Superformula

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Some superformula samples: a = b = 1; m, n1, n2 and n3 are shown in picture

The superformula is a generalization of the superellipse and was first proposed by Johan Gielis in 2003.[1] Gielis suggested that the formula can be used to describe many complex shapes and curves that are found in nature. The upcoming computer game No Man's Sky heavily employs the superformula for the procedural generation of its digital universe.[2]

In polar coordinates, with r the radius and \varphi the angle, the superformula is:

r\left(\varphi\right) =
\left[
        \left|
                \frac{\cos\left(\frac{m\varphi}{4}\right)}{a}
        \right| ^{n_2}
+
        \left|
                \frac{\sin\left(\frac{m\varphi}{4}\right)}{b}
        \right| ^{n_3}
\right] ^{-\frac{1}{n_{1}}}.

By choosing different values for the parameters a, b, m, n_1, n_2, n_3, different shapes can be generated.

The formula was obtained by generalizing the superellipse, named and popularized by Piet Hein, a Danish mathematician.

Extension to higher dimensions[edit]

It is possible to extend the formula to 3, 4, or n dimensions, by means of the spherical product of superformulas. For example, the 3D parametric surface is obtained by multiplying two superformulas r1 and r2. The coordinates are defined by the relations:

 x = r_1(\theta)\cos\theta \cdot r_2(\phi)\cos\phi,
 y = r_1(\theta)\sin\theta \cdot r_2(\phi)\cos\phi,
 z = r_2(\phi)\sin\phi,

where \phi (latitude) varies between −π/2 and π/2 and θ (longitude) between −π and π.

Plots[edit]

Sf2d.png

A GNU Octave program for generating these figures:

  function sf2d(n,a)
    u=[0:.001:2*pi];
    raux=abs(1/a(1).*abs(cos(n(1)*u/4))).^n(3)+abs(1/a(2).*abs(sin(n(1)*u/4))).^n(4);
    r=abs(raux).^(-1/n(2));
    x=r.*cos(u);
    y=r.*sin(u);
    plot(x,y);
  end



3D superformula: a = b = 1; m, n1, n2 and n3 are shown in the pictures.

A GNU Octave program for generating these figures:

 function sf3d(n, a)
  u=[-pi:.05:pi];
  v=[-pi/2:.05:pi/2];
  nu=length(u);
  nv=length(v);
    for i=1:nu
    for j=1:nv
      raux1=abs(1/a(1)*abs(cos(n(1).*u(i)/4))).^n(3)+abs(1/a(2)*abs(sin(n(1)*u(i)/4))).^n(4);
      r1=abs(raux1).^(-1/n(2));
      raux2=abs(1/a(1)*abs(cos(n(1)*v(j)/4))).^n(3)+abs(1/a(2)*abs(sin(n(1)*v(j)/4))).^n(4);
      r2=abs(raux2).^(-1/n(2));
      x(i,j)=r1*cos(u(i))*r2*cos(v(j));
      y(i,j)=r1*sin(u(i))*r2*cos(v(j));
      z(i,j)=r2*sin(v(j));
    endfor;
  endfor;
  mesh(x,y,z);
 endfunction;

References[edit]

External links[edit]