How could I systematically differentiate the two parts of a sliced mesh?

[swiss-knight]

Hello,

I try to make use of the "Compute Planar Section" within pymeshlab but I don't know how are the results structured (in case splitsurfacewithsection=True) i.e. how are the mesh indexes given, and what could help to systematically differentiate the two parts of the sliced mesh?

I have to be 100% sure on how to differentiate those sliced parts because I need to "chain" several steps of slicing.

It's probably a matter of slicing plane orientation, but relative to what exactly? I can't figure it out in the doc.

Many thanks!