Finding the profile line of a loft

Hey everyone, hows it going?

I have been thinking of a solution for this for too long and wanted to see if any of you had any better ideas.
Basically, i have lofted two circular curves and now would like to find (in gh) the line that goes along the most outer edge of the loft. I have made several attempts at this (shown in blue and yellow) but none of them seem to be very exact. For example, one of the approaches is to find the closest points to the centre of each curve and then making a line with those two.


Please let me know if you can think of a better way to do it, thanks in davance!

question on loft profile line.3dm (55.4 KB)

R7 .3dm file cannot be opened in R6. You could just internalize the geometry in the GH file.

But I don’t understand your question anyway?

ooops sorry!

here it is in r6:
question on loft profile line r6.3dm (92.7 KB)

sorry yes, i didnt explain very well. what i am trying to find is the line that goes along this edge:

so top view it would be something like this

oh and heres the gh script i used for the line shown in blue in the first image:
question on loft profile (16.5 KB)


Hey there!
As you know the loft command produces a surface which is made of the linear connection of the points of both curves(closest points)
so if you evaluate both curves with a single parameter, you can have access to the loft surface lines.
Good Luck. (9.9 KB)

thank you so much, thats quite close to what i wanted!

how would you now choose the right line? (20.2 KB)

P.S. Version ‘B’ using Iso Curve: (22.9 KB)

Which line do you mean ?
Check the Solution box btw. :slight_smile:

that looks great thanks!!

i now realise i didnt make this very clear at all. the lines im looking for are these two:

i now realise i didnt make this very clear at all. the lines im looking for these two lines:

So you can evaluate your curves with a t parameter and a (1-t) parameter at a same time,
Is it clear ?

oh i see thanks!
and is there a way for it to automatically find this parameter?

You can use the Expression component as shown below:

no no, i meant to find the value of that parameter for the curve in the desired position

let’s say you can import a point from rhino, which is completely on one of the curves, then you can use the “Curve Closest Point” component to find the parameter of the location of the point on the curve, and you can use this t parameter as an evaluator for the next steps. It is important to remember to reparametrize your curve

thank you!!

but what i want is that this curve (and therefore point) is automatically selected, as i have to do this for a very large number of components and choosing the right point for every one of them would be almost impossible.

So, I recommend you using the t parameter for all of them, not the points.
I mean evaluating all curves with a single parameter.

each of these lofts is different to the next, as the circles are in different angles and orientations. precision is quite important, so I don’t think that would fit my purpose very well

If you upload your file it might be easier to understand your aim. :slight_smile:

unfortunately i can’t give you the full model as the project is confidential. sorry!

heres a bit more info:
question on loft profile line (78.0 KB)

i have included another loft to show that they are not all the same.

i am trying to take that loft and split it in two parts, using the surface that i have created from the lines as a cutting tool. however, the split is not working at the moment

This from Your first file, based on Max Curvature and Intersect.