I imported a number of windows as breps into Rhino and now I would like to convert them into a flat planar geometry representing the whole in the wall including frames and wonder if someone knows how to this? The position could be outside, inside or middle of the window. The blue surface in the image represent what I am looking for.
You can now do a bounding box on the geometry, do note that you will want to get plane (Element Location Component) to generate the bounding box with. That way as you go around the building you can get the face you need consistently (deconstruct brep> list item)
Depending on where you are going with this you may want to look at Pollination, they convert Revit Geometry to flat surfaces like you are looking for.
Thanks a lot for your reply. The idea is to get a valid energy/daylight model into IDA ICE from grasshopper/Rhino. I do believe Pollination is the best thing since sliced bread but it would be nice with some more flexibility and therefore I am also trying Rhino inside Revit. Unfortunately I was not able to reproduce a script based upon your description and wonder if you have some form of example I can build upon?