Evgheny - If you seriously need to fit such a surface in spherical coordinates, I might be able to help you out with a separate, un-posted toolbox that is capable of fitting a surface in spherical coordinates. You would need to contact me directly.
Thanks, function does do its job great!
Does anyone know alternative of this function for closed surface (sphere-like).
If I try this function with spherical coordinates, it works fine, but there are problems with the seam (line of joint)
Sorry. I've never heard of a Java implementation. Not that it counts, I've written it 7 times in MATLAB, once each in Fortran and APL, those last were very old though. The difference each time was what I learned from the previous incarnation. Were someone to do a Java implementation perhaps the most important thing is to use sparse linear algebra capabilities for the solve, else it would take forever.
Just to add my $0.02 to this whole sphere discussion. By math definition of what is function it means for each x we have only one F(x). If there are more than one F(x) relation between x and F(x) is not a function.