Sweep1 elliptical rail + section -> untrimmed surface

[Eef_Weenink]

I am working on a splint (for finger correction). It is made of 3-4 elliptical curves and I am not able to get the end-result to a closed brep.
The issue is caused when using sweep1 to create a closed ring of an elliptical closed curve with as section(s) a small closed elliptical curve.
This always ends in an untrimmed surface.
As you see, I tried:

• correcting the seam
• working with more sections (then the sweep1 does nothing but gives error state)
• tried closing with Cap Holes (Ex).
• also tried to do extrude along curve what gives same result.

So maybe I am trying to do something impossible? What to do to get a closed brep here?
Regards, Eef

PS: At the bottom a summary of this thread + what worked for me

Sweep1 elliptical rail + section -> untrimmed surface

@jeremy5 Thank you for your answer. (and surely the time you gave to it). In the image below you can see that the solution @martinsiegrist gave just worked fine. (with the Area component still in it). You are probably very correct that the Area component is not the best choice here. However it shows how flexible Grasshopper can be. (if you look at some image uploads I did in this thread, you will find that I was able to do a Move action just by inserting the Curve Middle points into the T input…

Sweep1Untrimmed.gh (13.4 KB)

[martinsiegrist]

I don’t think there’s anything wrong. If you really want a closed brep / polysurface, split the profile into two and join the resulting two surface halves.

srf-untrimmed-closed-brep.gh (21.0 KB)

[Eef_Weenink]

Thanks. Added shatter; dropped seam and works fine with Brep Join to get it closed.

[Joseph_Oster]

Project arabic text referenced from rhino onto a donut shaped building

This bothered me - I knew the model wasn’t fully parametric with a ‘nudge’ (fudge) slider. It took awhile but was simple to fix, once I fully understood the geometry. This image shows the ellipse and its center point/plane (in green) created by the cyan group: [ellipsoid_2024Oct21a2] The ‘nudge’ slider value was: (117 - 40) / 2 = 38.5 [ellipsoid_2024Oct21a] ellipsoid_2024Oct21a.gh (28.0 KB)

Project arabic text referenced from rhino onto a donut shaped building

Version ‘V.Sweep’ uses two ellipses as rails and two ellipses as sections. It’s more precise. This image shows the rails of ‘V.Sweep’ in green and your ‘Original’ in red. Look very carefully. [ellipsoid_2024Oct20b3] This image shows ‘V.Sweep’ on the left and your ‘Original’ on the right. (parallel view) [ellipsoid_2024Oct20b4] Even if you don’t see differences (and I do), because of how they are constructed, it’s just impossible for your ‘Original’ to be as fair as ‘V.Sweep’. P.S. Th…

[Joseph_Oster]

@martinsiegrist

If you really want a closed brep / polysurface, split the profile into two and join the resulting two surface halves.

Good insight. Looks like you meant to reparametrize the section curve before Shatter, but it worked anyway!

I applied the same technique (white group below) to ellipsoid_2024Oct21a.gh:

ellipsoid_2025May4a.gh (25.0 KB)

P.S. I wonder if it works to split the sweep surface and then join the two halves? Yep, it does!

ellipsoid_2025May4b.gh (24.1 KB)

Sorta silly but we do what must be done.

[martinsiegrist]

@Joseph_Oster

reparametrize

Yes I would do that for cleanliness but the important part is that it is split

[Eef_Weenink]

Hello Joseph,

Thanks for your reply (and I see you added more).
I understand that splitting the input curve solves this. (The why of this is beyond my understanding, but I can work with this).
Looking at the example you explained, and the solution of Martin, I see that in the my example the rail curve is splitted and in your example the section curve(s).
The results are both the same. Question: Does it matter wich one is choosen to be splitted?

[Joseph_Oster]

@Eef_Weenink

Looking at the example you explained, and the solution of Martin, I see that in the my example the rail curve is splitted and in your example the section curve(s).

Looks like you discovered a third way!

@Eef_Weenink

(The why of this is beyond my understanding…).

Mine too.

P.S. You didn’t post the GH file for your solution and I don’t know icons well.

[Eef_Weenink]

I will upload. What have you installed to get the text above the components? Bifocals?

[Joseph_Oster]

@Eef_Weenink

What have you installed to get the text above the components? Bifocals?

NO, not Bifocals! Sunglasses is way better.

[Eef_Weenink]

Tried sunglasses, does not work as I hoped on MacOs. Probably have to read the manual, or it just does not work.

Sweep1Untrimmed_Split+Names.gh (13.7 KB)

[Joseph_Oster]

Odd that your Orient component is the only one showing an icon

If you hover the mouse over it, “(Orient ee)” appears

[Eef_Weenink]

no, it is my (mis-)setting, I was experimenting with sunglasses. Typed in some text
“Orient ee” Clicked the icon at the right side and changed to “Always draw Icon”.
Forgot to set it back.

[Joseph_Oster]

@Eef_Weenink

no, it is my (mis-)setting, I was experimenting with sunglasses. Typed in some text
“Orient ee” Clicked the icon at the right side and changed to “Always draw Icon”.
Forgot to set it back.

So does Sunglasses work on MacOs or not

[Eef_Weenink]

Sunglasses do not work. That is a pity.

NB: In this thread you @Joseph_Oster showed how you solved the Oct2024 issue with the Sweep2 with very nice explanation!

I decided to use this for another part I am working on (arches connected with interpolated curves + elliptical section)

Used shatter + curve middle + move to get two rails.
Input them with original section curve
Closed Brep (no strange kinks/splits.

Sweep2_Does_Better_Job.gh (14.5 KB)

[Joseph_Oster]

@Eef_Weenink

Sunglasses do not work. That is a pity.

It obviously does something so I wonder if it’s user error

[Eef_Weenink]

@Joseph_Oster

It obviously does something so I wonder if it’s user error

Well, maybe, but then I do not know how to solve it.
Searching on the forum showed that other MacOs users have problems too (not all). It seems to show only the group name (small).
I can live without

[Joseph_Oster]

@Eef_Weenink

I can live without

What a pity. Please avoid Bifocals, it’s very annoying.

[davidcockey]

Note: I’m not a Grasshopper user currently.

Perhaps of interest, perhaps irrelevant, is Rhino Sweep1 command creates a single closed polysurface/brep with ellipses as the rail and sections. Aligned the seams, and verify and the direction of the sections and flip if needed, and check the box for the Closed sweep option.

[martinsiegrist]

The comparison would have to be done with one section only. In that case, the result is a closed surface.