I'm having some trouble with the interface between Grasshopper (GH) and RFEM 6 and was hoping someone here might have experience with this.
I’m trying to export a closed Brep (volume) from Grasshopper into RFEM for a solid analysis. Ideally, I would like to send the Brep directly as an RFEM solid, but as far as I can tell, this isn’t supported.
So I’ve been testing a workaround: GH Brep → Deconstruct Brep → export each face as a GH Surface → use those surfaces as boundary faces for an RFEM Solid → export to RFEM.
This seemed to work for simple geometries, but as soon as I try more complex shapes—curved surfaces, NURBS boundaries, etc.—the export fails or doesn’t create a valid solid in RFEM.
Does anyone know:
What’s the best method for exporting volumes/solids from Grasshopper to RFEM?
What are the available options for exporting curved surfaces?
Is there a reliable workflow for exporting surfaces with NURBS boundaries into RFEM?
Any insights or tips would be greatly appreciated!
Currently, volumes can only be defined by the boundary surfaces. So deconstruct the Brep is a necessary step. In general, the Export of NURBS surfaces is working. There are some limitations related to trimmed curved NURBS surfaces, but I would like to check this in detail.
For some surfaces, it is possible to use the boundary lines from the surfaces as an alternative to the GH-Surface Input.
To analyse the problem more precisely, the model file would be very helpful: Upload the file here so the community can also contribute to the solution. Prefer not to share the file publicly? Send it to me via direct message: click on my profile picture or user name → Message.
The GH interface need some additional development for trimmed surfaces. There are some limitations for trimmed nurbs e.g. for surfaces with more than 4 boundary lines.
Regarding your model you could export your structure as STEP-File from Rhino.
To get valid surfaces follow this steps:
Import the STEP-File into RFEM 6. Some invalid surfaces will be imported due to too large tolerances in the Base Data.
Thank you for your response and help.
I tried your approach, but without success on my side. Maybe I'm missing something...
Could you give me a quick step by step description of your process?
What Tolerances did you use?
How are your surfaces defined?
Could you also upload your imported RFEM File?
Even after adjusting the tolerances on 0.1mm I still don't manage to receive a adequate result.
For the first attempt, I selected a very small tolerance as the model is very small.
5) Import the STEP File again: File→Import→STEP
This will load the STEP File into the existing RFEM File with the adjusted tolerances.
I use RFEM 6.13.0004 and got less invalid surfaces after importing your attached STEP File with the default tolerance setting of 0.5mm.
I attached the RFEM File with the tolerance adjustments. 2025 09 28_Unit Cell - BCC - V2.rf6
Upload the file here so the community can also contribute to the solution.
