%% D'apres une idee et un code original de Maxime Chupin

usecolor
-6 6 setxrange
-5 3 setyrange
30 setxunit
/ScreenDist .05 def

-10 0 6 SetCamPos
0 0 0 SetCamView
2 setlinejoin 

/a 2.85 def

/g {
3 dict begin
   /t exch def
#rpn# a*Sin(t)/(1+(Cos(t))^2)
1
#rpn# a*Sin(t)*Cos(t)/(1+(Cos(t))^2)
end
} def

%% /g' { % derivee premiere
%% 3 dict begin
%%    /t exch def
%% #rpn# (4*Cos(t)*Sin(t)^2)/(Cos(t)^2+1)^2+(2*Cos(t))/(Cos(t)^2+1)
%% #rpn# (2*Sin(t)^2)/(Cos(t)^2+1)+(4*Cos(t)^2*Sin(t)^2)/(Cos(t)^2+1)^2+(2*Cos(t)^2)/(Cos(t)^2+1)
%% 0
%% end
%% } def
%% 


%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% %% 1ere compilation : on calcule les 2 parties du tore
%% %% sectionne, puis on sauvegarde
%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% 
%% 3 5 [36 36] newtore
%% [1 0 -4 3 div 0] solideqplansepare
%% 
%% %% maintenant les 2 parties sont sur la pile
%% dup videsolid
%% dup (jaune) (rouge) inoutputcolors
%% /villarceau1 exch def
%% 
%% dup videsolid
%% dup (jaune) (rouge) inoutputcolors
%% /villarceau2 exch def
%% 
%% %% on sauvegarde
%% villarceau1 (villarceau1) writesolidfile
%% villarceau2 (villarceau2) writesolidfile
%% villarceau2 drawsolid**
%% stop

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% 2eme compilation et suivantes : on charge les donnees du tore
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

/villarceau1 (villarceau1) readsolidfile def
/villarceau2 (villarceau2) readsolidfile def


.1 setlinewidth
gris
%% 
%% %on trace
%% solidfuz
villarceau2
drawsolid**

%% villarceau2
%% {0 2 0 addv3d} solidtransform
%% drawsolid**

%le lemniscate
% t_min t_max rayon_tube [resolution]
%% -0 6.28 (g) .1 [100 10] newtube
%% dup [.5 .6] solidputhuecolors

%% %% plutôt qu'un tube, on utilise un simple trait
%% bleu
%% 2 setlinewidth
%% 0 6.28 {g} CourbeR3

%% %% pour visualiser les axes
%%  -2 1 2 axesRVB

[1 0 -4 3 div 0] eq2plan
dup [-6 6 -9 9] planputrange
dup [.5 dup] planputngrid
newplan
dup (.3 setfillopacity AntiqueWhite) solidputcolors
dup videsolid
drawsolid**

bleu
2 setlinewidth
newpath
0 0 5 cercle_
0 3 0 [1 0 -4 3 div] false projpath
stroke
0 0 5 cercle_
0 -3 0 [1 0 -4 3 div] false projpath
stroke