I want to plot some ellipsoids like the following ones in tikz but I don't know how can I do it. How can they be plotted in tikz?
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The package pgfplots might be preferable to tikz-3dplot, as it is being actively maintained, and it seems to be able to produce these sort of plots. – Benjamin McKay Dec 17 '18 at 19:42
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Related: pgfplots: Tilted and Rotated sphere The question is about spheres but the answer uses the more general ellipsoids. – Henri Menke Dec 17 '18 at 20:29
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See e.g. here for some tikz-3dplot example. The analytic expressions to distinguish between the visible and hidden parts have AFAIK not yet been derived on this site. – marmot Dec 17 '18 at 20:31
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Here's a possible solution
\documentclass[border = 5pt]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat = newest}
\begin{document}
\begin{tikzpicture}
\pgfmathsetmacro{\p}{1.0}
\pgfmathsetmacro{\q}{1.5}
\begin{axis}[
xlabel = {$x$},
ylabel = {$y$},
zlabel = {$z$},
view = {60}{30},
domain = 0 : pi,
y domain = 0 : 2 * pi,
z buffer = sort,
unit vector ratio = 1 1,
hide axis,
colormap/violet,
declare function = {
xp(\x, \y) = sin(deg(\x)) * cos(deg(\y));
yp(\x, \y) = \p * sin(deg(\x)) * sin(deg(\y));
zp(\x, \y) = \q * cos(deg(\x));
}, ]
\addplot3[patch]({xp(x, y)}, {yp(x, y)}, {zp(x, y)});
\draw[->] (1, 0, 0) -- (2, 0, 0) node[right]{$x$};
\draw[->] (0, \p, 0) -- (0, 2, 0) node[right]{$y$};
\draw[->] (0, 0, \q) -- (0, 0, 2) node[above]{$z$};
\end{axis}
\end{tikzpicture}
\end{document}
You need to adjust the axis ratios p and p to get different version
p = 1.0, q = 1.5(prolate) figure
p = 1.0, q = 0.5(oblate) figure
