Ball and Socket joint

I’m working on a shoulder and would like a ball-and-socket joint. The standard IKA just isn’t working because the arm goes all twitchy if I try to move it out of a single plane.

I tried searching this site and others, but wasn’t coming up with any tutorials, examples, or previous discussion on this topic. If something has been discussed or is available elsewhere, I’d love a pointer to it. Else, if someone can give easy to follow directions, that would be nice too. Words and sentences of minimal syllables is appreciated as I’m not exactly the most advanced user in the world. Hey…I’m proud of myself 'cause I just figured out the concept of action window, NLA, and walk cycle.

I had a little trouble with that too… Once you mess with it a bit it makes more sense.

An arm (for example), you would place the 3D cursor at the shoulder ball-joint and add bones. Add three (an IK chain) and name them something like “UpperArm.L”, “LowerArm.L”, and “ArmNull.L” (or whatever, just be consistent).

It helps to make sure they are not all in a perfectly straight line, this will cause twitching later on. Try to put an ever slight bend in the chain at the elbow, pointing toward the elbow.

Select the elbow joint and Shift-S, Cursor->Selection. Add a single bone and name it “Elbow.L” (or whatever). Select the wrist joint and add a single bone “Wrist.L”.

Now (this is important), select all your new bones and Ctrl-N to auto-align the bone rotations to their optimal values. Not doing so is also known to cause twitching. Ctrl-Tab to pose mode, select ArmNull and add an IK solver to the Wrist, and select LowerArm and add an IK solver to Elbow. Tab back to Edit mode and hide the bones you don’t need to look at in Pose mode.

Now you can (in Pose mode) grab the Wrist and move the arm about without difficulty or twitching. Grab the Elbow to point the crook of the arm how you want.

Now I only hope that the new armature system can import this stuff…

Good luck!


Not perfect, but better control over the elbow than I had before.

Definitely looking forward to the new armature/joint system…