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DWG/SAT Solids conversion to IFC

I use a DWG to IFC export functionality that seems to break geometry. Thanks @Moult (*)
I would like to investigate these principles a little more.

1.What happens when SAT definitions are converted? Does IFC support solids, how?
2.What influence does ‘block definitions’ have on the quality of IFC ecxport

Possible Bim tools

AutoCAD Architecture
(other coming from ODA initiatives)


First thing i did is explode all the blocks that came in from STEP. Export both file sets as DWG and their exports to IFC. The effectiveness of blockdef. is 7x filesize

When i open them in BIMviewer i notice these things

  1. Round segmentation can only be 8
  2. The name of objects disappairs. Seem like the data is not attached to subelement but ‘in group’(?)
  3. These parts look good but is see some parts not being good translated (?)
    Something goes wrong with some elements with the IFC conversion.
  4. In DWG these look just fine. Nothing wrong here.
  5. Strange behaviour

Btw. I am running this on software called Autodesk AutoCAD Architecture … which has VERSION !2020! people

Using BricsCAD BIM
Import STEP / Export IFC4 is fine.
Blender import gives strange results. All very unpredictable (?)

In blender other parts missing now.
IFC4 this time through DWG.

Good morning @Hans_Lammerts - I looked at your file and the reason the import is failing in Blender is because the IfcAdvancedBrep geometry representation is not fully supported in IfcOpenShell yet. IfcOpenShell is not alone in this issue, unfortunately - as you can see many viewers have issues with this type of geometry. If I import your IFC2X3 file (which doesn’t have IfcAdvancedBrep), then it works perfectly :slight_smile: - however this issue should be solved. The good news is that there is already a known bug for this. Do you mind sharing your file with @aothms ? If so, he is the IfcOpenShell expert who can help fix this!

I have attached XBim’s attempt to load your IFC4 model with IfcAdvancedBrep - it also seems to have issues. I did manage to load it in BIMCollab, though, so that’s a good sign!

Latest version of v0.6.0 IfcOpenShell imports the file correctly now

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Looking good!!

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