PR: Export contains parameters not defined in export mapping table

[kohout-lukas]

Problem Description

Using Revit Export user defined property set option results in invalid IFC. Attached TXT file contains two property sets, both containing one parameter. Parameter Area is exported even though it is not definod. My understanding is that it exports Revit internal parameter HOST_AREA_COMPUTED. Exporter somehow subtracts preifxes in parameter definition and exports it anyway.

See attached files:

1. In RVT there is no user visible parameter named Area, only through RevitLookup.
2. In TXT file there is no mapping for parameter Area, only CZ_M2_Area
3. In IFC file there are both property sets and both parameters. IFC_EXPORT_bug.zip

Revit Version

2024.0.x

IFC for Revit Addon Version

24.x.x

Windows Version

11 22H2

[denizmaral]

You mapped CZ_M2_Area to Area in property set CZ_M2. It is about your setting, isn't it?

[kohout-lukas]

Yes, I mapped it like you say. But the element in screenshot does not have CZ_M2_Area, only Area, which is not being mapped and still gets exported.

So I do not think it is about the mapping table. On further investigation, if I change the IFC class in Revit to anything, like IfcColumn, and update the mapping table respectivly, it works as expected. So I guess it might have something to do with higher level IFC classes like IfcElement defined in the mapping table.

[denizmaral]

Your goal is then something like that:

PropertySet:    CZ_M2   I   IfcElement
CZ_M2_Area  Area
PropertySet:    CZ_M3   I   IfcElement
CZ_M3_Volume    Volume

[kohout-lukas]

Well, no. TXT file in the post is correct, that is how I want it. In the images below, there are snapshots of element in IFCand RVT. In RVTthere is no parameter CZ_M2_Areaa and yet, it gets exported as seen in IFCsnapshot.

[AngelVelezSosa]

Can you re-summarize the problem (just for area?) You want a property set for all IfcElement called CZ_M2, and it should have a property called Area that is an area calculation that comes from a Revit parameter called CZ_M2_Area? And it doesn't work, but if you change IfcElement to IfcColumn, it does?

[denizmaral]

Now I got it. I could not open the file because I don't have Revit 2025 on my computer. You don't see Area parameter in Revit UI but there is an API-Parameter unter parameters that is being mapped to your parameter. Even though you don't assign the user defined parameter to that family, it still creates a property set and take the Area value.

[kohout-lukas]

Yes, exactly. Thanks.

[AngelVelezSosa]

That seems by design, unless I am missing something.

[kohout-lukas]

OK, if it is by desing, can you describe the reasoning behind it? How can parameter you do not define to be exported still be exported?

[AngelVelezSosa]

You are looking for a parameter called "Area". There is a parameter called "Area" (at least in English), it just isn't visible in the parameters dialog. If you called it anything else, it wouldn't show up. Unless I am missing the issue.