A quick script I wrote that helps you copy blendshapes from a target mesh to only the selected vertices of another mesh, which is useful if you have models with identical faces but different bodies (that are a single object).

For example, if you want to copy a face blendshape from a character onto a copy of the character with identical face geometry but different body topology, you would :

1. Duplicate the character with different body topology.
2. Select the original blendshape mesh that you want to transfer to the duplicate.
3. Shift select the vertices on the duplicate character that you want to be affected (such as all the head vertices).
4. Run my script.
5. Blendshape >> Add the result to your skinned character.

I’m unsure if there is a better way of doing this, but this script worked for a simple cartoon character.

import maya.cmds as cmds
 
selection = cmds.ls(sl=True)
 
if len(selection) > 0:
    targetMesh = selection[-1]
    affectedVertices = selection[0:-1] # Assume the rest of the selection is made of vertices
    affectedMesh = cmds.listRelatives(cmds.listRelatives(affectedVertices[0], p=True), p=True)
    
    vtxSet = cmds.sets(affectedVertices, v=True, n="SelectionSet")
    print cmds.sets(vtxSet, q=True)
    
    # Move to origin
    cmds.move(32, 0, 0, affectedMesh, ws=True)
    cmds.move(32, 0, 0, targetMesh, ws=True)
    
    # Select target mesh and affected vertices
    cmds.select(cl=True)
    cmds.select(targetMesh)
    cmds.select(vtxSet, add=True)
    
    cmds.transferAttributes(transferPositions=1, transferNormals=1, transferUVs=2, transferColors=0, sourceUvSpace="map1", sampleSpace=3, searchMethod=0, flipUVs=0, colorBorders=1)
    
    cmds.hide(targetMesh)
    
    cmds.select(cl=True)
else:
    print "Select vertices to move and target mesh"