Vertex Order

K, so your vertex order is extremely important when it comes to blendshapes(and a lot of other things, but blendshapes are probably what we are gonna use the most.)

There are lots of things that will change your vertex order. Seperating your mesh, deleting faces, adding edgeloops, etc. If you do any of those things your blendshapes wont work. Which can cause problems.

For example. I needed to add edgeloops to the fingers, there weren't enough to keep the volume in the knuckles. Unfortunately, my facial rigs mesh includes the entire upper body. How can I add those edgeloops while still keeping a clean mesh?

First, I corrected my mistake from earlier and copied all of my facial rig clusters over to a new mesh that was only the face and neck. This new face mesh had a different vertex order though, so I cant just create a blendshape from that to my new face and body mesh. So, I make a duplicate of my new face mesh. This duplicate will accept blendshapes from the old mesh, but it doesn't have a body attached to it. Not very useful.

So I duplicate my old face with body, and chop off the head. Then I add all of the edgeloops I want to the fingers. Then I do something very sneaky.

I combine the two pieces of geometry. Select the face first, then the body, and combine. Maya will keep the vertex order of the first piece you selected, in this case the face. So now my face has a body, but still has the same vertex order as the new face mesh. Blendshapes will work.

All that is left to do is delete the history on the new mesh, create the blendshape, and viola.