import IFC, mulitple layer wall

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bernd
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import IFC, mulitple layer wall

Post by bernd »

Attached a multiple layer wall from ArchiCAD. FreeCAD does import the materials of the two layers, but the wall does not have any of them. We should handle the multiple layer information somehow.

Code: Select all

#189= IFCMATERIAL('D\S\dmmung, Aussen');
#206= IFCMATERIALLAYER(#189,0.24,.U.);
#208= IFCMATERIAL('MW, Backstein');
#223= IFCMATERIALLAYER(#208,0.15,.U.);
Two options from my point of view.

- import as multiple layer wall (AFAIK FreeCAD supports this kind of walls allready) parametric arch shape
- import any layer as separate wall or shape (I will need this option for sure !)

What do you guys think of this?
Attachments
wall_multiple_layer_ArchiCAD.ifc
(101.94 KiB) Downloaded 209 times
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yorik
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Re: import IFC, mulitple layer wall

Post by yorik »

the difficulty is that the wall object comes as one complete object. The layers are apparently only defined by the IfcMaterialLayer. Translating this into the actual object would mean complex boolean operations, that will certainly do the wrong thing in many cases (we have not enough information for how and where to "cut" into the wall). I think there is in IFC a way to represent multiplayer walls as different geometrical objects, but I can't find it back...

We could invent a new type of arch material, a kind of "compound" material, that could host several others with additional properties to define where each sub-material is used. I could see many immediate uses for this, such as multi-layered walls, multi-material windows (or any other kind of "compound" object), concrete objects with a coat of painting, etc. We could define a way to relate these materials to subelements (faces, solids, etc) of objects. But in this specific case, that won't work.

Maybe what we need first s a kind of "layering" tool that would split a wall (or any other object) into layers. A mille-feuille tool :)
Joyas
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Re: import IFC, mulitple layer wall

Post by Joyas »

I think that a wall could have assigned a "layer structure" object.

If the wall has a layer structure assigned, It ignores the width and material values.

A layer structure could have these values:
  • Layer A - material - thickness.
  • Layer B - material - thickness.
  • Layer C - material - thickness.
  • ...
  • Center (for example, if a wall has an structure of 2-16-4 mm, the user could prefer to have the center in the middle of the 8 mm layer (10 mm) instead of 11 mm).
This is close to the Autodesk Revit workflow.
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bernd
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Re: import IFC, mulitple layer wall

Post by bernd »

Thanks for your answers. Yorik your informations helps very much! BTW Nemetschek Allplan has same problems we have! By the time being the architect I'm working with could export the multilayer walls without insulation. It works but it is a rather bad workaround to just leave out the insulation if you export BIM models.
yorik wrote: I think there is in IFC a way to represent multiplayer walls as different geometrical objects, but I can't find it back...
I'll have a look too.
yorik wrote:Maybe what we need first s a kind of "layering" tool that would split a wall (or any other object) into layers.
Ahh yes, than we'd be flexible.
yorik wrote:A mille-feuille tool :)
YEAH, Cremeschnitte, Mhhh
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bernd
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Re: import IFC, mulitple layer wall

Post by bernd »

Tested how Allplan itself export an multilayer wall, and if it reimports. It does reimport his own exported multilayer wall. Allplan uses the same entities to define multilayered walls like ArchiCAD uses. The wall itself like ArchiCAD is one solid.

Code: Select all

#117= IFCMATERIAL('D\X2\00E4\X0\mmstoff hart');
#120= IFCMATERIALLAYER(#117,0.24,$);
#141= IFCMATERIAL('Beton');
#142= IFCMATERIALLAYER(#141,0.15,$);
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wall_multiple_layer_Allplan.ifc
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yorik
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Re: import IFC, mulitple layer wall

Post by yorik »

yes, this is a broad question, objects that are represented as one "simple" geometry, but is in reality made of many layers or components. IFC seems to have several mechanisms for that
Bezu Menez
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Re: import IFC, mulitple layer wall

Post by Bezu Menez »

Hi there,

I don't know if you're aware about this, but IFCOpenShell got the ability to slice walls and return several TopoDS_Shape for one wall with different layers :
http://blog.ifcopenshell.org/2015/10/se ... erial.html

Just by activating a settings. But beware, this feature got a real impact on importing performance...
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bernd
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Re: import IFC, mulitple layer wall

Post by bernd »

Wow, that would be great. Big question is if we can access this by pyhton ?

Ahh the ifc I posted earlier had windows. Attached two really simple multiple layer walls without windows to test with. Would be cool if someone could post this wall as Revit ifc export!

cheers bernd
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ArchiCAD--mulitlayer_Wall--no_Window.ifc
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Allplan--mulitlayer_Wall--no_Window.ifc
(8.76 KiB) Downloaded 175 times
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yorik
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Re: import IFC, mulitple layer wall

Post by yorik »

Bezu Menez wrote: I don't know if you're aware about this, but IFCOpenShell got the ability to slice walls and return several TopoDS_Shape for one wall with different layers
Excellent!! I had forgotten that!
bernd wrote:Wow, that would be great. Big question is if we can access this by pyhton ?
Apparently yes, you need to set the APPLY_LAYERSETS to True ( https://github.com/aothms/IfcOpenShell/ ... dfe385e02c ), check in importIFC.py, there are many other ifcopenshell properties set that way (BREP_DATA, etc)

But this is not in master apparently, it's in a separate ifcopenshell branch
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sgrogan
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Re: import IFC, mulitple layer wall

Post by sgrogan »

Looks like it was merged into master.
https://github.com/aothms/IfcOpenShell/ ... 6525c77b13
EDIT: Never mind wrong commit.
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