\documentclass{article}

\usepackage{tikz}

%--------------------------------------------------
%: math3d
\tikzset{math3d/.style={x={(-0.353cm,-0.353cm)},z={(0cm,1cm)},y={(1cm,0cm)}}}

%--------------------------------------------------
\begin{document}

\begin{tikzpicture}[math3d,fill=gray!20]
% demi-sphere inferieure
\foreach \t in {1,0.9,...,0} {
    \filldraw plot[domain=0:2*pi] 
    ({sqrt(1-\t^2)*cos(\x r)}, {sqrt(1-\t^2)*sin(\x r)}, -\t);
}
% demi-sphere superieure
\foreach \t in {0,0.1,...,1} {
    \filldraw plot[domain=0:2*pi] 
    ({sqrt(1-\t^2)*cos(\x r)}, {sqrt(1-\t^2)*sin(\x r)}, \t);
}
\end{tikzpicture}
\end{document}