46c615ec$1@news.povray.org...
> M_a_r_c wrote:
>
> Thanks, yes, the constant radius on your flutes are one of the problems I 
> wanted to overcome, but obviously, tha can be adjusted by eyeball or a 
> static calulation beforehand, and I now see the possibilities.  Also it 
> renders much faster than my spline solution.

I didn't study the greek architecture, it's a fast try at a sphere_sweep 
solution as Shay suggested :-)
I wondered wether the flute radius had to be constant or not but I see no 
problem at making it vary as a fraction of the shaft radius.
That's better I think.


#declare P1=.7;
#declare P2=.9;
#declare P3=1.6;  // Obelix nudged my elbow here ;-) just to show as flute 
radius follows shaft radius... better with 1.1
#declare P4=1.15;


#declare Shaft=
sphere_sweep {

  cubic_spline

  5,
  <0, 12.5, 0>, P1
  <0, 10.0, 0>, P2
  <0, 5, 0>,P3
  <0, 0.0, 0>,P4
  <0, -2.5, 0>, P4

}

#local N_flutes=20; //Number of flutes
#local Flute_Ratio=.95; //flute radial coverage
#local F_fctr=pi*Flute_Ratio/N_flutes;

 #declare Flute =
  sphere_sweep {
  cubic_spline
  5,
  <P1,  12.5,  0>, F_fctr*P1
  <P2,   10,   0>, F_fctr*P2
  <P3,   5,   0>, F_fctr*P3
  <P4,  0,   0>, F_fctr*P4
  <P4,  -2.5, 0>, F_fctr*P4
}

#declare Flutes= union{
#declare C_Flute =0;

#while (C_Flute<20)
object{Flute rotate y*C_Flute*360/N_flutes}
   #declare C_Flute =C_Flute+1;
#end
}
difference{
object{Shaft}
object{Flutes}
 pigment {color rgb 1 }
}

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