When I use mirror to copy some faces, the inside becomes the outside

I want to fix the second side of a SubD by mirroring faces from the other side. When I do this, the inside faces of the original side become the outside faces of the second side.

Looks like Flip fixes this for me. But it seems like this shouldn’t happen?

Hi Mitch,

You’re correct, a mirrored face should not have it’s normal flipped. I am not seeing this issue here though to file it as a bug. Can you post the 3dm?

Here you go

Mirror Flip Normal.3dm (2.4 MB)

I had been extracting the faces first and then mirroring which doesn’t make this happen. If I sub-object select the faces and then mirror, I see what you reported… filed as https://mcneel.myjetbrains.com/youtrack/issue/RH-60826 Thanks.

RH-60826 is fixed in the latest BETA