\fresh{}

\section{Conclusion}

In this chapter, we have described a basic interface that allows a user to navigate in a scene that is being streamed.
It allowed us to understand the problems linked to the dynamicity of both the user behaviour and the 3D content:

\begin{itemize}
    \item Navigating in a 3D scene can be complex, due to the many degrees of freedom, and tweaking the interface can increase the user's Quality of Experience.
    \item The tweaks operated on the interface may have a drawback on the streaming aspect of the system.
    \item Depending on how the interface is tweaked, the behaviour of the users may change and heuristics can be determined to benefit from this.
\end{itemize}

However, the system described in this chapter has some drawbacks:

\begin{itemize}
    \item \textbf{It doesn't support materials and textures}: these elements are downloaded at the beginning of the interaction, and since they can have a massive size, this solution is not satisfactory for a system streaming an NVE\@.
    \item \textbf{It still requires a heavy load on the server side}: even though the server is not performing online rendering of the scene, it still has to perform frustum and backface culling to find the faces to send to the client, and it also has to keep track of what each client has already downloaded, and what remains to be downloaded.
    \item \textbf{The performance of the rendering has not been taken into account}: of course, a system for navigating in 3D scenes must have a sufficient framerate to guarantee a good Quality of Experience for users, and this chapter does not tackle at any point the difficulty to have many tasks to do at the same time (downloading data, uploading the OpenGL buffers, managing the user interaction, rendering the scene, etc\ldots).
    \item \textbf{No multi-resolution techniques are used}: in modern 3D streaming, mutli-resolution is a must-have. It prevents the user from waiting until all the data is arrived while still having a global, lower-resolution view of the content he's trying to access.
\end{itemize}

After learning these lessons, we show, in the next chapter, what is possible to do in order to alleviate these issues.
