Modifiable Curve Along a Surface

I am new to Rhino and one week into working in Grasshopper. I came from a solid modeling background using Siemens NX and AutoCAD Inventor. I have a shape that I want to be able to modify the inside curve (Red). Being able to stretch and pull it and having the corresponding attached curves translate the modified curves direction into the desired shape. I want to add, I find Grasshopper the be an incredible tool and will make use of it in the future as my skill gets better. I have seen some incredible works online and hope to be able to add to the community.

Thanks in advance! Shaun
Modding_Wing_Forum.3dm (453.6 KB)

I didn’t open your file, it’s a rhino file, not grasshopper file - either way, though, no images attached either. Can you show an image or sketch of your goal?

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How about this? A simple sketch could help.

Your description can be interpreted in different ways. For example: do you intend to have the entirety of each curve follow a deformation of the “red” curve or only the points (extremities) that intersect with it? You could use spatial deform, or point deform, or maybe neither!


Sailboat keel? Looks like this project, all done with Grasshopper - for fun, seven years ago.



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Hello Rene,
Thank you for your suggestions. I played with Point Deform and that could be a solution to my project. I’ll Grass-Hopper it up and share with ya’ll what I find.


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This should look familiar. I found a GH file that was close to what I was trying to achieve. I modified it a bit but was unable to get the inside cross section to move how I wanted.

The part of the cross section that would be moved is in the picture below.

But also, the corresponding surfaces would move with the adjusted edge.

Ideally, a few sliding numerical adjusters to adjust in the Y an Z axis for each section would be cool. (19.1 KB)

Why? Did you start with something I wrote? Doesn’t look familiar or correct.

The Crv params in your GH file are not internalized. Opening the Rhino file you posted doesn’t help. (40.8 KB)

Sorry, Like I said before Im totally new to Grasshopper…



Even if you get this to work, it doesn’t look correct to me.

P.S. Is this supposed to be for a boat? Because these profiles look nothing like a NACA foil shape :exclamation:

Mr. Oster,
You helped a guy in 2020 with a hull parametric surface problem. He was a Newby, having never posted anything in the past and did not give a GH file for the problem he was trying to overcome. There were two responses given, yours was example was called surfboardloft_2019…

The surface is not an NACA airfoil, it is a panel that will be going on a car I’m currently working on. It attaches to the bottom front valence panel to direct air towards the brake caliper (right side) left will be mirrored after I get the end result. The adjustability is so that I can tweak the shape before 3D printing it and flitting for shape then having it made out of Sheet Aluminum.

After scouring this message board, I found the surf board file and thought I could use it as a initial base file for my panel.

Like I have said multiple times, I am an Newby to GH and have only been using Rhinoceros for a little over a year. I previously used Siemens NX Mach 3, but started using Rhino as I did not want to spend $14K/year for a home license.

OK. This paragraph I’ve quoted above is the only part that sheds a little light on the subject, though I don’t know what don’t know what “the bottom front valence panel” means? And I don’t have an image of the final shape, which might be useful? Honestly, being a newby to GH is no excuse. If you can’t make something work, I’m just doing your work for you. :frowning:

In any case, I see several problems in your file:

  1. Area doesn’t work on an open curve, as the error message says:
    “Curve must be closed for Area calculation”

  2. You are scaling the first curve smaller(?) without a proper center point, and without a correct location as the Orient you are using makes no sense to me? If you don’t move that scaled curve somewhere else, it won’t loft.

  3. Sweep2 won’t work without two rail curves so is useless.

Where to begin? (30.4 KB) (33.1 KB) (37.5 KB)

What do you want to do with the scaled curve? Your newby card is expired, show me something.

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Newby Card!!! LOL

I’m serious :exclamation: That broken code was awful. If you can’t do something better, forget about it.

Like I said. I’m new to this!! Also I would be appreciative of any help ANYBODY could give in pointing me in the right direction. The comment " That broken code was awful" should tell you that I’m not even going in the right direction!!!

I guess I should have named it Boat Hull, or Sail , or something nautical as you gave Micheladelcarlo a completed project and he spent a whole 11 minutes total on this forum!!

LOOK at my profile, I have been on here a total of 8 hours total with 1400!!! Articles reviewed, I’m not asking for handouts!!!

Your comments of what its for or you have no idea what a Valance is, doesn’t have any bearing of what this forum is about, You don’t need to know what’s its for!!! I gave you its purpose, but in reality its really none of your damned business what it is for.

I think you are. You copied some old code that I wrote years ago and botched it badly. We’re done.

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I have sent a message to McNeel associates about your unprofessional behavior!