How to detect an object?

[num3rical]

How would one detect whether there is an object/an item on top of a node? I'm trying to make an ABM that spawns an item on top of a certain type of node, but only when there is no item currently on top of it.

[Astrobe]

Use get_node() if you want to detect a node, or get_objects_inside_radius() for anything mobile.

[num3rical]

Use get_node() if you want to detect a node, or get_objects_inside_radius() for anything mobile.

Thanks for the response. I gave this a shot, however I can't seem to get it working still.

Code: Select all

minetest.register_abm({
	nodenames = {"weirdworld:mud"},
	neighbors = {"default:water_source", "default:water_flowing", "default:river_water_source", "default:river_water_flowing"},
	interval = 5,
	chance = 1, --1 in 75
	action = function(pos, node, active_object_count, active_object_count_wider)
		
		local above_node = minetest.get_node({x = pos.x, y = pos.y + 1, z = pos.z})
		local above_objects = minetest.get_objects_inside_radius({x = pos.x, y = pos.y + 1, z = pos.z}, 0)

		if (minetest.registered_nodes[above_node.name].buildable_to and above_objects == nil) then
			minetest.add_item({x = pos.x, y = pos.y + 1, z = pos.z}, "weirdworld:worm")
		else
			return
		end
	end
})

There aren't any errors, it's just that the weirdworld:worms don't spawn at all.

[Krock]

Code: Select all

		local above_objects = minetest.get_objects_inside_radius({x = pos.x, y = pos.y + 1, z = pos.z}, 0)

		if (minetest.registered_nodes[above_node.name].buildable_to and above_objects == nil) then

First consider to increase the radius to 1m to prevent from rounding errors and to ensure the object range checks are not simply skipped in the engine code. Also check against the returned amount of objects. When there are none, get_objects_inside_radius will return an empty table, not nil!

Code: Select all

local above_objects = minetest.get_objects_inside_radius({x = pos.x, y = pos.y + 1, z = pos.z}, 0.5)

if (minetest.registered_nodes[above_node.name].buildable_to and #above_objects == 0) 

Also notice that you're using the index [above_node.name], which may return a nil value when the node above is unknown (disabled/removed mod).

[num3rical]

Code: Select all

		local above_objects = minetest.get_objects_inside_radius({x = pos.x, y = pos.y + 1, z = pos.z}, 0)

		if (minetest.registered_nodes[above_node.name].buildable_to and above_objects == nil) then

First consider to increase the radius to 1m to prevent from rounding errors and to ensure the object range checks are not simply skipped in the engine code. Also check against the returned amount of objects. When there are none, get_objects_inside_radius will return an empty table, not nil!

Code: Select all

local above_objects = minetest.get_objects_inside_radius({x = pos.x, y = pos.y + 1, z = pos.z}, 0.5)

if (minetest.registered_nodes[above_node.name].buildable_to and #above_objects == 0) 

Also notice that you're using the index [above_node.name], which may return a nil value when the node above is unknown (disabled/removed mod).

Works perfectly, thank you very much! Guess I need to read up a bit more on tables in Lua :P