Illusion d’optique à base d’ellipse

Auteur ou autrice : Jean-Louis Garcin.

Mise en ligne le 11 avril 2023

Code

% Jean-Louis Garcin
% 2010

beginfig(1); 
 
 path pcg, gcg, pcd,gcd,inter, trait;
 numeric u,d, i,j;
 pair A, B,C;
 
%%%%% 
 
 d=24; % prendre une valeur paire.
 u=0.3cm;
 picture pic;
 
 
 %%%%
 for i= 0 upto (d-1):
 
    pcg:=halfcircle scaled ((2*i)*u);
   gcg:= halfcircle scaled ((2*i+2)*u);
 
      for  j= (d-i) upto (d+i-1):
 
      pcd:=halfcircle scaled ((2*j)*u) shifted (d*u,0);
      gcd:=halfcircle scaled ((2*(j+1))*u) shifted (d*u,0);
 
       if (i+j)/2 =floor((i+j)/2):
        inter:= buildcycle(gcg,gcd,pcg,pcd);
         fill inter withcolor  ((i+j)/(3*d))[blue,white];
        fi
     endfor;
  endfor;
 
  for i=0 upto (d-2):
     pcg:=halfcircle scaled ((2*i)*u);
     gcg:= halfcircle scaled ((2*i+2)*u);
     j:=d+i;
      pcd:=halfcircle scaled ((2*j)*u) shifted (d*u,0);
     gcd:=halfcircle scaled ((2*(j+1))*u) shifted (d*u,0);
     trait:=((-i)*u,0)--((-(i+1))*u,0);
     inter:= buildcycle(gcg,gcd,trait,pcd); 
     fill inter withcolor  ((2*i+d)/(3*d))[blue,white];
    draw trait withcolor  ((2*i+d)/(3*d))[blue,white];
  endfor;
 
  pic:=currentpicture;
  draw pic yscaled -1;
  pic:=currentpicture;
 
  draw pic rotatedaround (((d/2)*u,0),180); 
 
  endfig; 
 end;