Foliage issue

Hello.
I’m new here, so sorry if I make mistakes (Kind of ignorance of anything).
I apologize for my English language. Google translator

But to the point. I design a game, and I want to add elements of the environment, grass, trees, etc.
I do this by painting Foliage, and everything goes well, ie objects appear on the map surface, only in some radius from its center. But when I move to the edge of it, then the brush does not want to paint it. But the hand models of this grass, trees, or I can put on the site.
So my question is.
Are there any settings that limit the brush? Or something like Kill Z?
Thank you for any help.
Regards
Svinx

Yes, check here: