The 3ds Max FBX plug-in supports the turning of hidden edges. This support is through triangulating the affected Poly objects into Editable Mesh objects. Once the mesh is triangulated, all invisible edges are exposed and baked, whether they are turned or not.

Editable polys have hidden edges. When you view a polygon in 3ds Max, the hidden edge is invisible unless you turn on its Visibility. A hidden edge with Visibility turned on appears as a dotted line when the Turn tool is activated. This gives the impression that the Editable poly model is composed of polygons when it is composed of triangles. The only difference is that the edges that complete the triangles are normally hidden from view.

You can turn hidden edges in editable poly and mesh objects to modify the shape of the hidden triangles within your polygons. This is a refining process useful if you want to modify how polygons are subdivided. Turning the edges lets you avoid thin triangles in your polygons, for example. Turning hidden edges is a refining process some 3ds Max modelers go through as a last step.

To turn an Edge in 3ds Max:

1. Create a Plane primitive in 3ds Max.
2. Convert the Plane01 object to Editable Poly.
3. Go to the Polygon sub-object level in the modifier stack and choose Edit Polygons > Turn.
4. Press F4 to show hidden edges in the viewport.
5. If you click any hidden edges you can see that the edge now becomes a solid line.

   When you export this scene, hidden edge directions are retained by converting editable poly objects to editable mesh objects.