38 lines
4.3 KiB
TeX
38 lines
4.3 KiB
TeX
\section{Contributions}
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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}.
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To answer those problems, we presented three main contributions.
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\paragraph{}
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Our first contribution analyzes the links between the streaming policy and the user's interaction.
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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.
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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.
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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.
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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.
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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.
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Simulations on the traces we collected during the user study quantify how these precomputations \textbf{improve the QoS}.
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This work has been published at the ACM MMSys conference in 2016~\citep{bookmarks-impact}.
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\paragraph{}
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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.
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The objective of this contribution was to introduce a system able to perform \textbf{scalable, view-dependent 3D streaming}.
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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.
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We drew massive inspiration from the DASH technology, a standard for video streaming used for its scalability and its adaptability.
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We exploited the fact that DASH is made to be content agnostic to fit 3D content into its structure.
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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.
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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.
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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.
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This work has been published as a full paper at the conference ACMMM in 2018~\citep{dash-3d}.
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A demonstration paper on the DASH-3D implementation was also published~\citep{dash-3d-demo}.
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\paragraph{}
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Finally, we brought back the \textbf{3D navigation bookmark within our DASH-3D framework}.
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We developed interfaces that allow navigating in 3D scenes for both \textbf{desktop and mobile devices} and we reintroduced bookmarks in these interfaces.
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The setup of our first contribution considered only geometry, triangle by triangle, which made precomputations and ordering straightforward.
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Moreover, as the server knew exactly the client needs, it could create chunks adapted to the client's requirements.
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In DASH-3D, the data are structured a priori (offline), so that chunks are grouped independently of a client's need.
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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.
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Evaluations showed that the QoS is positively impacted by those policies.
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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.
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A journal paper will be submitted shortly to value this third contribution.
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