\section{Techniques}

\subsection{Head tracking}

\subsection{Stereo vision}

To be able to view a world in 3 true dimensions, one must offer the eye with an image each. The 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 then as to be in synchronization with the screen. So frame A is renderd, the left eye is open and eye right eye is closed. Then frame 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 aleast 100Hz, since each eye will only get a refresh rate of 50Hz. Anything below that will become very noticable as flikkering. most laptop screens, if not all are not apable of doing this. \\
A different approach is using Red-Blue 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 simulataniously a second time, in red, for the left eye. Here both frames are rendered simulataniously, so there is no refresh rate issue. The disadvantage however is that the feel of true colors is lost and bleeding can occur, if the reds and blues of the glasses do not exactly match. \\
