When the mesh is thin that smooth brush backfacemask is not working right
and smooth directional or smooth perpendicular is not working right with symmetry too.
hi @Yune !
in your case as you have different polygroups on both side, you can set the mask by polygroup to 100 so it gonna affect only the front side.
I noticed that backfacemask on smooth brush do not work too i am on the latest 2021.6.6.
Hope it helps!
Same here, and I’m working on a thicker mesh. I don’t recall this being a problem before, it seems backface masking is completely broken with smooth brushes