%% d'apres les donnees de
%% http://www.mathcurve.com/courbes3d/solenoidtoric/solenoidtoric.shtml

-6 6 setxrange
-6 6 setyrange
50 setxunit

0.01 0 50 SetCamPos
0 0 0 SetCamView


-10 10 setxrange3d
-3 3 setyrange3d
2 setlinejoin


/m 15 def %% ex R
/r 6 def
/n 2 def

/g {
3 dict begin
   settvar
#rpn# (m+r*Cos(n*t))*Cos(t)
#rpn# (m+r*Cos(n*t))*Sin(t)
#rpn# r*Sin(n*t)
end
} def

/g' {
3 dict begin
   settvar
#rpn# -n*r*Sin(n*t)*Cos(t) - (m+r*Cos(n*t))*Sin(t)
#rpn# -n*r*Sin(n*t)*Sin(t) + (m+r*Cos(n*t))*Cos(t)
#rpn# n*r*Cos(n*t)
end
} def

/g'' {
3 dict begin
   settvar
#rpn# -n^2*r*Cos(n*t)*Cos(t) +n*r*Sin(n*t)*Sin(t) + n*r*Sin(n*t)*Sin(t) - (m+r*Cos(n*t))*Cos(t)
#rpn# -n^2*r*Cos(n*t)*Sin(t) -n*r*Sin(n*t)*Cos(t) - (n*r*Sin(n*t))*Cos(t) - (m+r*Cos(n*t))*Sin(t)
#rpn# -n^2*r*Sin(n*t)
end
} def

%% rouge
  0 pi 2 mul {g} CourbeR3
%  stop

.1 setlinewidth

GetCamPos setlightsrc
%solidgridOff

0 pi 2 mul (g) 2 [200 8] newtube
dup [.5 .6] solidputhuecolors
%dup videsolid
drawsolid**