truncated cone plot

Hi everybody, I'm just trying to plot and save a 3D matrix of points that describes a truncated cone. I've realized it with a set of concentric circles (or, better to say, one-period-spirals) reducing the external size from floor to floor. May i ask you if you know how to realize a truncated cone (just the surface) with only one spiral growing from the base to the top? Thanks for your time

Answer 1

[the cyclist]

It is not perfectly clear to me what you want, but here is a parameterization that sounds close to what I think you mean:

t = 30:0.1:100;

az = 0.1;
z = az*t;

r0 = 10000;
ar = -1;
r = r0 + r0*t;

at = 0.05;
theta = at*t;

x = r .* cos(t);
y = r .* sin(t);

figure
plot3(x,y,z,'.-')

[Lorenzo]

Thank you very much, that's what i needed.