\section{Techniques}

\input{wiimote_ir.tex}

\subsection{Head tracking}

\input{headtracking.tex}

\subsection{Stereo vision}

To be able to view a world in 3 dimensions with realistic depth, one must offer each eye an image of its own, taken from a different angle. A problem arises however when there is only one screen available. How can both eyes get one image each from one screen? \\

There are several solutions available. There are so called shutter glasses. These glasses first block one eye, then the other and then back to the first one again. This process has to be in synchronization with the screen. So frame \textit{A} is rendered, the left eye is open and the right eye is closed. Then frame \textit{B}, with the left eye closed and the right eye opened. The problem with this solution however is that you need a screen capable of refreshing at at least 100Hz, since each eye will only get a refresh rate of 50Hz. Anything below that will become very noticeable as flickering. Most laptop screens, if not all, are incapable of doing this. \\

\begin {center}
  \includegraphics[width=100mm]{img/stereo_vision.png} \\
  Figure 1: The stereo vision demo application \\
\end {center}

A different approach is using red-blue stereo glasses. These glasses allow the left eye to see everything that is not red and the right eye to view everything that is not blue. The application then draws the scene twice, once so that it is only viewable by the right eye in blue and simultaneously a second time, in red, for the left eye. Here both frames are rendered simultaneously, so there is no refresh rate issue. The biggest disadvantage however is that the feel of true colors is lost. In both techniques cross talk can occur. For the case of stereo vision, this is explained in chapter 2.3. \\

With the additional head tracking information, the red-blue images can be improved. If the distance  between the user and the screen is getting smaller, the distance between the red and blue images will be larger. This effect is easily checked when looking at your hand and drawing it nearer to your eyes. 