Problem with splitting a lofted surface




I have two lofted surfaces (option loose). The upper surface with the green loft curve is resulting in a surface that can not be splitted by the cutting plane. The lower surface with the cyan loft curve is resulting in a surface that can be splitted. I can not find out what is wrong with the green problem curve. Can you help me?

See attached rhino file.

Problem with split of a lofted surface.3dm (396.2 KB)



Hi Bas,

 I thought I recognized that hull form. You did the lofting tutorial a few years ago with the RhinoNL group right? 

 I haven't downloaded your attachment and taken a look yet but my first guess (before making some coffee and looking at your lofts) is that there may be some co-incident points. I've been given Maxsurf generated hulls that wouldn't split that had chines and greases formed by stacking control points. Just a guess and I will take a closer look.

(Pascal Golay) #3

Hi Bas - the stern splits but the long curve of intersection with the plane comes up a little short at the bow end. I ExtendSrf-ed the front vertical edge of the surface by 100 to give a little more overlap with the plane, then it works OK.



Hi Joseph,

This hull is made by a student at the technical university of Delft. I am teaching them hull form generation with Rhino. The method is indeed the same as published by Hope you can help after your coffee, :slight_smile:



Hi Pascal,

Thanks, I did that test too. Extend surface is too much a trick which I can not teach to my students. I would like to know why one curve fails while the other doesn’t.

(Pascal Golay) #6

Hi Bas - I can’t tell you why in any detail, myself… it looks to me like it is a weakness in the surface-surface intersector that appears to be fixed in V6 - the Split works there. The Intersection curve in V5 ends on a knotline, V6 takes the curve to the edge as expected…



Hi Pascal,

This is good news. Does that mean that this split will work in Grasshopper V6 (within Rhino V6) ?

(Pascal Golay) #8

Hi Bas - yep, that seems to work:



Great, good to see that Rhino V6 is getting better.

(Michaelmartinez) #10

This method does not work for Smart 3D.


Dear Michael Martinez, what do you mean with this method? Cheers, Bas

(Michaelmartinez) #12

Hi Bas, I just mean the lofting method that you speak of. The trimming of the surface isn’t accepted by Smart 3D. Just been looking for a way to make this hull that I’ve been working on.


Hi Michael, there are a few tricks that might help. Can you share your model? Did you try _ShrinkTrimmedSrf?
Cheers Bas