Invalid IFC 4 export result from a wall with layers of the same material in Revit

[FranziWM]

Hi,

see attached PDF file.

Invalid IFC4 export result of walls consisting of layers.pdf

[AngelVelezSosa]

I believe this is a duplicate issue that we're already addressing but I will verify.

[t-vasyi]

https://jira.autodesk.com/browse/REVIT-203986

[JOuellette-Autodesk]

@FranziWM and @AngelVelezSosa I think the only thing that is incorrect is that the namings are not consistent between the IfcMaterialConstituent and IfcShapeAspect of the same material layers of the wall. It was not the intent to say every component has a unique name, only materially and dimensionally different components have unique names.

Thus, if you have an interior fire rated wall with 2 layers of gypsum board on both sides and the gypsum board is the same thickness and specifications for each layer, there is ONLY ONE name, with multiple entries (e.g. "15mm gypsum board") If you had 2 different types of gypsum board, then these would need to be called out accordingly and have different names for each type (e.g. "15mm gypsum board type x" and "10mm gypsum board"), with whatever combination (e.g. 2 layers of the 15mm and 2 of the 10mm.). But each layer would not have a distinct name, you'd have two of one and two of the other, per example.

[JOuellette-Autodesk]

@FranziWM What versions of Revit and the IFC Add-in are you using?

[guenter1holzeder]

@JOuellette-Autodesk
In my opinion the mapping between IfcMaterialConstituent and IfcShapeAspect ist a design weakness in IFC. No matter if you are using layers with the same material (name), each layer has its OWN geometry. Thus each constituent material need to have an unique name which can be mapped to UNIQUE geometries.

Or is there another way to find a "bridge" between material and geometry in this case?

[FranziWM]

@JOuellette-Autodesk
I use Revit version 23.1.10.4 and IFC4 Reference View.

[FranziWM]

Attached you can find a Revit and an IFC file. It containes just one example wall.

ORCA-AVA Beispieldatei.zip

[FranziWM]

An interesting point: In IFC2x3 the problem doesn't occur.

[guenter1holzeder]

In the given sample above there are unique names to the IfcMaterialConstituents (numbers in brackets) but not for their according geometries (IfcShapeAspects). So this is the missing mapping of both.

This cannot happen with IFC 2x3 because the mentioned IFC classes were introduced with IFC 4.