Loft without pinching/twisting?

I have read a lot on here, but this is my first post…
The directions of the curves have already been adjusted to match, and the seam point is determined by a closest point to an adjustable point along the first curve when all are aligned in the same plane. If you look at the last portion of my code shown, I have tried both loft and sweep each with the rebuild and refit options and always have the same issue. Any suggestions on what else I should try or something I might be missing?

Difficult to say what the problem is without a file.

Does the same thing happen when you loft the curves in Rhino?

I quickly created a curve and lofted something similar.
Identical point structure is helpful if not necessary.

I’m a little hesitant to share my code/files because this is for the company I work for…
I still have the same issue lofting in Rhino, and I believe it is because the point structure is different. I hoped using the rebuild or refit options would resolve the issue but I guess that doesn’t really change the structure…? I’m also now wondering if the way I’m choosing my seam point is part of the issue. You can see in the front view the green point is my reference seam and the seam point for the middle profile is based on closest point, not the respective point along curve… Could that be the main issue, or would the point structure still mess it up in more complex designs? Can you “rebuild” the point structure to be closer to each other?

loft pinch curves.3dm (68.6 KB)
Here’s a file with just those three curves if that helps…

Rebuilding the curve does help. You can drag the seam to minimize or shift twisting

Attached is a file with three curves with identical point structure. Not your curves.

21_03_08_loft.3dm (392.2 KB)

Yea it does help along with adjusting the seam, but for what I am doing I have to completely eliminate all of the pinching rather than find a good seem that minimizes it…

Check this file. You could split the curves to create a lofted front part and then sweep2 the rear part

loft pinch curves.3dm (337.0 KB)

That is a good strategy for handling it manually so to speak… If I can’t find another way to go about it I’ll have to see if I can translate something like that into code that will work for multiple designs. Thanks!
Also, just to give some context I am working on making a component that has many options like dimensions and profiles to choose from so that a customer could “design” their own bench with the options I provide to them.

Good Luck!

In many situations you first need to understand a manual solution.