CheckIFC fails

[MDHering]

We tried the bim2sim workflow with a simple .ifc-File that was created from scratch and drawn in bonsaibim. Loading this file in bim2sim gives an error in the check_ifc function:

[DEV-ERROR] - 2025-05-28 09:17:38,464 bim2sim.Playground.run_task: Task '<Task (CheckIfcBPS)>' failed!
Traceback (most recent call last):
File "C:\Users\DominikHering\Git\bim2sim\bim2sim\tasks\base.py", line 110, in run_task
result = task.run(**read_state)
File "C:\Users\DominikHering\Git\bim2sim\bim2sim\tasks\common\check_ifc.py", line 89, in run
self.error_summary_sub_inst = self.check_inst(
File "C:\Users\DominikHering\Git\bim2sim\bim2sim\tasks\common\check_ifc.py", line 228, in check_inst
error = validation_function(inst)
File "C:\Users\DominikHering\Git\bim2sim\bim2sim\tasks\common\check_ifc.py", line 786, in validate_sub_inst
self.apply_validation_function(self._check_segments(bound),
File "C:\Users\DominikHering\Git\bim2sim\bim2sim\tasks\common\check_ifc.py", line 1096, in _check_segments
return (s.is_a('IfcCompositeCurveSegment') for s in bound.ConnectionGeometry.SurfaceOnRelatingElement.
OuterBoundary.Segments)
TypeError: 'NoneType' object is not iterable

The function assumes an IFCCompositeCurveSegment, however the walls drawn in bonsaibim have no segments.

[MDHering]

ChatGPT gives a possible explanation:

BIM2SIM seems to expect IFCCompositeCurveSegment, but different CAD-tools yield different curve-types.

[MDHering]

While searching for the cause of this error, I found that you try to catch this error already in lines 778-780 of check_ifc.py:
if hasattr( bound.ConnectionGeometry.SurfaceOnRelatingElement.OuterBoundary, 'Segments'):

I compared my file with the ExampleHOM.ifc File. Interestingly, the bounds differ, but I cannot find the difference in the .ifc-files.

• Evaluating ExampleHOM.ifc, bound.ConnectionGeometry.SurfaceOnRelatingElement.OuterBoundary does not have an attribute called "Segments".
• Evaluating my local .ifc-file, bound.ConnectionGeometry.SurfaceOnRelatingElement.OuterBoundary does have an attribute called "Segments", which is None --> this leads to the error.

Do you know this error? Is it linked to my 3D-model, or should I try to catch this error in the check_ifc-function?

I created an example of this error with the corresponding .ifc file in a project fork:
https://github.com/MDHering/bim2sim/tree/issue807_checkifc_segmentedWalls