Surface between curves
Script
A1 = (0, 0)
A2 = (1, 0)
A3 = (1, 1)
A4 = (0, 1)
q1 = Polygon(A1, A2, A3, A4)
P1 = PointIn(q1)
P2 = PointIn(q1)
P3 = PointIn(q1)
P4 = PointIn(q1)
P5 = PointIn(q1)
s1 = Spline({P1, P2, P3, P4, P5})
F = (0, 0, 0)
l1 = PerpendicularLine(F, xOyPlane)
G = Point(l1)
B1 = (-2, 0, 0)
B2 = (0, -2, 0)
B3 = (1.68, -1.36, 0)
B4 = (2.18, 0.85, 0)
B5 = (0.59, 2.5, 0)
B6 = (-1.56, 1.55, 0)
b1 = Spline({B1, B2, B3, B4, B5, B6, B1})
mySurface = Surface(y(s1(k)) (x(b1(t)) - x(G)) + x(G), y(s1(k)) (y(b1(t)) - y(G)) + y(G), (1 - k) z(G), k, 0, 1, t, 0, 1)
b2 = Curve(mySurface(0, t), t, 0, 1)
Based on Homotècia i superfície, Author: Bernat
https://www.geogebra.org/m/wnhyfsbz