16 Sep 2015 14:49
A cutplane is a "wall" (not with a collision, it's just a bit how it acts), which, if you place it, makes every object behind it invisible that's useful especially in cities, where you can divide streets with it (but carefully).
Then, if placed correctly, they make streets (streets which are not normally visible, for example if they are hidden behind building) totally invisible so the game doesn't load them before they should be visible, which increases perfomance a lot.
Except the awfully writtten sentences, I think it's quite a good simple explanation...