Changes

:''See also [[Markerless inside-out tracking]], [[Markerless outside-in tracking]], [[Positional tracking]]''

:''See also [[Markerless inside-out tracking]], [[Markerless outside-in tracking]], [[Positional tracking]]''

Markerless tracking is a method of [[positional tracking]] - the determination of position and orientation of an object within its environment. This is a very important feature in [[virtual reality]] (VR) and [[augmented reality]] (AR), making it possible to know the field-of-view and perspective of the user - allowing for the virtual environment to react accordingly or the placement of augmented reality content in accordance with real objects. For a complete motion tracking experience, the tracking system needs to measure movement in six degrees-of-freedom.<ref name=”1”> Ziegler, E. (2010). Real-time markerless tracking of objects on mobile devices. Bachelor Thesis, University of Koblenz and Landau</ref><ref name=”2”> Virtual Reality Society. Virtual reality motion tracking technology has all the moves. Retrieved from https://www.vrs.org.uk/virtual-reality-gear/motion-tracking/</ref>

Markerless tracking is a method of [[positional tracking]] - the determination of position and orientation of an object within its environment. This is a very important feature in [[virtual reality]] (VR) and [[augmented reality]] (AR), making it possible to know the field-of-view and perspective of the user - allowing for the virtual environment to react accordingly or the placement of augmented reality content in accordance with real objects. For a complete motion tracking experience, the tracking system needs to measure movement in six degrees-of-freedom.<ref name=”1”> Ziegler, E. (2010). Real-time markerless tracking of objects on mobile gadgets. Bachelor Thesis, University of Koblenz and Landau</ref><ref name=”2”> Virtual Reality Society. Virtual reality motion tracking technology has all the moves. Retrieved from https://www.vrs.org.uk/virtual-reality-gear/motion-tracking/</ref>

While marker-based methods of motion tracking use specific optical markers, markerless positional tracking does not require them, making it a more flexible method. It also avoids the need for a prepared environment in which [[fiducial markers]] are placed beforehand, for example. Contrary to marked-based tracking, a markerless approach allows the user to walk freely in a room or a new environment and still receive positional feedback, expanding the applicability range.<ref name=”1”></ref><ref name=”2”></ref><ref name=”3”> Zikas, P., Bachlitzanakis, V., Papaefthymiou, M. and Papagiannakis, G. (2016). A mobile, AR inside-out positional tracking algorithm, (MARIOPOT), suitable for modern, affordable cardboard-style VR HMDs. In Digital Heritage. Progress in cultural heritage: documentation, preservation, and protection. Springer International Publishing, Switzerland</ref><ref name=”5”> Lima, J.P., Roberto, R., Simões, F., Almeida, M., Figueiredo, L., Teixeira, J.M. and Teichrieb, V. (2017). Markerless tracking system for augmented reality in the automotive industry. Expert Systems With Applications, 82: 100-114</ref>

While marker-based methods of motion tracking use specific optical markers, markerless positional tracking does not require them, making it a more flexible method. It also avoids the need for a prepared environment in which [[fiducial markers]] are placed beforehand, for example. Contrary to marked-based tracking, a markerless approach allows the user to walk freely in a room or a new environment and still receive positional feedback, expanding the applicability range.<ref name=”1”></ref><ref name=”2”></ref><ref name=”3”> Zikas, P., Bachlitzanakis, V., Papaefthymiou, M. and Papagiannakis, G. (2016). A mobile, AR inside-out positional tracking algorithm, (MARIOPOT), suitable for modern, affordable cardboard-style VR HMDs. In Digital Heritage. Progress in cultural heritage: documentation, preservation, and protection. Springer International Publishing, Switzerland</ref><ref name=”5”> Lima, J.P., Roberto, R., Simões, F., Almeida, M., Figueiredo, L., Teixeira, J.M. and Teichrieb, V. (2017). Markerless tracking system for augmented reality in the automotive industry. Expert Systems With Applications, 82: 100-114</ref>

For AR, a model-based approach might be used in order to determine the placement of virtual objects with real ones. The model of the real object can be encoded as a computer-aided design (CAD model). Markerless augmented reality tracking would therefore continuously search and compare the image it receives with the known 3D model.<ref name=”6”></ref>

For AR, a model-based approach might be used in order to determine the placement of virtual objects with real ones. The model of the real object can be encoded as a computer-aided design (CAD model). Markerless augmented reality tracking would therefore continuously search and compare the image it receives with the known 3D model.<ref name=”6”></ref>

While markerless tracking is a technology that is expected to improve VR and AR application, especially mobile VR and AR, current technological limitations still require a trade-off between precision and efficiency. According to Ziegler (2010), “On the one hand, the more information the application gathers and uses, the more precise is the tracking. On the other hand, the fewer information the calculations have to consider, the more efficient is the tracking. Efficiency is a huge issue for tracking on mobile devices. The available resources are very limited and the tracking cannot even use all of them, as the rest of the application needs processing power too.” <ref name=”1”></ref>

While markerless tracking is a technology that is expected to improve VR and AR application, especially mobile VR and AR, current technological limitations still require a trade-off between precision and efficiency. According to Ziegler (2010), “On the one hand, the more information the application gathers and uses, the more precise is the tracking. On the other hand, the fewer information the calculations have to consider, the more efficient is the tracking. Efficiency is a huge issue for tracking on mobile gadgets. The available resources are very limited and the tracking cannot even use all of them, as the rest of the application needs processing power too.” <ref name=”1”></ref>

==Factors affecting markerless tracking==

==Factors affecting markerless tracking==