Controlling long toes with IK reverse foot

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  03 March 2013
Controlling long toes with IK reverse foot


I have a pretty basic setup on this frog I'm working on. The toes are all three joints, and I'm using group nodes to create the reverse foot. I'm pretty new to rigging, and I'm not really sure how other people handle this bit.

The issue is that, as opposed to other rigs I've seen, the Frog's toes are all long and spread out, so they won't all stay planted with the reverse foot, or "heel peel." So I selected the main toe that will stay planted and added an extra joint, from the top of the toe hierarchy to the tip and created an IK handle on this. The toe controllers are all connected to the toe joints in the connection editor.

This all works ok except that when the heel peels up the toes on either side of the main toe pivot down through the floor. So I put a set driven key animation on those toe's controllers, driven by the "heel peel" attribute to compensate.

This seemed like an ok solution except now that I've started animating I see that the SDK and any animation on the toe controller come into conflict and break the joint (SDK quits working when the toe is animated at any time). I tried to create SDK offset nodes for the toe controllers to be parented to, but when these nodes rotate they don't change the values on the controller object and so they don't work with the connections. So I tried changing out the connections in the connection editor for orient constraints but when I constrain each of the toe joints to the controller only the joint highest in the hierarchy rotates instead of curling each joint like I need.

I'm all out of ideas on this so any help would be greatly appreciated. Thanks.

Maya 2012
  03 March 2013
It's just a matter of creating 'root nulls' for each joint, ie a group node with the same position/rotation as the joint as a parent of each one. Then you hook the SDKs to the group nodes and drive them how you want, but the animator can still animate freely with each controller/joint while they just follow along with the rotation of their parent groups.

  03 March 2013
That's exactly what I was trying to do. I was calling them "SDK offset nodes" or something but that's the idea. This is not working for me however because like I said, if I use the connection editor the values of the toe control object don't change. So the parent node rotates, and gets an x rotation of -90, the control object has a value of 0, and the joint doesn't move.

That's why I said I tried to use the orient constraint instead. The problem there is, there are two joints that need to be controlled, and if I apply an orient constraint to each of these joints, only the parent inherits the rotation (and this is the part that has me befuddled, it doesn't seem like it should work like this so I'm wondering if something is fouled up here).

So basically, the Set Driven Keys are on the parent node, creating the offset and working fine, then I put an orient constraint on the middle joint, and everything works fine. So I add another orient constraint to the knuckle joint, and now only the knuckle rotates, and the middle joint stays straight, making the perfectly straight no matter what the control object does.

Lastly, what I tried to do is orient constrain the Knuckle joint, then use the connection editor to connect the middle joint to the knuckle. This works fine for the normal setup, but when I use the "heel peel" attribute it creates a weird rotation. So I'm stuck

This is probably easier with the file. So you can find it at the link below. The left rear foot is the new setup, and all the other feet have the old setup. Feel free to poke around the file and find as many problems as you like. Thanks to anyone who is willing to take a look. I'm very stuck here.

ps. bonus points to anyone who can tell me why when the toes are parented to the foot they create an empty transform node in-between the connection that you can't get rid of. happens other places, but not everywhere. Started happening late in the rigging process.
  04 April 2013
I've made this sound too complicated

I may have included too much detail. And I don't expect anyone to download the file and do it for me. But the truth is I'm semi desperate on this. I've rigged this 10 different ways and nothing is working.

The problem is simple. I have a toe controller like this:

L_toe_SDK (transform node)
L_toe_ctrl (nurbs curve)

These two nodes have identical translation/rotation/scale information. How do I control a joint's rotation with the nurbs curve such that the joint will also rotate when the transform node is rotated.

The only catch is, it has to be applied to two joints. So that when I rotate the transform node the toe "curls." That's it.

I am seriously stuck, I've done this so many different ways with different types of connections. It's possible my bone setup is some how ill-conceived. So if it sounds like that's the problem you can look in the file above. I'm semi-begging here, so please if you are at all inclined, just a little hint would be great. Thanks.
  04 April 2013
Hmmm, I'm fiddling with your rig now, but I'm somewhat lost as to what it is you're trying to accomplish. If you don't mind, could you say what is is you're trying to do with which joints/controls in your rig? I'm having trouble finding which objects/joints I'm supposed to be playing with, hehe. I'm no rigging expert by any means, but I'd still like to try to help.
  04 April 2013
Check out this video by Jeremy Ernst, it goes through setting up similar controls to what your after. Granted it's on a hand but the concept could be used on a foot with toes also.

Hope it helps

  04 April 2013
Thank you both very much for your responses. I haven't watched the video yet but I will tonight.

But since I just finished it I thought I would stick this here to (hopefully) clarify.

Here is a simplified version of the rig. It is just the IK chain. There is a simple animation showing the deformation I'm after, but then if you just add some keyframes to the toe controls you'll see what the problem is. This example isn't breaking quite as bad as the original, which I can't account for, but it is obviously not working sufficiently. Anyway, hopefully that will make it a bit more clear.

You can also notice here that if you select the transform nodes above the toe controllers and rotate them they have no effect. This the basic issue. How do I get this type of control, but set up in a way that allows me to get deformation by rotating any node in the controller's hierarchy.

Thanks again.
  04 April 2013
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