Hi Steve,

> But the meshes exported from MoI are very smooth in Cinema. It's
> also about the first time I've seen Cinema's 'normal' tag on the
> imported .obj make any difference to a model :-)

Yeah, getting the accurate normals in makes a big difference with MoI-generated (or really mostly CAD-generated in general) polygon models.

Those normals come from the original NURBS object so they're kind of the "true" normal for that point.

The automatically generated type normals (like what you will get if you remove the 'normal' tag) are usually calculated by averaging together the face-normals of faces that surround a vertex. If you have a sub-d generated model you tend to get polygons that are of a really uniform size and don't have any really abrupt changes in angle between any 2 of them. This kind of arrangement is good for an averaging type approach.

But a mechanical type CAD-generated model will often have things like large polygons adjacent to small curved fillets. That's not good for automatic normal generation by averaging - stuff like a small polygon in a fillet gets averaged with a neighboring really big planar cap polygon and it has too much of an effect on the normal pulling it too much away form the big planar poly... Anyway, it's because of stuff like this that having the true normals instead of averaged normals tends to make such a big difference in mechanical models.

- Michael