It disappear on certain angles when I move camera away. I set ground slope angle to 0 - 180, in settings of foliage in enabled Preserve Area, but it still disappear at certain angles, on flat surface it works perfectly.
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Could it be landscape LOD causing some foliage to disappear? Steep angles could create non ideal topology once LODs kick in. Either way I can’t see anything obviously different in the two screenshots besides some fading around the edges of your foliage clusters.