write something there

mods/minetest_game/spawn/init.lua

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+-- Always load the API
+----------------------
+dofile(minetest.get_modpath(minetest.get_current_modname()) .. "/api.lua")
+
+-- Disable biome-search implementation on unsuitable mapgens
+------------------------------------------------------------
+
+local mg_name = minetest.get_mapgen_setting("mg_name")
+if mg_name == "v6" or mg_name == "singlenode" then
+	return
+end
+
+
+-- Parameters
+-------------
+
+-- Resolution of search grid in nodes.
+local res = 64
+-- Number of points checked in the square search grid (edge * edge).
+local checks = 128 * 128
+-- Starting point for biome checks. This also sets the y co-ordinate for all
+-- points checked, so the suitable biomes must be active at this y.
+local pos = {x = 0, y = 8, z = 0}
+
+
+-- Table of suitable biomes and matching API function
+
+local biome_ids = {}
+
+function spawn.add_suitable_biome(biome)
+	local id = minetest.get_biome_id(biome)
+	assert(id ~= nil)
+	biome_ids[id] = true
+end
+
+for _, name in ipairs({
+	"taiga", "coniferous_forest", "deciduous_forest", "grassland", "savanna"
+}) do
+	local id = minetest.get_biome_id(name)
+	if id then
+		biome_ids[id] = true
+	end
+end
+
+-- End of parameters
+--------------------
+
+-- Direction table
+
+local dirs = {
+	vector.new(0, 0, 1),
+	vector.new(-1, 0, 0),
+	vector.new(0, 0, -1),
+	vector.new(1, 0, 0),
+}
+
+
+-- Initial variables
+
+local edge_len = 1
+local edge_dist = 0
+local dir_step = 0
+local dir_ind = 1
+local searched = false
+local success = false
+local spawn_pos = {}
+
+
+-- Get world 'mapgen_limit' and 'chunksize' to calculate 'spawn_limit'.
+-- This accounts for how mapchunks are not generated if they or their shell exceed
+-- 'mapgen_limit'.
+
+local mapgen_limit = tonumber(minetest.get_mapgen_setting("mapgen_limit"))
+local chunksize = tonumber(minetest.get_mapgen_setting("chunksize"))
+local spawn_limit = math.max(mapgen_limit - (chunksize + 1) * 16, 0)
+
+
+-- Functions
+------------
+
+-- Get next position on square search spiral
+
+local function next_pos()
+	if edge_dist == edge_len then
+		edge_dist = 0
+		dir_ind = dir_ind + 1
+		if dir_ind == 5 then
+			dir_ind = 1
+		end
+		dir_step = dir_step + 1
+		edge_len = math.floor(dir_step / 2) + 1
+	end
+
+	local dir = dirs[dir_ind]
+	local move = vector.multiply(dir, res)
+
+	edge_dist = edge_dist + 1
+
+	return vector.add(pos, move)
+end
+
+
+-- Spawn position search
+
+local function search()
+	for iter = 1, checks do
+		local biome_data = minetest.get_biome_data(pos)
+		-- Sometimes biome_data is nil
+		if biome_data and biome_ids[biome_data.biome] then
+			local spawn_y = minetest.get_spawn_level(pos.x, pos.z)
+			if spawn_y then
+				spawn_pos = vector.new(pos.x, spawn_y, pos.z)
+				return true
+			end
+		end
+
+		pos = next_pos()
+		-- Check for position being outside world edge
+		if math.abs(pos.x) > spawn_limit or math.abs(pos.z) > spawn_limit then
+			return false
+		end
+	end
+
+	return false
+end
+
+
+function spawn.get_default_pos()
+	-- Search for spawn position once per server session
+	if not searched then
+		success = search()
+		searched = true
+	end
+	return success and spawn_pos
+end