Thanks a lot tim. Your Definition was exactly what i have been looking for. And sorry for the unclear problem.
I implemented your definition to my university project. In the next step i would like to convert the selected brep into a solid witch reaches down to the base plane:
I know this is a newbie question but maybe you can help me once more. I also added the .gh file of my project. Its about randomly furnish a room but where the furniture isnt a barrier. A new floor will be created witch then shifts to the furniture and creates a new topography in the room.
Just if you are interested.
180114_room_topography.gh (36.7 KB)
180114_room_topography.3dm (29.0 KB)