Alain <aze### [at] qwertyorg> wrote:
> After some testing, my best result is with the following:
>
> #declare Radius = 42;
> isosurface{
>  function{f_spiral(x,
> y/45-sqrt(pow(x,2)+pow(z,2))/30,
> z,
>   7, // The spacing between turns.
>   0.12, // Controlls the thickness of the ribon. Keep small.
>   Radius, // How large
>   0, 0, // 2 throw away parameters
>   0.06)} // Controls the shape. Almost square but slightly rounded.
>  contained_by{box{<Radius,-3,Radius><-Radius,Radius/2,-Radius>}}
>  threshold 0
>  max_gradient 20
>  all_intersections // As it is transparent, you need it.
>  pigment{cylindrical // for the colour.
>   color_map{[0 rgbf<0.01,0.01,1,Filter>][0.25
> rgbf<0.01,1,1,Filter>][0.50 rgbf<0.01,1,0.01,Filter>][0.75
> rgbf<1,1,0.01,Filter>][1 rgbf<1,0.01,0.01,Filter>]}
>   scale Radius} //Adjust to the overall size.
>  finish{specular 0.7 roughness 0.001 reflection{0.001, 0.6
> fresnel}conserve_energy ambient 0 diffuse 0.8}
>  interior{ior 1.4}
>  }
>
> "y/45" effectively act as "scale<1,45,1>". It controlls the width of the
> ribon as well as the overall height of the spiral.
> "-sqrt(pow(x,2)+pow(z,2))/30" controlls how fast the spiral climb.
> Adjust "/30" to change the rate of ascention. SMALL = steep, LARGE =
> slow climb.
> You can declare the colours of the color_map any way you want. You can
> hace up to 255 entries, but don't need as many.
>
>
> Alain

Wow, Alain, that is fantastic!

Thank you so much for your help!

Have a great weekend,

Ruy

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