private static bool IsMultiMaterial(Kn5Node node) {
return node.NodeClass == Kn5NodeClass.Base &&
node.Children.Any() &&
node.Children.All(x => x.NodeClass == Kn5NodeClass.Mesh) &&
Enumerable.Range(0, node.Children.Count).All(x => node.Children.Any(y => y.Name == node.Name + "_SUB" + x));
}