Epic/mods/other_worlds/redsky_asteroids.lua

if otherworlds.settings.redsky_asteroids.enable then

   -- Approximate realm limits
   local YMIN = otherworlds.settings.redsky_asteroids.YMIN or 6000
   local YMAX = otherworlds.settings.redsky_asteroids.YMAX or 7000

   -- Register on_generated function for this layer

   minetest.register_on_generated(otherworlds.asteroids.create_on_generated(YMIN, YMAX, {
      c_air = minetest.get_content_id("air"),
      c_obsidian = minetest.get_content_id("default:obsidian"),
      c_stone = minetest.get_content_id("asteroid:redstone"),
      c_cobble = minetest.get_content_id("air"),
      c_gravel = minetest.get_content_id("asteroid:redgravel"),
      c_dust = minetest.get_content_id("asteroid:reddust"),
      c_ironore = minetest.get_content_id("asteroid:ironore"),
      c_copperore = minetest.get_content_id("asteroid:copperore"),
      c_goldore = minetest.get_content_id("asteroid:goldore"),
      c_diamondore = minetest.get_content_id("asteroid:diamondore"),
      c_meseore = minetest.get_content_id("asteroid:meseore"),
      c_waterice = minetest.get_content_id("default:ice"),
      c_atmos = minetest.get_content_id("asteroid:atmos"),
      c_snowblock = minetest.get_content_id("default:snowblock"),
   }))


   -- Deco code for grass and crystal

   local TOPDECO = 200 -- how often surface decoration appears on top of asteroid cobble

   local crystal = {
      "crystals:ghost_crystal_1", "crystals:ghost_crystal_2",
      "crystals:red_crystal_1", "crystals:red_crystal_2",
      "crystals:rose_quartz_1", "crystals:rose_quartz_2",
   }

   -- Add surface decoration
   minetest.register_on_generated(function(minp, maxp)
      if minp.y < YMIN or maxp.y > YMAX then
         return
      end
      local bpos, ran
      local coal = minetest.find_nodes_in_area_under_air(minp, maxp,
         {"asteroid:redgravel"})
      for n = 1, #coal do
         bpos = {x = coal[n].x, y = coal[n].y + 1, z = coal[n].z }
         ran = math.random(TOPDECO)
         if ran == TOPDECO then -- crystals
            minetest.swap_node(bpos, {name = crystal[ math.random(1, #crystal) ] })
         end
      end
   end)
end