Trees exist so we have something to swing between.

The way they do the leaves on these large canopies is interesting: instead of doing any kind of 3D hull with an alpha cutout texture - as in speedtree and other “standard” solutions - they use a few textures on billboarded cards.

That style of foliage hasn’t been a common practice for years, especially not in games where there’s this much in the way of graphical fidelity. But it works, because the texture resolution and the lighting are good enough that you don’t realize you see the same leaf pattern staring at you a thousand times unless you’re looking for it.

Just Cause 2 (2010)