Difference between expectations and reality of IFC Standards

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Hello,

I am a French architect and I am working for an organism that wish to create a IFC national reference model based on the “average” practices of French architects. It’s a model of 80 dwellings.

It is intended to serve as a basis for a set of “realistic” BIM experience and experimentation feedback.
Many actors have worked on this project, and we expect a lot from the conclusions of this project to show the interest of BIM.

The modelling part was made on Revit and Tekla.

Our problem is related to the Export IFC Revit part. And especially around the Walls and IfcWall or IfcWallStandardCase export.

Although the software is IFC certified, objects as simple as walls are not exported as we would like to into IFCWallStandardCase, to be able to show the pset with the width and composition of the layers.
We want to keep these layers and their widths in order to guarantee the interoperability with the thermal software.

Autodesk’s answer is simple: we are certified, we follow the Building Smart scheme, your walls are exported to IfcWall and not IfcWallstandardCase because their geometry is complex.

However, the walls are very simple, and we spent hours doing tests (removing windows, floors, railings, everything barely…). Some simple walls are exported to IfcWall and others more complex ones to IfcWallstandardCase with no apparent reason.the building have 5 similar storeys. On some storey, walls are IfcWall, on others IfcWallStandardCase, no matter the wall joints, width, floor assembly.

We have no more explanation and no similar experience on the web.

How can we say that BIM ensures perfect interoperability when we stop at a major problem at 20% of what we really wanted to do? We have 10 years of experience in this field and we though our model was almost perfect.

Do you have similar experiences?

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I have similar experiences in Australia. Our office has had better luck with ArchiCAD.

More recently, I am focusing on more flexible modeling approaches where modeling tools and IFC data are not coupled together, such as in FreeCAD, where any geometry can be any IFC type and you can assign it manually. Another example is using Blender + IfcOpenShell scripts, where again, you have complete control over your IFC data and you have a proper 3D modeling environment. I suspect work done on GeometryGym and Rhino is similar. However, these are rather beta developments, so not many architects use them and they are not so user friendly and workflows are perhaps not quite so polished, however they can produce much more detailed IFCs :slight_smile:

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Hi Antoine,
If you are exporting using the IFC2x3 Coordination View 2.0, then yes, the use of IfcWall and IfcWallStandardCase are both valid. And yes, the idea was to allow applications the ability to export complex wall structures, like those with multiple components and where each component may have a different base and top height offset due to the way an end user may have created the model.

This MVD’s primary purpose is to certify the ability of an application to exchange IFC information. Secondarily, it may be used for design coordination purposes, as well as quantity takeoff (with the QTO add-on). The purported workflow was to enable simple the referencing and compositing of architectural, structural, and MEP domain models for design coordination/clash detection. If your exchange purposes are different than this, or have differing specific requirements, then it sounds like you and your colleagues need to define a different MVD and use the open source Revit IFC support tools to create exactly the support you want. In addition, you may have to develop BIM authoring “best practices” for end users to make sure the elements are modeled consistently to get the desired results.

In reality, this is the way IFC works. The schema is large and complex and has lots of flexibility in the way information can be encoded. The use of IFC depends on an MVD to properly capture information exchange requirements and determine their best IFC-coded expression, unique to many, if not all, workflows. So one MVD may not satisfy all workflows, while IFC has the potential to serve all of them.

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As for the specifics of your Revit experience, as Chair of the ISG, I will stand by Autodesk’s efforts past and present to support IFC robustly. All products are different and have internal user interfaces and experiences that make the use of IFC different in each case. IFC2x3 CV2.0 certification was a HUGE step forward compared to the previous status quo. IFC4 efforts and certification are another step forward. Autodesk, along with their peers at Trimble, Bentley, the various Nemetschek brands, and many others continue to make progress in IFC support. At this time, the use of IFC is not as “hands-free” as the use of HTML and the Web. Someday I do hope we get there, or very close. But it will require dedication and effort on the end users’ part to work with these companies and bSI to build the adequate knowledge to execute. In the meantime, I encourage you to continue engaging with Autodesk and buildingSMART to see if there is a way to best meet your needs.

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Hello everyone,

@Moult
Thank for your answer and your time
What’s bother me is that communication seems to be unclear with autodesk. Their specialists says they respect the IFC Schemes and are certified. Perhaps they are focusing on upcoming Ifc MWD and doesn’t bring support on 2x3 coordination view 2.0.

For the use on Free IFC modeling tools, interesting but structurally unfeasible. our company is too big to imagine a switch from autodesk to any other solution. (too much investments, new processes, interchangeability with clients & staff formation…). But your use of blender + scripts is really interesting. We need to learn how to get around the problem with smart solutions that might not be the norm.

@jwouellette
Thanks for sharing your experience.
I know i may seem too demanding. you’re right about the progress they made.

what saddens us is that such a simple feature does not work. we’re talking about straight, constant-thickness concrete walls. the IfcWall doesn’t have the layer pset, contrary to IfcWallStandardCase.
The thermal engineer says its thermal software cannot use them and he has do do data re-entry, that isn’t suppose to happen. Maybe issue is coming from the export-options limitations form the thermal software.

About making our own MWD, or own Revit export settings, we did think about it, but Revit has hardcoded families including walls, and have very little options, for not power-users at least. And this experimentation is for most average size architectural firm.

i’ll keep explore forums and others MWD schemes to check on it.
Thanks for you support toward the implementation support group, i wish we could create something that could make our jobs more simple and the way we exchange more robust.

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Best thing to do is to continue to engage directly with the Autodesk customer support. There are some Autodesk people active inside the buildingSMART community, but we can’t really provide technical support to proprietary products here.