I have a custom hlsl directx shader, it takes vertex normals for rim light calculation. and vertex tangent(it stores unified normals) for edge render(enlarge model & cull front).
I can export one fbx with auto smooth normals, and one fbx with unify normals, combine them in unity, it works but the process is slow. I just wonder if I can do it directly in 3ds max, so 3d artist can preview the result directly in their tools.
I tried storing unify normals data in texture coordinate or vertex color, but the data will be wrong once bone animation is running. So I believe normal + tangent is the only way to go if I want to have rim lighting & edge render together for a animated character model use in Unity3D.
I guess FBX SDK will help, but I have no experience in using it.
I wish someone could tell me a way to store vertex normals data into tangent. or tell me is it not possible so that I should consider another solution.