Sudden frame rate drop

I’m getting a frame rate drop from capped 60fps to 12fps, yes 12fps, as soon as I get within a certain altitude of the ground, a few hundred metres. If I pop up above that height my frame rate goes straight back to 60fps. It’s isolated to this map, and only is rectified by dropping my view distance to medium or low. What is odd is that my system seems more than capable of holding 60fps, and neither my GPU usage or CPU usage is hitting the limits. It seemed like a VRAM issue, but I’m only using 6 out of 11 GB. Perhaps it’s a terrain object LOD issue? But then I would expect more people reporting it. I have dialed down ground clutter, shadows, AA etc and they make no difference. I’m not running vsync. It’s odd that it drops so much and so precisely.

Your system specs seem more than capable of holding 60 fps even at 4k. Please keep in mind that at lower altitudes the graphics are very demanding, so fps usually drops. but 12 fps is in no way acceptable. You will have to find out the bottle neck.