\section{Contributions}

In this thesis, we attempted to answer four main problems: \textbf{the content preparation}, \textbf{the streaming policy and its relation to the user's interaction}, \textbf{the evaluation}, and the \textbf{implementation}.
To answer those problems, we presented three main contributions.

\paragraph{}
Our first contribution analyzes the links between the streaming policy and the user's interaction.
We set up a basic system allowing navigation in a 3D scene (represented as a textured mesh) with the content being streamed through the network from a remote server.
We developed a navigation aid in the form of \textbf{3D bookmarks}, and we conducted a user study to analyze its impact on navigation and streaming.
On one hand, consistently with the state of the art, we observed that navigation aid \textbf{helps people navigating in a scene}, since they perform tasks faster and more easily.
On the other hand, we showed that benefiting from bookmarks in 3D navigation comes at the cost of a negative impact on the quality of service (QoS): since users navigate faster, they require more data during the same time span.
However, we also showed that this cost is not a fatality: using prior knowledge we have about bookmarks, we are able to \textbf{precompute an optimal data ordering offline} so that the QoS increases when users click on bookmarks.
Simulations on the traces we collected during the user study quantify how these precomputations \textbf{improve the QoS}.
This work has been published at the ACM MMSys conference in 2016~\citep{bookmarks-impact}.

\paragraph{}
After studying the interactive aspect of 3D navigation, we proposed a contribution focusing on the content preparation and the streaming policies of such a system.
The objective of this contribution was to introduce a system able to perform \textbf{scalable, view-dependent 3D streaming}.
This new framework brought many improvements upon the basic system described in our first contribution: support for texture, externalization of necessary computations from the server to the clients, support for multi-resolution textures, rendering performances considerations.
We drew massive inspiration from the DASH technology, a standard for video streaming used for its scalability and its adaptability.
We exploited the fact that DASH is made to be content agnostic to fit 3D content into its structure.
Following the path set by DASH-SRD, we proposed to tile 3D content using a tree and encode this partition into a description file (MPD) to allow view-dependent streaming, without the need for computation on the server side.
On the client side, we implemented loading policies that optimize a utility metric estimating how much geometry and texture segments contribute to the visual rendering of the scene at a particular viewpoint.
We thoroughly tested our solutions by running simulations with different parameter values, as well as different loading policies, to propose an efficient framework that we name DASH-3D.
This work has been published as a full paper at the conference ACMMM in 2018~\citep{dash-3d}.
A demonstration paper on the DASH-3D implementation was also published~\citep{dash-3d-demo}.

\paragraph{}
Finally, we brought back the \textbf{3D navigation bookmark within our DASH-3D framework}.
We developed interfaces that allow navigating in 3D scenes for both \textbf{desktop and mobile devices} and we reintroduced bookmarks in these interfaces.
The setup of our first contribution considered only geometry, triangle by triangle, which made precomputations and ordering straightforward.
Moreover, as the server knew exactly the client needs, it could create chunks adapted to the client's requirements.
In DASH-3D, the data are structured a priori (offline), so that chunks are grouped independently of a client's need.
We therefore focused on precomputing an optimized order for chunks from each bookmark, and, altered the streaming policies from our second contribution to switch to this optimized order when a user clicks a bookmark.
Evaluations showed that the QoS is positively impacted by those policies.
A demo paper was published at the conference ACMMM in 2019~\citep{dash-3d-bookmarks-demo} showing the interfaces for desktop and mobile clients with bookmarks, but without the streaming aspect.
A journal paper will be submitted shortly to value this third contribution.
