The case for Sweep3 rail...who would like sweep3?


Please let there be a sweep3 !

See attached.
I wanted the curve as the profile, I had three rails to run it along, there is no sweep3…I wish there was.

Compare sweep1 using profile as rail to sweep2 in which I had to split my beloved curve.

would they differ, yes they do, see sections.

would sweep3 be like sweep2 I dont know. Would keeping the curve intact make a difference ?

I cant do a netwrkSrf as I dont know what the profile the other end is. Lets try it o what we have, I select the blue NotSplit curve then rails A B and C in that order then get asked to select first direction so select my blue NOT SPLIT curve, then enter for second driection and select rails A B then C and it says unable to use.

sweep3 wouldnt do that. I am forever getting that secondary selection request with NetworkSrf followd by unable to use, this cant be any simpler one curve and 3 lines.

give me sweep3 any day !

It also saves having to slice up profiles with split, which after making them is a nuisance.

As such profiles have to be split…or is there another way ? Sweep3 is so easy and programmable.

anyone with some code ?

Sweep1 v Sweep2 and need for sweep3.3dm (102.6 KB)


NetworkSrf should usually do for a ‘Sweep3’ that has at least a starting and ending profile curve.


Hi Pascal,
but as you can see only one profile, so definite need for sweep3


Sweep1 using the single “profile” as the rail, and the “rails” as the profiles?

Hi, that was one of the two methods as seen in the 3dm, and it differs as can be seenin the 3dm from sections significantly from the profile as profile method, and profile was significant as its the front of an aerofoil section .


If these are airfoil section and you are looking to make aircraft surfaces that will be made from sheet metal then:

  1. You should use Loft, never sweep
  2. If you’re looking to make say a leading edge section out of one piece of sheet metal, then the ONLY sections you need are the root and tip. If you have 3 sections all you’re doing is adding shape to the surface that may not be conducive to being manufactured.

Is this for an airfoil shape to be made out of sheet metal?

but as you can see only one profile,

I guess I was suggesting, in my obscure and inscrutable way, making a new one.


In not too technical Terms, here’s what the sweeps basically do:

sweep1 moves the cross section along a given path, creates a few copies, then lofts those sections.
The section copies are only translated and oriented.

sweep2 moves the cross section between two given paths, creates a few copies and lofts those. Between any two points along the path, you can find a straight line. In relation to the line between the path starts, you can use that to scale the section as it move along.
The section copies are translated, rotated and scaled to fit between the rails.

Now what would a third rail mean?
If the third rail stays in the same relation to the other two rails, you can omit it, as it does not provide any more information on how to scale and rotate the section.
If the third rail diverges from the other two, you would need to define a non uniform spatial transform, that scales, moves and rotates the section accordingly. While perhaps possible, that is probably not trivial.
In the end, the final section will be a transformed version of your original. So if all fails, you should be able to create that manually and then use NetworkSrf.