\caption{A coin is hidden behind the curtain\newline}
\end{subfigure}
\caption{3D bookmarks propose to move to a new viewpoint; when the user clicks on the bookmark, his viewpoint moves to the indicated viewpoint.\label{bi:bookmark}}
\end{figure}
% Bookmarks are virtual objects that represent a point of view, that are rendered with the scene and that can help user navigation.
When the user's cursor hovers a bookmark, a preview of the point of view is displayed to the user, and when the user clicks on a bookmark, the camera smoothly moves from its current position to the bookmarked point of view.
We conduct a within-subject user-study on 51 participants, where each user starts with a tutorial to get used to the 3D navigation controls, and then tries successively to perform a task with and without bookmarks.
We show that not only the presence of bookmarks causes a faster task completion, but also that it allows users to see a larger part of the scene during the same time span.
In the last part of this chapter, we simulate a streaming setup and we show that knowing the positions of the bookmarks beforehand allows us to pre-compute information that we can reuse during streaming to compensate for the harm caused by the faster navigation with bookmarks.
