Soft rendering & self shadowing?

Hi.

I'm trying to understand how to achieve a softer rendering effect in Unity. My programming background is solid but I have little knowledge of rendering and shaders.

I'm trying to achieve an effect much like the one here: You'll notice the darkening & shadows within the scene. I realize that for performance reasons the effect would likely need to be baked in, and that's fine. I'm open to solutions both commercial (asset store etc) or not.

A poke in the right direction alone would be most helpful and appreciated.