[BTS] How to change the shape of the terrain?

[AstrokauzazITS994]

Hello everyone, when I was playing civilizations, I was thinking about creating a mod for civilization IV, which I told in earlier posts.
I thought to myself what to do to change the shape of the terrain in the sense that in civilizations the terrain has the shape of a square and pawned what to do to make it have any other shape.
Does anyone know how to do this?

 

[Nightinggale]

The core game engine (not modable) view all plots as squares. I'm not sure it will accept terrain in any other shapes than that.