Rhino STEP export refuses to keep surface count in other CAD packages

[eobet]

Here’s a file that I had a surprising issue with:

1.stp (190.7 KB)
1.3dm (377.9 KB)

When exported from (and imported into) Rhino it looks like this, single surfaces in the corners:

However, when imported into NX it looks like this:

And I even asked a coworker with Catia how it looks and this was their result:

Siemens already got back to me saying that this is an issue with the Rhino export, so what does McNeel say?

(Actually, they say that because the tangency deviation is too high, in order to maintain tangency for the result in the imported document, they have to split up the surfaces, and if I get time I guess I could tweak the surface further, but I’ve already rebuilt it in NX and I’ve never seen this happen before.)

[pascal (Pascal Golay)]

Hello- that surface is degree 1 in the V direction - i.e it has kinks

RemoveKnot the interior knots or RebuildUV in V to four points.

-Pascal

[eobet]

Ok… I guess that snuck in either from the “refine match” option or the original EdgeSrf command… but still, I just ran InsertKink on the neighboring surface after extraction (several times in fact), and joined it back into the polysurface and it still imported as a single face in NX. So I’m still not clear about what makes that corner surface so unique?