[IFC Export] Problems with IFC (structural view) export

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Jesusbill
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Re: [IFC Export] Problems with IFC (structural view) export

Post by Jesusbill »

Hi @balrobs I have attached a modified version based on your latest upload.

The materials assigned look good for Surface Members but for Curve Members assigning a Material is not the way to do it. I think this is one of the first things to "digest" when dealing with IFC. We, as civil engineers, are used to think as if materials and profiles/sections are two separate things, but here it is not. So, you need to define a MaterialProfileSet, which contains at least one MaterialProfile, which in turn has Material and Profile. I know, a bit confusing, and there's more, like the IfcMaterialProfileSetUsage. In any case, I have made this modification in BlenderBIM, defined a Rectangular 0.3x0.3 profile and a MaterialProfileSet that is assigned to all Curve Members. I also added some of the connections missing (not all but just to show), like for example the PointConnection at the top of the ground-floor column, which has to be connected with the bottom of the first-floor column as well as with the plate (so I added two RelConnectsStructuralMembers for this case). Another one is the line between two walls and the slab where the connection to slab was missing. Also, you will need connections at the base like supports, I forgot to do those I can do it for the next update.

Regarding the issue with BIMcollab ZOOM I am not sure what is the problem, looks weird that you can see the curve members but not the surface members, perhaps I would have expected the opposite.
I see though that the representation sub-context is 'Analysis' and 'Axis'
#27=IFCGEOMETRICREPRESENTATIONSUBCONTEXT('Analysis','Axis',*,*,*,*,#24,$,.GRAPH_VIEW.,$);
while the correct would probably be 'Reference' and 'Model' like
#27=IFCGEOMETRICREPRESENTATIONSUBCONTEXT('Reference','Model',*,*,*,*,#24,$,.GRAPH_VIEW.,$);
Is that right @Moult ?
But in any case I do not think this is the reason for not showing in BIMcollab ZOOM. In BlenderBIM there is no problem visualizing everything.
Cheers

Edit: Forgot to mention that all changes in the IFC file are at the end, #599 removed and #604 - #622 added (#604 - #608 related to MaterialpProfile), if you have a diff tool for txt or sth could be useful.
Attachments
test_FreeCAD.ifc
(28.89 KiB) Downloaded 115 times
balrobs
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Re: [IFC Export] Problems with IFC (structural view) export

Post by balrobs »

Thanks @Jesusbill for your detailed description :)
Jesusbill wrote: Sun Jun 13, 2021 8:50 pm The materials assigned look good for Surface Members but for Curve Members assigning a Material is not the way to do it. I think this is one of the first things to "digest" when dealing with IFC. We, as civil engineers, are used to think as if materials and profiles/sections are two separate things, but here it is not. So, you need to define a MaterialProfileSet, which contains at least one MaterialProfile, which in turn has Material and Profile.
I'm aware of this and I was thinking to tackle the problem only after I have solved it for surfaces. Thank you for confirming me it's working for surfaces.
Jesusbill wrote: Sun Jun 13, 2021 8:50 pm I also added some of the connections missing (not all but just to show), like for example the PointConnection at the top of the ground-floor column, which has to be connected with the bottom of the first-floor column as well as with the plate (so I added two RelConnectsStructuralMembers for this case). Another one is the line between two walls and the slab where the connection to slab was missing. Also, you will need connections at the base like supports, I forgot to do those I can do it for the next update.
I will try to improve connection generation further but I think it will remain difficult for me to handle certain cases (i.e. column nodes that don't have a corresponding slab node ).
Jesusbill wrote: Sun Jun 13, 2021 8:50 pm Regarding the issue with BIMcollab ZOOM I am not sure what is the problem, looks weird that you can see the curve members but not the surface members, perhaps I would have expected the opposite.
I see though that the representation sub-context is 'Analysis' and 'Axis'
#27=IFCGEOMETRICREPRESENTATIONSUBCONTEXT('Analysis','Axis',*,*,*,*,#24,$,.GRAPH_VIEW.,$);
while the correct would probably be 'Reference' and 'Model' like
#27=IFCGEOMETRICREPRESENTATIONSUBCONTEXT('Reference','Model',*,*,*,*,#24,$,.GRAPH_VIEW.,$);
Here I will make this change and then try to import the file in BIMcollab ZOOM. Let's see what happens :twisted:
Cheers
balrobs
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Re: [IFC Export] Problems with IFC (structural view) export

Post by balrobs »

Hi @Bernd,
out of curiosity I imported my generated IFC file back into FreeCAD using the option "import_struct_IFC_objects=non_parametric_Arch_objects".
The result looks amazing (material colors were corrected by me. I'm not writing them to IFC so obviously they could not be imported :D )
Screenshot.png
Screenshot.png (91.54 KiB) Viewed 5038 times
BTW I noticed some minor issues:
  • surfaces thickness are all zero in the IFC attributes shown in the property panel
  • all structural properties of the imported materials are empty
Cheers
Jesusbill
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Joined: Wed Jun 10, 2020 11:53 pm

