In virtual reality (VR) and augmented reality (AR), a pose tracking system detects the precise pose of head-mounted displays, controllers, other objects or body parts within Euclidean space. Pose tracking is often referred to as 6DOF tracking, for the six degrees of freedom in which the pose is often tracked.[1]
Pose tracking is sometimes referred to as positional tracking, but the two are separate. Pose tracking is different from positional tracking because pose tracking includes orientation whereas and positional tracking does not. In some consumer GPS systems, orientation data is added additionally using magnetometers, which give partial orientation information, but not the full orientation that pose tracking provides.
In VR, it is paramount that pose tracking is both accurate and precise so as not to break the illusion of a being in virtual world. Several methods of tracking the position and orientation (pitch, yaw and roll) of the display and any associated objects or devices have been developed to achieve this. Many methods utilize sensors which repeatedly record signals from transmitters on or near the tracked object(s), and then send that data to the computer in order to maintain an approximation of their physical locations. A popular tracking method is Lighthouse tracking. By and large, these physical locations are identified and defined using one or more of three coordinate systems: the Cartesian rectilinear system, the spherical polar system, and the cylindrical system. Many interfaces have also been designed to monitor and control one's movement within and interaction with the virtual 3D space; such interfaces must work closely with positional tracking systems to provide a seamless user experience.[2]
Another type of pose tracking used more often in newer systems is referred to as inside-out tracking, including Simultaneous localization and mapping (SLAM) or Visual-inertial odometry (VIO). One example of a device that uses inside-out pose tracking is the Oculus Quest 2.
Wireless tracking uses a set of anchors that are placed around the perimeter of the tracking space and one or more tags that are tracked. This system is similar in concept to GPS, but works both indoors and outdoors. Sometimes referred to as indoor GPS. The tags triangulate their 3D position using the anchors placed around the perimeter. A wireless technology called Ultra Wideband has enabled the position tracking to reach a precision of under 100 mm. By using sensor fusion and high speed algorithms, the tracking precision can reach 5 mm level with update speeds of 200 Hz or 5 ms latency.
Pros:
Cons:
Optical tracking uses cameras placed on or around the headset to determine position and orientation based on computer vision algorithms. This method is based on the same principle as stereoscopic human vision. When a person looks at an object using binocular vision, they are able to define approximately at what distance the object is placed due to the difference in perspective between the two eyes. In optical tracking, cameras are calibrated to determine the distance to the object and its position in space. Optical systems are reliable and relatively inexpensive, but they can be difficult to calibrate. Furthermore, the system requires a direct line of light without occlusions, otherwise it will receive wrong data.
Optical tracking can be done either with or without markers. Tracking with markers involves targets with known patterns to serve as reference points, and cameras constantly seek these markers and then use various algorithms (for example, POSIT algorithm) to extract the position of the object. Markers can be visible, such as printed QR codes, but many use infrared (IR) light that can only be picked up by cameras. Active implementations feature markers with built-in IR LED lights which can turn on and off to sync with the camera, making it easier to block out other IR lights in the tracking area.[5] Passive implementations are retroreflectors which reflect the IR light back towards the source with little scattering. Markerless tracking does not require any pre-placed targets, instead using the natural features of the surrounding environment to determine position and orientation.[6]
In this method, cameras are placed in stationary locations in the environment to track the position of markers on the tracked device, such as a head mounted display or controllers. Having multiple cameras allows for different views of the same markers, and this overlap allows for accurate readings of the device position.[5] The original Oculus Rift utilizes this technique, placing a constellation of IR LEDs on its headset and controllers to allow external cameras in the environment to read their positions.[7] This method is the most mature, having applications not only in VR but also in motion capture technology for film.[8] However, this solution is space-limited, needing external sensors in constant view of the device.
