IFC export workaround and question

[bernd]

it is more difficault than I expected to find where is the best place to fix the problem ...

For BuildingParts with IfcType set to "Undefined" the ifctype for IFC export is set to IfcBuildingStorey https://github.com/FreeCAD/FreeCAD/blob ... 1696-L1697

but when creating the product the Attributes are still created with the FreeCAD object with IfcType Undefined this results in different kwargs for a real building storey and for the tweaked building storey.

Code: Select all

 real IfcBuildingStorey
16:03:40  {'GlobalId': '3zYEt1WErDlxVgLzyyHODP', 'OwnerHistory': #5=IfcOwnerHistory(#3,#4,$,.ADDED.,1677164620,#3,#4,1677164620), 'Name': 'BuildingPart', 'Description': '', 'ObjectPlacement': None, 'Representation': None, 'CompositionType': 'COMPLEX', 'LongName': 'BuildingPart'}

BuildingPart set to Undefined and ifctype set to IfcBuildingStorey on export
16:02:54  {'GlobalId': '3zYEt1WErDlxVgLzyyHODP', 'OwnerHistory': #5=IfcOwnerHistory(#3,#4,$,.ADDED.,1677164574,#3,#4,1677164574), 'Name': 'BuildingPart', 'Description': '', 'ObjectPlacement': None, 'Representation': None, 'PredefinedType': 'COMPLEX'}

A building storey does not have a PredefinedType but a CompositionType thus IfcOpenShell does break creating the Product ... https://iaiweb.lbl.gov/Resources/IFC_Re ... storey.htm

the different kwargs happen because the ifctype was changed but in method exportIfcAttributes() https://github.com/FreeCAD/FreeCAD/blob ... C.py#L1753 does not use the changed type but the original type instead which creates wrong attributes for the changed type.

[bernd]

generally it is a bad idea to introduce the ifctype and set it different to the FreeCAD object but later on creating the parameter kwargs for ifcopenshell use again the original IfcType from the FreeCAD object but pass the ifctype which was changed to ifcopenshell. This could be fixed in various ways. I will just make a small fix and let this decide this to others.

BTW: IMHO we should totally get rid of undefined. Ifc has something for undefined IfcBuildingElementProxy or IfcBuildingElementPart.

cheers bernd

[bernd]

git commit 2e5c518cec308ee and git commit 65938f9bc2ae41

[thomas-neemann]

...

Switch to Ifc2x3 ....

so it runs for me without stopping, but it is incomplete

Bildschirmfoto_2023-02-23_17-14-44.png (16.51 KiB) Viewed 2918 times

[bernd]

Have you used BREP pref? if you are interested in improving the export, you should make a simple FreeCAD file with a missing object open a new topic, post your export preferences. This topic was mainly because the export was broken.

[thomas-neemann]

...

here are my settings

Bildschirmfoto_2023-02-24_08-22-02.png (88.47 KiB) Viewed 2804 times

[yorik]

Interesting, I didn't know about BuildingElementPart... That seems totally right to use it in this context, much better than undefined.

[bernd]

Interesting, I didn't know about BuildingElementPart... That seems totally right to use it in this context, much better than undefined.

lately ArchiCAD and VectorWorks do use it to export multilayered objects into ifc, each layer gets its own product and its own representation ... much better than multilayered material and IfcComplexAttributes and only one Representation for all layer as it has been for years ...

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[bernd]

BTW: native importer somehow does not support them ... Will make an issue at github ...

screen1.png (137.47 KiB) Viewed 2718 times

[bernd]

damn, just realised in ArchiCAD the layer is IfcBuldingPart and the container is IfcWall ... Mhh than the IfcBuildingPart would be wrong for the container. I will have a closer look at this and come back.

cheer bernd