problem with curve fitting toolbox equation variables

Let’s assume that:

phi=[0 ; pi/2 ; pi/2 ; pi/2 ; pi/2 ; pi/2 ; pi];

theta=[0 ; 0 ; pi/2 ; pi ; 1.5*pi ; 2*pi ; 0];

c=[1.175 ; 0.4664 ; 2.226 ; 0.4664 ; 2.226 ; 0.4664 ; 1.175];

Selecting Biharmonic(V4) 3D interpolation from MATLAB cftool I get the following curve:

I need the equation (F(phi,theta,c)) of the curve but apparently it is too complicated to extract.

Is there any way to obtain F(phi,theta,c) for any given amounts of phi,theta and c beside the ones that I already specified?

Thank you