Suggesting G4 and G5 for the Loose Lofting function


Dear Mc Neel,

For advanced hull design and fairing (ship building & naval architecture) I am missing the options of G4 and G5 for the Loft function, option Loose. If all curves are build up as G5 curvature, the loose lofting results in a G5 surface in one direction, but the other direction is still G3. Can this whish be included on the wishlist? Is there a way around to get a G5 surface in both directions via control points?

Friendly Regards,
Bas Goris

(Menno Deij - van Rijswijk) #2

Do you mean degree 5 or are you looking for G5-continuous curvature across surface boundaries? I think you mean the former, and you could, I think, Rebuild the surface from degree 3 to degree 5.


Dear Menno,

I have made a mistake indeed about the naming. Thank you for noticing. I ment degree 4 and 5 in both U as V direction.
If all curves are build up as degree 5 curvature, the loose lofting results in a degree 5 surface in the U direction, but the other direction is still degree 3. I know the rebuild function, but I am looking for an option within loose loft that results into a degree 5 surface in both U and V direction. Does that make sense to you?


(Pascal Golay) #4

Hi Bas - this has come up before, though not, as I recall, specifically in the context of a loose loft. @lowell - does this seem reasonable to set the degree in a loose loft? I guess you’d need a minimum number of curves for the degree as in the Curve command.


(Lowell Walmsley) #5

I asked @dalelear about this.
He said that there are facilities for making higher degree lofts available, and that the results aren’t good.
He thought that Loft had that option quite a while ago and it was removed because it was unhelpful.


Dear Lowell,
Has it been available in a previous Rhino release, so I can play with this functionality? It will be usable for advanced users if it works with the same principles as a degree 5 curve reacts on its control points and knots. If the results where not working the same as a degree 5 curve, than I understand that it has been of no help. But that is not clear to me via your answer.

(Pascal Golay) #7

I do not recall this ever being available (to the user, at least) in Rhino, myself… But it has been a long time.


(Lowell Walmsley) #8

I couldn’t find any history of it either. Just something Dale mentioned in the conversation, but he wasn’t at all sure either.


Dear all,

Sorry for my late reply, I had a flu. But I am happy I am back again.

I have done a test to see if it is worth introducing a 5 degree fairing method with the benefits of the loose loft method. Look at the beautiful fair result of this test, made of a 5 degree flat plate. I used the command _Flow to get the control points of the 5 degree flat plate on the target curves. (Unfortunately the Record History is not working on Flow in this case, is it possible to get that working?). The result of the loose Loft with 5 degree will be the same. Very nice and fair and usable as input for CFD calculations. 5DegreeHullFairing.3dm (108.6 KB)

Bas Goris

(Lowell Walmsley) #10

It’s a nice example. I’ll see what I can do about getting that added to Loft.


Hi Lowell,

My colleague Bas mentioned this wish a long time ago.
In my projects of modeling and fairing ship and yacht hulls, I also feel the need for 5-degree loft. Is there any news about this?

(Lowell Walmsley) #13

No, there is no new news about it.
There is a wish list item specifically about this thread.


(David Rutten) #14

I’ve been trying to convert your manual steps into a GH component, results are pretty close (though not exactly the same):

Point deviation between our two surfaces is well within tolerance though. The difference may be explained by me using more straightforward maths than the _Flow command.

I can create another component which generates ‘lofts’ of variable transverse degrees, provided all input curves are of the same degree, and all have the same number of control points. I’d rather not try to add too much smarts to this stuff right away, partly because it’s not clear to me where potential problem lie, and partly because it would be silly of me to start duplicating algorithms already used in the native Lofter.

V7-Wish for 5-degree loft

Dear David,

A “loft function of variable transverse degrees, provided all input curves are of the same degree, and all have the same number of control points” sound great.

Is the grasshopper component as shown in the picture available for sharing?


(David Rutten) #16

Yep, [Control Point Loft] and [Fit Loft] should be available in recent Rhino WIP releases.


Dear David,

I played with the Fit Loft function. First of all: Great!

By designing my shapes, I am used to the fact that the loft function always goes tight through the end curves, but this loft function is even loose at the end curves. (7.8 KB)