Custom Pset from Revit to IFC4

Users IFC
1

Hi all,
I’m having any problems about “data type” value to write in .txt file of custom Psets to export from Revit to IFC format.
I need to export in IFC4 the “Flow” Revit parameter expressed in u.m. m3/s.
In IfcMeasureResource schema visible at IFC4-Add2 Documentation the Revit parameter “Flow” correspond to “Volumetric Flow Rate” measure.

If I write “Real” as data type suggested from “IfcVolumetricFlowRateMeasure” page of IFC4-Add2 Documentation the IFC value results that you can read is expressed in ft3/s.

If I write “VolumetricFlowRate” as data type the value is expressed in m3/s as the IFC4 documentation tells.

I have the same problem exporting “Color Temperature” parameter of Ligthing Fixtures expressed in Kelvin.
Using “ThermodynamicTemperature” as data type the value is expressed in °C in the IFC model
while I have the correct value expressed in Kelvin using “ColorTemperature” as Data Type.

So, there is criteria to associate Data Type to a Measure?
What are the supported data types of IFC4?
There are any list of supported data type from Revit Parameter to IFC I can use?

Thanks a lot,
Antonio

2

I think this is a more general issue where IFC allows you to define units, but also in the spec it sometimes refers to specific units (which seem to be metric). This creates confusion among implementations where the Real data type inherits from the IFC unit definition, but the VolumetricFlowRate takes on the IFC spec recommendation. To add further confusion, in the IFC files produced by Revit, it may also store units as an IfcConversionBasedUnit, so you should definitely check exactly what it is storing before jumping to conclusions.

I think there is a list of supported data types here:

# Data types supported: Area, Boolean, ClassificationReference, ColorTemperature, Count, Currency, 
#	ElectricalCurrent, ElectricalEfficacy, ElectricalVoltage, Force, Frequency, Identifier, 
#	Illuminance, Integer, Label, Length, Logical, LuminousFlux, LuminousIntensity, 
#	NormalisedRatio, PlaneAngle, PositiveLength, PositivePlaneAngle, PositiveRatio, Power, 
#	Pressure, Ratio, Real, Text, ThermalTransmittance, ThermodynamicTemperature, Volume, 
#	VolumetricFlowRate

I suspect that any stdlib data type (real, integer, number) will all inherit from the IFC unit assignment. Everything else might be special and on a case-by-case basis.

3

Thank you for your answer,
Where I can find an official IFC documentation about “Data Types supported” mentioned by you?

Thanks so much,
Antonio

4

I assume you are using the open source IFC exporter for Revit. If so, this file comes with the open source exporter:

1 Like
5

Thank you Moult