@MarkusvonBroady in a recent answer to me you said "Perhaps a more efficient way would be to delete geometry later and sample by indices if neighboring points are scheduled to be deleted or not" that appears to be useful to me now could i have a more in depth explaination

the floors of my building are represented by points, any point which is unsupported from below (i.e. the point below it is scheduled for deletion) I'd like to also remove, as I don't want floating floors/

im currently trying capture attribute to compare mesh vertex indices pre and post deletion but it only works for vertices with a higher index number than that of the lowest deleted room

@ruckus sure, the logic is, if you spawn a grid of points, you can easily figure out what are the indices of the neighboring points. On the same row: left point is the current index-1, right point is the current index+1. And on other rows it's the top point on current index-row_length, and current index + row_length

Actually, since "Instance on Points" has "Selection", all you have to do is reverse the selection to get what you keep rather than what you delete, and then replace the proximity logic with sample index logic as explained above

the points dont maintain their original index after vertex count is reduced>

Oh, I remember now, you can't do it in a single step in instance on points, because the logic relies on checking if a point is deleted. So you need to capture a boolean attribute instead of deleting, then when you use the index logic to sample indices, you use that to read this attribute

and then you also read this attribute to decide if a point is supposed to spawn something or not

yes thanks!

@ruckus

See this, it spawns on a point based on it having a point above it and that point being chosen to stay

no deletion needs to happen

The real optimization however, is elsewhere - don't realize instances. You may need to calculate custom normals similarly to how I do it here: blender.stackexchange.com/a/294496/60486

Whoops it had an error i.imgur.com/ee9fSd7.png