IfcAdvancedBRep and IfcSweptSolid in Representations, in IFC export of Columns

In my Building Model(Revit), few columns are exported as SweptSolid and few as IfcAdvancedBRep in the Representations. Based on what factors the objects are exported as SweptSolid or IfcAdvancedBRep. Is there any option to set these export settings for Representations.

This is actually a question that only Autodesk can answer properly. You can file the questions as an issue in their IFC-Exporter repository. In general, every swept solid can also be expressed as advanced BREP, but not vice versa. For example a sweep followed by a boolean subtraction can (in most cases) no longer be directly represented as a swept solid.

I can’t tell from the top of my head what the agreement is on that and where it is specified. But from my gut feeling every geometry that can be expressed as swept solid should be exported as such. However, the agreement could also be that export as swept solid must only happen when the author has explicitly constructed an object this way, for example by drawing a footprint and specifying height. Only in that case we have a uniquely defined profile and sweeping path.

To what extent an application follows such agreement, if it exists, one can only tell from the implementation or from formal verification - or to a limited extent by testing edge cases.

Yeah, this is a problem with Revit, brought to my attention by @jonm. In IFC4 exports, they seem to be too keen on unnecessarily representing simple shapes as IfcAdvancedBRep when an IfcSweptSolid should do. This is definitely counterintuitive - the modeling tools in Revit are primarily swept solids, with only a few types which should fall back into an advanced BRep.

Here’s the bugreport back in July: Option to prevent export of IfcAdvancedBrep · Issue #480 · Autodesk/revit-ifc · GitHub