Is there a way to spawn things but only on a specific tile like grass for example, I have a city and rather than create tons of spawners I want to set one to a large radius to spawn things like birds, cats, dogs, etc. but I'd rather they not spawn in the buildings.
 
I'd look through the green thorn code to get a clue. It does different things on different terrain so theres got to be a function for that to examine. Wish I could help you more.
 
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