\begin{tikzpicture}[line join=round]%
\begin{scope}%
\clip (-0.5,-0.5) rectangle (7.5,7.5);%
\draw[->] (3.5,3.5) -- (4.5249,4.0124);%
\draw[->] (5.25,5.0155) -- (1.75,1.9845);%
\draw[->] (0.4689,4.375) -- (6.5311,2.625);%
\draw[->] (3.5,0.4689) -- (3.5,6.5311);%
\draw[dashed] (3.5,5.9249) -- (4.5249,4.0124) -- (4.5249,1.5876) -- (3.5,3.5);%
\draw[dashed] (2.1,2.2876) -- (4.5249,1.5876) -- (5.9249,2.8);%
\draw[draw=none,fill=cyan,fill opacity=0.8] (2.625,2.7422) .. controls (3.029,2.6256) and (3.5024,2.5945) .. (3.9529,2.6548) -- (3.5,3.5)--cycle;%
\draw[->] (2.625,2.7422) .. controls (3.029,2.6256) and (3.5024,2.5945) .. (3.9529,2.6548);%
\draw[draw=none,fill=cyan,fill opacity=0.8] (3.5,5.0155) .. controls (3.6478,4.7398) and (3.7845,4.2478) .. (3.8698,3.6849) -- (3.5,3.5)--cycle;%
\draw[->] (3.5,5.0155) .. controls (3.6478,4.7398) and (3.7845,4.2478) .. (3.8698,3.6849);%
\fill[opacity=1,ball color=black] (3.5,3.5) circle [radius=0.075cm];%
\draw[-] (1.6625,1.9087) node[] {\footnotesize $x$} (6.6826,2.5812) node[] {\footnotesize $y$} (3.5,6.6826) node[] {\footnotesize $z$} (4.5249,4.0124) node[right] {\footnotesize vers observateur} (3.5,3.5) node[above left] {\footnotesize $O$} (3.3124,1.9376) node[above=0.15cm] {\footnotesize $\theta$} (4.0124,4.9687) node[below=0.25cm] {\footnotesize $\varphi$};%
\draw[-] (3.5,0) node[above] {\footnotesize viewdir=\{'ortho',$\theta,\varphi$\} (en degrés)};%
\end{scope}%
\end{tikzpicture}%