Exporting block and stud walls - how should it export?

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Moult
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Exporting block and stud walls - how should it export?

Postby Moult » Mon Jan 14, 2019 12:09 pm

The current behaviour is that a block wall, when exported to an IFC, is exported as whatever you choose it to be, but it loses its individual block geometry in the process.

I am unsure what is the more "correct" approach and what has the most "benefit" for various usecases. The questions are:

1. Should it be an IfcWallStandardCase? It certainly can be simplified as such, and this is what Revit does. This is not, however, a true representation. This limits the benefit of the IFC for purposes such as lighting simulation, and block setouts. It may lose valuable QS information in terms of number of blocks.
2. How do you export it as an IfcWallElementedCase?

Similarly, has anybody built a stud wall yet which exports as a correctly defined IfcWallElementedCase?
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yorik
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Re: Exporting block and stud walls - how should it export?

Postby yorik » Mon Jan 14, 2019 4:09 pm

The blocks system is pretty new, I haven't looked yet as how to export it correctly to IFC. I actually don't think IFC has proper support for that... One easy "workaroud" is to right-click the wall in the tree view, edit its IFC properties, and there check the option to export it as Brep (or menu utils -> Toggle brep flag). The will make the IFC exporter discard the extrusion information of the wall, and export its geometry "as is" (as an IfcFacetedBrep geometry). This should export the blocks.
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Re: Exporting block and stud walls - how should it export?

Postby Moult » Mon Jan 14, 2019 8:43 pm

I see, the workaround of forcing a BREP is great! However, it is not necessarily semantically correct, as I believe it should be a IfcWallElementedCase made up of something, uh, else that I'm also not quite sure. I'll go ask on the BSi forums and see what they believe.
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Re: Exporting block and stud walls - how should it export?

Postby yorik » Mon Jan 14, 2019 9:32 pm

If we have a clear view of how such an object should be handled (stud walls too), it should not be hard to adapt the IFC exporter to export it the proper way...
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Re: Exporting block and stud walls - how should it export?

Postby Moult » Mon Jan 14, 2019 9:38 pm

I've just asked on the BSi forums on how to properly export a block wall. Even after reading the IfcWallElementedCase page, I am not sure.

However, I believe the IfcWallElementedCase page does describe how to deal with stud walls quite well. Do you mind reading through it? Can you put together a quick test in FreeCAD demonstrating the export of a stud wall?
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Re: Exporting block and stud walls - how should it export?

Postby yorik » Tue Jan 15, 2019 1:19 pm

Can you give the link to your buildingsmart post?
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Re: Exporting block and stud walls - how should it export?

Postby yorik » Tue Jan 15, 2019 1:58 pm

Link to IfcWallElementedCase http://www.buildingsmart-tech.org/ifc/I ... edcase.htm

Indeed this is pretty much what we want...
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Re: Exporting block and stud walls - how should it export?

Postby yorik » Tue Jan 15, 2019 2:16 pm

So the way i see it:

1) We need a solid, reliable way to identify in FreeCAD walls that are such elemented wall. One thing is easy, the IFC role/type of an object can already be set as such. Maybe that's the only rule we need, actually.

2) When exporting to IFC, if an object is set to IfcElementedWall, then we should look at a) its explicit components (either additions, or it is made from a compound) b) implicit components (blocks, or, in the future, if we extend the wall tool to be able to make its own studs)

3) We need to decide how to export the components that have no IFC type explicitly defined, but we can export them as IfcBuildingElementPart for now.
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Re: Exporting block and stud walls - how should it export?

Postby Moult » Tue Jan 15, 2019 8:24 pm

This is the BSI post:

https://forums.buildingsmart.org/t/how- ... k-wall/872

No replies yet, it is a pretty small community currently. Maybe there is no answer.
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