# What's a good set-up for a spine?

I want a character to be able to lean forwards and backwards without having to move each bone in the spine individually - any suggestions (or examples!) on the best way to achieve this?

cheers!

add 2 bones start the bones in the pelvic region and end near neck
*
| 2 |
| 2 |
| 1 |
| 1 |
^

|=character mesh
1=bone one
2=bone two
^=start bone here
*=end here

hope it helps

Thanks but not quiet what I was after - If i have a spine with 4 or 5 bones in it and I want to have a control bone to control all of them, is there a clever way to make the spine able to bend backwards but also bend forwards with it snapping from one position to another…? Maybe I’m not being quiet clear enough… does that make sense?

It sounds like you’re trying to use IK to work the spine. I think you might run into problems there. Try FK - at least you can control the forward / backward problem.

Yeah I figured that might be the case but always worth asking!

Cheers,

Kuba

what’s an FK?

Forward Kinematics
The inverse of IK.

Inverse Kinematics
The inverse of FK.

Hurray for recursive definitions.

Martin

Once again Theeth god of blender

FK is when you move/angle/whatever each bone individually, IK calculates the angles of bones in a chain

At least, that’s what I think it all means

FK is simply the rotating of your bones. It gives more control, but brings along more work. At least for animation. Rigging of a decent IK is far more difficult.

• Bentagon

those might help:

EDIT: oups links were outdated. here a new one - using the hooks and path-deform-feature.

To distinguish between IK and FK, extend your finger. How would you describe to the computer the motion of your finger? (No, no, not that finger, and I said how, not why!)

With Forward Kinematics (don’tcha just love buzzwords?), you would start at the base of the finger and describe the motion of each joint leading out to the fingertip.

With Inverse Kinematics, you would position the fingetip and let the computer calculate the location and angle of the other bones.

IK is convenient, but it is not “smart.” If you let it, IK calculate anatomically-impossible (ouch!) positions for bones. Still it is usally the first thing to try.

Also, when designing skeletons, remember that while we are “fearfully and wonderfully made,” an adequate armature for a character may only contain maybe a couple dozen bones.

put as many segments in the back as you want it smooth. 2 - 4 is a good range
you can use IK or FK, depends on preference. I do two bones per segment- a bone that represents the acutal segment, and a small child at the tip. the next segment up isn’t a child of the first one, but has a translate to constraint to this small child. this is true all the way up to the neck and head.
i usually do tail bone differently (more complicated, slightly) but don’t have a rig to look at.
basically the idea is to do indivisual rotations without propagation. gives more control.

Those spine hooks look quiet promising - thanks for posting that!

What do people prefer to use? IKs or FKs? So far I’ve found walk cycles a bit harder to do with IKs than Fks…

I’ve been trying to get a good IK setup for a body but keep finding problems - I think I’ve got the legs and arms susssed so movement of the spine is the last hurdle really before seeing how it all fits together. At the moment I think I’ve got a leg set-up (with a half decent walk cycle!) that’s a bit better than the blendo example, I’ll post it if anyone fancies clubbing together to make a decent human rig (the model isn’t brilliant)