Tricky Mouth Rigging

I am having trouble figuring out how to rig a cartoon mouth that I have modeled. Basically the mouth appears on the side of the face like so.

But I can’t figure out how to rig the mouth and have it form certain sounds without having the mesh look too deformed. I’d like it to stay roughly on the same path as the original sphere. But trying to close the mouth or form any kind of movement results in something like this.

I’d say I’m trying to go for something like this, in fact it’s just about the same. Any advice? This has been puzzling me for months and I could use any help I can get.

Try applying this eye rig to the mouth.

1 Like
  1. Add a bone to the center of the sphere if you don’t already have one. We’ll call it boneCenter.

  2. Duplicate all mouth bones, make non-deforming.

  3. Snap cursor to center of sphere. Normalize all duplicate mouth bones to the cursor.

  4. Give duplicate mouth bones a limit distance constraint (surface) targeting boneCenter and a locked track constraint targeting boneCenter (to Z, lock Y).

  5. Parent deforming mouth bones to duplicate mouth bones. Give damped track (defaults) to deforming mouth bones, targeting the next mouth duplicate bone in the chain.

You now have a mouth that’s glued to the surface of the sphere. Adjust the strength of the constraints to keep them less glued if you want.


I understand a bit, but I’m still very confused about this process… would you mind explaining the process a little more please?

Do you mean add those bones with those steps after I have the kind of bones in paticl3s video?

What is a damped track?

How do I set limit constraints?

I am not very adept at rigging, so I thank you for all of your help. :slightly_smiling_face:

I mean that as an alternative.

If you’re not yet familiar with constraints, then it’s worth spending some time learning about them-- as I’ve said, they can make your bones do what you want. Start with the manual. There are plenty of tutorials if you google “blender constraint tutorial.” Or “blender rigging tutorial” for that matter.

Looks like your kind of cartoon mouth is better done with shape keys.

But if you want to use bones, I suggest Bendy Bones. You won’t got back to clunky bone chains after you get the hang of Bendy Bones for face. My “realistic human” face rig is 95% bendy.

For your cartoon head, I suggest this user’s experimental (and fun way) of using Bendy Bones.

Yeah, Shape keys is what I initially tried, so I think I’ll try Bendy Bones.

One more quick question, though, is he using rigify in this tutorial? I’ve seen this type of rigging all over the place and I am not familiar with it.

Okay, I have one more question though, because I’m having a hard time finding answers to it.
How do I “normalize all duplicate mouth bones to the cursor” as you said in #3 earlier in the forum?

Place a cursor. Enter edit mode on your armature. Select a bone. Ctrl-n-> cursor. Calculates roll such that the bone’s +Z axis points at the cursor. Very handy for a lot of constraints, very handy for fingers.

As far as I know Rigify doesn’t use bendy bones. And the tutorial I pointed you to, is the user’s custom rig.

You don’t even need that many Bendy bones to shape a cartoon mouth.

Think of upper mouth and lower mouth as two bendy bone eyebrows as shown in this amazing awesome demo by Pepe School Land