Product(s):	OpenBuildings Designer
	Version(s):	CONNECT Edition
	Area:	Architectural Design
	Subarea:	Curtain Walls

Problem

When placing a Curtain Wall using From Shape as the Place By method with a "U" or "E" type shape representing door openings, I sometimes get a "Cannot create Curtain Wall with selected options" error. It's unclear why since many of the shapes I'm using are very similar to each other.  

Solution

The reason for this issue is fairly complex, but involves the way in which Curtain Walls store and use the base curve (shape in this case) in order to compute panels and mullions. As the number of the shape edges increases, such as with cutouts for doors, the position and orientation of these edges can decrease the odds of correctly computing those panels and mullions. Other factors may also come into play such as the Curtain Wall's panel size, length of the edges, etc.. This combination of factors explains why the issue appears to be somewhat random:

Bentley has filed Defect 990081 to help improve these edge algorithms and provide more consistent results.

As an interim (and potentially better) solution for cases where the curtain wall cannot be generated as-is, place a full rectangle to use for Curtain Wall placement instead of a complex shape with openings:

Then after the Curtain Wall is placed, adjust the mullions and panels to accommodate the openings:

As an extra benefit, if you were to place a parametric cell into the opening it should remain associated with the Curtain Wall, unlike when a complex shape with a "built-in" opening is used.