init.lua

local DEMO_GENNOTIFY = true

assert(minetest.register_mapgen_script)

minetest.register_mapgen_script(minetest.get_modpath(minetest.get_current_modname()) .. "/inner.lua")

minetest.set_mapgen_setting("mg_name", "singlenode", true)

minetest.register_on_respawnplayer(function(player)
	player:set_pos(vector.new(0, 1.5, 0))
	return true
end)

minetest.register_on_newplayer(function(player)
	player:set_pos(vector.new(0, 1.5, 0))
end)

-- Demonstrates the use of user-defined gennotify
if DEMO_GENNOTIFY then
	minetest.set_gen_notify({custom=true}, nil, {"flatgen:place_light"})
	minetest.register_on_generated(function(minp, maxp, blockseed)
		local g = minetest.get_mapgen_object("gennotify")
		--print(dump(g))

		local array = g.custom["flatgen:place_light"] or {}
		for _, pos in ipairs(array) do
			minetest.place_node(pos, {name="default:torch", param2=1})
		end
	end)
end

inner.lua

local GROUND_LEVEL = 1
local DEMO_GENNOTIFY = true

local c_filler = minetest.get_content_id("default:stone")

local global_buffer = {}

local function profile(descr, func)
	local pt = 0
	local b = {}
	return function(...)
		local dt = minetest.get_us_time()
		local r = {func(...)}
		dt = minetest.get_us_time() - dt
		table.insert(b, dt)
		if pt ~= os.time() then
			pt = os.time()
			local s = 0
			for _, n in ipairs(b) do
				s = s + n
			end
			print(("%s took %.1fms (%d samples)"):format(descr, s / #b / 1000, #b))
			b = {}
		end
		return unpack(r)
	end
end


local function generate(vm, minp, maxp, blockseed)
	local va
	do
		local pos1, pos2 = vm:get_emerged_area()
		va = VoxelArea:new({MinEdge = pos1, MaxEdge = pos2})
	end

	if minp.y > GROUND_LEVEL then
		return
	end
	local data = vm:get_data(global_buffer)
	for i in va:iter(minp.x, minp.y, minp.z, maxp.x, math.min(maxp.y, GROUND_LEVEL), maxp.z) do
		data[i] = c_filler
	end
	vm:set_data(data)

	minetest.generate_ores(vm, minp, maxp)

	vm:calc_lighting()

	-- Demonstrates the use of user-defined gennotify
	if DEMO_GENNOTIFY then
		local pos = {}
		if maxp.y > GROUND_LEVEL then
			for x = minp.x, maxp.x, 16 do
			for z = minp.z, maxp.z, 16 do
				pos[#pos+1] = vector.new(x, GROUND_LEVEL+1, z)
			end
			end
		end
		minetest.save_gen_notify("flatgen:place_light", pos)
	end
end

minetest.register_on_generated(generate)
--minetest.register_on_generated(profile("generate", generate))

mod.conf

name = flatgen
description = Flat mapgen based on new, innovative technologies