600 setwidth
400 setheight

-7 8 setxrange
-3 5 setyrange

%% la source d'eclairage
/src {-3 -3 7} def
/kp 8 def

/f {
   0 0 distance sqrt
} def

/vect_I {-.7 -.7} def
/vect_J {1 0} def
/vect_K {0 1} def
/f {
   dup mul exch dup mul add
   sqrt .5 mul
} def

/vect_J {.7 .7} def
/vect_I {1 0} def
/vect_K {0 1} def

%% syntaxe : nx ny (f) src_pt [color] kp x_min x_max y_min y_max surfz
150 150 (f) src [1 .65 0] kp -6 6 2 copy surfz