3D world-to-local and local-to-world transform using Python (numpy and transforms3d)

transform-3d-world-local.py

# pip install transforms3d numpy

import transforms3d as t3d
import numpy as np

scene_transform = {"pos": [0,0,0], "rot": [0,0,0,1], "scale": [1,1,1]}

# https://forum.unity.com/threads/whats-the-math-behind-transform-transformpoint.107401/#post-709765
def local_to_world(p):
	v = np.multiply(p, scene_transform["scale"])
	v = t3d.quaternions.rotate_vector(v, scene_transform["rot"])
	v += scene_transform["pos"]

	return v

# https://forum.unity.com/threads/whats-the-math-behind-transform-transformpoint.107401/#post-709778
def world_to_local(p):
	v = np.subtract(p, scene_transform["pos"])
	v = np.divide(v, scene_transform["scale"])
	q = t3d.quaternions.qinverse(scene_transform["rot"])
	v = t3d.quaternions.rotate_vector(v, q)

	return v