefit of overloading everything on to one rig.

My personal preference is for a system that allows easy swapping out of pieces, allowing the animators to pick the ‘right’ spine for their circumstances and tastes. I like to treat rigs like photoshop layers - they’re useful for tweaking things out, but ultimately disposable. However I’ve found many animators only want to learn one rig and nothing else – the big wrinkle being that no two of them can agree on which one rig.

All part of the territory, alas.

#4

I guess my problem might be that I’m solving a “if it ain’t broke don’t fix it” problem. lol I appreciate the response. I guess, like everything else, it’ll all depend on the animator and like you said Theodox, it’s like working in layers (which I never really thought of it that way till now). Giving options rather than an all in one might be a better way of going about it.

#5

It’s always worth pushing the boundaries to see what can be improved.

There’s usually an animator on the other side, pushing back :slight_smile: