well it depends on how big we are speaking. i guess everyone here assumed really big environmental pieces. it is just a matter of texel density or memory usage. a uniquely textured rock will likely eat a lot of texture memory or look very blurry compared to other, smaller elements in the game.
It is hard to tell on that render but there seems to be a bunch of creasing occurring on the front element of the gun with the 5 holes. Or maybe it is just mass out geometry that is faceted.