Hi Barry

<< Are there any restrictions on what surfaces the nod can be applied to.>>

Yes, it will only work with 4 edged surface patches.

<< just tried to run nod on half sphere surface and just a tangled result.>>

This is a difficult one because you can't start with sphere solid, because it won't work with trimmed surfaces.
Attached is method for retopologizing a 3 edged hemisphere made by networked curves.


James