set isosample 21
set dummy u,v
sinc(u,v) = sin(sqrt(u**2+v**2)) / sqrt(u**2+v**2)
set view 70,20,1
set zrange [-0.5:1.0]
set ztics -1,0.25,1
splot [-12:12.01] [-12:12.01] sinc(u,v)
