What makes a tubular shape transition from surface to polysurface (brep)?

Hey all!
I have a filleted polygon that gets offset (towards the center) and then lifted then i make a loft surface from the two curves.
If I change the offset value from 16 to 17, it becomes a polysurface, rather than a surface.
I would like to learn what determines this shift, if anyone can help me out.
Mention: if i offset it on the outside (make it larger than the base curve), this problem doesn’t occur.
Many thanks!

surf vs brep.gh (28.9 KB)

Here is another way to explore that idea with polygons from three to 12 sides.

surf_brep_2019Dec11a.gh (10.3 KB)

1 Like