Problem making a "spiral" that is not "circular"

I have used all the options I could think of, I think, but it can’t be a spiral because the “scroll” is not round. Does this make sense? This isn’t a railing, but it’s the best way I can illustrate what I want to do.
H E L P!

I added a photo of the thing, but I only need one of these lines in the middle of the thing.

If it is a spiral staircase you are trying to design, maybe I can help. I have developed a script for that, but you have to give me the exact details, like the starting inside radius, the starting angle, the end inside radius, the end angle, the height to be covered, the number of steps, and the width of the steps.


Maybe you should make it circular and deform it in BoxEdit or CageEdit afterwards? It will give you good control over your geometry.


I think the approach I’d take would be fix this form into a set position (i.e. fastening it to a board—which will represent the x,y ground plane)… and then project some measurements onto it at various elevations.

If you can capture the coordinates of specific points along your form (i.e. their X,Y,Z locations) then you’ll easily be able to input that into Rhino using the Points command,… and from there follow it up with CurvesThroughPoints in order to draw in some curve/s.

… sweep & lofting functions following that, depending…

Do you have access to this form? or Are you relying entirely on the photographs?

this is what I have. the board in the photo is the one I have in hand.
railing.3dm (4.8 MB)

here is what I have:
railing.3dm (4.8 MB)


Your going to have to bear with me hear… as I’m still not sure what the finished goal is for your project.

I like your 2D drawing better than I like the actual wood cap that’s being shown in the photos. The drawing elevations have the smooth curvature I’d expect to see in a climbing volute arrangement.

Whereas the wood wall cap shown in the photos doesn’t really match the climb angles that are created given the Tread Layout you show in the 2D drawings.

So the main questions I have are… What’s the main priority here?..

  1. Do you need to model the wood cap accurately?.. and if so then what’s the next step from there?..will you then want to build a set of treads around it?.. so that the treads match the climb angles that the cap was based on?

  2. or, are you trying to fix the 2D drawing so that those elevations match what happening in your cap form?

  3. … and of course Rhino is also a 3D modeling program… so at what point do we switch into 3D mode here?

I was expecting to see a 3D model of the form shown in your photos, but instead was pleasantly surprised to see a nice 2D drawing of a tread arrangement that doesn’t really match what’s happening in the photo object.

Railing should follow the climb angle created by the treads… Your photo shows a shape that has a near vertical climb to it and that occurs when you have treads which create Rise, but Little, to no, Run.

[…But again, I don’t think this is really supported in the 2D Plan View and elevation drawing you’ve uploaded just now.]

Having said that, you could force this issue if you insisted on pushing down the lowest part of the volute arrangement… meaning the part sitting directly on top of the starting step. And narrowing climb angle to just the transition between tread 1 and tread 2) In doing that you create a near vertical climb at that juncture in the fittings, But, it’s at the expense of loosing the graceful natural curvature happening by considering the combination in the first three treads (…and shown in the 2D elevation drawings you made).

So there’s a few ways things could go here… but unfortunately I’m not wise enough to predict such things, and instead need the plain (dumbed down) version of the project, and/or the main goal.

OK, now I see where the confusion is. The wooden piece is what the railing will actually sit on. It’s that “skirt” or “pony wall” coming down the stairs, so that you don’t see treads from the outside of the rail. To be more specific, it’s the little curve at the bottom of the last steps and has a super tight turn. (It’s what the newel post sits on) Let me send you a drawing.

  1. I need to model that piece so that I can set the rail design on top of it accurately.
  2. N/A
  3. I’m trying to make that white piece in 3D. I already have my rail design done in 3d, I just need to have it sit on that piece accurately.
    Apologies for the drawing… that was just to get my point across, but ended up confusing the issue:)

I am sitting here trying to get this figured out and I think I’m closer than I was yesterday… LOL

This is as far as I got… and it’s soooo wrong… stair_1_oct5.3dm (2.8 MB)


For modeling your form in 3D, I think I still stand by my first comment… Where I’d fasten that object onto a board, so it doesn’t move… and from there I’d measure out specific points on the form at various heights.

Enter those measured (x,y,z) coordinates into Rhino as Points… and you can build the object around them.

I only have access to an overhand fitting right now… but here’s a picture of what I have in mind in terms of measuring.

I’d put together something a little better for your form… but in my case this was done fast, so I can upload it here fast.

The combination square provide elevation heights. and I can measure across horizontally to capture offset distances, based on a single vertical (plumb) reference point.

It would be better still to have a grid drawn out for the ground plane… that way I can reposition the measuring objects to align with those marks and get all of the rest of the coordinates factoring in what offsets I’m using.

I’m not suggesting you take 50+ measurements here… but with a few strategically chosen points at known, and fixed elevations… you should be able to pretty accurately determine how much twisting is happening at a given height… AND how far off that is from your original established Baseline.

that’s actually what I did, so the ground is correct, the top is correct, but the sweep down looks wonky and I’m not sure how to tell it to sweep correctly :frowning:

How many mid-way measurements do you have?

Rhino’s going to weight and tension the curves based on what your settings are. And I’m not an expert in adjusting all of those factors.

I tend to error on the side (or practice) of placing in short straight line segments… for construction purposes. which I’ll place them upon their own layer (that I can turn on and off). From there I draw in a new set of Curves, and adjust them until I find their best fit and compromise.

For your form I think I take height measurements at 2" increments to start with… and drop it down to 1", or 0.5" if I felt I didn’t have enough of the story.

This is in part a learned art… and generally the fewer control points you have the more fluid your curves are.

That’s the main reason I have two sets of curve happening… straight lines to cover important reference points… and offer guide line assistance.

The second set of curves so I can reduce and limit the amount of control points they need.

It’s typically a french way of design stairs. Is the stone stair (?) already built?

I check your 2D plan, it needs a clean-up! As it’s a sort of piece of art, it’s a little difficult to explain it straight forward. I check your draft, and try to find some french litterature about that to help you.

After some cleanup, here is the result:

railing.3dm (1.1 MB)