# Surface analyze with Zebra

That was the brilliant idea!

Hello Stefan,

According to my best knowledge you should not use the network suface but loft instead. Even it might give you more fair surface in the meters you mentioned (curvature and zebra).

If you take a look at the iso curves the network surface is complete mess and this shouldn’t be the case in yacht design at least according to my best knowledge. The less points you have the more fair the surface is and this is not the case with network surface vs loft
Check the surface properties
network surface :
NURBS Surface"U": degree =3 CV count = 51 (0 <= U <= 695.186)
“V”: degree =3 CV count = 21 (0 <= V <= 8722.63)

loft:
NURBS Surface"U": degree =3 CV count = 7 (0 <= U <= 8736.4)
“V”: degree =3 CV count = 4 (0 <= V <= 1193.1)

For example if you make the hulls in similar manner (i know you don’t do this but still… this might give you an idea why network surface is bad idea) as Farrier trimaran floats. First you make the frames for and after the frames you attach the battens to the frames.

In mathematical point of view I do believe that the iso curves actually tell you the exact placement of the frames and battens. Of course in real world this is not possible to achieve but at least you know where they should be and where you should have more dense frame spacing etc.

Sidskrov T30 grasshopper 2021-11-08_moilanen.gh (13.3 KB)

Just my thought, you are the master in this and I love your designs! Can’t wait to see the next one!

I Agree I never use Network surfaces for surfaces if I can avoid it.

The reason why I made a network surface was to compare that surface with a lofted surface using the <zebra analyze tool. The question is how to evaluate a surface, if the Zebra shows a bad result and I therefore change the settings for the Zebra pattern until it looks good. Is the surface ok in the first analyze but the setting for the Zebra pattern is off or is the surface not good even though the Zebra pattern looks ok with the new more forgiving settings.

The Zebra mesh settings should be set for a fine enough mesh that the edges of the zebra curves appear to be smoothly curved, not jagged, except along creases, edges, etc. Jagged edges over all or most a surface are the result of too coarse a Zebra mesh, not surface problems. An exception is degree 1 surface or a polysurface of flat surfaces such as created using ToNURBS on a mesh. For facetted surfaces refining the mesh will not eliminate the jagged zebra stripes.

Thin Zebra stripes are more sensitive to coarse Zebra meshes. Thin Zebra stripes can also reveal small scale problems problems which are masked by thick Zebra stripes. Make sure the Zebra mesh is sufficiently to eliminate artificial jagged edges for the stripe width being used before deciding tthe surface has problems.

Ok thanks for the tips. Helping me a lot.

fre 3 dec. 2021 kl. 17:28 skrev David Cockey via McNeel Forum <mcneel@discoursemail.com>: