minetest.register_on_generated(function(minp, maxp, seed)
    local vm, data, emin, emax = minetest.get_mapgen_object("voxelmanip")
    local a = VoxelArea:new{
        MinEdge={x=emin.x, y=emin.y, z=emin.z},
        MaxEdge={x=emax.x, y=emax.y, z=emax.z},
    }

    local c_dirt = minetest.get_content_id("default:dirt")
    local sidelen = maxp.x - minp.x + 1
    local noise = minetest.get_perlin_map(
        {offset=0, scale=20, spread={x=250, y=250, z=250}, seed=5, octaves=5, persist=0.6},
        {x=sidelen, y=sidelen, z=sidelen}
    )
    local nvals = noise:get2dMap_flat({x=minp.x, y=minp.z})

    for z = minp.z, maxp.z do
    for y = minp.y, maxp.y do
    for x = minp.x, maxp.x do
        local ni = math.floor((z - minp.z) * sidelen + (x - minp.x) + 1)
        if y < nvals[ni] then
            local vi = a:index(x, y, z)
            data[vi] = c_dirt
        end
    end
    end
    end

    vm:calc_lighting(
        {x=minp.x-16, y=minp.y, z=minp.z-16},
        {x=maxp.x+16, y=maxp.y, z=maxp.z+16}
    )

    vm:write_chunk(data)
end)