Re: [IFC Export] Problems with IFC (structural view) export

Post by Jesusbill »

balrobs wrote: Sun Jun 13, 2021 9:26 pm Here I will make this change and then try to import the file in BIMcollab ZOOM. Let's see what happens :twisted:
Sounds good, keep in mind that you should also replace all 'Analysis' with 'Reference' in IFCTOPOLOGYREPRESENTATION statements for members and connections, like for example #36 should be
#36=IFCTOPOLOGYREPRESENTATION(#27,'Reference','Edge',(#35));
balrobs
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Re: [IFC Export] Problems with IFC (structural view) export

Post by balrobs »

Jesusbill wrote: Sun Jun 13, 2021 10:01 pm
balrobs wrote: Sun Jun 13, 2021 9:26 pm Here I will make this change and then try to import the file in BIMcollab ZOOM. Let's see what happens :twisted:
Sounds good, keep in mind that you should also replace all 'Analysis' with 'Reference' in IFCTOPOLOGYREPRESENTATION statements for members and connections, like for example #36 should be
#36=IFCTOPOLOGYREPRESENTATION(#27,'Reference','Edge',(#35));
I made the mentioned changes but the result in BIMcollab ZOOM is still the same. Considering that BIMcollab ZOOM is the only viewer I tested not showing the StructuralSurfaces, for now I will assume that it's a ZOOM-problem and not make any changes to my code in this regard.
Thanks @Jesusbill for your support :)

PS: This is my changed file:
test_structure_with_stairs_SurfaceMember_01.ifc
(27.32 KiB) Downloaded 118 times
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bernd
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Re: [IFC Export] Problems with IFC (structural view) export

Post by bernd »

balrobs wrote: Sun Jun 13, 2021 4:49 pm ... Since in FreeCAD it's possible to export a hybrid model (both architecture and structure) I have to be careful not to create any duplicates with the materials ...
AFAIK The architectural modell (KoordiantionView) and the structural modell (StructuralAnalysisView) are not connected at all, ATM.

Thus in theory you could even use different materials for both. Which could makes sense. In our architectural modells all building site concrete is just one material, but in our structural model we do use different concrete materials due to different Young's-Modulus. Thus any object does have two materials, the material and the structural analysis material.

Neverless ... Since this connection would be cool to have it has been disscoused already. AFAIK on OSArch forum. @Mould @Jesusbill Does one of you guys is able to find the topic on osarch? I failed ...
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bernd
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Re: [IFC Export] Problems with IFC (structural view) export

Post by bernd »

balrobs wrote: Sun Jun 13, 2021 9:45 pm out of curiosity I imported my generated IFC file back into FreeCAD using the option "import_struct_IFC_objects=non_parametric_Arch_objects".
The result looks amazing (material colors were corrected by me. I'm not writing them to IFC so obviously they could not be imported :D )
Screenshot.png
BTW I noticed some minor issues:
  • surfaces thickness are all zero in the IFC attributes shown in the property panel
  • all structural properties of the imported materials are empty
When I coded the import Arch workbench did not even have materials :mrgreen: Since I have not touched it since than material import ist not supported AFAIR. Futhermore I did not implement any properties import like thickness etc AFAIR. Just the geometric representation is imported. Since the FEM mesh has geometric representation too it is imported as well if it exists in the structural ifc.
paullee
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Re: [IFC Export] Problems with IFC (structural view) export

Post by paullee »

bernd wrote: Mon Jun 14, 2021 12:02 pm Thus in theory you could even use different materials for both. Which could makes sense. In our architectural modells all building site concrete is just one material, but in our structural model we do use different concrete materials due to different Young's-Modulus. Thus any object does have two materials, the material and the structural analysis material.
This is a very good understanding of construction rather than just modelling a 3D representation of a building structure :D

This should be understood by all architectural student IMHO.
balrobs
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Re: [IFC Export] Problems with IFC (structural view) export

Post by balrobs »

bernd wrote: Mon Jun 14, 2021 12:02 pm Thus in theory you could even use different materials for both. Which could makes sense. In our architectural modells all building site concrete is just one material, but in our structural model we do use different concrete materials due to different Young's-Modulus. Thus any object does have two materials, the material and the structural analysis material.
So even if my approach at first sight looked strange to me because of a material duplication when exporting the FreeCAD model to a hybrid IFC maybe it could make sense to go this way.
So every material related to a structural object in FreeCAD will result in two same named IFCMATERIALS, one related to a structural element and the other to an architectural element. AFAIK the IFCMATERIAL for the architectural element holds only color informations for the moment while the IFCMATERIAL generated for the structural element could stores all mechanical properties!
screencast.gif
screencast.gif (932.48 KiB) Viewed 4892 times
Let's here what @Jesusbill and @Moult think about it!
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Moult
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Re: [IFC Export] Problems with IFC (structural view) export

Post by Moult »

Sorry for the late reply. Yes, Reference is more correct than Analysis.

IFC materials do not distinguish between architectural and structural. All IFC materials can store properties (e.g. youngs modulus) regardless of which discipline uses it. The same Ifc Material may be shared between disciplines (in an ideal, integrated world).

The relationship between the architectural model (i.e. body shapes) and structural model (i.e. stick model with analysis) is given by IfcRelAssignsToProduct.There are some discussions here: https://community.osarch.org/discussion ... nalysis/p1
I also blog about 3D rendering, architecture, software and other on thinkMoult.com. RSS / Atom feed available for your convenience.
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