Normal Mapの混ぜ方
https://blog.selfshadow.com/publications/blending-in-detail/
@cristobalvila: The correct way to Combine two Normal Maps in Blender (applicable to any other app, I suppose).
Thank you so much to @quackarooners for the tip!!!
The theory behind this: https://blog.selfshadow.com/publications/blending-in-detail/
https://gyazo.com/6838b848bf260b34974970141aa281ee
https://gyazo.com/8197883988b6a36e3ae8a2355c0353a6
Normal