private void writeLines(XmlWriter xml, LineElement obj)
{
Joint i = obj.I;
Joint j = obj.J;
xml.WriteStartElement("Frame");
xml.WriteAttributeString("Frame", obj.Id.ToString());
xml.WriteAttributeString("JointI", i.Id.ToString());
xml.WriteAttributeString("JointJ", j.Id.ToString());
xml.WriteAttributeString("IsCurved", "No");
xml.WriteAttributeString("Length", obj.Length.ToString());
xml.WriteAttributeString("CentroidX", ((i.X + j.X) / 2.0F).ToString());
xml.WriteAttributeString("CentroidY", ((i.Y + j.Y) / 2.0F).ToString());
xml.WriteAttributeString("CentroidZ", ((i.Z + j.Z) / 2.0F).ToString());
xml.WriteEndElement();
}