Consider a parametrically described curve (x(t),y(t))
with t
in some interval [a,b]
.
To plot the surface of revolution obtained by rotating this curve
about the x
axis, we do:
plot3d( [x, y*cos(s), y*sin(s)], s=0..2*Pi, t=a..b);
Example 1: Rotating the curve [t+3*sin(t), 4+3*cos(t)], t=0..4*Pi
about the x
axis:
> plot3d([t+3*sin(t), (4+3*cos(t))*cos(s), (4+3*cos(t))*sin(s)], s=0..3/2*Pi, t=0..4*Pi);
Example 2: Rotating the curve y=3+sin(x), x=0..4*Pi
about the
x
axis. The parametric form of the curve is
[t, 3+sin(t)], t=0..4*Pi
. Therefore we obtain the surface of
revolution by:
> plot3d([t, (3+sin(t))*cos(s), (3+sin(t))*sin(s)], s=0..2*Pi, t=0..4*Pi);
Rotations about other axes or lines follow a similar idea.