empty_to_bone.py

# Original source code: https://github.com/artellblender/empties_to_bones
# Author: artellblender
# This code has been modified to create bones for an existing armature.

import math
import bpy
from mathutils import Euler, Matrix, Vector

armature_name = "Avatar_Girl_Claymore_Noel_Manekin"
empty_parent_ary = [
    {"empty": "+HairS L B01", "parent": "Bip001 Head"},
    {"empty": "+HairS L B02", "parent": "+HairS L B01"},
    {"empty": "+HairS L B03", "parent": "+HairS L B02"},
]
tail_multiply = 0.06


def mat3_to_vec_roll(mat):
    vec = mat.col[1]
    vecmat = vec_roll_to_mat3(mat.col[1], 0)
    vecmatinv = vecmat.inverted()
    rollmat = vecmatinv @ mat
    roll = math.atan2(rollmat[0][2], rollmat[2][2])
    return vec, roll


def vec_roll_to_mat3(vec, roll):
    target = Vector((0, 0.1, 0))
    nor = vec.normalized()
    axis = target.cross(nor)
    if axis.dot(axis) > 0.0000000001:
        axis.normalize()
        theta = target.angle(nor)
        bMatrix = Matrix.Rotation(theta, 3, axis)
    else:
        updown = 1 if target.dot(nor) > 0 else -1
        bMatrix = Matrix.Scale(updown, 3)
        bMatrix[2][2] = 1.0

    rMatrix = Matrix.Rotation(roll, 3, nor)
    mat = rMatrix @ bMatrix
    return mat


def get_edit_bone(name):
    return bpy.context.object.data.edit_bones.get(name)


armature = bpy.data.objects.get(armature_name)

for obj in empty_parent_ary:
    empty_name = obj["empty"]
    parent_name = obj["parent"]
    emp = bpy.data.objects.get(empty_name)

    vec, roll = mat3_to_vec_roll(emp.matrix_world.to_3x3())
    new_bone = armature.data.edit_bones.new(empty_name)
    new_bone.head = emp.matrix_world.to_translation()
    new_bone.tail = new_bone.head + (vec) * tail_multiply
    new_bone.roll = roll

    bone_parent = get_edit_bone(parent_name)
    get_edit_bone(new_bone.name).parent = bone_parent

1. Edit L6-L11

armature_name = "Avatar_Girl_Claymore_Noel_Manekin"
empty_parent_ary = [
    {"empty": "+HairS L B01", "parent": "Bip001 Head"},
    {"empty": "+HairS L B02", "parent": "+HairS L B01"},
    {"empty": "+HairS L B03", "parent": "+HairS L B02"},
]

2. Run