Maya: exporting skinned mesh as .fbx loses/unlocks vertex normals


I’ve come across a problem that I feel would have been noticed and addressed long ago, but it seems like something that’s been happening for a while, based on the history of forum posts discussing this.

Basically, we have a character in separate body parts (arm, hand, etc.) all skinned to the same skeleton. When I load both pieces together in the same scene, I can confirm that the vertex normals along the shared seamline are the same for verts in both meshes along that line. Once I export to fbx, I load both fbx’s into a scene and see a clear seam along the line. Displaying vertex normals also shows that the verts along the seam where the hand and arm connect have unlocked normals that don’t match up anymore.

From everything I’ve found, it sounds like this has been a known issue with Maya/fbxsdk for a while now and am wondering if anyone has ever dealt with this before or found a good workaround. Thanks!


What version of FBX / Maya?

Also are you exporting with tangents and binormals? Which to work properly I believe you also need to triangulate the mesh.

While I’ve not run into this problem myself (or I might have and never noticed), I find it unsurprising that it exists.

One potential solution is to write the vertex-face normals into something like blindData and then using the FBX SDK edit those vertices back to the values you want.