buildingSMART Forums

Creating federated IFC models

I am looking for ways to distribute a series of IFC models federated together into a “single file”.

The most straightforward way of doing this, I think, is to put all the IFC files into a single .ifczip. I did not see any official documentation that disallowed this, but viewers don’t seem to support multiple IFC files stored this way (tested with XBim and BIMCollab).

Another approach is by using references and anchors in the latest STEP standard, but again, no viewer supports this. This seems like the most “correct” approach, assuming that IFC-SPF is used.

Another approach is to use a utility (does someone know of one?) that will merge IFC files together into one file (preferably cleverly detecting same GlobalIds and merging that way).

How are people solving this issue?

BricsCAD DWG
import import import, export

dwg? what does it have in common with bim or ifc?

there’s support for multiple ifc files in bim vision and declining tekla bimsight (now taken over by trimble connect, where you can have some free functionality), but why do you want to send them over? the task is to collect the federated whole in an aproppriate bim management software (tekla bimsight, navisworks or, better still, smc)…

Are you familiar with the work of the Open Design Alliance, ODA? Dwg is perfectly capable to work with ifc. So you can import them and make you federated model. Move, erase and do some things. Apply the export to ifc function. Simple as any other file format.

that’s interesting :slight_smile:

  1. dwg is a proprietary autodesk file format. do they participate in the oda development?
  2. is there an ifc import and/or export buildingsmart certification for dwg format (any application)?

@gester, when you say there is support for multiple IFC files, do you mean it supports an .ifczip with multiple IFC files inside, or simply that it can load multiple files? I am looking for the former - the latter is quite common with IFC viewers but doesn’t quite answer my question.

@Hans_Lammerts that’s fascinating! I was not aware that DWG had a mapping to the IFC schema! I looked at the reverse-engineered ODA DWG Specification but did not find any reference to IFC. Can you point me at a document which describes the mapping?

Although I am interested in DWG, unfortunately, contractually we are not allowed to supply a DWG as it is considered a proprietary format and client requirements specify an open-data format - so for the moment I suspect I am limited to those listed on the BuildingSmart formats page. What about DXF? I wonder if DXF could become an IFC format :slight_smile:

Guys, have you been living under a stone ?? :stuck_out_tongue:

https://www.opendesign.com/blog/2019/september/buildingsmart-and-oda-announce-strategic-partnership

Here is me importing a Revit export last year.

“Although I am interested in DWG, unfortunately, contractually we are not allowed to supply a DWG as it is considered a proprietary format and client requirements specify an open-data format -”

That is a argrument that is told more often. I think it is kind of nonsens and think that the AEC software industry and Buildingsmart should acknowledge the key role the DWG format has been playing for years and still doen when it comes to 3D modelling en 2D CAD. DWG is the defacto standard allthough it is not “open” (enough (for some)).

“What about DXF?”
I have been wondering the same question. Why is DXF not “BIM” , not “Open”, neither both?

… Now, … lets just go cack to the subject of federating 3D models…

@Hans_Lammerts nice video, but that video demonstrates Revit --(IFC)–> BricsCAD. The function of importing and exporting IFCs is well known.

My question was about whether DWG had an IFC schema mapping as you claim? Specifically, I am not talking simply about carrying geometry - I have no doubts that DWG can store the same geometry that IFC can store, and conversion is already possible using tools like FreeCAD and Blender, and no doubt many other tools. Instead, I am talking about the more complex data relationships that IFC has, like Qtos, Psets, Space boundaries, spatial hierarchies, etc. Have you got an example of this?

I bet it can. My job and interest really are is geometry related mostly.
BricsCAD does a very good job at that part.
I googled this

I didn’t see DWG on that page you linked, but it would be awesome if you could export a simple DWG with IFC data captured in it so we can inspect it. I am not aware of an ASCII DWG format, so perhaps to investigate it properly it would have to be an ASCII DXF.

Back to my original question of federating IFC models, your technique of “import import import export” is the same as doing “import ifc import ifc import ifc export ifc” in any program, so it still doesn’t quite answer my question :slight_smile:

Maybe there isn’t yet a solution?

