Hi Steve,

> What vertex normal info is good for, is hiding the bad
> topology/ bad poly flow output from the conversion.

This is not quite accurate - the vertex normal info doesn't just hide bad topology, it ensures that the rendering is shaded using the exact same shading from the original CAD model.

But yes this happens regardless of topology.

It's not just about diffuse shading, using the exact vertex normals also gives reflections that will be true to the original NURBS geometry.

Normals that are cooked up automatically by averaging of facets can often have things like shimmery or wavering reflections in areas of shape transition. The normal generation gets affected by the topology in that case, and it's quite difficult to get the perfect polygon topology on many areas of transition.


> It is the same with the model I showed sliced up. If I render
> that with vertex normal info or smoothing, the results are
> the same.

Possibly not if you look at reflections in some areas where you've got some elongated diamond shape quads. Did you ever post any model file of the cut up version? If you can post that I'll see if I can find an area that shows a difference in reflections.

- Michael