Definition: <m>1-(((x-x_0)/a)^2/s2+((y-y_0)/b)^2/s2)^(s2/s1)-((z-z_0)/c)^(2/s1)</m>

Call: hfSuperell(x,center,a,b,c,s1,s2);

Parameters:

x - point coordinates array

center - center array

a,b,c - half-axes along x,y,z

s1, s2 - shape parameters, s1 - “sharpness” in z-direction, s2 - “sharpness” in xy-direction
s1, s2 close to 0 - “block” shape, s1, s2 » 0 - “star” shape

Test file: superell.hf