I had the same problem on a laptop once. I think it's the Intel integrated graphics which causes the problem. I seem to remember I fixed it by lowering the graphics quality, and possibly turning of VSync and Antialiasing.
It looks to me like the grass models are being messed up somehow, so turning of grass is probably the best option here.
My WIP: The Liberation of Manaan
Originally Posted by Totalbiscuit
Can tell it's been a busy day, 121 Chrome tabs open
on the geek test
keep you healthy, bright-eyed and slim