The source of the difficulty is that ellipses are constructed in a particular way in TikZ. They are paths that start from the x-axis and proceed counter-clockwise around their centre. The vast majority of the time, the exact parametrisation doesn't matter. You appear to have found the one situation where it does!
In the actual question, you only want to be able to mirror the ellipse, and so draw it starting from the negative x-axis (the title of the question suggests a more flexible approach). That's actually not too hard since we can exploit the symmetry of the ellipse. The key is to provide it with a negative x-radius, since then it will start from the negative x-axis (and proceed clockwise, but we could correct for that by negating the y-radius as well). To do this, we interrupt the call from the node shape to the drawing command and flip the sign of the x-radius. The simplest way to do this is to redefine the \pgfpathellipse macro to do the negation and then call the original macro. The following code does this.
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations,shapes,decorations.markings}
\makeatletter
\let\origpgfpathellipse=\pgfpathellipse
\def\revpgfpathellipse#1#2#3{%
#2%
\pgf@xa=-\pgf@x
\origpgfpathellipse{#1}{\pgfqpoint{\pgf@xa}{0pt}}{#3}}
\makeatother
\tikzset{
reversed ellipse/.style={
ellipse,
reverse the ellipse%
},
reverse the ellipse/.code={
\let\pgfpathellipse=\revpgfpathellipse
}
}
\begin{document}
\begin{tikzpicture}
\node[ellipse,
draw,
postaction={
decorate,
decoration={
markings,
mark=at position 1 with {
\arrow[line width=5pt,blue]{>}
}
}
}
] at (0,0) {hello world};
\node[reversed ellipse,
draw,
postaction={
decorate,
decoration={
markings,
mark=at position 1 with {
\arrow[line width=5pt,blue]{>}
}
}
}
] at (0,-2) {hello world};
\end{tikzpicture}
\end{document}
Here's the result:
(the arrow got clipped, but you can see where it lies)
Attempted with pgfplots:
\documentclass[tikz]{standalone}
\usepackage{pgfplots}
\begin{document}
\begin{tikzpicture}
\begin{axis}[
view={45}{30},
axis equal image,
axis lines=center,
xtick=\empty,ytick=\empty,ztick=\empty,
colormap={white}{color=(white)color=(white)},
mesh/interior colormap={blue}{color=(blue!20)color=(blue!20)},
z buffer=sort]
\addplot3 [domain=0:8,y domain=0:8,surf,opacity=0.6,shader=flat,samples=2] (x,8,y);
\addplot3 [domain=0:8,y domain=0:2*pi,mesh,black,samples=25] ({4+1*cos(deg(y))},{8},{4+1*sin(deg(y))});
\addplot3 [domain=0:8,y domain=0:2*pi,surf,shader=interp,samples=25] ({4+1*cos(deg(y))},{x},{4+1*sin(deg(y))});
\addplot3 [domain=0:8,y domain=0:8,surf,opacity=0.6,shader=flat,samples=2] (x,0,y);
\addplot3 [domain=0:8,y domain=0:2*pi,mesh,black,samples=25] ({4+1*cos(deg(y))},{0},{4+1*sin(deg(y))});
\end{axis}
\end{tikzpicture}
\end{document}
Result:
Remark:
Commands
\addplot3 [domain=0:8,y domain=0:8,surf,opacity=0.6,shader=flat,samples=2] (x,0,y);
and
\addplot3 [domain=0:8,y domain=0:8,surf,opacity=0.6,shader=flat,samples=2] (x,8,y);
draw planes y=0 and y=8. While command
\addplot3 [domain=0:8,y domain=0:2*pi,surf,shader=interp,samples=25] ({4+1*cos(deg(y))},{x},{4+1*sin(deg(y))});{x},{4+1*sin(deg(y))});
drawing a cylinder (a+bcos(y),x,a+bsin(y)), where a=4 and b=1. I also added:
\addplot3 [domain=0:8,y domain=0:2*pi,mesh,black,samples=25] ({4+1*cos(deg(y))},{0},{4+1*sin(deg(y))});
\addplot3 [domain=0:8,y domain=0:2*pi,mesh,black,samples=25] ({4+1*cos(deg(y))},{8},{4+1*sin(deg(y))});
to mark where the cylinder and plane intercept, as pgfplots couldn't handle that automatically.
You can rotate the view point freely by changing the view={...}{...} option. For example, view={60}{30} will give you:
Most of the options of pgfplots are quite self-explanatory, refer to the package document for further detail.
Best Answer
I don't know about cylinder patricians like Andrew Stacey, but if you don't neccesarily need the filled cylinders in any perspectivce, a cylinder pleb like me might do something like this:
If however you need them in other perspectives, I really can recommend Andrew Stacey's answer linked by Jake, it came in very handy when I had to do a exploded view drawing a while back.