I want to add 2 parabolas to a plot of a hyperbolic paraboloid, but I can't figure out (and couldn't find any information on the internet) how to keep pgfplots from closing the ends of the graphs. My plot looks like this:
\begin{tikzpicture}
\begin{axis}[
grid=major,
axis lines=middle,
inner axis line style={=>},
ticks=none
]
\addplot3 [draw=red,line width=1pt] ({x},0,{-x^2});
\addplot3 [draw=blue,line width=1pt] (0,{x},{x^2});
\addplot3 [surf,shader=flat,fill opacity=.4,draw=black] {y^2-x^2};
\end{axis}
\end{tikzpicture}
I basically want the same plot, only without the straight red and blue lines closing the parabolas.