Select surfaces of a plane

Hello there,
I’m trying to explode a brep in grasshopper and then select the surfaces oriented on the XY plane, and get rid of the other ones… Can somebody help me?

as an example. from this

to this

Hint: Faces with their Normal being parallel or anti-parallel to the Z-unit vector are the ones you want to keep. There are components for all of that.

I don’t have Rhino installed right now (just restored Windows after a total crash, thanks Acronis “Try & Decide” for killing my machine) so I can’t give an example, but that’s one possible strategy.

// Rolf

1 Like

Good idea Rolf! thank you
But I still couldn’t figure out how to make it work

following with Rolf’s idea I gave a try and got to an answer. (10.4 KB)

Doesn’t work very well. A lot of times this method fails.

I do found a solution that works much better: (9.6 KB)