Getting vertex coordinates with applied shape keys

Question

I'm trying to write a function that returns vertex coordinates including their transformation that was a applied by (one or multiple) shape keys. Currently this is how I tried, but I only get vertex coordinates before the shape keys are applied:

def get_vertex_coords():
    ob = bpy.data.objects['cc_base_body']
    curmode = bpy.context.object.mode
    bpy.ops.object.mode_set(mode='OBJECT')
    mesh = ob.to_mesh(preserve_all_data_layers=True, depsgraph = bpy.context.evaluated_depsgraph_get())
    bm = bmesh.new()
    bm.from_mesh(mesh)
    coords = []
    for vertex in bm.verts:
        if vertex.index in poi:
            coords.append(vertex.co) # ob.matrix_world @ 
    bpy.ops.object.mode_set(mode=curmode)
    return coords

Is there any way to do this?

Thanks to the comments I found a way, see my posted answer.

Answer 1

Bmesh.from_object

Would use this method for the modified / deformed coordinates

How do I get a mesh data-block with modifiers and shape keys applied in Blender 2.8? since we are going to load up a bmesh.

Modified and deformed cube shown in edit mode. Test script below, create a modified and deform applied mesh copy, or with cage = True the deformed cage mesh as shown in edit mode above, with modifiers intact.

Instead of printing result, returned mesh as a result and made object copies to visualize result.

import bpy
import bmesh
from bpy import context

def get_modified_mesh(ob, cage=False):
    bm = bmesh.new()
    bm.from_object(
            ob,
            context.evaluated_depsgraph_get(),
            cage=cage,
            )

    #bm.transform(ob.matrix_world)
    me = bpy.data.meshes.new("Deformed")
    bm.to_mesh(me)
    return me


context.object.update_from_editmode()
# make a modified and deformed copy
ob = context.object.copy()
me = get_modified_mesh(ob)
ob.modifiers.clear()
ob.data = me
context.collection.objects.link(ob)

# make a deformed copy (keep modifiers)
ob = context.object.copy()
me = get_modified_mesh(ob, cage=True)
ob.data = me
context.collection.objects.link(ob)

Note, if poi is a list of indices then

bm.verts.ensure_lookup_table()
coords = [bm.verts[i].co for i in poi]

looping over all and testing for inclusion is very unoptimal.

Answer 2

Edit: Thanks to Crantisz and this answer How to apply shape keys? I found a way:

I duplicate the object whose vertices I'm looking at, add a new shape key to the duplicated object:

ob.shape_key_add(name="temp", from_mix=True)

and then delete all shape keys from the duplicated object:

for key in ob.data.shape_keys.key_blocks:
    ob.shape_key_remove()

I can then get the vertex coordinates and delete the new object:

def get_vertex_coords():
    curmode = bpy.context.object.mode
    bpy.ops.object.mode_set(mode='OBJECT')
    #deselected all then select the object we want to copy (using operators since this seems to be the proper way to do it in blender)
    bpy.ops.object.select_all(action='DESELECT')
    bpy.data.objects['cc_base_body.001'].select_set(True) #The mesh name should be a parameter here
    bpy.ops.object.duplicate()     
    ob = bpy.context.active_object # This should now give us the duplicated object
    
    #Add the shape key
    ob.shape_key_add(name="temp", from_mix=True)
    #now remove all shape keys
    for key in ob.data.shape_keys.key_blocks:
        ob.shape_key_remove()    

    
    mesh = ob.to_mesh(preserve_all_data_layers=True, depsgraph = bpy.context.evaluated_depsgraph_get())
    bm = bmesh.new()
    bm.from_mesh(mesh)
    coords = []
    for vertex in bm.verts:
        if vertex.index in poi:
            coords.append(vertex.co) # ob.matrix_world @ 
    bpy.ops.object.delete()
    bpy.ops.object.mode_set(mode=curmode)
    
    return coords