Swaying trees without $treeSway$treeSway is a VMT texture parameter that allows trees and such to appear to sway from the wind. However this is not supported on older games such as CS:S, HL2 etc
It actually exists in GMod but flickers when lit by flashlight (bugged as of may 2019)
There's a workaround for this, and is pretty simple actually.This works for all games:
Just find what texture the leaves of the trees use, and open the VMT.
Next, add these proxies to it
"$translate" "[0 0]"
You can change the sineperiod for slower/faster swaying
You can add anything you like to make the apparent swaying motion more random.
If you see unexpected results, you'll need to tweak the sinemin and sinemax parameters.
That's because these values were typed in for a specific tree, and since we generally dont know what the UV map of each tree looks like, it might need some adjusting.
This is effect costs virtually no fps.