PR: Setting Classes / Predefined types in export

[MisunMartin]

Problem Description

In my Revit IFC exporter settings most of the elements are set as IfcBuildingElementProxy.NOTDEFINED

Unfortunatelly for some categories (specifically found out these) this is not working as expected as it always exports these as:

• Ceiling = IfcCovering
• Curtain Wall = IfcCurtainWall
• Sloped Glazing = IfcRoof
• Structural Column = IfcColumn
• Structural Framing = IfcBeam

Then I tried to force correct export I have tested also with parameters:

• Export to IFC As
• IFC Predefined Type
• Export Type to IFC As
• Type IFC Predefined Type

... that resulted into even bigger chaos:

1. Ceiling cannot be exported into anything else except for IfcCovering!
2. If Instance PredefinedType USERDEFINED is being used Type Predefined Type has to be set to "NOTDEFINED"! → If instance parameter is used and type parameter is empty - then Exporter should automatically put Type Predefined Type to "NOTDEFINED"!!! (https://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/concepts/Object_Attributes/Object_Predefined_Type/content.html)
3. Curtain Wall instance is exported as IfcWall with a type of IfcCurtainWall - complete nonsense 😆
4. Sloped Glazing instance is exported as IfcRoof with a type of IfcCurtainWall - complete nonsense 😆
5. Curtain Wall does not allow to edit export type - always resulting in IfcCurtainWall
6. Sloped Glazing does not allow to edit export type - always resulting in IfcCurtainWall

As an example Mullions and Panels in Curtain Walls are working nearly as intended just 2 general adjustments needed for Exporter:

1. If Instance is USERDEFINED, then Type shall be NOTDEFINED
2. If Type Predefined Type is defined then Instance should have empty values, as it is reading information from its Type.

PS: Using IFC4x3 schema.

Attached a table with Revit export /Expected results and Real Autodesk Export results for further info.

Revit Version

2026.0.x

IFC for Revit Addon Version

26.1.0

Windows Version

11 24H2