DeisgnBuilder: Exporting IDF from DXF or gbXML

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I want to export a IDF file through DesignBuilder.

It allows to import a DXF (2D) or a gbXML (3D) file.

I have a DXF file.

My question is: exporting an IDF from a DXF file is more difficult/onerous than exporting it from a gbXML one? in other words, exporting an IDF from a DXF needs more steps than if I start from a gbXML one?

I'm not an expert of CAD programs or DesignBuilder, so my question comes from the fact that DXF is 2D, while gbXML is 3D.

Is there anyone who could help me?

Thank you!