Wish: "Loft" to produce "Straight sections" if only two curves are used

Not sure why “Loft” is programmed to add an unnecessary and often unwanted amount of extra control points while building a lofted surface between two input curves with the default “Normal” style, but in my opinion it should use the “Straight sections” style instead. :slight_smile:

I just added a picture above to make the request easier to understand.

Hi Bobi -I am skeptical. I don’t see why it should be different than it is now - a user may well want and expect a degree 3 loft, being ‘smart’ means we create two differently behaving objects where the user does not ask for it…


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Hi Pascal, I don’t think that the majority of Rhino users who build “Loft” between just two input curves need those extra control points. :slight_smile: In fact, the reason to build a lofted surface between two curves is to have a simple surface that connects them together, which is a Degree 1 surface.

It’s a totally different story when the intention is to build a lofted surface with tangent sides (additionally activated “Match start tangent” and “Match end tangent” options) between two surface edges or a surface edge and a curve. then Degree 3 surface is needed.

I guess that the Rhino developers will refuse to devote time to make “Loft” more intelligent. However, as a workaround I just figured out that it’s possible to force Rhino use “Straight sections” by default for an alternative command that I set as a RMB command to the “Loft” icon. :slight_smile: I called it “Simple loft” and the macro is:
! _Loft _Pause _Pause _StraightSections=Yes

The same issue happens with the “Pipe” command, but I make a dedicated topic about it.

I don’t know what anyone actually uses Loft for, it just exists because it’s a thing people expect to have, it’s not hugely useful for NURBS workflows, but a common use case for any Rhino tool is to make a starting surface for further point editing, so…guess what’s useful in that case?

The majority of users expect more intelligent tools that produce good surfaces that won’t require an additional control point editing. “Loft” between two input lines or curves is most often used to build simple straight lofted surface that does not have unnecessary control points.

Hi Bobi - I don’t think what you propose is hard technically, it would not be the end of the world, but I find it hard to see an advantage other than ‘on paper’. Different behavior from the same command depending on the number of inputs seems incorrect, to me, and in any case the need for a degree 1 or degree 3 surface is impossible to predict, so making the behavior inconsistent when a control is there specifically for that putpose, seems only confusing and not helpful, to me.


Hi Pascal, other Rhino tools produce different output surfaces based on the number or complexity of the input object. Also, as I mentioned already, nearly every time when two input curves are used for “Loft”, it’s to build a simple straight surface that connect both curves with the minimum amount of control points.
I don’t think that making “Loft” smarter will cause any harm to those Rhino users who in extremely rare occasions will want to further modify the control points of the lofted surface between two curves, because the option to manually switch to the “Normal” style is still there. However, since the majority of time the need is to create a straight surface, picking just two input curves show tell Rhino that it must switch to the “Straight sections” style by default. :slight_smile:

As a workaround I use ! _EdgeSrf to make kind of a simple “lofted surface” between two curves, but my suggestion in this topic is to make “Loft” better in the future.

I kind of like the explicit nature of the loft settings as they are, and I disagree that my primary use for joining two curves is two create a straight section with the least amount of control points by default. In fact I will often times use the loft to match other surfaces to. Since the Normal setting uses degree 3 and both UV, I can already match to tangency without doing any extra work. If I know I don’t need the extra control, then I set it to straight.

You are correct that you should create a macro for your use case, as it is not everyone’s primary lofting requirement.

Something I use loft for on a regular basis. No need for sweeps or profiles and I can quickly adjust the curve structure to get my desired shape.

“Loft” is a very powerful tool, especially its “Loose” style combined with History that make it the preferred approach to create high quality editable freeform objects with controlled tangency or curvature ends. It’s perfect for creating bathtubs, sinks, architectural shapes etc. Examples:

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