/// <summary>
/// This code demonstrates how to process face geometry
/// </summary>
/// <remarks>
/// This method is invoked only if the custom exporter was set to include faces.
/// </remarks>
public RenderNodeAction OnFaceBegin(FaceNode node)
{
   // Get the get the actual geometric face and all information about it
   // and its edges by using standard API for Face and Edge
   Face theFace = node.GetFace();
   double area = theFace.Area;
   if (theFace.HasRegions)
   {
      IList<Face> regionedFaces = theFace.GetRegions();
   }

   // We can either skip this face or proceed with rendering it depending on 
   // whether our export process can handle face geometry or not. If we choose 
   // to proceed, we get calls to export tessellated meshes for this face.
   if (true == ExportAFace(theFace))
   {
      return RenderNodeAction.Skip;
   }
   return RenderNodeAction.Proceed;
}

/// <summary>
/// This code marks the end of processing a face
/// </summary>
/// <remarks>
/// This method is invoked only if the custom exporter was set to include faces.
/// </remarks>
public void OnFaceEnd(FaceNode node)
{
   // Note: This method is invoked even for faces that were skipped.
}

/// <summary>
/// Assuming this would be the method that processes faces and exports them in our proprietary format.
/// </summary>
/// <remarks>
/// For example, we can decide that our format supports planar faces only, but no curved surfaces.
/// Or we can support basic surfaces only (planar, spherical, cylindrical), but not complex faces.
/// This is, naturally, depending on what a particular custom exporter is designed to output.
/// </remarks>
/// <returns>
/// Should return True if the face could be handled (exported), False otherwise.
/// </returns>
private bool ExportAFace(Face face)
{
   return false;  // in this case, 
}

' <summary>
' This code demonstrates how to process face geometry
' </summary>
' <remarks>
' This method is invoked only if the custom exporter was set to include faces.
' </remarks>
Public Function OnFaceBegin(node As FaceNode) As RenderNodeAction Implements IExportContext.OnFaceBegin
    ' Get the get the actual geometric face and all information about it
    ' and its edges by using standard API for Face and Edge
    Dim theFace As Face = node.GetFace()
    Dim area As Double = theFace.Area
    If theFace.HasRegions Then
        Dim regionedFaces As IList(Of Face) = theFace.GetRegions()
    End If

    ' We can either skip this face or proceed with rendering it depending on 
    ' whether our export process can handle face geometry or not. If we choose 
    ' to proceed, we get calls to export tessellated meshes for this face.
    If True = ExportAFace(theFace) Then
        Return RenderNodeAction.Skip
    End If
    Return RenderNodeAction.Proceed
End Function

' <summary>
' This code marks the end of processing a face
' </summary>
' <remarks>
' This method is invoked only if the custom exporter was set to include faces.
' </remarks>
Public Sub OnFaceEnd(node As FaceNode) Implements IExportContext.OnFaceEnd
    ' Note: This method is invoked even for faces that were skipped.
End Sub

' <summary>
' Assuming this would be the method that processes faces and exports them in our proprietary format.
' </summary>
' <remarks>
' For example, we can decide that our format supports planar faces only, but no curved surfaces.
' Or we can support basic surfaces only (planar, spherical, cylindrical), but not complex faces.
' This is, naturally, depending on what a particular custom exporter is designed to output.
' </remarks>
' <returns>
' Should return True if the face could be handled (exported), False otherwise.
' </returns>
Private Function ExportAFace(face As Face) As Boolean
    Return False
    ' in this case, 
End Function