Loft Distortion After Mirroring Section — Help Aligning Loft Inputs

[Usagi]

Hi everyone,

I’m running into a problem with lofting between two section curves in Grasshopper.

In the image below, the left loft (between two unmodified sections) looks perfect. But on the right, I’ve mirrored and flipped the ceiling of the larger section — and now the loft gets twisted and distorted.

loft.gh (6.6 KB)
bad_loft.3dm (167.6 KB)

I’ve attached both the Rhino file with the section curves and the Grasshopper file that contains my lofting logic.

I tried exploding everything and lofting just the ceiling, walls, and floor separately, then joining the surfaces — this worked, but unfortunately it doesn’t fit with my workflow.

Is there a clean way to align two closed curves for lofting, especially after one has been mirrored?

Any tips or alternative approaches would be hugely appreciated!

Thanks in advance
Mikael

[atoosasarrafi]

Hi.

While the lofting problem stems from the direction of the curves and the number of control points I guess, by exploding the curves and having all 4 edges (Red ones) of each surface, you can use the NETWORKSRF command to construct the desired surface. I will attach my own file below.

LoftingProblem.3dm (347.3 KB)

[Joseph_Oster]

@atoosasarrafi

While the lofting problem stems from the direction of the curves and the number of control points…

Yes. There are many ways to do this properly, this is only one:

mirror_loft_2025Jun3a.gh (16.9 KB)

Geometry is internalized, no need for Rhino file. Most of this code is only positioning the mirror.