f(x) = 1 + sin(x) / 2
a = -0.6 (slider from -10 to 5, step 0.1)
b = 7.8 (slider from 0 to 15, step 0.1)
c = SurfaceCartesian(u, cos(v) * f(u), sin(v) * f(u), u, a, b, v, 0, 6.2831853072)