I faced this bugreport and hope to have found where's the problem.

It seems that when computing the normal of the superellipsoid some
kind of over/underflow occurs with n or e very small, reordering the
computation produces a better image. Here's the diff to be applied
to super.cpp and a scene that shows the difference.

Massimo

#macro S(E,N,P)
  superellipsoid { <E, N> translate P scale 2*y+1 pigment {rgb
<1,1,0>} }
#end
light_source { -35*z, rgb 1 }
camera {location -35*z look_at 0 }

#declare E = 5;
#declare P = -20*x;
#while (E > 0.00001)
  S(E,.1,P+3.5*y)
  S(E, E, P)
  S(.1,E,P-3.5*y)
  #declare P = P + 5*x;
  #declare E = E / 5;
#end


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<   DBL k, x, y, z;
<   VECTOR P, N, E;
481a480,481
>   VECTOR const& E = Superellipsoid->Power;
>   VECTOR P;
487,498c487,494
<   Assign_Vector(E, Superellipsoid->Power);
<
<   x = fabs(P[X]);
<   y = fabs(P[Y]);
<   z = fabs(P[Z]);
<
<   k = power(power(x, E[X]) + power(y, E[X]), E[Y] - 1.0);
<
<   N[X] = k * SGNX(P[X]) * power(x, E[X] - 1.0);
<   N[Y] = k * SGNX(P[Y]) * power(y, E[X] - 1.0);
<   N[Z] =     SGNX(P[Z]) * power(z, E[Z] - 1.0);
<
---
>   DBL x = P[X] != 0 ? power(fabs(P[X]), E[X]) : 0;
>   DBL y = P[Y] != 0 ? power(fabs(P[Y]), E[X]) : 0;
>   DBL z = P[Z] != 0 ? power(fabs(P[Z]), E[Z]) : 0;
>
>   P[X] = x ? (1 - z) * x / P[X] : 0;
>   P[Y] = y ? (1 - z) * y / P[Y] : 0;
>   P[Z] = z ? (x+y) ? (x + y) * z / P[Z] : 1 : 0;
>
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<   MTransNormal(Result, N, Superellipsoid->Trans);
---
>   MTransNormal(Result, P, Superellipsoid->Trans);

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