This surface is describable parametrically as:

X(s,t) = 0.05*s^2
Y(s,t) = 0.05*t^2
Z(s,t) = 0.001*s^3 - 0.002*s^2*t - 0.002*s*t^2 + 0.001*t^3
domain: s [-20, 20]; t [-20, 20];  (The holed version is missing
-10 to 10 in the s and t domains.)

rotated about the vertical axis a little.

with a hole cut out.

rendered as points and solid from the same perspective.