Apple Surface

Graphics by Paul Bourke
May 2000
x = cos(u) (4 + 3.8 cos(v))

y = sin(u) (4 + 3.8 cos(v))

z = (cos(v) + sin(v) - 1) (1 + sin(v)) log(1 - pi v / 10) + 7.5 sin(v)

0 <= u <= 2 pi, -pi <= v <= pi