Godot 4 interior mapping shader no cubemap

Fake interior shader with use single texture for room

Port of this shader: https://forum.unity.com/threads/interior-mapping.424676/#post-2751518

Interior mapping shader which instead of cubemap, it uses texture atlas with room tiles that are front room view automatically mapped into a cube.
The alpha channel value - uniform for whole tile - is used to determine the rear wall's relative distance.