In this method, the camera is placed on the tracked device and looks outward to determine its location in the environment. Headsets that use this tech have multiple cameras facing different directions to get views of its entire surroundings. This method can work with or without markers. The Lighthouse system used by the HTC Vive is an example of active markers. Each external Lighthouse module contains IR LEDs as well as a laser array that sweeps in horizontal and vertical directions, and sensors on the headset and controllers can detect these sweeps and use the timings to determine position.[10][11] Markerless tracking, such as on the Oculus Quest, does not require anything mounted in the outside environment. It uses cameras on the headset for a process called SLAM, or simultaneous localization and mapping, where a 3D map of the environment is generated in real time.[6] Machine learning algorithms then determine where the headset is positioned within that 3D map, using feature detection to reconstruct and analyze its surroundings.[12][13] This tech allows high-end headsets like the Microsoft HoloLens to be self-contained, but it also opens the door for cheaper mobile headsets without the need of tethering to external computers or sensors.[14]
Inertial tracking use data from accelerometers and gyroscopes, and sometimes magnetometers. Accelerometers measure linear acceleration. Since the derivative of position with respect to time is velocity and the derivative of velocity is acceleration, the output of the accelerometer could be integrated to find the velocity and then integrated again to find the position relative to some initial point. Gyroscopes measure angular velocity. Angular velocity can be integrated as well to determine angular position relatively to the initial point. Magnetometers measure magnetic fields and magnetic dipole moments. The direction of Earth's magnetic field can be integrated to have an absolute orientation reference and to compensate for gyroscopic drifts.[15] Modern inertial measurement units systems (IMU) are based on MEMS technology allows to track the orientation (roll, pitch, yaw) in space with high update rates and minimal latency. Gyroscopes are always used for rotational tracking, but different techniques are used for positional tracking based on factors like cost, ease of setup, and tracking volume.[16]
Dead reckoning is used to track positional data, which alters the virtual environment by updating motion changes of the user.[17] The dead reckoning update rate and prediction algorithm used in a virtual reality system affect the user experience, but there is no consensus on best practices as many different techniques have been used.[17] It is hard to rely only on inertial tracking to determine the precise position because dead reckoning leads to drift, so this type of tracking is not used in isolation in virtual reality.[18] A lag between the user's movement and virtual reality display of more than 100ms has been found to cause nausea.[19]
Inertial sensors are not only capable of tracking rotational movement (roll, pitch, yaw), but also translational movement. These two types of movement together are known as the Six degrees of freedom. Many applications of virtual reality need to not only track the users’ head rotations, but also how their bodies move with them (left/right, back/forth, up/down).[20] Six degrees of freedom capability is not necessary for all virtual reality experiences, but it is useful when the user needs to move things other than their head.
Sensor fusion combines data from several tracking algorithms and can yield better outputs than only one technology. One of the variants of sensor fusion is to merge inertial and optical tracking. These two techniques are often used together because while inertial sensors are optimal for tracking fast movements they also accumulate errors quickly, and optical sensors offer absolute references to compensate for inertial weaknesses.[16] Further, inertial tracking can offset some shortfalls of optical tracking. For example, optical tracking can be the main tracking method, but when an occlusion occurs inertial tracking estimates the position until the objects are visible to the optical camera again. Inertial tracking could also generate position data in-between optical tracking position data because inertial tracking has higher update rate. Optical tracking also helps to cope with a drift of inertial tracking. Combining optical and inertial tracking has shown to reduce misalignment errors that commonly occur when a user moves their head too fast.[21] Microelectrical magnetic systems advancements have made magnetic/electric tracking more common due to their small size and low cost.[22]
Acoustic tracking systems use techniques for identifying an object or device's position similar to those found naturally in animals that use echolocation. Analogous to bats locating objects using differences in soundwave return times to their two ears, acoustic tracking systems in VR may use sets of at least three ultrasonic sensors and at least three ultrasonic transmitters on devices in order to calculate the position and orientation of an object (e.g. a handheld controller).[23] There are two ways to determine the position of the object: to measure time-of-flight of the sound wave from the transmitter to the receivers or the phase coherence of the sinusoidal sound wave by receiving the transfer.
Given a set of three noncollinear sensors (or receivers) with distances between them d1 and d2, as well as the travel times of an ultrasonic soundwave (a wave with frequency greater than 20 kHz) from a transmitter to those three receivers, the relative Cartesian position of the transmitter can be calculated as follows:
x 0 = l 1 2 + d 1 2 − − --> l 2 2 2 d 1 {\displaystyle x_{0}={l_{1}^{2}+d_{1}^{2}-l_{2}^{2} \over 2d_{1}}} y 0 = l 1 2 + d 2 2 − − --> l 3 2 2 d 2 {\displaystyle y_{0}={l_{1}^{2}+d_{2}^{2}-l_{3}^{2} \over 2d_{2}}} z 0 = l 1 2 − − --> x 0 2 − − --> y 0 2 {\displaystyle z_{0}={\sqrt {l_{1}^{2}-x_{0}^{2}-y_{0}^{2}}}}
x 0 = l 1 2 + d 1 2 − − --> l 2 2 2 d 1 {\displaystyle x_{0}={l_{1}^{2}+d_{1}^{2}-l_{2}^{2} \over 2d_{1}}}
y 0 = l 1 2 + d 2 2 − − --> l 3 2 2 d 2 {\displaystyle y_{0}={l_{1}^{2}+d_{2}^{2}-l_{3}^{2} \over 2d_{2}}}
z 0 = l 1 2 − − --> x 0 2 − − --> y 0 2 {\displaystyle z_{0}={\sqrt {l_{1}^{2}-x_{0}^{2}-y_{0}^{2}}}}
Here, each li represents the distance from the transmitter to each of the three receivers, calculated based on the travel time of the ultrasonic wave using the equation l = ctus. The constant c denotes the speed of sound, which is equal to 343.2 m/s in dry air at temperature 20°C. Because at least three receivers are required, these calculations are commonly known as triangulation.
