Why everyone suggests all the hard ways of doing the most simple thing?
Isosurfaces? Patched versions for non-linear transformations? Come on!
You really don't need any patched version for this.

camera { location <0,2,-2> look_at y*.2 angle 35 }
light_source { <10,10,-5>, 1 }

#declare WPRadius = 1;
#declare WPCurvRadius = 1.5;
intersection
{ #declare IPH = sqrt(pow(WPCurvRadius,2)-pow(WPRadius,2));
  torus { WPRadius, WPCurvRadius translate -y*IPH}
  cylinder { 0, y*(WPCurvRadius-IPH), WPRadius }
  
  pigment
  { spiral1 1 color_map { [0 rgb <.5,.75,1>][1 rgb <0,.5,1>] }
    turbulence .1
    rotate x*90
    scale <.1,1,.1>
  }
  normal
  { spiral1 1 .15 slope_map
    { [0 <0,0>][.25 <.5,1>][.5 <1,0>][.75 <.5,-1>][1 <0,0>] }
    rotate x*90
    scale <.2,1,.2>
  }
  finish { specular .5 reflection .3 }
}


-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):_;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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