Idk what perinstancefadeamount does, but here’s how to set up a fade in using cameradepthfade and per instance random.
the functions are in the engine content so you’ll need to check the ‘show engine content’ checkbox to find them.
if you want the grass to pop in instead of fade in you can modify the camera fade function.
edit: figured out how the per instance fade amount works, it gives you a value from 0-1 based on the cull distance you give your foliage and if you don’t set a specific min or max cull distance it defaults to 1. The actual culling of meshes seems to happen in batches and the size of the batch seems to be somewhat related to the brush size. I’m thinking in your vid your using a spheremask and not culling the meshes? In which case you may not be aware where to find the culling setting to allow per instance fade amount to work. The cull setting is here:
So you could do something like this with the per instance fade.
