Manage parameter "Pset_ColumnCommon.IsExternal"

[Anonymous]

Good morning all,

I am not able to find, in the Columns Families, the way to correctly manage the parameter "Exterior/Interior".

I need to manage this parameter in order to export a correct IFC file with a customized classification.

For example in Wall Families you can manage this parameter in "edit Type" under the parameter "Function".

Thanks in advance.

Best Regards

Simone

[elzohry2007]

why you need to export IFC ? For What ?

[Anonymous]

@elzohry2007  Thanks for the question.

I need the IFC for the BIM coordination, I need to check the Ifc entities and Pset_*.IsExternal of the different elements.

[JF.K · Accepted solution]

@Anonymous, My answer to your question assumes that you are exporting your IFC based on the IFC2x3 scheme.

IsExternal can be easily be exported to IFC from Revit if:

• you create a new project parameter in Revit written the same exact way “IsExternal” (without quotes)
• assign it to the category you want (my example is based on the Structural Columns category)
• the parameter in Revit has the same data type as the IFC scheme requires. (See documentation https://standards.buildingsmart.org/IFC/RELEASE/IFC2x3/FINAL/HTML/ and search for the IfcColumn entity).

In this case, the data type is an IfcBoolean which in Revit is a Yes/No type of parameter.

Make it an instance parameter so it overrides any previous value that Revit automatically exports.

Once the parameter is created just edit the value according to your needs. It will be exported to IFC as you want it (see pictures).

Also:

The Function type parameter that you are trying to find is a Revit built-in parameter only present in the Wall, Floors, Stairs, Ramps and Doors categories (respectively IfcWall, IfcSalb, IfcStair, IfcRamp and IfcDoor in the IFC schema), which means that you need to create this IsExternal parameter in order to export that info.

This method works for the followings revit categories (please let me know if I am missing something):

• Structural Columns
• Roofs
• Railings

I hope it helps 🙂

[mileta_pejovic]

I believe that this is all a workaround for a very simple question.

We all know that a user can add new type/instance parameters and map them during the export process into respective Psets.
However, IFC 2x3 and now IFC 4 and very soon IFC 4.3 have a set of standardized Psets (Common) for each Entity, but unfortunately I couldn't find a place or forum explicitly describing how all these "common property sets" are being mapped and exported, since there is a lot of categories (entities) without these Psets defined within authoring tool, but after export - these common Psets are somehow exported. Users don't have a clear understanding how exactly these Psets are generated and from which existing properties - these are mapped from. 

Does anyone have an info where to find explanation form this common property sets mapping process? 

[JF.K]

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@mileta_pejovic wrote:

We all know that a user can add new type/instance parameters and map them during the export process into respective Psets.

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 @mileta_pejovic  I have to disagree with you on this since there are a lot of questions online about how to map parameters into Psets.

About the method:

Yes it is indeed a workaround because, as you mentioned,  it seems that there is no guideline about how revit built-in parameters and IFC entity properties correlate and are exported to a specific Pset_<entity>Common.

Nevertheless, throughout the time and mostly based on research, trial and error I put together an Excel list with Revit categories, its correspondent Ifc Entities and (for now 12) Ifc properties per entity. One can then check if the built-in parameter is automatically mapped, if there is the need to create a parameter and if that added parameter maps automatically to the common property set or need to be manually mapped to a custom one. If it helps, I could make this list public and editable so it can be expanded according to necessity.

I am not sure if something like this exists though.  

[mileta_pejovic]

Thanks for a fast response.
I would really like to have more mapping or any helpful documents related to IFC export available, not just from Autodesk, but from all authoring software as well.
If you could share some of mentioned mapping documents, I believe that great number of users would appreciate it to share it.
Currently I'm mostly interested in Common Psets (Pset_IfcEntityCommon), and in Base Quantities (Qto_IfcEntityBaseQuantities) and calculation and mapping process, since currently users don't have a clear understanding how (and from which existing properties) - common properties and base quantities are exported and calculated from. 

[JF.K]

@mileta_pejovicI am struggling to find some free time to do this kind of work but better later than never.

If you access the GitHub public repository https://github.com/xpt5/shareRevit/blob/main/revitCat_IfcEntities.ods you will find an downloadable Libre office document. This doc holds a very basic mapping scheme of Revit parameters to IFC entities. It is mainly focused on architecture parameters as it doesn't contain anything focused on MEP or Structural engineering. As with all databases it might contain errors which should be corrected and it certainly should grow with more information.

If you or anyone else would like to contribute to this table please PM me so I can add you to the repository. It is the first time that I am using GitHub as a kind of "dropbox" though.

Let me know what you think.