-5 5 setxrange
-2 3 setyrange

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

%% f (x, y) = sin (x^2 + y^2)
/f {
  dup mul exch dup mul add dup Sin exch .001 max div 
} def

/vect_I {-.7 -.5} def
/vect_J {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 -4 4 2 copy surfz