I have had similar proplems like this before where there is an ugly line in the shading where a quad has been triangulated, and usually the problem is fixed by just triangulating before exporting. But here I can’t find anything to fix it. Has anyone got any ideas as to waht might be wrong?
Looks like a normals/smoothing issue rather than the export settings. Try recalculating normals, checking for duplicate vertices, and making sure the quad is planar. Manually triangulating the face can also confirm whether the diagonal is causing the shading artifact. Tangent space likely won’t fix it if the underlying normals are wrong.
