Merging multiple OBJ files into one file with shape keys So, right now I have about a dozen different meshes that are all modified versions of a default head mesh. One for example is the same head but fatter, one with more pronounce eyebrows, one is smiling etc. 

I am slightly new to blender, and I did not make these models. What I'm trying to do is find a way to merge these multiple files into one file as different shape keys. I can find information about how to make shape keys by editing a mesh but can't for the life of me find a way to blend two meshes into one and use one as the "target" of a blend key. If this is making sense. 

The ultimate goal I have in mind is that I would like to have a single file with multiple sliders that I can ultimately export into Unity. I've learned how to export shape keys but I can't figure out how to get from where I am now with multiple meshes to where I want to be with multiple sliders. Thanks in advance for any help you can give a somewhat new user.
You can use this script to accomplish an obj sequence import to shapekeys.
Paste the script into the text editor in blender, and click the Run Script button. 

This will add a new command in the file menu called File>Import>OBJ as Shapekey. Select your target object, and then run the new command.



bl_info = {
    'name': 'Load Obj Sequence as Shape Keys',
    'author': 'cmomoney',
    'version': (0, 2),
    'blender': (2, 6, 7),
    'category': 'Import-Export',
    'location': 'File &gt; Import/Export',
    'wiki_url': ''}

# ##### BEGIN GPL LICENSE BLOCK #####
#
#  This program is free software; you can redistribute it and/or
#  modify it under the terms of the GNU General Public License
#  as published by the Free Software Foundation; either version 2
#  of the License, or (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  You should have received a copy of the GNU General Public License
#  along with this program; if not, write to the Free Software Foundation,
#  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
#
# ##### END GPL LICENSE BLOCK #####

import bpy, os
from bpy.props import *

class LoadObjAsShapekey(bpy.types.Operator):
    bl_idname = 'load.obj_as_shapekey'
    bl_label = 'Import OBJ as Shape Keys'
    bl_options = {'REGISTER', 'UNDO'}
    bl_description = "Import Obj sequence as shape key(s)"

    filepath = StringProperty(name="File path", description="File filepath of Obj", maxlen=4096, default="")
    filter_folder = BoolProperty(name="Filter folders", description="", default=True, options={'HIDDEN'})
    filter_glob = StringProperty(default="*.obj", options={'HIDDEN'})
    files = CollectionProperty(name='File path', type=bpy.types.OperatorFileListElement)
    filename_ext = '.obj'

    @classmethod
    def poll(cls, context):
        return context.active_object is not None and context.active_object.type == 'MESH'

    def execute(self, context):
        #get file names, sort, and set target mesh
        spath = os.path.split(self.filepath)
        files = [file.name for file in self.files]
        files.sort()
        target = bpy.context.scene.objects.active
        #add all ojs in sequence as shape  keys
        for f in files:
            fp = os.path.join(spath[0], f)
            self.load_obj(fp)
        #now delete objs
        sknames = [sk.name for sk in target.data.shape_keys.key_blocks]
        bpy.ops.object.select_all(action='DESELECT')
        for obj in sknames:
            if obj != 'Basis':
                target.data.shape_keys.key_blocks[obj].interpolation = 'KEY_LINEAR'
                bpy.context.scene.objects.active = bpy.data.objects[obj]
                bpy.data.objects[obj].select = True
                bpy.ops.object.delete()
            bpy.ops.object.select_all(action='DESELECT')
        #reselect target mesh and make active
        bpy.context.scene.objects.active = target
        target.select = True
        return{'FINISHED'}

    def invoke(self, context, event):
        wm = context.window_manager.fileselect_add(self)
        return {'RUNNING_MODAL'}

    def load_obj(self, fp):
        bpy.ops.import_scene.obj(filepath=fp,split_mode='OFF')
        bpy.ops.object.join_shapes()
        return

def menu_func_import(self, context):
    self.layout.operator(LoadObjAsShapekey.bl_idname, text="Obj As Shapekey(.obj)")

def register():
    bpy.utils.register_class(LoadObjAsShapekey)
    bpy.types.INFO_MT_file_import.append(menu_func_import)

def unregister():
    bpy.utils.unregister_class(LoadObjAsShapekey)
    bpy.types.INFO_MT_file_import.remove(menu_func_import)

if __name__ == "__main__":
    register()


Please note this is not my script, I'm just posting it here for convenience.