Comment # 3 on bug 92059 from Kenneth Graunke

It looks pretty much the same on i965/broadwell as well.  FWIW, I've overheard
that the game requires tessellation shaders for terrain and character
rendering, and if your driver doesn't support them, the game simply skips the
associated drawing.

But on radeonsi, you should have tessellation, so maybe there's something else
going on...