[math-fun] Parametrization of the sphube

The points of the sphube of radius of axis r and center the origin of the mark can be parameterized by: x=r*(qos(theta))*(qos(phi)); y=r*(qos(theta))*(qin(phi)); z=r*qin(theta); theta in [sigma/2,-sigma/2]; Phi in [sigma,-sigma]; for the sphube x ^ 4 + y ^ 4 + z ^ 4 = 1 we have: r = 1