Is there any method to get the IfcGuid of a Revit element?

[ongiao2301]

Hi, I am using the Revit 2019 and Revit BCF manager to work with issue, which is exported from an iModel that is converted using Revit bridge in iTwin. I find that in iTwin viewer, there is a IfcGuid that related to each element (for example this element's RevitId is 275624) in the properties panel as shown below:

I find that the last 8 digits of this IfcGuid (000434a8) is the hexadecimal format of 275624, which is the source element ID in Revit.

But I also find that the IfcGuid listed above is not the same as the IfcGuid that exported from Revit IFC, which is "3ijEQdd0510A518DuZdIwC" as shown below in the IFC viewer:

They are the same element of RevitId 275624. No matter how many times I export as IFC file, this IfcGuid remains the same as "3ijEQdd0510A518DuZdIwC".

The problem now is I don't know how to get this IfcGuild (3ijEQdd0510A518DuZdIwC). So when I do BCF Export, and import the BCF file into Revit using BCF manager without this IfcGuid, it can not locate the selected element/component:

I have research from the Internet and find a post (https://thebuildingcoder.typepad.com/blog/2009/02/uniqueid-dwf-and-ifc-guid.html), it says the Revit IfcGuid is calculated using some sort of encoding algorithm, but I can not generate the same one as "3ijEQdd0510A518DuZdIwC" in my example.

Do we have any solution to get that real Revit IfcGuid?

[yuryleb2]

Thanks for issue reporting! iTwin really should provide such IfcGUID properties in the same "compressed" IFC GUID format like Revit and IFC viewers. This will be fixed in a few weeks.

As a workaround, currently you may use the code and samples from the article you mentioned to convert such "extended GUID" values like "ecb4ea7-9c01-4100-a141-20de23991a24-000434a8" as Revit UniqueId into base64-encoded IFC GUID "3ijEQdd0510A518DuZdIwC":

• Cut EpisodeId GUID "ecb4ea7-9c01-4100-a141-20de23991a24"
• XOR last bytes with ElementId "000434a8"
• Encode into base64 format using getString64FromGuid() function from the code archive referenced in this article

[ongiao2301]

Thanks a lot for replying, I have worked on this and already can get the real Revit IFC_GUID based on the encoding algorithm in the article mentioned above.