Sorry for misunderstanding being not clear about the mapping. I wasn’t thinking about the IFC mapping and more advanced features. My demands on getting geometry over FIRST for federating and combining models. I personally have on three main principles the software needs to do. In order of importance

  1. good quality geometry. Meshing and round things
  2. ‘same objects’ need to come over as ‘same objects’ (parts, families, blocks, whatever you call them…) The name is not so important. The number of generated proxy is
  3. If the object has a color assigned than that color needs to be maintain.

I got BlenderBIM going :slight_smile: and i imported the same structure as ifc. So this was made from a step file which was exported as ifc using AutoCAD architecture. As you can see every (inventor) part is turned into unique proxy objects. So the imported does not seem to recognize ‘same objects’ (2.). The size of the ifc is 950 kB, the size of the blender file is 6 MB. This clearly indicates the ‘same object structure’ is lost. Can you fix this in your software? I tried FreeCAD, gives me the same results. BricsCAD however, will give me very good results on 1. and 2.

Why is this important? This is only a very small design, but for bigger projects and federated models rule nr 2. is absolutely necessary. Otherwise filesize will blow up in your face and you end up with everything being unique elements.


Cellar toren set_AutoCAD arch import.ifc (949.3 KB)

now i have a general question: can meshes carry all relevant ifc data?

hmm, i still can’t get your point in supporting the zipped ifcs. do you want to export your whole information model to another environment?

i’m importing my design consultants’ ifcs from revit and dds-cad for a few years now, but i use those models as a modelling reference only.

the real environment to federate ifcs is the bim management in the construction phase. do you guys manage the construction execution?

@Hans_Lammerts - thanks for providing your IFC file! I had a look inside and indeed all your objects are IfcBuildingElementProxy, so they are imported correctly by Blender and FreeCAD, but perhaps they are exported incorrectly from your authoring tool. Perhaps we can work together to fix this?

As for object re-use, BlenderBIM does support this (after all, we use it on large commercial projects!), but only recently (a bit of history: I focused first on BlenderBIM’s export, and only recently turned my attention to import). So if you download the latest version of BlenderBIM (I will release one today - so make sure it has today’s date), it will re-use meshes.

It was great for you to provide your file, as it did help make me notice a bug with re-used mesh locations (Revit and Blender don’t use a particular feature of mesh reuse, so I didn’t run into it before). I have now fixed this bug, and the fix will be available in today’s release :slight_smile: Thank you very much for bringing this to my attention!

Please see my import of your file, and I have highlighted in orange how one object has been re-used multiple times:

@gester in short, no, meshes cannot carry all relevant IFC data. In IFC, data comes first, and meshes are assigned to data. It is possible to have data without any assigned geometry / mesh.

I merely questioned whether or not an .ifczip should limit itself to one IFC file per zip.

BlenderBIM has been tested on a few stages during the design and construction process. However, it has not been as of yet extensively used during construction stage. In workflows here, federation occurs during early design phases.

@Hans_Lammerts a few more things I noticed in the import, some of the plate geometry seems a little broken as shown in the picture below. I have tested this with other viewers, such as XBim and BIMCollab, and all three have broken geometry. This makes me suspect that your authoring tool (BricsCAD?) might have a few issues with its IFC geometry export. If you’d like, I can take a closer look to try and debug it for you :slight_smile:

The ifc you are inspection is a step file from inventor that is loaded in dwg (autocad) and exported as ifc.

Just for the sake getting geometry over…

Autocad architecture has the most horrible ifc exporter. (Where IFC once started from… duuh) I can understand flaws. Need to test if BricsCAD does this one better.

The other route is expprting DWG directly from Inventor and exporting that to IFC. Next up to inspect

Did you try SimpleBIM???
http://www.datacubist.com/
Some years ago I needed to merge 4x IFCs into one, keeping the IFC Structure up from IfcProject down to IfcBuildingElements. Back then it did a pretty good job. As far as I know, you can also modify the IFC Structure.

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Hey @agron ! I haven’t tried SimpleBIM, but I have heard good things about it.

It seems as though the only approach so far is file merging, not actual federation (i.e. linking) as I initially hoped. Hopefully this can be solved in the future. Until then, I consider this issue closed.