Ellipsographes

Ellipsographe par anti-parallèlogramme

%@DATE: 30 mai 2005
 
input fichierps;
 
InitFichierPS(-120,-120,210,120);
u = 1cm;
 
% Les points fixes
pair A, B;
A = (0,0);
B = (3u,0);
 
% Les deux cercles
path cA, cB;
cA = fullcircle scaled 8u shifted A;
cB = fullcircle scaled 8u shifted B;
 
% Les articulations.
pair C,D,E;
 
vardef Point(expr p) =
    draw p withpen pencircle scaled 4;
    draw p withpen pencircle scaled 3 withcolor white;
enddef;
 
% L'ellipse;
path e;
 
 
for i=0 upto 90:
  beginfig(i+1);
 
    C := point (8*i/90.5+0.01) of cB;
    D := (C + A -B) reflectedabout(A,C);
    E := (B--C) intersectionpoint (A--D);    
 
    fill cB withcolor 0.8white;
 
    drawoptions(withcolor 0.6white);    
    draw cA;
    draw cB;
    drawoptions();
 
    drawarrow subpath (0,8*i/90.5) of cB;
 
    if i=0: 
	e := E;
    else:
	e := e -- E;
	draw e withpen pencircle scaled 1 withcolor blue;
    fi
 
    drawoptions(withpen pensquare scaled 2 withcolor (1,0.08,0.58));	
    draw A--D;
    draw B--C;
    draw C--D;
    drawoptions();
 
    Point(A);
    Point(B);
    Point(C);
    Point(D);
    Point(E);    
 
  endfig;
endfor;
 
end