b = 0.8 (slider from 0 to 3, step 0.1)
a = 0 (slider from 0 to 3, step 0.3)
e_z = (0, 1)
e_y = (1, 0)
e_x = (-0.4, -0.4)
f(a, b) = (((0.2 * a) * b) * b)
Q: (e_x * a) + (e_y * (b + 0.1)) + (e_z * f(a, b + 0.1))
P: (e_x * a) + (e_y * b) + (e_z * f(a, b))
c = Segment(P, Q)
R: (e_x * (a + 0.3)) + (e_y * b) + (e_z * f(a + 0.3, b))
d = Segment(P, R)