Why the mesh of my model do this after I attach it to another object?(both are SMD files).

I'm trying to rigg this model in order to create a skin for a videogame so I need attach all these separated SMD files in order to create a single object.

I'm using autodesk 3d max 2012

First of all, use an updated version of the software, that one is 13 years old and has many issues that have been solved since.

Second, the mesh only lost the smoothing groups. It would be a hassle in a hard surface model but here simply apply a smooth modifier to smooth everything again.

>>1014435 (OP)
This happens even in newer versions. After attaching try selecting all Polygons and adding a 1 smoothing group to everything.

>>1014435 (OP)
This

>>1014435 (OP)
you need to use editable poly instead of editable mesh. also, add an edit normal modifier on all objects before you attach.