Rigging complex joint?

I’m working on a robot and I’ve built the ankle using three pieces…
http://bentfx.com/BlenderArtistsForum/ankle.png

My initial intention was to simply parent the separate pieces to the individual bones of a Rigify rig, and that has largely been a success. The sticking point is this ankle.

Yaw is easy, I just parent to bone A.

The question is, is there a simple way to parent the pitch and roll sections to bone B but have them each affected by only one axis of its rotation?

EDIT: OK, I’m starting to figure it out, I think. It’s all about constraints. From what I’m seeing though it’s like a Rubik’s Cube, just with fewer correct solutions.

Should be even easier than using constraints… just make a bone for each joint… parenting them properly and restricting the Rotation of each bone in Pose mode…

Get out of town!!! that’s not your first Rigg!.. ha! :spin:

Reeeeeeallly nice model…

Jeas I’m going to have to work with it for awhile to figure anything out on this…

Daaaaaaannnng!

I’m so use to Uni-Mesh Riggs… and way simpler than this Mechnical Riggs…

I am amazed that you got those ‘Track too’ constraints to work as well as you did … the way you did… ‘Track to’ type constraints in many of the programs I have used in times past have always had very very bad problems with out adding more targets than what you have here… good work dude!

Also I really like the way you have your foot set up going there…

Only I might add some kind of a unified foot mover… that moves both the back and toe of the foot at the same time for the sake of the animator… as it is now your forcing the animator to move two controls with every step… that’s double the work… but just moving it around the way you have is … is really really nice… great work guy… Oh… wait I said that already… :yes:

If you’re interested, BentFX, these foot/leg rigging tutorials go into a fair amount of depth:

http://www.blenderguru.com/videos/introduction-to-rigging

Both have the ‘unified’ heel-toe roll control norvman mentioned, but each takes a different approach to getting it.

Thanks for the input guys.

I am new enough to this, that I didn’t understand till today what and empty was, or to put my x-ray bones in wire mode. One of the biggest impediments to my modeling is that at my core I’m a programmer, not an artist. I enjoy this rigging thing! Hope I can get good at it.

I just watched the Blender Cookie’s advanced face rig tutorial. It opened up all kinds of understanding about how controls and effects can be stacked to operate on one another.

@RiViT Thanks for the links. I haven’t watched the tuts yet, but it looks like promising material.

@norvman Yes, I need to figure out a “unified” control on the foot. That’s what I meant when I said “blah blah blah.” (I didn’t know the technical term) :wink:

Well I finally got back to this… I tore apart Tobs’ Foot rigging tutorial. It is the worst kind! Low volume, soft voice, an accent, and really great information that makes you listen over and over to get the gold nuggets. I downloaded all ten parts and played it locally probably about 50 times. I’d play with bones a bit, watch again, then play some more.

Finally, I loaded my model and top down rebuilt the rig, without the video. I think I nailed it. I do need to build a few more, and I’m sure I will, but I’ve got the basics down I think. I didn’t add the roll controllers he does in the last vids. The main foot target gives decent twist and roll control plus at this point in my career it’s expected that my feet should poke through the floor every now and then.

http://bentfx.com/BlenderArtistsForum/FembotLegs002.png
Here’s the .blend file if anyone cares to critique it. Now I’ve just got to get back to modeling(and rigging) the upper body, then we can blow her up, or set her on fire, or something.

EDIT: I forgot to ask. The hydraulic cylinders at the knee are about as simple as you can get. The top and bottom portions just “track to” each other. But they do weird things. They rotate on axis’ they shouldn’t and when I clear transforms to reset the pose I need to do it twice or the cylinders don’t line up. Any Ideas?

EDIT AGAIN: I did get the answer to my original question. As Norvman said, the joint was done with three bones each aligned with, and constrained to an odd angle. The the main foot bone was constrained to no rotation and the IK percolates up through the three ankle bones which each of the pieces are parented to. While the model does have problems with self intersection, the ankle remains pretty faithful to the angles it was built to bend at.

Yah Tobbs Rigging tuts are great… I pretty much use his method with some mods of my own…
I use IK_Contraints instead of track to constraints when doing hydraulic cylinders… that way I can set a poll target if I have too… just like you did for your knee control on the Tobb Rigg…

I hate to resurrect this thread, but it seems one problem hasn’t been properly addressed. The problem you are having with the hydraulic cylinders is a cyclic dependency. They cannot track to one another directly. Instead, you have to parent an empty or another bone to each cylinder, and have them track to these targets instead.

@xabotage, I did set IK on the cylinders rather than track to constraints, and that did seem more stable but still was just a bit wonky. I can see that having them directly following each other might leave a situation where they “quiver”. :smiley:

Thanks!