minetest/builtin/game/falling.lua

-- Minetest: builtin/item.lua

--
-- Falling stuff
--

core.register_entity(":__builtin:falling_node", {
	initial_properties = {
		visual = "wielditem",
		visual_size = {x = 0.667, y = 0.667},
		textures = {},
		physical = true,
		is_visible = false,
		collide_with_objects = false,
		collisionbox = {-0.5, -0.5, -0.5, 0.5, 0.5, 0.5},
	}

	node = {},

	set_node = function(self, node)
		self.node = node
		self.object:set_properties({
			is_visible = true,
			textures = {node.name},
		})
	end,

	get_staticdata = function(self)
		return core.serialize(self.node)
	end,

	on_activate = function(self, staticdata)
		-- Set gravity
		self.object:setacceleration({x = 0, y = -10, z = 0})
		self.object:set_armor_groups({immortal = 1})
		
		local node = core.deserialize(staticdata)
		if node then
			self:set_node(node)
		elseif staticdata ~= "" then
			self:set_node({name = staticdata})
		end
	end,

	on_step = function(self, dtime)
		-- Turn to actual sand when collides to ground or just move
		local pos = self.object:getpos()
		local bcp = {x = pos.x, y = pos.y - 0.7, z = pos.z} -- Position of bottom center point
		local bcn = core.get_node(bcp)
		local bcd = core.registered_nodes[bcn.name]
		-- Note: walkable is in the node definition, not in item groups
		if not bcd or
				(bcd.walkable or
				(core.get_item_group(self.node.name, "float") ~= 0 and
				bcd.liquidtype ~= "none")) then
			if bcd and bcd.leveled and
					bcn.name == self.node.name then
				local addlevel = self.node.level
				if not addlevel or addlevel <= 0 then
					addlevel = bcd.leveled
				end
				if core.add_node_level(bcp, addlevel) == 0 then
					self.object:remove()
					return
				end
			elseif bcd and bcd.buildable_to and
					(core.get_item_group(self.node.name, "float") == 0 or
					bcd.liquidtype == "none") then
				core.remove_node(bcp)
				return
			end
			local np = {x = bcp.x, y = bcp.y + 1, z = bcp.z}
			-- Check what's here
			local n2 = core.get_node(np)
			-- If it's not air or liquid, remove node and replace it with
			-- it's drops
			if n2.name ~= "air" and (not core.registered_nodes[n2.name] or
					core.registered_nodes[n2.name].liquidtype == "none") then
				core.remove_node(np)
				if core.registered_nodes[n2.name].buildable_to == false then
					-- Add dropped items
					local drops = core.get_node_drops(n2.name, "")
					for _, dropped_item in ipairs(drops) do
						core.add_item(np, dropped_item)
					end
				end
				-- Run script hook
				for _, callback in ipairs(core.registered_on_dignodes) do
					callback(np, n2)
				end
			end
			-- Create node and remove entity
			core.add_node(np, self.node)
			self.object:remove()
			nodeupdate(np)
			return
		end
		local vel = self.object:getvelocity()
		if vector.equals(vel, {x = 0, y = 0, z = 0}) then
			local npos = self.object:getpos()
			self.object:setpos(vector.round(npos))
		end
	end
})

function spawn_falling_node(p, node)
	local obj = core.add_entity(p, "__builtin:falling_node")
	obj:get_luaentity():set_node(node)
end

function drop_attached_node(p)
	local nn = core.get_node(p).name
	core.remove_node(p)
	for _, item in ipairs(core.get_node_drops(nn, "")) do
		local pos = {
			x = p.x + math.random()/2 - 0.25,
			y = p.y + math.random()/2 - 0.25,
			z = p.z + math.random()/2 - 0.25,
		}
		core.add_item(pos, item)
	end
end

function check_attached_node(p, n)
	local def = core.registered_nodes[n.name]
	local d = {x = 0, y = 0, z = 0}
	if def.paramtype2 == "wallmounted" then
		d = core.wallmounted_to_dir(n.param2)
	else
		d.y = -1
	end
	local p2 = vector.add(p, d)
	local nn = core.get_node(p2).name
	local def2 = core.registered_nodes[nn]
	if def2 and not def2.walkable then
		return false
	end
	return true
end

--
-- Some common functions
--

function nodeupdate_single(p, delay)
	local n = core.get_node(p)
	if core.get_item_group(n.name, "falling_node") ~= 0 then
		local p_bottom = {x = p.x, y = p.y - 1, z = p.z}
		local n_bottom = core.get_node(p_bottom)
		-- Note: walkable is in the node definition, not in item groups
		if core.registered_nodes[n_bottom.name] and
				(core.get_item_group(n.name, "float") == 0 or
					core.registered_nodes[n_bottom.name].liquidtype == "none") and
				(n.name ~= n_bottom.name or (core.registered_nodes[n_bottom.name].leveled and
					core.get_node_level(p_bottom) < core.get_node_max_level(p_bottom))) and
				(not core.registered_nodes[n_bottom.name].walkable or
					core.registered_nodes[n_bottom.name].buildable_to) then
			if delay then
				core.after(0.1, nodeupdate_single, p, false)
			else
				n.level = core.get_node_level(p)
				core.remove_node(p)
				spawn_falling_node(p, n)
				nodeupdate(p)
			end
		end
	end

	if core.get_item_group(n.name, "attached_node") ~= 0 then
		if not check_attached_node(p, n) then
			drop_attached_node(p)
			nodeupdate(p)
		end
	end
end

function nodeupdate(p, delay)
	-- Round p to prevent falling entities to get stuck
	p = vector.round(p)

	for x = -1, 1 do
	for y = -1, 1 do
	for z = -1, 1 do
		local d = vector.new(x, y, z)
		nodeupdate_single(vector.add(p, d), delay or not (x == 0 and y == 0 and z == 0))
	end
	end
	end
end

--
-- Global callbacks
--

function on_placenode(p, node)
	nodeupdate(p)
end
core.register_on_placenode(on_placenode)

function on_dignode(p, node)
	nodeupdate(p)
end
core.register_on_dignode(on_dignode)