Need help with rig: spine and tail


I have been working on rigging my cat recently and have run into a bit of a problem. The legs and head function the way I would like but the spine is giving me a little bit of trouble. What I would like to do is have a control for the shoulders, hips and then one to arch the back in the middle. I can get the ones on the shoulders and hips to work but placing a control bone for the middle of the spines does not give me the smooth bend that I would like. Does anyone know how to smoothly bend the spine in the middle while keeping it in the IK chain? Also is there a better way to pin the tail at the tip so that the bones leading up to hit bend with the spine while the tip stays in the same place? I got it to work by placing a target (empty or bone) at the tip of the tail but it did not allow a smooth bend when further keyframing it.

I based the rig partially on this video (shown about a quarter of the way through) from John Riggs; he works in Messiah:Studio: (“NEW OPENGL RIGGING DEMO”)
His works and website are very informative!

Here is my .blend containing the rig:

Any help would be appreciated!

Matt :slight_smile:

I didn’t download your .blend but two thoughts:

  1. If you use B-Bones and use a single bone, and then for each of the Spine and the Tail and give each bone the same amount of Sections as they had bones in their Chains, then you can set their In and Out Influences.

Example, you can then set an In Value for the tail that will take account of bending on the Spine end and leave the Out value at zero which will leave the Tip stationary.

  1. For the even bending of the Spine you can use an Action Constraint, Pose the spine in an even arc, and Keyframe that as an action which you then use as the Target for the Constraint.


Hey there Fligh %,

Thank you very much again for your reply! I really appreciate you taking the time to share your thoughts, they are most helpful! :smiley: Here is an image of what I ended up doing in the end:

Keyframing the spine didn’t work so well for me, so I tried it with IK constraints again. The spine is still not as flexible as I’d like it to be, but it bends pretty nicely.

Matt :slight_smile:

That looks very cool. I was imagining the classic arched back while a cat stretches and yawns.


Hey Fligh % thanks a lot! Yeah, that is what I wanted to go for too however the arch in the thrid pose is about as far as I could get it to bend. I have updated the origial file with the current rig if anybody is interested in taking a look at it. A cat’s spine is much stretchier than a human spine so I tried to use stretchy bones, both with a constraint and the option under the bone setup but both gave some odd results. :stuck_out_tongue:

Matt :slight_smile: