Hi,
This is still is still a work in progress and i haven't scripted it yet. But was finding it helpful to use lattices for sculpting a simple 2D mouth's mouth open and lip corner up blendshape. One lattice was used for the lip corner up shape and the second lattice was used on the lower mouth for the mouth open shape. I created a vertex group for the lower mouth (excluding 2 verts at extreme ends) and used that vertex group when creating lattice.
(to sculpt the simple 2D mouth created a plane subdivided and positioned it. then duplicated it and joined top and bottom together).
(to make the lattices used add lattice then shaped it in object mode and then created a modifier on the lip mesh and gave it the lattice to use)
one advantage of using lattice in Blender to sculpt lip corner up blendshape is it allows for more control of keeping the mouth closed when the lip corner is moving up.
Hope you find it helpful.
Thanks,
Nathaniel
also check out Chris Pagoria's example of using lattices for more complex meshes in his online tutorial "Fast Start For Facial Blend Shapes".
also check out the amazing work of Nima Azarba (nimaazarba dot blogspot dot com)
