mmgen_mytest = {}

function mmgen_mytest.generate(current_layer, vm, a, data, minp, maxp, offset_minp, offset_maxp,arg,seed)
    local t1 = os.clock()
 
    local c_dirt  = minetest.get_content_id("mcl_core:dirt")
    local c_stone = minetest.get_content_id("mcl_core:stone")
    local c_grass = minetest.get_content_id("mcl_core:dirt_with_grass")
    local c_water = minetest.get_content_id("mcl_core:water_source")
    local c_air = minetest.get_content_id("air")

    if arg.stone then c_stone =  minetest.get_content_id(arg.stone) end
    if arg.dirt then c_dirt =  minetest.get_content_id(arg.dirt) end
    if arg.water then c_water =  minetest.get_content_id(arg.water) end
    if arg.grass then c_grass =  minetest.get_content_id(arg.grass) end
    if arg.air then c_air =  minetest.get_content_id(arg.air) end
 
    local sidelen = maxp.x - minp.x + 1
 
    local nvals=multi_map.get_global_3dmap_flat("terrain", {x=sidelen, y=sidelen, z=sidelen}, {x=minp.x, y=minp.y, z=minp.z})
 
    local ni = 1
    for z = minp.z, maxp.z do
    for y = minp.y, maxp.y do
    for x = minp.x, maxp.x do
	local yy=multi_map.get_offset_y(y)
        if nvals[ni] - (yy - 25) / 55 > 0.5 then
            local vi = a:index(x, y, z)
            if yy < 1 then
                data[vi] = c_stone
            else
                data[vi] = c_stone
            end
        elseif yy < 1 then
            local vi = a:index(x, y, z)
            data[vi] = c_water
        end
        ni = ni + 1
    end
    end
    end
end