Check out a talk the artist gave at the Digital Art Conference 2017.
Check out a talk Simon Trümpler gave at the Digital Art Conference 2017 about how textures can be used for other stuff than color. The artist discussed some cool tricks he learned during the production of The Invisible Hours at Tequila Works.
The artist has also shared some materials/meshes for the smoke, rain and the leaves:
Here are some other videos from the artist you mind find useful:
Setting up a flow map material in Unreal:
Storing two images into one color channel of a texture:
Write the position of an object into a render target: