set term postscript color solid
set nokey
set noxtics
set noytics
set noztics
set noborder
set hidden3d
set view 30, 210, 1, 1
set isosamples 40, 40
set output "surf.ps"
set xrange [-4:4]
set yrange [-4:4]
a1 = 2.0
b1 = 2.0
a2 = -2.0
b2 = 2.0
a3 = -2.0
b3 = -2.0
a4 = 2.0
b4 = -2.0
a5 = 0.0
b5 = 0.0
a6 = 0.0
b6 = 3.0
a7 = 3.0
b7 = 0.0
a8 = 0.0
b8 = -3.0
a9 = -3.0
b9 = 0.0
s1(x, y) = exp(-(x-a1)*(x-a1) - (y-b1)*(y-b1))
s2(x, y) = exp(-(x-a2)*(x-a2) - (y-b2)*(y-b2))
s3(x, y) = exp(-(x-a3)*(x-a3) - (y-b3)*(y-b3))
s4(x, y) = exp(-(x-a4)*(x-a4) - (y-b4)*(y-b4))
s5(x, y) = exp(-(x-a5)*(x-a5) - (y-b5)*(y-b5))
s6(x, y) = exp(-(x-a6)*(x-a6) - (y-b6)*(y-b6))
s7(x, y) = exp(-(x-a7)*(x-a7) - (y-b7)*(y-b7))
s8(x, y) = exp(-(x-a8)*(x-a8) - (y-b8)*(y-b8))
s9(x, y) = exp(-(x-a9)*(x-a9) - (y-b9)*(y-b9))
s(x, y) = (s1(x, y) + s2(x, y) + s3(x, y) + s4(x, y) + 1.5*s5(x, y) + 0.5*(s6(x, y) + s7(x, y) + s8(x, y) + s9(x, y)))/1.5015886

splot s(x, y)