I imported this model into 3ds max. applying edit poly modifiers breaks the smoothing groups in it. How do I preserve smoothing group while applying the modifiers.
If you switch to max 2021 or newer, explicit normals will be preserved. If you prefer smoothing groups over explicit normals (for example if you plan on modifying the mesh and want more freedom), check "Smoothing groups" when importing the fbx - this will try to convert explicit normals to SGs.
Turn to mesh/poly and edit normals will sort the data out but it doesn't always preserve everything. When you bring a model in from Maya or something else that doesn't support smoothing groups discrepancies are inevitable. I remember some discussion on the matter on here a few years ago and i don't think anyone came up…