QUESTIONS ABOUT IFC_​PREDEFINEDTYPE GDL PARAMETERS ?

[Nader Belal]

Hi there,

As many of you may know IFC_predefinedtype is an ArchiCAD predefined integer parameter to communicate the library part with the ArchiCAD’s IFC add-on.

Does any of you have an insight for the values’ definition of IFC_predefinedtype in your API documentation? Because I have checked the GDL references in PDF and online and there is nothing?

[Péter Baksa]

Hi,

These are defined by the ICF standard. For example ifcCovering has a PredefinedType attribute, whose type is IfcCoveringTypeEnum. I am not sure where the exact numerical values are defined, maybe more help is available in an IFC forum.

Here is a document about how the built-in IFC 4 type mapping handles this parameter.

Péter Baksa
Library Platform, Software Engineer
GRAPHISOFT SE

[Nader Belal]

Hi,

Péter, the GDL Reference Guide for ArchiCAD 22 & ArchiCAD 23, do have a section for predefined IFC_type integer values and it’s not complete. Anyway, the IFCpredefined type does not.

The funny parts are that for IFCtype the section have been renovated, while there is nothing mention in any guide, any manual for IFCpredefined types, and there are library parts scripts that defines the value for both.

So my questions are:
1. Do Graphisoft intends to continue the use of these integer parameters or not ?
2. Where can I consult the integer values for IFCpredefined types ?

[Péter Baksa]

I got some clarification from the developers:

An IFC translator has a “Type Mapping” preset, where a classification-based or element-based rule set can be defined. In the template shipped with AC, the classification system “ARCHICAD Classification” is set up to work with the IFC translators, always defining an IFC type and Predefined Type. Using these translators, IFC_predefinedtype has no effect.

When an IFC translator is set up to use element mapping, the mapping is not customizable by the user, and depends on the AC version. For AC23 this document shows two MEP element types where IFC_predefinedtype is handled by the translator. On the AC side, these parameters are handled by the MEP add-on.

So IFC_predefinedtype is retired, it exists in GDL elements only for compatibility.

Péter Baksa
Library Platform, Software Engineer
GRAPHISOFT SE

[Nader Belal]

Thank you

[Author]

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