AC 14 IFC merge - problems

[Anonymous]

Hi! I have exported an IFC file from ArchiCAD, opened it in a room database and updated yhe IFCSpace's in the model. Now I want to merge the updated data back to ArchiCAD through IFC. The problem is that when I do a file special->merge I get double zones in my AC model. The IFCSpace GUIDS are identical... Any ideas how to merge to the same layer?

[Anonymous]

I presume that you are norwegian and work with dRofus.
"Dette dokumentet vil sette fokus på arbeidsflyt mellom ArchiCAd og dRofus. Vi ønsker å demonstrere, med utgangspunktet i et konkret prosjekt hvordan disse to applikasjonene kan spille sammen gjennom IFC."
This is the introduction to a 11 pages document I have recieved from Statsbygg. It is called "ArchiCAD - dRofus Cookbook". I guess that you have access to the same document, and that the answer should be in this document.

[Anonymous]

Yes, working with dRofus. I created that document with Graphisoft, and it worked fluently in ArchiCAD 13, but can't get it right in AC14. Everything gets duplicated when doing a merge, also walls, stories etc.

[Laszlo Nagy]

The way IFC is merged has changed in IFC.
In AC14 the original element is not deleted and updated with the element in the IFC file having the same IFC GUID.
This is because of the reference model concept based on which AC14 is developed.
So now the IFC should be imported into a separate layer and the original architectural model updated while using the imported IFC data as trace reference.

I was told by the IFC guys at GS that the reason it was done this way was because most architects/consultants they talked to wanted to work this way: keep their own model clean and use IFC data only for reference.

[Erika Epstein]

laszlonagy wrote:
The way IFC is merged has changed in IFC.
In AC14 the original element is not deleted and updated with the element in the IFC file having the same IFC GUID.
This is because of the reference model concept based on which AC14 is developed.
So now the IFC should be imported into a separate layer and the original architectural model updated while using the imported IFC data as trace reference.

I was told by the IFC guys at GS that the reason it was done this way was because most architects/consultants they talked to wanted to work this way: keep their own model clean and use IFC data only for reference.

This posting has continued to shock me. Graphisoft has been a leader incorporating the BIM process in Archicad. Tthis decision, if true, is anathema to archicad being BIM capable.

You cannot stop users from making the choice to use the program poorly. But you can make it an option and not restrict those who rely on its BIM capabilities.

[Laszlo Nagy]

Actually, I agree with you, from a user standpoint, definitely.
I guess what we would like to see is that true and smart conversion between applications occurs through IFC at every level and with all element types. Just like Revit MEP families are converted into ArchiCAD MEP objects.

On the other hand this may be an impossible task, there are just so many different application with so many different data formats so true conversion in all cases is a near impossible task. Maybe this is why some decided that using the consultants' data as a reference model only is a better way to go at this stage of the game. Actually, I would also be doing it the reference model way because that is what can work under today's circumstances.

I am curious how this plays out in the future.

[Erika Epstein]

That is the point of using IFC; it allows users of many programs to work together. Data is automatically updated. Translators can refine which data is updated.

Relying on manual labor to transfer data increases the potential for error, the opposite of a BIM process.

[Link]

laszlonagy wrote:
I was told by the IFC guys at GS that the reason it was done this way was because most architects/consultants they talked to wanted to work this way: keep their own model clean and use IFC data only for reference.

Therein lies the problem. IME this is way off the mark and almost a cop-out.

Of course we want to incorporate other consultants data. Why, for example, should we model the structural information when the engineer has already done it?

Once this notion is realized to fall short, and GS makes IFC completely round-trip, then we'll be doing interoperable and collaborative BIM.

My 2 cents, but it's hard to tell 'em!

Cheers,
Link.

[owen]

We should be able to choose which of the two methods we want to use when doing an IFC Merge.

Currently we are using the structural model as a reference only. We modelled the structure from the start to produce drawings. During this time the structural engineer was feeding us the design via sketches or 2D drawings. Now that the design is settling down they are developing a detailed structural model in Revit.

Now many might say this is not how BIM should really be done and that the engineer should have been modelling from the start (i agree somewhat) .. but the reason behind that lies with lawyers and people running practices who have not yet grasped what the process really means. But i digress ..

Now although the engineer now has a far more detailed structural model than we do, we cannot simply merge in their model and delete our own - we have to reference it, track changes and manually update ours to suit.

Why? Contract drawings. The reason we modelled the structure in the first place was to prepare (among other things) detailed concrete setout drawings including extensive tower core penetrations ... all of which have to be dimensioned. What happens when you delete your structural model and replace with the structural engineers? The GUID's change and the dimensions no longer know what they were dimensioning ... meaning you would need to re-dimension EVERYTHING related to the structural model.

One day we may be in the situation where dimensioned drawings are not required of the architect and everyone is working off the BIM. At that time I think directly using an external model via IFC Merge is viable, but until then I do not think you can rely on a merged IFC model to dimension - too many things can go wrong resulting in extensive rework. The reference model workflow Graphisoft are talking about is the right way to go for some projects, but the merged model might suit others (If i could i would 😉 ).

Let us pick which suits the requirements of our project - don't limit us to a certain way of doing things, especially when the alternative was already supported in earlier versions

cheers,

os

[Gerald D Lock]

owen wrote:
Let us pick which suits the requirements of our project - don't limit us to a certain way of doing things, especially when the alternative was already supported in earlier versions

I'm about to begin leading documentation of a project in AC14. Our office has just upgraded their hardware to run AC14, allowing us to jump from AC12 to 14 (we skipped v.13 while waiting to see how it panned out with the new BIM server technology)
This resulted in an inability to run AC12, due to graphics card incompatibility (!) but that's another story...

We will be working with an engineering practice who are proposing sharing an IFC model, which I had assumed (!) would be fine, as I've had experience working with IFC in v.12

I'm a little unsure which way to take this, as I'd anticipated being able to merge the engineer's model (rather than just reference it) then update as it develops.
The practice principal has been told we won't need to build our own structural model - with associated time savings - but it looks like GS is forcing us to do so now...?

Why have you painted us all into a corner Graphisoft???!!
Annoyed & confused.