A Stretchy IK

I have been helping a co-worker learn some rigging techniques, and since I'm essentially making tutorials, I figured I might as well post them for others to benefit from as well!  Today's topic is how to make an IK limb stretchy.

The basic idea is that we will measure the original length of the IK from start joint to handle, and any time that distance increases beyond its original value, the bones of the IK limb will scale to make up the extra distance rather than rotating beyond what makes sense (the cause of popping).


Let's dive right in!

Joints and orients and iks, oh my!

A lead rigging position in a decentralized studio means lots of emails about the proper way to do things. Here's one more I shall share with you! Kernels of wisdom about joint orientations (and how you shouldn't forget them) as well as a couple of comments on quadruped rigging.

Robo Ball

This is a little animation using my RoboBall rig! The rig is free to download and use. If you know maya, I hope you'll download it and give it a spin! Okay. Bad pun, but I had a lot of fun making this little guy and I'm really excited to share it.

If you make any videos using this rig, please post them as video responses on youtube. I'd love to see what you do with it!

The rig should be pretty self explanatory, but creators always seem to think that. ;) If you can't read my mind when you open the file, here's a demonstration of the rig's basic functions.

There's some technical insights if you stick around after the jump!

Clean rotate values from your FK controls

Here's some basic rigging info that my coworkers needed.  As long as I put the effort into collecting it, I might as well share it with others too!

A lot of higher level rigging problems, particularly in the set-driven fixes area, can be avoided if your basics are solid.  While its amazingly easy to make a basic rig that moves things and appears to work, making one that will have clean values computed quickly, and thus make higher-level rigging easier, requires attention to some details that can be easily overlooked.