Autodesk Revit Argument Exception, The curves do not form a closed contiguous loop

Question

I have this code for a Revit plugin made in C#:

    namespace CreateFloors
    {
        [Transaction(TransactionMode.Manual)]
        public class Command : IExternalCommand
        {
        public Result Execute(
          ExternalCommandData commandData,
          ref string message,
          ElementSet elements)
        {
            UIApplication uiapp = commandData.Application;
            UIDocument uidoc = uiapp.ActiveUIDocument;
            Application app = uiapp.Application;
            Document doc = uidoc.Document;

            FilteredElementCollector levels
              = new FilteredElementCollector(doc)
                .OfClass(typeof(Level));

            FloorType floorType
              = new FilteredElementCollector(doc)
                .OfClass(typeof(FloorType))
                .First<Element>(
                  e => e.Name.Equals("Generic - 12\""))
                  as FloorType;

            Element profileElement
              = new FilteredElementCollector(doc)
                .OfClass(typeof(FamilyInstance))
                .OfCategory(BuiltInCategory.OST_GenericModel)
                .First<Element>(
                  e => e.Name.Equals("WP1"));

            CurveArray slabCurves = new CurveArray();

            GeometryElement geo = profileElement.get_Geometry(new Options());

            foreach (GeometryInstance inst in geo)
            {
                foreach (GeometryObject obj in inst.SymbolGeometry)
                {
                    if (obj is Curve)
                    {
                        slabCurves.Append(obj as Curve);
                    }
                }
            }

            XYZ normal = XYZ.BasisZ;

            Transaction trans = new Transaction(doc);
            trans.Start("Create Floors");

            foreach (Level level in levels)
            {
                Floor newFloor = doc.Create.NewFloor(slabCurves, floorType, level, false, normal);

                newFloor.get_Parameter(BuiltInParameter.FLOOR_HEIGHTABOVELEVEL_PARAM).Set(0);
            }

            trans.Commit();

            return Result.Succeeded;
        }
    }
}

When I trace this code from a Revit project containing a Generic Model, the next exception is thrown:

Autodesk.Revit.Exceptions.ArgumentException: 'The curves do not form a closed contiguous loop.

I have an structure that is continous. How can I fix this?

Answer 1

Your curves are probably not sorted into the correct contiguous order.

You could implement some graphical debugging display showing the curves one by one as model lines and adding a number next to each one to see what order you actually have.

Here is a discussion by The Building Coder on Sorting Face Loop Edges.

You may be able to use the ExporterIfcUtils to sort and validate them.