As I am playing with 5 degree ship hull surfaces, I noticed strange behavior of both Rhino 5 and 6.
I found out that advanced display settings of my 5-Degree surface isn’t used for display.
In the attached file, you can find the original Nurbs surface with advanced display quality settings showing poor in glossy display
ExtractRenderMesh shows a rough mesh with poor display quality that seems to be used for the actual display of the Nurbs surface
A Mesh extracted from the Nurbs object with the same settings as the advanced render mesh settings, does show smooth.
5DegreeDisplayQuality.3dm (4.8 MB)
Bad display of Nurbs object with advanced display settings:
Nice display of mesh: