How to seamlessly stack materials with Materializer?

Rudy Michau writes:

Well, chances are you don't know how to make this texture.

Can't you see the problem?
Anything in particular? Sound easy?
Well, that's what I told myself...until I had to do it.

Here's what you need to see: 2 materials assigned to different parts of the geometry.
So far you're going to say to me "Rudy, it's easy, we make 2 slots of material, each slot is assigned to a part of the geometry and basta.”

Yes, of course. That's what I started doing too...until I needed to add a third material that overlapped the previous two.

I started by bugging, before finding an elegant solution that has given rise to a new feature in Materializer addon. Let me explain.

English Version:

French Version: