View source for Inside-out tracking

{{see also|Markerless inside-out tracking‎|Positional tracking}}
[[File:F2Ak4iE.jpg|thumbnail|Figure 2. Early [[Lighthouse]] prototype, an inside-out tracking system with 2-dimensional barcodes as [[fiducial markers]].]]
[[File:Acer mixed reality headset inside-out.png|thumb|Figure 3. Inside-out tracking HMD (image: www.wareable.com)]]
'''Inside-out tracking''' is a method of [[positional tracking]] commonly used in [[virtual reality]] (VR) technologies, specifically for tracking the position of [[head-mounted display|head-mounted displays]] (HMDs) and motion controller accessories.

It is egocentric. It usually involves [[SLAM]] or [[VIO]] for markerless tracking.<ref name="m249">{{cite web | title=Inside-out tracking | website=XVRWiki | date=2024-09-30 | url=https://www.xvrwiki.org/wiki/Inside-out_tracking | access-date=2024-10-05}}</ref>

It differentiates itself from [[outside-in tracking]] by the location of the cameras or other sensors that are used to determine the object’s position in space (Figure 1). In inside-out positional tracking, the camera or sensors are located on the device being tracked (e.g. HMD) while in outside-in the sensors are placed in a stationary location. <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> <ref name=”2”> 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> <ref name=”3”> Ishii, K. (2010). Augmented Reality: Fundamentals and nuclear related applications. Nuclear Safety and Simulation, 1(1)</ref>
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A VR device using inside-out tracking looks out to determine how its position changes in relation to the environment. When the headset moves, the sensors readjusts its place in the room and the virtual environment responds accordingly in real time. This type of positional tracking can be achieved with or without markers placed in the environment. The latter is called [[markerless inside-out tracking]]. <ref name=”4”> Langley, H. (2017). Inside-out v Outside-in: How VR tracking works, and how it's going to change. Retrieved from https://www.wareable.com/vr/inside-out-vs-outside-in-vr-tracking-343</ref>

The cameras (or any other optical sensors) that are placed on the HMD observe features of the surrounding environment. When using markers, these are designed to be easily detected by the tracking system and placed in a specific area. These [[fiducial markers]] include primitive shapes like points, squares, and circles (Figure 2). QR codes are an example of positional markers that can be placed in the outside world to serve as reference points for the tracking camera. Inside-out positional tracking can also be achieved using infra-red (IR) markers and a camera that is sensitive to this type of light. In case of using markers, the inside-out system works only as long as it can detect the markers. If these are out of its field of view, positional tracking will be affected. <ref name=”2”></ref> <ref name=”3”></ref> <ref name=”5”> Mehling, M. (2006). Implementation of a Low Cost Marker Based Infrared Optical Tracking System. PhD thesis, Fachhochschule Stuttgart</ref>

With markerless inside-out tracking - a method based on natural features - uses distinctive characteristics that originally exist in the environment to determine position and orientation. The system’s algorithms identify specific images or shapes and uses them to calculate the device’s position in space. Data from accelerometers and gyroscopes can also be used to increase the precision of positional tracking. <ref name=”3”></ref> <ref name=”6”> Boger, Y. (2014). Overview of positional tracking technologies for virtual reality. Retrieved from http://www.roadtovr.com/overview-of-positional-tracking-technologies-virtual-reality/</ref>

==Devices using Inside-out tracking==
* ''See also: [[Markerless, inside-out tracking#Markerless inside-out tracking Devices|Devices using markerless inside-out tracking]]''

'''[[HTC Vive]] (including [[HTC Vive Developer Editions|developer editions]])'''

'''[[Microsoft HoloLens]]'''

'''[[Nintendo Wii Remote]] (not officially used for VR)'''

'''[[Samsung HMD Odyssey]]'''

'''[[Oculus Quest]]''' <ref name=”7”> AR/VR Tips (2020). VR Headset Comparison. Retrieved from https://arvrtips.com/vr-headset-comparison-tool/</ref>

'''[[Oculus Rift S]]'''

'''[[HP Reverb G1 & G2]]'''

==Inside-out tracking systems==
* ''See also: [[Markerless, inside-out tracking#Markerless, inside-out tracking Systems|Systems using markerless inside-out tracking]]''

'''[[Lighthouse]] - [[SteamVR]]'''

'''[[Nintendo Wii Sensor Bar]] (not officially used for VR)'''

'''NMERSO'''

[[Category:Terms]] [[Category:Technical Terms]]

==References==