When I export FBX with default settings, I mean 'Smoothing' option on 'Geometry' tab, which by default reads 'Normals Only', this setup makes the whole mesh smooth-shaded and marks certain edges sharp.
When I change this option to 'Faces', I receive unmodified mesh.
Both meshes are identical visually, but first one, smoothed, has less vertices count because of that smoothing.
I tried looking at the code, but it is very complicated for me. The only thing that I understood, that 'Normals Only' represents switched off smoothing in exporter, so it appears to do nothing with smoothing, when this option is selected.
But exporter uses some mesh functions like
How this exporter does this thing with edges? What is that magic function?