"Cousin Ricky" <rickysttATyahooDOTcom> wrote:
> "LanuHum" <Lan### [at] yandexru> wrote:
> >
> > Thank you. I understand macros very poorly, but I can create a spiral from a
> > sphere_sweep. Then subtract the spiral from the cylinder. But, I want to achieve
> > a realistic profile.
>
> Either of the isosurface solutions Robert Munyer and I posted would satisfy this
> profile.
>
> https://news.povray.org/5eec257c%241%40news.povray.org
> https://news.povray.org/875zph8073.fsf%40munyer.com

Thanks. The best option for me is this:

isosurface { //-------------------------------------------------------------
  function{
     f_helix1(
        x,y,z,
        1,    // number of helixes, (1 = single helix, 2 = double helix etc.)
        44,   // period,      turns on the length of 2*pi
        0.07, // minor radius,
        0.8, // major radius,
        1,    // shape parameter,
        0.3,  // cross section type, (0.0 to 1.0 = square ... rounded to circle
              //                 over 2.0 to 3.0 = rounded to diamond and
concave diamond
        45     // cross section rotation angle
      )
  }
 contained_by {box {<-1,-1,-1>,<1,1,1>}}
 max_gradient 8

 texture{ pigment{ color rgb <1,0.9,0.5>}
          finish {specular 0.1 roughness 0.1 phong 0.2}
        }

} // end of isosurface -------------------------------------------------------

Proper geometry with a radius on the edge and little text.
Mr, this needs to be added to the Pov@ble Blender addon : Menu Add/ Povray
shapes / Add Thread/  )))

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