Revit surfaces to mesh per Revit element - double loop


Hi, I’m trying to create a Dynamo script to filter out (parts of) surfaces from Revit elements that intersect with a Room geometry. These surfaces, grouped per Revit element in sublists, are then each transformed to a mesh (one sublist of meshes per group of surfaces from one Revit element). These meshes should then be combined to one mesh per Revit element.

I’m stuck with the last part, where I need some kind of double loop for performing a Mesh.BooleanUnion over each mesh in every sublist (sublist of surfaces per Revit element). This function works only for two meshes, while I can have one or more than two meshes per Revit element. Anyone who can help with the LoopWhile node or with some Python?

An alternative may be to do a union of the different surfaces per Revit element, before making meshes from them.

Dynamo Meshes - unstable?