Beyond its position, determining a device's orientation (i.e. its degree of rotation in all directions) requires at least three noncollinear points on the tracked object to be known, mandating the number of ultrasonic transmitters to be at least three per device tracked in addition to the three aforementioned receivers. The transmitters emit ultrasonic waves in sequence toward the three receivers, which can then be used to derive spatial data on the three transmitters using the methods described above. The device's orientation can then be derived based on the known positioning of the transmitters upon the device and their spatial locations relative to one another.[24]
As opposed to TOF methods, phase-coherent (PC) tracking methods have also been used to locate object acoustically. PC tracking involves comparing the phase of the current soundwave received by sensors to that of a prior reference signal, such that one can determine the relative change in position of transmitters from the last measurement. Because this method operates only on observed changes in position values, and not on absolute measurements, any errors in measurement tend to compound over more observations. Consequently, this method has lost popularity with developers over time.
In summary, implementation of acoustic tracking is optimal in cases where one has total control over the ambient environment that the VR or AR system resides in, such as a flight simulator.[2][25][26]
Magnetic tracking relies on measuring the intensity of inhomogenous magnetic fields with electromagnetic sensors. A base station, often referred to as the system's transmitter or field generator, generates an alternating or a static electromagnetic field, depending on the system's architecture.
To cover all directions in the three dimensional space, three magnetic fields are generated sequentially. The magnetic fields are generated by three electromagnetic coils which are perpendicular to each other. These coils should be put in a small housing mounted on a moving target which position is necessary to track. Current, sequentially passing through the coils, turns them into electromagnets, which allows them to determine their position and orientation in space.
Because magnetic tracking does not require a head-mounted display, which are frequently used in virtual reality, it is often the tracking system used in fully immersive virtual reality displays.[21] Conventional equipment like head-mounted displays are obtrusive to the user in fully enclosed virtual reality experiences, so alternative equipment such as that used in magnetic tracking is favored. Magnetic tracking has been implemented by Polhemus and in Razer Hydra by Sixense. The system works poorly near any electrically conductive material, such as metal objects and devices, that can affect an electromagnetic field. Magnetic tracking worsens as the user moves away from the base emitter,[21] and scalable area is limited and can't be bigger than 5 meters.
