private void ExportCollada_Scene(XmlWriter xml) {
xml.WriteStartElement("visual_scene");
xml.WriteAttributeString("id", "Scene");
xml.WriteAttributeString("name", "Scene");
ExportCollada_Node(xml, RootNode);
xml.WriteStartElement("evaluate_scene");
xml.WriteStartElement("render");
xml.WriteElementString("layer", "Visible");
xml.WriteEndElement(); // render
xml.WriteEndElement(); // evaluate_scene
xml.WriteEndElement(); // visual_scene
}