autocrop
15 setxunit
%quadrillage marks
-22 8 setxrange
-8 18 setyrange

%% le plan de base
/P1 {-9 -5} def
/P2 {4 -7} def
/P3 {8.5 0} def

/o {0 0 0} def
/i {0 0 7} def
/o' {0 0 14} def

/M {-12 2} def
/N {-7 -3} def

/vect_I {15 cos 15 sin} def
/vect_J {135 cos 135 sin .8 mulv} def
/vect_K {0 1} def

/xyz2xy {
3 dict begin
   /z exch def
   /y exch def
   /x exch def
   vect_I x mulv
   vect_J y mulv
   vect_K z mulv
   addv addv
end
} def

[/I /O /O'] 
[i o o'] {xyz2xy} capply
mapnp

/r1 6 def
/r2 1.5 def
/ell [O r1 r2 0] def
/ell' [O' r1 r2 0] def
0 ell epoint /A defpoint
0 ell' epoint /A' defpoint
180 ell epoint /B defpoint
180 ell' epoint /B' defpoint

O M ell interdroiteell /m defpoint /m' defpoint 
O O' m paral I M interdroite /M' defpoint
O O' m' paral I M interdroite /M" defpoint
gsave
   .8 setlinewidth
   orange
   pointilles
   [m' M M"] ligne
   [m M'] ligne
   [m' M"] ligne
grestore

/dotscale {2 dup} def
[I O O' M] {times} plot
[M' M"] {times2} plot

1.2 setlinewidth
-180 0 ell Ellipse
ell' ellipse
[A A'] ligne
[B B'] ligne
M N 1.5 hompoint N 1.2 trait

gsave
   .8 setlinewidth
   pointilles
   0 180 ell Ellipse
   [O O'] ligne
grestore

2 setlinewidth
[-12 P2 P1 xdpoint P2 P3] ligne

12 setfontsize
setTimesItalic
   (I) I drtext   
   (O) O drtext   
   (O') O' drtext   
   (d) 5 M N ydpoint urtext
   (M) M dltext   
%   (N) N dltext