fit and plot surface and get acces to fitted surface parameters

I use

f = fit( [X1, Y1], Z1, 'poly44' )

and

plot(f, [X1,Y1], Z1)

functions to fit (and plot) surface to scattered data.

Is it any way to get acces to fitted surface data,

i.e. x, y ,z values of fitted surface in arbitraty

chosen x, y regular grid?

[darova]

BUt you already have your function f(x,y)

DOesn't it work?