Logarithmic Spiral Along Truncated Cone


Post search, I have not been able to find a solution to my project. Several posts were tangential to my problem.

The goal: Create a logarithmic spiral along a truncated cone surface (identical points = matching UV).

The reason: Need a stair with a steady gradient (rise/tread) along a truncated cone

What I do not want (but have): A spiral around a truncated cone. Each revolution has the same increase in height (Z) but different lengths (see screenshot). I want the opposite; a steady increase in height resulting in varying heights for each revolution due to the longer spiral curve.

The ideal solution would allow control over riser and tread but I think I can work that out once the spiral is figured out.

I look forward to learning from you. Thanks for reading this far.

Log_Spiral_Surface_Tapered.gh (31.6 KB)

I have a vast variety of things (C#) related with stairs … but are done via C#. Notify if you want one as demo.

In the mean time:

BTW: Given the opportunity you should always check the 2*rise+run value for a valid non fire escape stair (or the slope for a ramp).

1 Like

‘riser’ and ‘tread’ sliders in blue group:

Spiral_Stair_Cone_2019Nov16a.gh (12.6 KB)

Refinements including treads and risers:

Spiral_Stair_Cone_2019Nov16b.gh (17.2 KB)


Hi Joseph,

Thank you for sharing your solution. Exactly what I need. I will be able to take it from here and once I have completed the script I will post it here.

I appreciate your quick response!

Hi Peter,

Thank you for sharing your C# script solution. I have been wanting to learn C# but will be able to work with Joseph’s solution below more autonomously. I appreciate your willingness to help!