public override void Append(Accessor accessor, IEnumerable <int> map)
            {
                var scalar = accessor.AsVector4Array();

                foreach (var index in map)
                {
                    _stream.Add(scalar[index]);
                }
            }
		private static void ParseVerts(TextParser parser, ListMeshStream<Vector3> vertices)
		{
			for (;;)
			{
				var attribute = parser.Lexem;
				if (attribute == "}")
				{
					parser.Consume();
					break;
				}
				if (attribute == "numVerts")
				{
					parser.Consume();
					vertices.Capacity = parser.ConsumeInt();
					continue;
				}
				if (attribute == "v")
				{
					parser.Consume();
					vertices.Add(parser.ConsumeVector3());
					continue;
				}
				parser.UnknownLexemError();
			}
		}