pgfplots 3d: un-render overwritten graph

Question

Is there a way to tell pgfplots not to render the parts of a 3d graph that are overwritten?

Here is a minimal example

\documentclass{standalone}
% pgfplots
\usepackage{pgfplots}
\pgfplotsset{
    compat       = newest,
    width        = 10cm,    % width
    height       =  7cm,    % height
    samples      = 20,
}
\begin{document}
\begin{tikzpicture}
    \begin{axis}[hide axis]
    \addplot3 [
        % Aparence
        surf,
        opacity=0.5,
        fill opacity= 1,
        faceted color = white,
        shader=faceted interp,
        % Scope
        data cs = cart, % cart/polar/polarrad
        % Variable
        domain   = -1:1,
        domain y = -1:1,
    ]{
        x^2-y^2
    };

\end{axis}

\end{tikzpicture}
\begin{tikzpicture}
    \begin{axis}[hide axis]
    \addplot3 [
        % Aparence
        surf,
        opacity=0.5,
        fill opacity= 1,
        faceted color = white,
        shader=faceted interp,
        % Scope
        data cs = cart, % cart/polar/polarrad
        % Variable
        variable   = u,
        variable y = v,
        domain   = 0:360,
        domain y = -180:0,
    ]
    (
        {cos(u)*sin(v)}, 
        {sin(u)*sin(v)}, 
        {cos(v)}
    );

\end{axis}

\end{tikzpicture}
\end{document}

that yields:

it is possible to see that everything that is overwritten is rendered, slowing down the compilation process, is there any way to optimise this?

---

Update 2

Opened an issue with problems related to the implementation of external library here