rigging ED-209


Hey maybe some of you have seen the robot I’m working on:


It’s getting close to the time where I have to rig him up, so I’ve been doing some tests. I set up a more basic version just to try and get the movement down:

I haven’t even bothered with the toes yet, as it’s the leg piece giving me a problem. If you haven’t seen RoboCop in a while, the leg is one piece that slides slightly inside the hip joint:

So that poses like this are possible:

As you can see, the toes are no longer inside the mesh, because I manually translated the leg :shrug:. I know that there must be a way to automate/constrain that leg’s sliding…but I can’t get my head around it. Any ideas?


Right off the top of my head, I can imagine maybe a set driven key that was linked to the forward and backward rotation of the leg, so that that it translated upwards when the leg rotated backwards, and downwards when the leg rotated forwards.

scott bell


I think this is what you want… (attached)

I used skel, IK, constraints (point and orient)
and SDK…



thanks, friends.

JoeSchmo, I am working with Maya 5.0. Is there some way for you to “Save As…” Maya 5?

I’m anxious to see what you’ve discovered…

Thanks again.


Hy M8, just converted it for you :slight_smile:

enjoy it…

get it

btw, how the hell can I attach a file??? or change my avatar?? :frowning:


its threads like this that show how wonderful cgtalk is!

AcidX you can’t upload or change your avatar until 20 posts.


Ohhh, me stupid :rolleyes:

(knows that something like RTFM exists, but is avoiding it everytime :slight_smile: )
thx :love:


kgkraeer: Make sure to tear this one apart so that you fully understand why it works. Just follow the logic of it, and you’ll see it’s not too complicated. I remember when hydrolics were first explained to me. My classmate make a hole with his index finger and thumb of his left hand then took a pen with his right hand and put it into the hole, making sure to keep the pen perpendicular to the hole. “Just pay attention to exactly what’s happening here and then try to copy that exactly using constraints.” All perverted thoughts aside, the answer clicked. Most problems are usually quite simple if you just think if it like this. Again, just make sure you understand exactly what JoeSchmo did to make this rig work… less his efforts go wasted.

The orient, point, aim and (now) parent constraints are a godsend. Also pay close attention to what options are set before you APPLY the constraints. The aim constraints will sometimes get crazy flipping, unless you configure the up vector.

Also, I think you can delete the following two constraints, and the rig should still work. Just in case they were confusing you. shrug Unless there’s somethin I’m missing.


Hope to see some of you at Siggraph!!!

  • Jeremy


Indeed, threads like this are a great example of a forum that works really well.

The rig, of course, is perfect. Verbal007, I definitely know what you’re saying about tearing the rig apart. I found it slightly disturbing that I couldn’t get something to work myself. So I’ll be examining this rig very carefully, and probably adding controls or IK for the toes before it’s applied to the hi-res model.

This helps immensely. Thank you all for your help!


It’s not perfect… it got a little lazy

with the SDK ( which turns the hip joints arc

into a straight line ) if you spend a little more

time getting a nicer SDK curve the slide will

be perfectly smooth instead of sloppy and wiggly.

and those extra constraints mentioned above probably are’nt needed-
they are just leftovers from trying to figure it out that I forgot to delete.


I would add a double controller on the foot
(one that controls the foot and one that
controls the IK toes that the foot controller
is parented to)

so that as he takes a step you can make the toes look like
they dangle and then compress down… and also you won’t have
to worry about keying on and off a parent constraint, which is a pain in the A–.


Thanks dude. Yeah, I only needed the basic setup…it was making that slide happen that was giving me trubs.

You’ve done more than enough with that mockup.

I’ll take a look at that curve…this next question is gonna make me look bad. Where is the SDK curve?


select the joint (the Hip) that has the SDKs on it and

open the graph editor- the relationship curve should look like
a smooth arc- ( because its compensating for the arc of the joint
to a straight line)



what does SDK stand for, what is it?


Hmm, the curve for joint1.scaleX > joint2.rotateZ (hip joint - and only curve I could find) is actually a relatively straight line.

I think I’m missing something…btw, how did you create that relationship curve? Is there a tute somewhere?


I created the curve with Set Driven Keys (SDK)

If you look at it move in wireframe you will notice that
the hip joint scales in X as the knee rotates in Z.

If the curve looks flat in the Graph editor - select it and press f

For SDK help -search in the help files under ‘driven keys’-
of course the ver5 help files suck. :frowning:


Sweet, thanks man.

What did I do when I pressed “f”?


OK. Got everything working, more or less; the SDK curve is working, but I was wondering if I could get your input on “Wobbliness”…

It seems to get really, really wobbly at the extremes. I didn’t simply plug in your sample scene; I looked at what you did and re-did it with my ED. After several adjustments and hours of frustrating experimentation, I think I finally see what’s going on; how the curve relates to everything and how this is basically a digital model of a hydraulic system.

The wobbliness, though has been tough to deal with. If you could spare a minute and give me some background on how/why that occurs I should be able to fix it (my personal theory is that the curves are too steep).

Thanks for all your help on this. Toughest rig I’ve ever done:sad:.


Got som sample pics of the madness:

The extremes, when the bottom leg bone reaches the limit (-50), are fine:

As is the standing pose, before he does anything (final modelling pose). However, on his way to each extreme, the following phenomenon happens at hi-speed:

As I move the torus (leg controller) or the body controller back and forth, the bottom leg piece frantically vibrates in and out of the ‘knee’ box. It never vibrates way out of position, but it does this jittering really rapidly. I thought it was a matter of smoothing my curve out, but how can you get smoother than this(?):

Now, when I did a simple test animation, moving the leg from one place to another, or moving ED upwards on his ‘haunches’, it animated correctly…no wobbles. But when I hit “Undo” or if I return the Torus to its starting point by manually typing 0,0,0 in the Translate boxes, it comes back a little funky and disjointed. The leg doesn’t resolve again until I nudge the torus in the viewport again.

Just seems like a messy way to work. I feel like I’m missing something really simple.


Yeah, I have the same problem with some of my more complex rigs. There something in the circular calculations that causes it. I actually feel kinda lucky to have it work for me at all, and it’s something I’ve learned to work with. shrug

  • Jeremy



Yeah, I mean it animates ok. I have a pretty complex animation planned though, so I was hoping to get it resolved. I know I’m gonna wind up accidently keying Ed with his leg all messed up and it’s gonna cost me.

I dunno if you downloaded the file JoeSchmo made on page 1, but it’s really smooth (there’s the slightest wobble, but not even close to how bad mine is). So I know it’s possible to get this stuff working right.

I feel like I’m copping out at this point if I use it as I have it. I want to learn how to make this work.