Wish: Use grouped curves as a single profile for "Sweep 2 rails" and "Sweep 1 rail"

The idea is pretty straightforward - to be able to use a number of grouped curves as a single cross-section profile for commands such like “Sweep 2 rails” and “Sweep 1 rail”. It could be done two ways:

  1. Add an option in the Command prompt, as shown in the attached image).
  2. Upon picking grouped curves Rhino could evoke the usual “selection menu” pop-up window and ask whether the user wants to use the entire group as a profile or only an individual curve which is part the group.

Currently, Rhino will cancel the command immediately after selecting grouped curves as a profile while running one of those tools. This forces the user to ungroup the curves and then repeatedly run the command multiple times to extrude every curve individually along the rail(s).

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Is it not possible to join the individual curves into a single curve? After the sweep, you could explode the join if required. I often do the following to keep surfaces “clean” for a sweep 1 or sweep 2: join all curves that are not joined that will be used for profile curves. Then divide the profile curves a desired number of times. so that a single curve may be created using the divide points, delete the original curve and use the newly created one for the sweep. Often curves are created from surfaces that give a vast number of control points. Should those curves eventually be used for profiles for sweeping, the resultant surface can be overly complex. The least number of control points in a NURBS surface that results in the desired shape is good practice.

The grouped curves were made like a decade ago as a cross-section for making extrusions along two curves (not straight extrusion) with internal holes for manufacturing, but the majority of the curves can’t be joined as they are separate objects. Up until Rhino 6 joined curves had a big disadvantage - even the straight lines with degree 1 were converted by Rhino to use the same degree like the one with the highest degree. That has been fixed in Rhino 7 last year.
However, in my case I ended up repeating the “Sweep 2 rails” multiple times, because every hole was represented by a separate curve far away from the outside profile (they all lay on the same plane and are then grouped to avoid accidental moving of individual pieces).

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Off-topic: Cool, I’m happy to hear that you enjoyed your time visiting Bulgaria! :slight_smile: I live in Plovdiv, which is, in my opinion, the best and most diverse city for living in my country. Cheers

On-topic: @Pascal or somebody else from “McNeel”, it would be interesting to hear your opinion about my proposition to enable the use of a bunch of grouped curves as a single profile for the “Sweep 1 rail” and “Sweep 2 rails” tools? :slight_smile: I will repeat that this qould very handy for cases where the intent is to extrude a multitude of internal cross-section profiles to form objects with holes. Without that option, the user is forced to repeat the operation for every individual profile.

I’m not sure it will work in your case but most of the time you could just pre select a bounce of curve and the sweep solves the rails and section alone.
Did you already tried?

Both, “Sweep 1 rail” and “Sweep 2 rails” refuse to extrude more than 1 cross-section profile (curve) at a time. The idea is to be able to extrude multiple curves as a single cross-section (just like what “Extrude” does) but along 1 or 2 rails that have some non-linear path.

Not sure I follow, here.
In general though, I get the idea - Rhino would join curves internally, presumably, and any refit or rebuild setting would be applied to the joined curve. I do not see any need to pay attention to grouping, myself - I mean, it could, I guess, but that would hide the functionality as opposed to a command line setting for chaining shape curves.


Note that that is only the case if those grouped cross section curves are in the same plane - as in your situation…

Grouping is actually not necessary, if we take into account how the “Extrude” tool handles multiple curves on the same plane. However, the limitation of “Extrude” is that the geometry it extrudes can’t follow one or two curve rails. The advantage of “Sweep 2 rails” and “Sweep 1 rail” is exactly the opposite - they both could extrude a profile along one or two curve rails and adapt the scale and size accordingly. However, they are unable to extrude more than one curve section on the same plane at a time.

Exactly. My request was about enabling extrusion of multiple curves that share a common plane. A great example is using a cross-section profile for extruding a rubber sealing along the opening of a car door or trunk. Or any non-linear extrusion along rail(s) used in architecture. :slight_smile:
Rubber sealing 1.3dm (62.3 KB)

Thankfully, Rhino 7 could join curves while preserving their degree, so this minimizes the mouse clicks needed to extrude such multi-curve profile along one or two rails. Up until Rhino 6 it was a real pain to deal with joined curves that lost their original degree and added an unwanted amount of control points.

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Ah, so we’re not chaining the curves - got it now.


That’s right, the intent is for Rhino to extrude the curves simultaneously along one or two rails as a single profile. :slight_smile:

Be very careful mixing the concepts of “extrude” and “sweep” in Rhino. The Extrude commands and the Sweep commands have several major differences.

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I know that they are different tools and work in a different way, but in essence both “Sweep 2” rails" and “Sweep 1 rail” are adaptive extrusions following a predetermined free-form path, whereas the path of “Extrude” is always a directional vector. :slight_smile: “Revolve” is also an extrusion, but along an axis or a rail.
If “Sweep 2 rails” could make free-form extrusions from a single curve, then there is no technical limitation for it to do so with multiple curves at once, as well.

You can try that with my sample 3dm file posted below. Use curve #1 to make a “Sweep 2 rails” extrusion along the two closed curves, using the “Maintain height” option and the grouped points to add more control over the shape with the “Add slash” button. Then repeat with curve #2. In my opinion, these two operations could be executed as a single operation, because they share the same rails and settings.
Sweep 2 rails extruded rubber sealing.3dm (100.4 KB)

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