Editable stretchy chain

Hello everyone. Post on this forum because i need some help.

I would like to create an editable stretchy IK chain. So you can move the position of the chain to modify the proportion of the ik Rig. Doing this is not very hard, BUT, if you want to implement stretchy system, you get some problems. If i move the elbow for exemple, to modify lowerArm section for exemple. Then if i go stretch, the ratio i have to add to match the IK control position is not good, so the chain keep stretching, but the stretch ratio is not not good anymore and so the wrist doesn’t match ik control.

So do you know if there’s a way to stretch based on something else than distance, so the ratio kick on the bones is always the same whatever i move the bones positions the stretch always be the same.

I tried some vector and local matrix position but i didn’t success.

Does anyone already tried this? Or just have some idea about eh way to do it??

Thx for your reading and sorry for my english, not my native :s.


Are you trying to change the ratio between the length of the forearm and the length of the bicep in an animation?

Hello! I’m trying to change the ratio before animation. I want to be able change the proportions of the ik chain without breaking the rig with stretchy etc.

And so i figured out and to be honnest, it’s quite tricky but no so hard f when you get all the concept.

For those who want to see, i could make a tutorial about it, but for now i need to test it with full rig implementation before. Still need some work, but the basics idea seems to be Ok.

The cool thing is that now i can edit de rig, i can move the proportions of a character, without breaking the rig and keeping a full synchro with the controllers, no need to edit, run a script to get new position etc, it’s all layered .

This is could avoid systematic rebuild the rig in case of retakes.

So maybe it’s a just a thing that many riggers already done etc etc, i’m pretty sure it’s not new, but i couldn’t find any help to do it, so if people wants to see i could share it, just contact me.

See you techs!

Hi Ssky,

the way you describe it , in concept seems similar to how Houdini works(procedurally), if i remember well i heard of it before, and it was also used/tested in a few of the vfx companies/projects a while back in maya, alto i personally never looked into it.

I still feel that rebuilding everything from scratch (using a tool), makes and saves the rig data in a cleaner way.
For example, perhaps for one character you initially decide to add every option on the arm module, and you start adding stretchy and or bendy, but then you realise that you might not want to have that anymore, since the animators will not need it, and perhaps they prefer to have a lighter rig, in that case you still will need to re-build the rig (or in your case would you need to delete that module all the extra nodes connected and also attributes and import another one?)

Is an interesting concept, that perhaps can be used for other kinda things , one that im thinking of, could be a re-adaptable FACS face system ?(based on muscles…and or some sort of muscle shapes)

If you have time , i would like to see how you have achieved the procedurality :slight_smile:!


Hi, yes you totaly right :slight_smile: As i said, it’s not new, a long time ago i also saw some things about i did some research and yes it seems to be close from Houdini methods, not sure it’s completely the same.

And you also right about modularity, my autoRig proto is build in this way, you can install and uninstall systems on a chain etc. It’s cleaner, AND less cpu consuming. And i think this is the method you need to have on autoRig system.

I’m in test, i need to run the system in a fully rigged character , i need to play with some spaceSwitch tests etc, to control all those things and be sure it’s ok on a production rig.
And think about some automation after, sooo looooott of work to do.

For now, it works on FK, IK and IKStretch, so i think it will work because all other rigs are attached to ikStretch or bind chain, so.

I keep you in touch when i get something robust and complete and will breakdown it.

Once again, yep, not new, it’s not a magic feature and as i said i’m pretty sure many riggers got it and have some systems close to this one, no doubt.

At the moment, the problem is performances, the guide system is not free talking about ressources. It’s a “save your production” feature, just in order to react very late retakes from agency or clients.



Hello there,

Here"s a quick demo about the system i’m working on. Just the arms for now.
First layer of proportional editing in Maya.

Will add more when the system it’s done.



1 Like

Looks really cool, good work!

Thx, yes it is, but it requires some work. I just noticed we need very consistant spaces, and you need to be also very accurate building the rig . The foot also needs some rig so you can edit the pivots without moving the leg Ik handle. I will show all those things later.

This method must be 0 errors on Ik Builds otherwhise you could break the ik/fk switch. Notice that in 2018 we do fk Ik match so… but i like to keep things clean.

See ya!

Hello people. Just a tiny update, system now supports global scale, rotation for each module.