/// <summary>
        /// construct as a copy of the list
        /// </summary>
        /// <param name="list"></param>
        public VectorOfPointNormal(List <PointNormal> list)
        {
            var arr = list.ToArray();

            _ptr = Invoke.std_vector_pointnormal_ctor_count(arr.Length);

            var dptr = (PointNormal *)Data;

            for (var i = 0; i < arr.Length; i++)
            {
                dptr[i] = arr[i];
            }
        }
 public VectorOfPointNormal(int count)
 {
     _ptr = Invoke.std_vector_pointnormal_ctor_count(count);
 }