Help please! Curved surfaces, floating stairs ... confused!

Hi SketchUp forums! May I request advice/guidance on what, to me, is a very confusing model I am working on? If you look at the 2d plans, I am working on the periscoping arches of the entry portal for a rotunda house entry. I cannot figure out how to get surfaces for the decorative top band that follows the segmental arch on the face of the rotunda. I drew a cage of arcs and pointed to it with an arrow; this “cage of arcs” is what I’d like to fill in with surfaces. I hope the question is clear and really appreciate advice!

I really appreciate your time!

Something like this?

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Also, request #2, inside the rotunda may I have advice on how to smooth the bottom of the stairs? I can create the floating stairs but cannot figure out how to get the bottoms to be one continue smooth curving and ascending surface. I’ve include a real photo of what the bottom of the stairs should look like.

You can try my stairmaker plugin. With a bit of effort you can achieve this.

How did you make the stairs? Are the steps component instances? Can you share your model of the stairs by uploading the file here (7th icon on top of post) so we can see how you have it set up.

With Shape Bender plugin

With Flowify plugin

And the staircase made manually with the Curviloft plugin for the curved side underneath.

Here is a model I did 5 years ago.

stair5_ver2013.skp (2.3 MB)

Curious, if you put one result (bender) on top of the other (flowify), do they seem to be the same?

@whiterabbitdesigncompany Both are the same:

but with a plus for ShapeBender - more easy to use and makes edges hidden, in this case. But Flowify does more when it comes to more complex shapes.

Thank you very much! Yes this is perfect.

I’ll have to try the different plugins; those seem to create the stairs exactly as designed by the architect. I am not sure if my extremely old version of SketchUp Make supports plugins … in case it does not, is there a way to do this without the use of a plugin?

Thanks to all for taking the time!

It can be done without plugins, the 3rd version being mostly done manually. You can replace the Curviloft plugin with Line tool from SketchUp.

Plugins used can be installed even on SketchUp 7.

Thank you mihai.s for the swift reply! Are you able to do a video of the manual creation with the Line Tool? Because of the age of my SU version I am unable to open the arc-stair.skp file you included.

Which version of SketchUp are you using?

According to the error I message I have version 15.3.329

These are the steps to draw on the curved stair with standard tools only.
I’ll add the clips as I finish them. I have to make a maximum of 5 MB each to add them to the forum.





a. use Soft and Smooth for hidding edges.

In broad terms, these are the steps to follow for this model of curved stair, without plugins.


You are extremely generous with your time; I really appreciate it! Once I replicate on my model I’ll post some screenshots.

You’re welcome!
This is my file, it’s in centimeters and it’s not in the photo scale (I used the door opening as 100 cm), being a file for quick illustration only. arc-stair-2015.skp (724.7 KB)

Interesting, I use both for different things but have never had the occasion to directly compare them. Thanks for checking that out.

Have you tried ThomThom’s “Truebend”

With pleasure!
On this occasion I worked with Flowify for the first time and I find it interesting.

I have not used it yet (TrueBend), but I will look again at a tutorial and then I will test it with this stair.

//edit - SKP file (2017) st3.skp (548.8 KB)

At first glance, for accuracy, the stair should be drawn manually.