When you try to export an IFC file from ARCHICAD 21 7000, Curtain Walls, Stairs or Railings may not go out when their geometry conversion is set to "Convert to single element".
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How to convert IFC files into GDL objects.
ARCHICAD supports the OpenBIM concept, using a common language available for software vendors. This common file format is called IFC (Industry Foundation Classes) developed by buildingSmart®.