from sympy import *
from spb import *
import numpy as np
x, y = symbols("x y")
surf_series = surface(
    cos(x*y) * exp(-sqrt(x**2 + y**2) / 4), (x, -pi, pi), (y, -pi, pi),
    use_cm=True, color_func=lambda x, y, z: np.sqrt(x**2 + y**2)
)
graphics(
    surf_series,
    wireframe(surf_series[0], n1=11, n2=11),
    backend=PB, aspect=dict(x=1.5, y=1.5, z=1)
)