Runtime painting on mobile Game

https://www.youtube.com/watch?v=N5T8WTRmwFw

Do these modify the textures of the materials, or add decals on the things the balls hit?

Good question, I was wondering the same kind of things.
What and how does it modify it?
The ground in the video, is it one big plan, or several plans put together? Does its texture have to have a high resolution in order to get fine stains? What about the UVW unwrapping? Can any mesh do, or does it have to be a specific shape with clean unwrapping?