Low poly world

I searched over 10 hours and can't find some code or a libary for a low poly game.

I want to create a low poly world like this http://b.vimeocdn.com/ts/407/486/407486446_640.jpg
from modifying a terrain.

I found an expensive asset for low poly. How does he make this? Shaders or Scripts?
Can someone tell me how I can get a low poly effect on my terrain?

I despair.

I don't want to export a model from a 3d program like blender.

I hope someone can help me.