Three.js - Getting a low poly image

I am trying to create a low poly style terrain, for reference, this style:

By this I mean that each triangular is one shade.

When I try something like this, the shading is very smooth. Here's an example with several triangulars:

_{(source: willdonohoe.com )}

I also tried adding drop shadows, but that also didn't give the desired effect. Here's a shot with lots of triangulars with shadows added:

_{(source: willdonohoe.com )}

Looking at Three's documentation, the shading property in the material class sounds like it would work, but THREE.FlatShading and THREE.NoShading don't seem to have any effect.

Is there a special technique I need to use to create this effect? Any direction you can point me to would be much appreciated.

You can find my first demo here

Many thanks,

Will be