And now for the final hard part? Curved stair case handrail

Pic 1 shows the rail I used. Pic 2 shows the result. you can see that:

  1. Individual pieces were made and they did not trim each other.
    2 The handrail pieces rotated on the sweep rail and so are incorrectly aligned.

I believe when I tried Rhino a couple years ago, a handrail like this required a sweep2 using 2 rails. However, I don’t know how to copy or offset the existing rail so that the second one is accurate to the curve/rise and is correctly parallel for the sweep.


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It looks to me like with just a bit of work this would work with sweep one rail. On the upper end I would have the rail stop where you try to have it go up, this is where your encountering your problem.

Once you have this part of the rail done it would not take much to complete.

Post your drawing so others can be of more help to you.

All my best … Danny

have you tried the ‘roadlike top’ option in sweep1?
that should keep it from twisting and may even allow the sweep to complete with your current setup geometry.

otherwise, we’ll probably need you to share the file in order to figure it out… even if it’s just the curve and profile instead of the whole model.

I tried the single rail and experimented with the options. Still got odd results. "Road like Top helped for the main rail but resulted in a wild vertical. (pic) I’ve attached the model as requested.

STAIRS_3D.3dm (12.5 MB)

Yeah - the problem is there is no correct miter for the curved bit to the vertical section. If you can finish the rail there so it just gets straight for a moment before it hits the vertical and stays in the plane pf the top two segments, , you may have better luck.

Stairs_PG.3dm (38.8 KB)


I am not saying that any modeling system is perfect, but every once in a while I see something that makes me a little nervous to model, such as the co-planar section in the lower part this crosswalk button.

A person with a scrap of sandpaper and a daub of putty can fix geometrical atrocities.

…or a person who extrudes sections of rail and mitres it, and connects or blends the mitred section to the swept section.

"…or a person who extrudes sections of rail and mitres it, and connects or blends the mitred section to the swept section.
I am trying to learn Rhino through this project. Therefore, I automatically assume errors are my fault. Wrong tool or wrong procedure. The first time I used SolidWorks on a very simple object, I got an error I could not solve. The SolidWorks people eventually confirmed I had discovered a bug. Days spent thinking I was doing something wrong.

A year ago I modeled this stair in Sketchup quite easily. It was constructed and featured in the TV show “Underground.” I can attest that a lot of sandpaper and epoxy was used on the formed and mitered handrail. I just was under the impression that Rhino, with is vast tool set, would offer better/more accurate methods than Sketchup or putty.

Well, the grim truth is there is no exact miter that will connect the curved to the polyline part of your rail and make the edges all meet up cleanly - as far as I can tell it just does not exist - so you either need to make some kind of transition piece there or make sure that the path is all planar in the area where the miters fall, as in my example, or sand and putty.


I think the only way you’re going to be able to do it is with cutting planes… You’re going to need to move the posts though.

STAIRS_2DCube.3dm (8.2 MB)


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Erm… Ignore the end and the sweep :smiley:

That’s the easy bit - I wasn’t looking at that - just the mitres. If anything - that goes to prove you can mitre just about anything :blush:

I just did a demo of this exact situation and you nailed it.
Here are the steps for anyone interested:

  • Make sure you have curves where the railing profiles were swept or extruded. You need path curves.
  • In a side view, draw a line using an angle bisector. Make it way longer than needed and go ‘both sides.’
  • Make the two profile/sweeps go well past the point of intersection. They should overlap.
  • Extrude the bisector line so you now have a cutting plane.
  • Use the plane to trim each railing/sweep. Delete cutting plane.

This is designed for complex profiles that typically get schmangled when they go around sharp corners.

Thanks, but It’s not quite right :slight_smile: I wasn’t paying attention to the sweep as I drew a curve from the centres of the baluster for a quick example so it’s not bang on, but it could be.

I worked with extrusions and used silhouette in plan to rotate and align them to be central. In order to get the correct plane I used Boolen Intersect then created the plane by using the opposing corners of the Intersect output. Then it’s a case of splitting and joining.

Interesting problem though :slight_smile:

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The exact intersection between the curved section and straight section is not a plane. Close to a plane but not exactly a plane. Check the distance between the edges. For a stair railing it probably is better than “close enough”.

In that case, I’d just straighten it out for the last few inches. It might even look better if it terminates at a perpendicular as opposed to a slightly-off-90° ending.

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I’m not sure what you mean by “cutting planes” whether that is a command or just the object used to trim? I still have difficulty getting objects where I want them as I am very accustomed to Sketchup’s excellent inferencing. This make it very difficult of precise mitering. At any rate, I managed to do it using Boolean subtract. I was hoping Rhino had something along the lines of Sketchup’s Follow-me. Mitering like this is a whole lot of work and still not the accuracy I was expecting, or any better than I did in Sketchup. I expect trying to create the volute will be even more problematic. Granted I’m a Rhino beginner, so perhaps a little more time will pay off.

At any rate, thanks to all for your help, suggestions and support. This forum is excellent.

In Rhino

In sketchup

Accuracy should not be lacking - if you have an example of this, please post it. I still think the underlying problem is that there is no good miter plane for this situation - that is why I suggested making sure all the miters are planar.


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Not a true Miter, in order for something like this to connect (helical rail to straight miter). One of the sections either needs to be distorted, the miter must be a curved or twisted joint, or both. There are a couple tricks to accomplish this in the field not involving any bondo, but it’s pretty tricky. Generally a situation like this would be resolve by using a transitional fitting. @CalypsoArt. I build stairs and rails professionally, and use Rhino Exclusively, so if you’d like to send me a PM i can probably help you through this process.

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Follow up to Pascal’s comment. The intersection of a curved shape and a straight shape, both with the same cross section, is not planar. That is geometry, and does not depend on software.

I get what you’re saying. I guess I just thought the software would accommodate for it–perhaps some sort of mini loft.

To point out the obvious, you can’t make a good mitre between the downrail and the swept rail because the swept rail is curved, and the ends of the result with not mate, or the part would be twisted. That’s probably why solidworks barfed, because it tried to make a non-manifold part.

Though, you can make the result airtight, perhaps by removing the short down rail and re-create it to make the horizontal stub and the curved rail meet, and lofting or connecting the two pieces on the outside.

In theory, that part could not be cut from length of rail. In reality, you could, and use a little paint would cover the discrepancy.