// TUBE / Golden Vortex '99.02
// By Tsutomu HIGO  E-mail: nj2t-hg@asahi-net.or.jp

#version 3.1;
global_settings { assumed_gamma 2.2 }

#include "colors.inc"

#macro Texture_c ( Cred, Cgreen, Cblue, Ctr )
  texture {
    pigment {color rgbt <Cred, Cgreen, Cblue,Ctr>}
    finish {
      ambient 0.5
      phong 3
      reflection 0.4
      specular 0.8
      brilliance 1
      }
    }
#end

#macro Gold_ring (Ro, Nt)
  #declare Pne = 4*Nt*Nt;
  #declare Rt = pi*2/(Nt-0.5);
  #declare Yt = 2*pi/Nt/4/Nt; 

  #macro Ka (P)
    Yt*P
  #end

  #macro Rs (P)
    0.85*Ro*pow(0.999164911685,P)/1.146351//Nt=12 0.85*Ro*pow(0.99666382864,P)/1.146351
  #end

  #macro Rl (P)
    Ro*pow(0.999164911685,P)//Nt=12 Ro*pow(0.99666382864,P)
  #end

  #macro Ptri (P)
    <cos(Ka(P))*( Rs(P)*cos(Rt*P)+Rl(P) ),
      ( cos(Rt*P)+Rl(P) )*sin( Ka(P) ), Rs(P)*sin(Rt*P) >,
    <cos(Ka(P))*cos(Rt*P), sin(Ka(P)), sin(Rt*P)>
  #end

  #macro Triangle_units (P1,P2,P3)
    smooth_triangle { 
      <cos(Ka(P1))*( Rs(P1)*cos(Rt*P1)+Rl(P1) ),
        ( Rs(P1)*cos(Rt*P1)+Rl(P1) )*sin( Ka(P1) ), Rs(P1)*sin(Rt*P1) >,
      <cos(Ka(P1))*cos(Rt*P1), sin(Ka(P1)), sin(Rt*P1)>
      <cos(Ka(P2))*( Rs(P2)*cos(Rt*P2)+Rl(P1) ),
        ( Rs(P2)*cos(Rt*P2)+Rl(P2) )*sin( Ka(P2) ), Rs(P2)*sin(Rt*P2) >,
      <cos(Ka(P2))*cos(Rt*P2), sin(Ka(P2)), sin(Rt*P2)>
      <cos(Ka(P3))*( Rs(P3)*cos(Rt*P3)+Rl(P1) ),
        ( Rs(P3)*cos(Rt*P3)+Rl(P3) )*sin( Ka(P3) ), Rs(P3)*sin(Rt*P3) >,
      <cos(Ka(P3))*cos(Rt*P3), sin(Ka(P3)), sin(Rt*P3)>
      Texture_c ( 0.5+0.5*cos(Rt*P1),0.5+0.5*sin(Rt*P1),0.5-0.5*cos(Rt*P1),0.8-P1/5000 )}
  #end

  union {
    #declare Pn =0; #while (Pn < 3*Pne-Nt)
      Triangle_units (Pn,Pn-1,Pn-Nt)
      Triangle_units (Pn,Pn-Nt+1,Pn-Nt)        
      #declare Pn =Pn +1;   #end
    }     
#end
   
camera {
  location <0,100,50>
  angle 3.8//12.5
  look_at <1.6, 0, -1.2>
  }

light_source {<500, 1000, -200> color rgb <1,1,1>}

object {
  Gold_ring (3, 24)
  rotate <-90,0,0>
  translate <-0,0,0>
  }

background { color rgb <0,0,0.2> }