Terrain details won't spawn past an invisible line on the terrain.

I'm prototyping a level and needed to get some rocks placed out across the terrain but I've had a really hard time trying to figure out why so many quirks just stop it from working at all. I did manage to get rid of the LOD and colliders on the detail asset I was using (rocks from Quixel's Megascans library) and now need to figure out why I can't place them across much of the terrain and why, when I delete details, hidden ones seem to leap into view around the outside of the brush. For awhile they were seemingly sliding towards an invisible center line.

Changing the detail resolution per patch down from 128 eliminated that boundary (with detail resolution at 1024), but I still get hidden rocks appearing as I delete others. It's as if they're being pushed out from the mouse into open space rather than being deleted.

I can probably find a stable workaround so long as I learn which parts of the workflow I shouldn't touch, yet I'd prefer to know why this is happening in the first place.

 

reduce your brush density