ASSH = Asset Handler
There are different ways to setup scatter systems. The easiest way is through the ASSH.
“Viewport Scatter Mode” (look at the Tooltip for obstacle definement) while selecting a asset item. This mode is for single items.
“Add” (look at the Tooltip for obstacle definement) while selecting a existing OBJ node. This mode is for single items.
Another way is to selecting a bunch of already placed assets and hit Right-Click and add a scatter node. This option is for multiple items.
Last not but least you can of course setup the scatter node and the inputs completely by yourself.
