Curtain Wall Panel Geometry with Basic Wall Panel

A quick geometrical question on retrieving geometry from a basic wall being used as a panel in a curtain wall:

Question: I am struggling to retrieve the geometry data from a curtain wall that contains a Basic wall in one of the curtain wall panels.

My example curtain wall has two panels. With one of the panels, a basic wall type is associated. I need to get the geometry data (i.e., the faces) for the entire curtain wall. When I reach the second panel in my code, the SymbolGeometry contains zero objects, so my code cannot retrieve any geometry for it. As a result, it is not able to handle the basic wall to retrieve its geometry face data.

Answer: Here is a code snippet that handles this situation correctly.

The main point is this: we need to find the panel-wall which corresponds to the curtain wall and then retrieve its geometry in a second step:

  // First, find solid geometry from panel ids.
  // Note that the panel which contains a basic
  // wall has NO geometry!

  Wall wall = doc.GetElement( curtainWallId ) as Wall;
  var grid = wall.CurtainGrid;

  foreach( ElementId id in grid.GetPanelIds() )
  {
    Element e = doc.GetElement( id );
    solids.AddRange( GetElementSolids( e ) );
  }

  // Secondly, find corresponding panel wall
  // for the curtain wall and retrieve the actual
  // geometry from that.

  FilteredElementCollector cwPanels
    = new FilteredElementCollector( doc )
      .OfCategory( BuiltInCategory.OST_CurtainWallPanels )
      .OfClass( typeof( Wall ) );

  foreach( Wall cwp in cwPanels )
  {
    // Find panel wall belonging to this curtain wall
    // and retrieve its geometry

    if( cwp.StackedWallOwnerId == curtainWallId )
    {
      solids.AddRange( GetElementSolids( cwp ) );
    }
  }

I added this code in the method GetCurtainWallPanelGeometry to The Building Coder samples release 2018.0.134.6 ↗ module CmdCurtainWallGeom.cs L35-L66 ↗.