Successful blendshapes require that the multiple copies of your model that you are deforming share the same vertices order that the original model has. That's fine and all works well if you stay inside of Maya but I've run into a snag while exporting my models as OBJs to be remodeled in other programs such as Zbrush. Actually, the problem begins the minute you hit the EXPORT button. I've exported the poly model then imported it back into Maya without ever having brought it into another program and the vert order changes. This creates a big problem. So, how do people deal with the situation of exporting their model (or parts of the model) then bringing it back with the vertices order preserved?

I've discovered that if I export the original model then import it back in then create blend shapes from THAT model, the problem doesn't exist but, what if you break the model down into pieces: head, arms, legs to create blendshapes for each then you combine the pieces back together and merge the vertices. I haven't tried this yet but I'm anticipating that such manipulation will change the vertices order. Is there a utility within Maya or a Mel script available that combats this problem? Vlad, I'm sure you know what I'm talking about. Do you ever create blendshapes outside of Maya? If so, what is the proper workflow to make all these pieces of geometry play nice when you use them to create the blendshape nodes?

Here is the workflow that I'm using now:
Create poly model

EXTRACT faces for a part of the model (the head) with the 'seperate extracted faces' checked, and 'keep faces together' on.

Export the head as an OBJ

Import the head back into Maya

Copy imported head for blendshape modeling

Export copied head as OBJ

Import and remodel head(s) using Zbrush

Export head(s) from Zbrush as an OBJ

Import Zbrush head(s) back into Maya

Create a blendshape node(s) as usual.

This works well but I haven't tried reattaching the head to the rest of the model yet so I don't know if that will create a problem. Plus, the head is just one piece of extracted geometry from the model. I feel like the problem will be compounded when I extract the legs and arms to create blendshapes for them as well. I suppose that as long as the verts on the edge of each piece of geometry is not altered then the blendshape creation can be told to not check the topography of the model. I just fear that each piece of seperated geometry that is exported will be assigned identical vert numbers that have already been assigned to verts on other parts of the seperated model. Any help is greatly appreciated.