In this lab, we shall create a simple loft form using the new conceptual design API as shown in the image below -

To begin with, we have to be in Family creation environment in Revit and specifically, the active document should be the conceptual massing template file.

using System;
using System.Collections.Generic;
using System.Text;

using Autodesk.Revit;
using Autodesk.Revit.Geometry;
using Autodesk.Revit.Elements;
using Autodesk.Revit.Enums;

namespace Labs
{
  /// <summary>
  /// Create a loft form using reference points and curve by points.
  /// </summary>
  public class Lab7_1_CreateForm : IExternalCommand
  {
    public IExternalCommand.Result Execute(
      ExternalCommandData commandData,
      ref string message,
      ElementSet elements)
    {
      Application app = commandData.Application;
      Document doc = app.ActiveDocument;

      if (doc.IsFamilyDocument && doc.OwnerFamily.FamilyCategory.Name.Equals("Mass"))
      {
        . . .

        return IExternalCommand.Result.Succeeded;
      }
      else
      {
        System.Windows.Forms.MessageBox.Show("Please load a conceptual massing family document!");
        return IExternalCommand.Result.Failed;
      }
    }
  }
}

Imports System
Imports System.Collections.Generic
Imports Autodesk.Revit
Imports Autodesk.Revit.Geometry
Imports Autodesk.Revit.Elements
Imports Autodesk.Revit.Enums
Imports XYZ2 = Autodesk.Revit.Geometry.XYZ

Namespace Labs

#Region "Lab7_1_CreateForm"
    Public Class Lab7_1_CreateForm
        Implements IExternalCommand
        Public Function Execute( _
            ByVal commandData As ExternalCommandData, _
            ByRef message As String, _
            ByVal elements As ElementSet) _
        As IExternalCommand.Result _
        Implements IExternalCommand.Execute

            Dim app As Application = commandData.Application
            Dim doc As Document = app.ActiveDocument

            If (doc.IsFamilyDocument And doc.OwnerFamily.FamilyCategory.Name.Equals("Mass")) Then

                . . .

                Return IExternalCommand.Result.Succeeded
            Else
                System.Windows.Forms.MessageBox.Show("Please load a conceptual massing family document!")
                Return IExternalCommand.Result.Failed
            End If
        End Function
    End Class
#End Region

Next, we shall create an instance of ReferenceArrayArray object which will contain all the reference arrays of profiles. The form will eventually be comprised of these profiles. To begin with creating the first profile, we shall create an instance of the ReferenceArray which will be appended to the ReferenceArrayArray collection. Using the Autodesk.Revit.Geometry.XYZ class, we specify three points which will be used to create respective three reference points. These reference points will be appended in a ReferencePointArray collection and using this collection, we shall create a CurveByPoints object. This reference of the geometry curve property of this curve will be appended to the ReferenceArray which eventually will be appended to the ReferenceArrayArray collection.

Add the following code to create curve by points and reference arrays:

  // Create profiles array
  ReferenceArrayArray ref_ar_ar = new ReferenceArrayArray();

  // Create first profile
  ReferenceArray ref_ar = new ReferenceArray();

  int y = 100;
  int x = 50;
  XYZ ptA = new XYZ(-x, y, 0);
  XYZ ptB = new XYZ(x, y, 0);
  XYZ ptC = new XYZ(0, y + 10, 10);
  CurveByPoints curve = FormUtils.MakeCurve(app, ptA, ptB, ptC);
  ref_ar.Append(curve.GeometryCurve.Reference);
  ref_ar_ar.Append(ref_ar);

    ' Create profiles array
    Dim ref_ar_ar As New ReferenceArrayArray()

    ' Create first profile
    Dim ref_ar As New ReferenceArray()

    Dim y As Integer = 100
    Dim x As Integer = 50
    Dim ptA As New XYZ2(-x, y, 0)
    Dim ptB As New XYZ2(x, y, 0)
    Dim ptC As New XYZ2(0, y + 10, 10)
    Dim curve As CurveByPoints = FormUtils.MakeCurve(app, ptA, ptB, ptC)
    ref_ar.Append(curve.GeometryCurve.Reference)
    ref_ar_ar.Append(ref_ar)

Curve By Points object (created in the utility module in the piece of code above) can be created out of new instances of reference points each corresponding to the XYZ points and storing these reference points in the ReferencePointArray. This collection can be used an an argument in the NewCurveByPoints creation method available on the FamilyCreate method on the active document.

