planetoids/mapgen_oreplanet.lua

local has_vacuum_mod = minetest.get_modpath("vacuum")


-- http://dev.minetest.net/PerlinNoiseMap

-- basic planet noise
local planet_params = {
	offset = 0,
	scale = 1,
	spread = {x=2000, y=200, z=2000},
	seed = 345465738,
	octaves = 3,
	persist = 0.6
}


local c_base = minetest.get_content_id("default:stone")
local c_air = minetest.get_content_id("air")
local c_ignore = minetest.get_content_id("ignore")
local c_vacuum

if has_vacuum_mod then
	c_vacuum = minetest.get_content_id("vacuum:vacuum")
end

local planet_perlin

local planet_perlin_map = {}


planetoids.mapgen_oreplanet = function(minp, maxp, vm, area)

	local data = vm:get_data()

	local side_length = maxp.x - minp.x + 1 -- 80
	local map_lengths_xyz = {x=side_length, y=side_length, z=side_length}

	planet_perlin = planet_perlin or minetest.get_perlin_map(planet_params, map_lengths_xyz)
	planet_perlin:get_3d_map_flat(minp, planet_perlin_map)

	local i = 1
	for z=minp.z,maxp.z do
	for y=minp.y,maxp.y do
	for x=minp.x,maxp.x do

		local index = area:index(x,y,z)

		if data[index] == c_air or data[index] == c_vacuum or data[index] == c_ignore then
			-- unpopulated node
			local planet_n = planet_perlin_map[i]

			if planet_n > planetoids.min_chance then

				-- planet
				data[index] = c_base
				for _,ore in pairs(planetoids.ores) do
					if planet_n > ore.chance then
						if ore.id then
							-- "plain" layer
							data[index] = ore.id

						elseif ore.id_list then
							-- mixed layer
							data[index] = ore.id_list[math.random(1,#ore.id_list)]
						end

						break
					end
				end
			end
		end

		i = i + 1

	end --x
	end --y
	end --z

	vm:set_data(data)
	minetest.generate_ores(vm, minp, maxp)

end