I would like to fill all the empty space below a certain point with water. The trouble i'm having is filling the empty space with water. It doesn't seem possible to select/change the property of nothing. Is there a way to do this?
for i, use -1. This means "create if empty space". There are other options, -3 creates it even if it's not empty, and a number >= 0 will delete the particle with that ID and give it to yours.