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[[File:Outside in tracking.png|thumb|Figure 1. Outside-in tracking (Image: www.wareable.com)]]

[[File:Outside in tracking.png|thumb|Figure 1. Outside-in tracking (Image: www.wareable.com)]]

'''Outside-in tracking''' is a form of [[positional tracking]] and, generally, it is a method of optical tracking. When referring to [[virtual reality]] (VR), tracking is the process of tracing the scene coordinates of moving objects in real-time, such as [[head-mounted display|head-mounted displays]] (HMDs) or motion controller peripherals.<ref name=”1”> Ribo, M., Pinz, A. and Fuhrmann, A.L. (2001). A new optical tracking system for virtual and augmented reality applications. Instrumentation and Measurement Technology Conference Proceedings</ref>

'''Outside-in tracking''' is a kind of [[positional tracking]] and, generally, it is a method of optical tracking. When referring to [[virtual reality]] (VR), tracking is the process of tracing the scene coordinates of moving objects in real-time, such as [[head-mounted display|head-mounted displays]] (HMDs) or motion controller peripherals.<ref name=”1”> Ribo, M., Pinz, A. and Fuhrmann, A.L. (2001). A new optical tracking system for virtual and augmented reality applications. Instrumentation and Measurement Technology Conference Proceedings</ref>

Outside-in VR tracking uses cameras or other sensors placed in a stationary location and oriented towards the tracked object (e.g. a headset) that moves freely around a designated area defined by the intersecting visual ranges of the cameras (Figure 1). The object is therefore observed from outside by the fixed tracking device. Usually, the tracked object has a known set of markers that are essential for the calculation of its position relative to the sensors. Also, while this type of positional tracking can be achieved using the visible light spectrum, it is common to use infra-red (IR) markers and cameras that can detect that type of light.<ref name=”1”></ref><ref name=”2”> Mehling, M. (2006). Implementation of a Low Cost Marker Based Infrared Optical Tracking System. PhD thesis, Fachhochschule Stuttgart</ref><ref name=”3”> Boger, Y. (2014). Positional tracking: "Outside-in" vs. "Inside-out.” Retrieved from http://vrguy.blogspot.pt/2014/08/positional-tracking-outside-in-vs.html</ref>

Outside-in VR tracking uses cameras or other sensors placed in a stationary location and oriented towards the tracked object (e.g. a headset) that moves freely around a designated area defined by the intersecting visual ranges of the cameras (Figure 1). The object is therefore observed from outside by the fixed tracking device. Usually, the tracked object has a known set of markers that are essential for the calculation of its position relative to the sensors. Also, while this type of positional tracking can be achieved using the visible light spectrum, it is common to use infra-red (IR) markers and cameras that can detect that type of light.<ref name=”1”></ref><ref name=”2”> Mehling, M. (2006). Implementation of a Low Cost Marker Based Infrared Optical Tracking System. PhD thesis, Fachhochschule Stuttgart</ref><ref name=”3”> Boger, Y. (2014). Positional tracking: "Outside-in" vs. "Inside-out.” Retrieved from http://vrguy.blogspot.pt/2014/08/positional-tracking-outside-in-vs.html</ref>