tnt mapgen

tnt_mapgen.lua

local c_air = minetest.get_content_id("air")
local c_tnt = minetest.get_content_id("tnt:tnt")

minetest.register_on_generated(function(minp, maxp)
	local vm, emin, emax = minetest.get_mapgen_object("voxelmanip")
	local data = vm:get_data()
	local area = VoxelArea:new{MinEdge=emin, MaxEdge=emax}

	for i in area:iterp(minp, maxp) do
		if data[i] ~= c_air then
			data[i] = c_tnt
		end
	end

	vm:set_data(data)
	vm:write_to_map()
end)

Put that into a mod folder, call it init.lua, add a depends.txt to the folder and write tnt into it.