View Full Version : How to rig a tail...?

02-21-2005, 09:28 AM
Guys, I hope you can help me on this... :confused:

I'm creating a bipedal dinosaur character for a client who wants a mascot. I'm in the process of setup/weightmaps/rigging...and am noticing a problem, presumably with IK.

I've set up the IK in Layout, and have noticed that when I test move the arms or legs, the 8 bone tail 'jitters'. The tail was modeled in a drooping position with the end upswinging (See attached).


I set it up with the same basic IK that I used on the legs. I'm having similar problems with them, but that's because I didn't pre-bend them enough. Problem is, knees, as we all know, only bend forward, so I can pre-bend for that...

How do you pre-bend a tail that is gonna use IK? :confused: :confused:

There is no pressure so far, the customer isn't really asking for it yet, but the boss wants it to be set up and ready.

Any suggestions would be appreciated... :cool:

02-21-2005, 09:32 AM
have you terminated your IK chains??? Does tha tail have to be controlled with IK? Have you turned on only the channels you want effected by IK? Have you tried using IK Booster for the tail instead of regular IK? Just some suggestions. :)

02-21-2005, 11:29 AM
Have you terminated your IK chains???

The bone going into the hip bone has "Unaffected by IK of Decendants' activated.

Does the tail have to be controlled with IK?

I figured it would help pose it easier than with FK. Does it have to be? No. I could do without, but it'd take more time to pose, and later, to animate.

Have you turned on only the channels you want effected by IK?

THAT'S one of the $20,000 dollar questions. A tail like that can bend in all 3 axes at each joint...so how do you know what functions to activate & what to DEACTIVATE?

Have you tried using IK Booster for the tail instead of regular IK?

No, I haven't gone thru the video yet, but I'll give it a shot & see if it helps....

Thanks for the response, Spec24.

02-21-2005, 12:14 PM
THAT'S one of the $20,000 dollar questions. A tail like that can bend in all 3 axes at each joint...so how do you know what functions to activate & what to DEACTIVATE?

I would guess the IK is getting confused - as it often does :) It has a hard time dealing with long chains - especially when all 3 axis are controlled. I would definetely turn off the pitch rotation as vertebrae like this tend to be pretty stiff in that particular direction. This may help but I bet you still get some twitching. It's just inherent in LW's IK. :(

02-21-2005, 01:27 PM
Just my opinion (naturally, I haven't seen your story boards), but unless you require the tail to grab hold or hang from things (monkey-style), I'd say that you're better off going with forward kinematics. Posing would be more precise and you would avoid the floating, popping characteristics common to IK. Simply select all (or just a few) bones at once and rotate on any axis to pose quickly. You could even apply follower to the child bones, but I find that less automation tends to lead to more flexibilty.

02-21-2005, 01:50 PM
OK jump all over me for this if you like cause I am a LW8 newbe.

But this idea of strange characteristics with IK is- well seems not right.

First of did you set up the bone chain as skellegons and apply whieght maps in modeler? If so would the tail NOT be effected by any of the other bones? IK or none?

Also if there is such a problem with IK, could you not have two or more chains in one object?

For instance have two seprate bones placed in the body, run one set of bone chains for the legs and another chain set for the tail running off the other parent bone?

I mean to move the body forward through space you move the object, right? And the bones follow and create deformation wich translates to walk cycles etc. Right?

If so, why can't you have more than one set of bone chains? Especially for something like a tail.

There is a fine line between genious and stupidity....

Hope I'm ranging toward the former...


02-21-2005, 01:52 PM
I'd just animate it with FK. You can after all, multi-select the bones and rotate them simultaneously (they'll rotate according to their hierarchy).

In the amount of time you've spent trying to rig it up via IK, you probably could've multi-selected the bones, rotated them into position on your desired keyframes, and collected a few bucks from the completed project. ;)

02-21-2005, 08:22 PM
I have a tentacle rig on my website that shows how to use selection sets to easily animate something like a tail. :)

02-21-2005, 10:13 PM
Try turning off Keep Goal Within Reach, if it`s on. This can cause jittering sometimes; and without it the rig`ll run faster too.

I`ve just had a look at the new RV Spine rig plugin (Flay). Can`t say for sure, but it looks quite promising and could well be used to manipulate your tail. Maybe.



02-21-2005, 11:50 PM
Another thing I would recommend is learning to use IKBooster. It makes animating things like tails/tentacles a real breeze. Long IK chains behave the way you expect them to plus you have IK and FK available full time. Everything you need to do this is already built into LW. :)

02-22-2005, 12:25 PM

Thanks for the feedback.

Larry, I've just started up on your IK Booster CD...but have gotten interrupted by various jobs shoved in front of me. What I've seen so far (Part 1) seems to be the potential answer, and I'll start on it soon.

Providing it works, I may try another version with just FK...
see which'll work best for me.

This may not have come at a better time, as I just put together an Anime-style cat-girl (Inspired by the work of a poster on CGTalk.com), with a tail. This may well make it easier to set her up.

On another related note,
Larry, when you rig/bone your characters, do you use weight maps at all, or do you just 'spread out' the character's default position to reduce negative distortions?

02-22-2005, 02:10 PM
Once you go thru the IKB CD youll find that you can use IK and FK at anytime, both are available. I would recommened going thru the whole CD first because it will clear up a lot of issues.

As far as weight maps go I look at them generally as a tool of last resort. Bones work in LW immediately upon resting them. Its just a more logical workflow to test your defomations with bones first. After that see if a few hold bones can fix any issues. After that then I see if I need to use any weight maps or not. The worst case is that the weight mapping process will take as long as it would doing it up front. Best case is you might not need them at all. Im not against weight maps at all. Rigging is simply an evil that must be endured to be able to animate so why make it even longer and more tedious then it needs to be? :)