Well it seems it's only me who uses Forester right now, but at least I give feedback
So now the next problem (or weird behaviour):
After putting the generated bgl files in the scenery folder and loaded up the sim (p3d v3), I obtained very low fps (below 5). Ok, I thought 300.000+ trees would be too much, but here comes the weird part.
When slewing up to about 1000 ft, fps suddenly increases back to normal (25-35 for my setup). And the change is really sudden as if there was an invisible scenery barrier or something. And doing it while the trees are still there. So it's not the vast number of trees that causes the fps drop but something else.
Anyone else experienced this?
I'll try now with much less trees and maybe decreasing the autogen complexity, we'll see if it helps.
Update:
I did some tests.
Only putting the smallest BGL in the scenery folder: good fps on ground
Increasing the amount and size of BGL's in the folder: after a few files (few MB in total) the ground fps is way too low (under 5). Putting back even more, fps is under 1 (yeah, it's almost just a still picture)
Playing with the scenery complexity slider: decreasing it to normal or dense only helps with few bgl's (trees), even the very sparse setting is not helping with all the trees. Yeah, I have hundreds of thousands on my big photoscenery, so I guess I have to make them way less dense...
But the question still remains: why is it perfect above a certain height (800-1000 ft) even with so many trees, and why does fps suddenly drop to almost 0 below this altitude??
I attach two screenshots with the fps counter in the corner.