I've long wanted to try making custom figures and have recently had time to give thought to attempting it.  I'm not particularly daunted by sculpting/modeling or any other aspects of creating my base figure, and I think I'm up to the challenge of rigging as well...

What I do not understand is how people go about creating morphs involving the mouth and jaw, especially when the head mesh includes the teeth as Poser figures generally do...  I know there has to be some way to soft-select the chin and jaw bone area so they can be rotated around the hinge of the jaw, yet it seems the lower teeth must also be moved around this same pivot while maintaining complete rigidity... 

I just can't get my mind around the process of creating an open mouth morph, whether for a custom or existing figure!

I generally use Wings3D, but do have access to zBrush and 3DCoat.  I am curious how these morphs are usually created, whether the lower parts of the head and teeth can be moved in the same step, and just where exactly the pivot of the jaw should be located.

 In terms of modeling - model the mouth with a little bit of an opening for easier selection. Then use whatever app you prefer to create your morphs.  For the cartoon characters, one of the reasons you can turn on all their expressions at the same time and still get something useable is because I localized my morphs to key areas and then combined them via dependencies to create the expressions. Would love it if we could have weight mapped translations - right now only rotations are weight mapped. Then I could do some higher end stuff but anyway, what app you make it in doesn't matter as much as your approach.

 One major factor to making this easy is that we separate the teeth, gums and tounge from the head geometry now.  Similar approach to what is often done in animated films. So then you can create a obj of your figure that is just the head or just the body for easier morphing. I usually import the figure into zbrush, isolate the internal bits - teeth, eyes, gums, tongue and delete them. Then I save the file out as "Character name-FBM".  I will then select the head, inverse the selection, delete and save the head out as "Character name-Base Head".  

Hope that helped.

Here's my process:  After loading the object, I create a morph target of it in the Tool menu (toward the bottom of the tool list).  Then I create a layer - you always want to work on layers, as it will allow you more control of your morphing.  Then, using the masking feature with a lasso selector, I mask out the mouth area. It's okay if your mask isn't perfect, that's why we stored a morph target. Next I'll hold down CTRL and click in an empty space in the window to invert the mask. Then, I place the Rotate Transpose tool along the center line of the bottom of the jaw. Then from the left or right, I rotate the jaw so that the mouth opens - you may also need to move it with the Move Transpose tool. Alternatively - if you're comfortable with with the tools you can line up the rotate line with the location of where the mandible starts (in some cases having symmetry on would help here but be careful).  

After this action, depending on how careful you were with your selection you may have pulled some of the upper lip also. To correct this once you're satisfied with the jaw's position, switch to the MORPH brush and clear your mask by hodlind CTRL and dragging in an empty area of the scene.  Then, using the morph brush, brush along the upper lip area until it has returned to its original shape. For the final part of this, you'll switch to the Smooth brush at a lowish setting - 35-25 should be fine - and smooth the transition from lower lip to upper lip. You may also want to run the Smooth bush along the rest of the lower part of the face to help the look of the morph.  Once done, you can stop your layer recording and then export out the OBJ as MouthOpen.

 The more familiar you get with Zbrush the more options you'll find in helping you do this - like blurring the mask before rotation or the Move Topological Brush which will let you adjust the mesh in specific areas without affecting surrounding geometry. It's a very powerful program. I'll cover the next steps shortly.

Now, nine times out of ten, upon leaving ZBrush via OBJ export, you'll end up with an OBJ that no longer has the correct group names. To resolve this, you'll need to import your base file's UV data. So load your morph into UVMapper or UVMapper pro. Then, go FILE>Import UVs and select the unaltered base file (I hope you didn't save over it). Check to make sure the groups have returned and that the vertex order is unchanged by going Select By>Group and making a selection. If the expected area highlights correctly, you're good to go. Export the morph under a new name and that's it for the morph creation.

Then you'll need to tie the lower teeth x rotation to the morph, so that they work in unison.

Have you tried both the morph putty tool and the morph brush?

Quote - Have you tried both the morph putty tool and the morph brush?

That would have been my first thought, as I think I probably could drag the chin and jawline into the desired shape.  I just don't think it would work as well with the teeth, though (and how to affect one without affecting the other?).  They need to remain un-distorted but must still be rotated around the jaw's pivot... 

(Maybe the morph brush could use rotation as well as moving?)

Quote - Personal opinion - you may have an easier time blending between morphs if you have the jaw as its own actor (using a ghost bone) and localize your morphs.

 In terms of modeling - model the mouth with a little bit of an opening for easier selection.

 One major factor to making this easy is that we separate the teeth, gums and tounge from the head geometry now. 

Hope that helped.

Yes, that is very helpful.  I suppose, when making an original figure, those are things I should try to remember.

As far as soft selections, locating the jaw's pivot, etc., I was hoping for a method that would work equally well for creating morphs for existing figures (and I use a lot of older ones also). 

It sounds like this is something that would be much easier to do in zBrush than in Wings...  I'd need a soft selection for the chin and jaw, and a hard selection for the teeth while also being able to rotate both around the same pivot.