Question: Animating combined 3d plots

Hi everyone,

I am using the following code (by dr. Corless) to animate a Riemann surface:

restart;
with(plots);
B := 1.5;
u2 := r*cos(th); v2 := r*sin(th);
w1 := u1+I*v1; w2 := u2+I*v2;
z1 := evalc(w1^2); z2 := evalc(w2^2);
x1 := evalc(Re(z1)); x2 := evalc(Re(z2));
y1 := evalc(Im(z1)); y2 := evalc(Im(z2));
f1 := proc (theta) options operator, arrow; plot3d([-x1, -y1, v1], u1 = -6 .. 1, v1 = -B .. B, grid = [50, 50], orientation = [theta, 80], color = u1) end proc;
f2 := proc (theta) options operator, arrow; plot3d([-x2, -y2, v2], r = 1 .. 1, th = -Pi .. Pi, grid = [50, 50], orientation = [theta, 80], color = black) end proc;
display(seq([f1(10*k), f2(10*k)], k = -17 .. 18), insequence = true, axes = box, view = [-1 .. 1, -1 .. 1, -B .. B]);

f1 is the Riemann surface and f2 is the winding curve.

The animation works fine on the individual plots, i.e. when I do:

display(seq(f1(10*k), k = -17 .. 18), insequence = true, axes = box, view = [-1 .. 1, -1 .. 1, -B .. B]);

or

display(seq(f2(10*k), k = -17 .. 18), insequence = true, axes = box, view = [-1 .. 1, -1 .. 1, -B .. B]);

but with both f's (as in my modification)  the animation does not combine correctly the two plots and shows them separately. Is there any way I can combine the plots so that display produces a smooth animation with each rotated frame containing its winding curve?

Many thanks,

Yiannis