Markerless inside-out tracking: Difference between revisions - VR & AR Wiki

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:''See also [[Inside-out tracking]], [[Markerless tracking]], [[Positional tracking]]''

==Introduction==

[[File:Intel Project Alloy.jpg|thumb|Figure 1. Intel's Project Alloy (Image: gizmodo.com)]]

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Markerless tracking is a method of motion tracking that avoids the use of markers (also known as [[fiducial markers]]). These markers are usually placed in the environment or in the head-mounted displays (HMDs), helping the system determine the users or camera position. The Markerless method uses instead natural features already present in the environment, for tracking purposes. <ref name=”3”> 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> <ref name=”4”> Klein, G. (2006). Visual tracking for augmented reality. Ph.D. thesis, University of Cambridge, Department of Engineering</ref> This method is considered more flexible and effective since there isn’t the need for a prepared environment with markers. <ref name=”5”> 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=”6”> 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> The decreasing cost of computer vision is another factor that has made markerless tracking an attractive alternative of tracking. However, this method still has some problems, such as motion blur and fast motion affecting tracking. <ref name=”7”> Fang, W., Zheng, L., Deng, H. and Zhang, H. (2017). Real-time motion tracking for mobile augmented/virtual reality using adaptive visual-inertial fusion. Sensors, 17</ref> It also demands a trade-off between precision and efficiency. <ref name=”2”></ref>

Inside-out is a term that defines the position of the cameras or other sensors relative to the object to be tracked. If they are placed in a stationary location exterior to the HMD, for example, it is considered [[outside-in tracking]]. In inside-out, the camera is placed in the HMD. <ref name=”8”> Boger, Y. (2014). Positional tracking: "Outside-in" vs. "Inside-out." Retrieved from https://vrguy.blogspot.pt/2014/08/positional-tracking-outside-in-vs.html</ref> There is great interest in inside-out tracking since it simplifies the setup and allows the user a greater sense of freedom by not being limited to a specific tracking space. Inside-out positional tracking has the potential to make VR completely wireless, more convenient and accessible. Some have gone as far as saying that it was the “holy grail” of the VR scene. <ref name=”9”> Robertson, A. (2017). Self-tracking headsets are 2017’s big VR trend — but they might leave your head spinning. Retrieved from https://www.theverge.com/2017/1/12/14223416/vr-headset-inside-out-tracking-intel-qualcomm-microsoft-ces-2017</ref> <ref name=”10”> Durbin, J. (2016). Google: Wireless positional tracking “solved”, but heat still a problem for VR. Retrieved from https://uploadvr.com/inside-out-google-solve-tracking/</ref>.

Inside-out is a term that defines the position of the cameras or other sensors relative to the object to be tracked. If they are placed in a stationary location exterior to the HMD, for example, it is considered [[outside-in tracking]]. In inside-out, the camera is placed in the HMD. <ref name=”8”> Boger, Y. (2014). Positional tracking: "Outside-in" vs. "Inside-out." Retrieved from https://vrguy.blogspot.pt/2014/08/positional-tracking-outside-in-vs.html</ref> There is great interest in inside-out tracking since it simplifies the setup and allows the user a greater sense of freedom by not being limited to a specific tracking space. Inside-out positional tracking has the potential to make VR completely wireless, more convenient and accessible. Some have gone as far as saying that it was the “holy grail” of the VR scene. <ref name=”9”> Robertson, A. (2017). Self-tracking headsets are 2017’s big VR trend - but they might leave your head spinning. Retrieved from https://www.theverge.com/2017/1/12/14223416/vr-headset-inside-out-tracking-intel-qualcomm-microsoft-ces-2017</ref> <ref name=”10”> Durbin, J. (2016). Google: Wireless positional tracking “solved”, but heat still a problem for VR. Retrieved from https://uploadvr.com/inside-out-google-solve-tracking/</ref>.

With inside-out, the data that is gathered is generally processed by the headset, giving the user an increased mobility within a room. It can also be the case that the sensors are connected to a computer that is carried by the user or the signal is sent wirelessly to a stationary processing unit, but since inside-out tracking aims to provide more freedom of use the optimal solution is the headset providing all the computational power. <ref name=”2”></ref>

There is a great deal of interest in markerless technology. While marker-based systems are still better for accuracy and latency, there has been big investments in researching and developing markerless tracking for it to become the leading positional tracking technology. Indeed, it became the big VR trend of 2017, with the potential to make VR more convenient and accessible. <ref name=”4”></ref> <ref name=”7”> Robertson, A. (2017). Self-tracking headsets are 2017’s big VR trend — but they might leave your head spinning. Retrieved from https://www.theverge.com/2017/1/12/14223416/vr-headset-inside-out-tracking-intel-qualcomm-microsoft-ces-2017</ref>

There is a great deal of interest in markerless technology. While marker-based systems are still better for accuracy and latency, there has been big investments in researching and developing markerless tracking for it to become the leading positional tracking technology. Indeed, it became the big VR trend of 2017, with the potential to make VR more convenient and accessible. <ref name=”4”></ref> <ref name=”7”> Robertson, A. (2017). Self-tracking headsets are 2017’s big VR trend - but they might leave your head spinning. Retrieved from https://www.theverge.com/2017/1/12/14223416/vr-headset-inside-out-tracking-intel-qualcomm-microsoft-ces-2017</ref>

High-end VR headsets use external cameras or external markers to calculate the user’s position in space and translate it to the virtual environment, and mobile VR systems have no positional tracking. Markerless technology could not only simplify the setup for high-end headsets but also expand the capabilities of mobile VR. <ref name=”7”></ref>