  /// <summary>
  /// This class is utility class for form creation.
  /// </summary>
  public class FormUtils
  {
    /// <summary>
    /// Create a CurveByPoints element by three points
    /// </summary>
    /// <param name="app">Revit application</param>
    /// <param name="ptA">point a</param>
    /// <param name="ptB">point b</param>
    /// <param name="ptC">point c</param>
    /// <returns>CurveByPoints instance</returns>
    public static CurveByPoints MakeCurve(Application app, XYZ ptA, XYZ ptB, XYZ ptC)
    {
      Document doc = app.ActiveDocument;
      ReferencePoint refPtA = doc.FamilyCreate.NewReferencePoint(ptA);
      ReferencePoint refPtB = doc.FamilyCreate.NewReferencePoint(ptB);
      ReferencePoint refPtC = doc.FamilyCreate.NewReferencePoint(ptC);

      ReferencePointArray refPtsArray = new ReferencePointArray();
      refPtsArray.Append(refPtA);
      refPtsArray.Append(refPtB);
      refPtsArray.Append(refPtC);

      CurveByPoints curve = doc.FamilyCreate.NewCurveByPoints(refPtsArray);
      return curve;
    }
  }

    ''' <summary>
    ''' This class is utility class for form creation.
    ''' </summary>
    Public Class FormUtils

        ' Create curve by points element by three points
        Public Shared Function MakeCurve( _
            ByVal app As Application, _
            ByVal ptA As XYZ2, _
            ByVal ptB As XYZ2, _
            ByVal ptC As XYZ2) _
        As CurveByPoints
            Dim doc As Document = app.ActiveDocument
            Dim refPtA As ReferencePoint = doc.FamilyCreate.NewReferencePoint(ptA)
            Dim refPtB As ReferencePoint = doc.FamilyCreate.NewReferencePoint(ptB)
            Dim refPtC As ReferencePoint = doc.FamilyCreate.NewReferencePoint(ptC)

            Dim refPtsArray As ReferencePointArray = New ReferencePointArray()
            refPtsArray.Append(refPtA)
            refPtsArray.Append(refPtB)
            refPtsArray.Append(refPtC)

            Dim curve As CurveByPoints = doc.FamilyCreate.NewCurveByPoints(refPtsArray)

            Return curve
        End Function

    End Class

Repeat the steps for profile creation for three other profiles

  // Create second profile
  ref_ar = new ReferenceArray();

  y = 40;
  ptA = new XYZ(-x, y, 5);
  ptB = new XYZ(x, y, 5);
  ptC = new XYZ(0, y, 25);
  curve = FormUtils.MakeCurve(app, ptA, ptB, ptC);
  ref_ar.Append(curve.GeometryCurve.Reference);
  ref_ar_ar.Append(ref_ar);

  // Create third profile
  ref_ar = new ReferenceArray();

  y = -20;
  ptA = new XYZ(-x, y, 0);
  ptB = new XYZ(x, y, 0);
  ptC = new XYZ(0, y, 15);
  curve = FormUtils.MakeCurve(app, ptA, ptB, ptC);
  ref_ar.Append(curve.GeometryCurve.Reference);
  ref_ar_ar.Append(ref_ar);

  // Create fourth profile
  ref_ar = new ReferenceArray();

  y = -60;
  ptA = new XYZ(-x, y, 0);
  ptB = new XYZ(x, y, 0);
  ptC = new XYZ(0, y + 10, 20);
  curve = FormUtils.MakeCurve(app, ptA, ptB, ptC);
  ref_ar.Append(curve.GeometryCurve.Reference);
  ref_ar_ar.Append(ref_ar);

    ' Create second profile
    ref_ar = New ReferenceArray()

    y = 40
    ptA = New XYZ2(-x, y, 5)
    ptB = New XYZ2(x, y, 5)
    ptC = New XYZ2(0, y, 25)
    curve = FormUtils.MakeCurve(app, ptA, ptB, ptC)
    ref_ar.Append(curve.GeometryCurve.Reference)
    ref_ar_ar.Append(ref_ar)

    ' Create third profile
    ref_ar = New ReferenceArray()

    y = -20
    ptA = New XYZ2(-x, y, 0)
    ptB = New XYZ2(x, y, 0)
    ptC = New XYZ2(0, y, 15)
    curve = FormUtils.MakeCurve(app, ptA, ptB, ptC)
    ref_ar.Append(curve.GeometryCurve.Reference)
    ref_ar_ar.Append(ref_ar)

    ' Create fourth profile
    ref_ar = New ReferenceArray()

    y = -60
    ptA = New XYZ2(-x, y, 0)
    ptB = New XYZ2(x, y, 0)
    ptC = New XYZ2(0, y + 10, 20)
    curve = FormUtils.MakeCurve(app, ptA, ptB, ptC)
    ref_ar.Append(curve.GeometryCurve.Reference)
    ref_ar_ar.Append(ref_ar)

Finally, we can use this ReferenceArrayArray to create the new loft form. This form can be created using the FamilyCreate.NewLoftForm method available on the document object.

  Form form = doc.FamilyCreate.NewLoftForm(true, ref_ar_ar);
  return IExternalCommand.Result.Succeeded;

    Dim form As Form = doc.FamilyCreate.NewLoftForm(True, ref_ar_ar)
    Return IExternalCommand.Result.Succeeded

Compile the code, start Revit, open the new conceptual mass family template and run the external command.