180 winder stairs Modeling With smooth bottom

I am trying to make 180 degree winder stairs. MAJ Stairs is very helpful in this regard, but since the bottom of the stairs is not smooth, there are light refractions in the renders and it looks bad. I have been using Sketchup for a long time, but I do not know how to do this or which extensions I can use. Do you have any suggestions?

The smoothness I am talking about is not done by selecting lines and choosing smooth and soft.

You can look at the wooden staircase model I posted as an example. This is the look I want to achieve.




Have you tried the Curviloft extension? there is a “skin by contour” that might work well.

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Yes but, I have to draw all the outlines as they should be, and that’s not always possible.

How else is it supposed to know what you want?

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I tried it but Its not give the exact thickness to here; On the curvi parts

you need to draw that thickness first as that’s part of the stringer not the underside.