Definition: <m>1-((x-x_0)/a)^2-((y-y_0)/b)^2-((z-z_0)/c)^2</m>
Call: hfEllipsoid(x,center,a,b,c);
Parameters:
x - point coordinates array
center - ellipsoid center array
a,b,c - ellipsoid half-axes along x,y,z
Test file: ellipsoid.hf