I need to plot a spiral around an inverted truncated cone, starting and ending at the centre of both bases. Something like this:
I've searched and found a similar solution, but for cylinders only: Helix on a cylinder
I couldn't adapt it to my geometric shape in question, so any help would be appreciated.
The code for the cone only:
\documentclass[border=0.125cm]{standalone}
\usepackage{tikz}
\usetikzlibrary{3d,calc}
\begin{document}
\begin{tikzpicture}
\draw (-1,0) arc (180:370:2cm and 1cm);
\draw (-1,0) arc (180:10:2cm and 1cm);
\draw (0,-3) arc (180:360:1cm and 0.5cm);
\draw[dashed] (0,-3) arc (180:0:1cm and 0.5cm);
\draw(0,-3) -- (-0.97,-0.18);
\draw(2,-3) -- (2.97,-0.18);
\shade[left color=blue!5!white,right color=blue!60!white,opacity=0.3] (-0.97,-0.18) arc (190:350:2 and 1) -- (2,-3) arc (360:180:1cm and 0.5cm) -- cycle;
\shade[left color=blue!5!white,right color=blue!60!white,opacity=0.3] (1,0) ellipse (2cm and 1cm);
\draw[dashed] (0.7,-3) arc (180:0:0.3cm and 0.15cm);
\draw[dashed] (0.7,-3) arc (180:360:0.3cm and 0.15cm);
\end{tikzpicture}
\end{document}
Thanks in advance,
Dinis Nunes
EDIT:
Following Ignasi suggestion, I've added a spiral function, but my goal was making the line follow closely the wall of the cone.
Code:
\node[xshift=1cm,yshift=-3cm] (dummy) {};
\draw[densely dotted,scale=0.09,variable=\x,shift=(dummy)] plot[domain = 0:10*pi, samples = 400] ({\x*0.6*sin(0.3*pi*deg(\x))},{\x},{\x*0.6*cos(0.3*pi*deg(\x)});