Lofting issue; how do you create a straight loft with uneven profiles


I’ve attached a file with a series of profile curves that I need to loft together in a clean tube. Does anybody know why the loft doesn’t work/does anybody have a solution for when profile have uneven amount of sides/points

(Doesn’t need to be done through loft necessarily, as I’ll be making it into a mesh)


Loft (312.6 KB)

Hi Charlie,

First of all, it is important to understand how loft command works. I’ve seen your script and almost all the sections are duplicated, that’s one of the problems. Furthermore, how these sections are created is quite important since loft command takes the section number 0, number 1, number 2 etc in order to construct the surface. If the sections are not sorted and the 0 section is located in the middle of the curve, the loft does not work.

I have culled the duplicated sections and sorted them and it perfectly works, independently of having even or uneven number of sections.

Hope it helps!


Loft (318.1 KB)

Hi Bbalbastre,

Thanks for your reply, however this solution doesn’t seem to fix my problem. From what I can tell you’ve just sweeped one profile along a line. Unfortunately it isn’t this simple, as I need a ‘tube’ the is made up of many different profiles and many different intervals.

I should explain this is only a section, so maybe the section I took does have profiles that are all the same, but it isn’t like this elsewhere

Can you attach a file with what you are trying to do?

I used sweep command since the solutions fitted with what you have. However, if different sections are used, you just have to construct a list with these sections and add it to the section input on the sweep command.


Those profiles aren’t the same, but similar. I presume you’ve just looked at them visually and assumed they are the same? You can confirm this by looking at the vertices of each profiles, which will show a differing number between them. A sweep would miss out on some details.

Hello @user948

Currently the issues I’m finding within your definitions

1- Tons of duplicate section curves that are overlapping, you need to remove these duplicates.

2- the section curves are not sorted, as @bbalbastre said. Rhino is very particular about the order of cross sections when it comes to lofting.

3- I suggest simplifying your section curves, especially most of your curves have control points that don’t contribute to the discontinuity of the edges.

4- as a good practice, I always align the curve seams before lofting.

5- You can use Pufferfish to directly loft a mesh using a component called “Parameter Loft Mesh”

this is what I got from lofting, you can see the difference of polyline curves can cause

Loft (327.2 KB)

Hey tay.0,

Thanks for your reply. I still don’t think the lofting suggestions work. I also don’t want to use plug-ins. I’ve attached another file with the same problem with just 2 profiles, same amount of vertices.

Loft issue (7.7 KB)

Although it is the same number of vertices it is not aligned and somehow we need to instruct the software how to clean it up, for this condition I found aligning vertices by Closest points (on the other Curves) Worked properly

Things like these intermediate points needs to be excluded since they don’t contribute anything to the mesh

Loft issue (9.7 KB)

I’d also suggest simplifying the curves to get a the coplanar points out.

Also, if Accuracy is your priority, you can go with the expensive option of further dividing your curve. Although personally I don’t suggest this.

What are you actually trying to do here? Where did these curves come from? Why is this 5’ long tube literally 5 miles from the origin? Lofting 575 curves is an entirely awful Rhino workflow–beginners shouldn’t even be taught Loft exists!–and you don’t really seem to be trying to listen to the advice on how to actually use Loft. It has specific requirements, it doesn’t magically know what you’re trying to accomplish and fudge over all the errors in the input.

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Helpful input Jim. I’ve thought i’ve pretty clearly explained the outcome I want, I didnt make the curves but I dont see how that is relevant. Happy to listen to advice, but a lot of these solution accuracy, which is obviously required

Of course it’s relevant. Garbage In, Garbage out, and your curves need work. They are duplicated, they aren’t aligned, they are unnecessarily complex, they aren’t even in the right order. Where did they come from, a scanning process? An algorithm, that maybe could clean them up better at the source? And again, making a ton of cross-sections through something and Lofting is just not how anything in any CAD product is efficiently and accurately made, that’s not how it works, you’ve been set up for failure.

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The curves being out of order is my fault, I clean that up later on but forgot to add in the script, same with the duplicates. Its a very simple operation so didnt bother correcting. Again, the curve original is irrelevant if the outcome has to be a certain way. The curves can’t change, they are a fixed varible. All I needed was a simple tube through the curves, and the solution I’ve found is way simpler than I thought…ruled surface.

I totally agree with @JimCarruthers , bad inputs provide bad output. I know it seems a simple problem but, how can you loft two geometries with different number of vertex without fixing the geometry before? That problem is not solved since it is impossible, Sections must have the same number of vertex