Hi Jamie, thanks for testing it.

> For my understanding are the vertex normals in
> the .obj or in the .mtl file?

They're in the .obj file - you can actually see them listed if you open the .obj file up in a text editor (try a text editor a bit more advanced than notepad, like notepad2 or notepad++), they're the "vn" entries that look like this:

vn 0.08659345 0.01440297 -0.99613961
vn 0.16999357 0.05883424 -0.98368731
vn 0.08664738 0.03098550 -0.99575706


When MoI exports an OBJ file, it puts the vertex normals from the smooth NURBS surface in there at the corners of each polygon that was created, so that when the polygon is rendered it can be shaded to closely resemble the original surface.

But if the stored vertex normals are not used and instead are just calculated by averaging the normals of adjacent polygon face normals together, it won't produce the same result.

- Michael