Which (any) MVD for IFC 4.3?

[Mats Knutsson]

Hi,
I understand the possibility to open/save ifc4x3 is just a pigs makeup. Howevere when I choose 4.3 as format I can't chose an MVD. Anyone knows what to do here or just leave it at custom?

/Mats

Operating system used: Windows

[Marcus Scott]

Hi Mats, 

You can leave the MVD as custom. The MVD's just mean that some requirements/options are force-checked/unchecked in the IFC translator.

In the future we will provide deeper support for IFC4x3 in which we will likely add the MVD's outlined by Building Smart here: https://ifc43-docs.standards.buildingsmart.org/IFC/RELEASE/IFC4x3/HTML/content/introduction.htm 

• Reference View
• Alignment Based View
• Design Transfer View

Cheers,

Marcus

[Mats Knutsson]

Thanks Marcus! Is the save to 4x3 option basically a change in the FILE_SCHEMA part of the header?

I saved out an IFC4 and an IFC 4x3 and copied the row "FILE_SCHEMA(('IFC4X3_ADD2'))" from 4x3 model and pasted it into the 4 model. According to ChatGPT the file is a valid 4x3...

This means 4x3 could be made from a 4 just by changing the FILE_SCHEMA in Notepad or similar. Is this correct?

/Mats

[Marcus Scott]

Hi Mats,

We wouldn't suggest modifying the FILE_SCHEMA part as the IFC4x3 schema is different in many places, even if ~98% backward-compatible with IFC4.

It may be that some IFC viewers are happy with it, but a lot of the entities in the file may require extra data or cannot have as many as an IFC4 file. I suspect it may likely lead to invalid IFC files if the FILE_SCHEMA is modified in such a way. 

Cheers,

Marcus

[Ben D]

What is the process for hotlinking an IFC4x3 model?  I get an error message when I try.  This is a huge problem for anyone working on large collaborative projects where the the BEP specifies IFC4x3 as the standard for file exchange.

 

[Laszlo Nagy]

Are you using Archicad 29? It does support IFC4x3.

 

By the way, just a personal note: I do not think it is a good idea to require IFC4x3 in the BEP. It is still very new as a format and many applications still do not support it or support it only partially. 

[Ben D]

I'm using AC28.  I agree requiring IFC4x3 is a problem.  Unfortunately, we are often not in a position to make that choice on large projects, and this is the case here.  If I can't get an IFC4x3 into Archicad 28, then I'll be constantly having to ask other collaborators to make special exports just for me, which leads to all kinds of problems.

[Laszlo Nagy]

According to the following video, it is possible to use Bonsai BIM to downgrade your IFC 4X3 files to IFC 4. This way, at least you will not have to rely on someone else to provide you with the IFC with the correct version:

https://www.youtube.com/watch?v=XYeasHbyw-U&t=211s

I have not tested it, so I don't know if this conversion causes any data loss.

Obviously, the best solution would be to be able to get IFC 4 from the other application directly without any need for conversion.

[iltonmpacheco]

Indeed it´s not a good thing. The IFC4 has nearly 780 entities where IFC4x3 has over 1000 entities...nearly 25% more entities. Just to mention one difference. 

So, there is a real chance of losing information. 

Cheers,

ilton