{{cite book}}
Yehezkiel 28Kitab Yehezkiel 30:13–18 pada suatu naskah bahasa Inggris dari awal abad ke-13, MS. Bodl. Or. 62, fol. 59a. Teks bahasa Ibrani disalin sebagaimana dalam kodeks bahasa Latin. Terjemahan bahasa Latin ditulis di bagian marjin.KitabKitab YehezkielKategoriNevi'imBagian Alkitab KristenPerjanjian LamaUrutan dalamKitab Kristen26← pasal 27 pasal 29 → Yehezkiel 28 (disingkat Yeh 28) adalah bagian dari Kitab Yehezkiel dalam Alkitab Ibrani dan Perjanjian Lama di Alkitab Kristen. Be…
Series of highway corridors in the Appalachia region of the eastern United States Appalachian Development Highway SystemMap of the Appalachian Development Highway SystemSystem informationMaintained by state or local governmentsLength3,090 mi (4,970 km)FormedMarch 9, 1965 ADHS signs for U.S. Route 78/Alabama State Route 4/ADHS Corridor X with their distinctive blue color. Most other states do not have distinctive highway shields for ADHS, however. The Appalachian Development Highwa…
Округ Жекс фр. arrondissement de Gex[1]фр. Gex[1] Адм. центр Жекс Країна Франція[2] Регіон Овернь-Рона-Альпи Департамент Ен Населення - повне 98 257 осіб (1 січня 2019)[3] Площа - повна 426 км² Вікісховище має мультимедійні даніза темою: Жекс Округ Жекс (фр. Arrondissement …
Eucalipto de Gunn TaxonomíaReino: PlantaeDivisión: MagnoliophytaClase: MagnoliopsidaSubclase: RosidaeOrden: MyrtalesFamilia: MyrtaceaeSubfamilia: MyrtoideaeTribu: EucalypteaeGénero: EucalyptusEspecie: Eucalyptus gunniiHook.f.Distribución DistributionSubespecies E. gunnii subsp. archeri E. gunnii subsp. divaricata E. gunnii subsp. gunnii [editar datos en Wikidata] Eucalyptus gunnii, el Eucalipto de Gunn,[1] Gunnii o eucalipto sidra, es una especie de Eucalyptus endémi…
Brazilian mixed martial artist Joaquim SilvaBornJoaquim Antônio Magalhães da Silva (1989-02-05) February 5, 1989 (age 34)Anápolis, Goiás, BrazilOther namesNetto BJJHeight5 ft 8 in (1.73 m)[1]Weight155 lb (70 kg; 11.1 st)DivisionLightweightReach69 in (175 cm)[1]StyleBrazilian Jiu-Jitsu, Muay ThaiStanceOrthodoxFighting out ofCuritiba, BrazilTeamEvolução ThaiRankBlack belt in Brazilian Jiu-Jitsu[1] Black kruang in Muay Thai&…
This article is about the 2003 album by Rogério Skylab. For the NASA SL-4 mission, see Skylab 4. For the NASA SLM-4 mission, see Skylab 5. For other uses, see Skylab Four (disambiguation). 2003 studio album by Rogério SkylabSkylab IVStudio album by Rogério SkylabReleased2003RecordedJanuary 2003StudioEstúdio Rock HouseGenreExperimental rockart rocknoise rocksamba rockMPBLength48:12 (original release) 55:06 (with bonus tracks)LabelSelf-releasedProducerRogério SkylabRogério Skylab chr…
Los ricos no piden permiso Os Ricos Não Pedem Permissão (BR) Los ricos no piden permiso Informação geral Formato Telenovela Gênero Drama Duração 60 min (1 hora) Estado Concluída Criador(es) Adrián Suar País de origem Argentina Idioma original espanhol Produção Diretor(es) Gustavo Luppi Rodolfo Antúnez Produtor(es) Adrián Suar Produtor(es) executivo(s) Leonardo Blanco Editor(es) Juan Pablo Lloret Juan Martín Riancho Roteirista(s) Marcos Carnevale Elenco Luciano CastroAra…
Ten artykuł dotyczy herbu szlacheckiego. Zobacz też: inne znaczenia tego słowa. Szreniawa Herb Szreniawa Typ herbu szlachecki Zawołanie Śreniawa, Ocele Alternatywne nazwy Ocele, Śrzeniawa, Śrzeniawita, Śrzeniewita[1] Pierwsza wzmianka 1371 (pieczęć),1403 (zapiska) Multimedia w Wikimedia Commons Szreniawa – polski herb szlachecki, noszący zawołanie Śreniawa i Ocele[1]. Wzmiankowany w najstarszym zachowanym do dziś polskim herbarzu, Insignia seu clenodia Regis et Regni Poloniae, sp…
هذه المقالة يتيمة إذ تصل إليها مقالات أخرى قليلة جدًا. فضلًا، ساعد بإضافة وصلة إليها في مقالات متعلقة بها. (فبراير 2016) يفتقر محتوى هذه المقالة إلى الاستشهاد بمصادر. فضلاً، ساهم في تطوير هذه المقالة من خلال إضافة مصادر موثوق بها. أي معلومات غير موثقة يمكن التشكيك بها وإزالتها. (…
فرانكلينفيل الإحداثيات 42°18′20″N 78°30′00″W / 42.3056°N 78.5°W / 42.3056; -78.5 [1] تقسيم إداري البلد الولايات المتحدة[2] التقسيم الأعلى مقاطعة كاتاروغوس، نيويورك خصائص جغرافية المساحة 51.98 ميل مربع ارتفاع 607 متر عدد السكان عدد السكان 3128 2802 (1 أبري…
Pennsylvania-based roller coaster manufacturer Great Coasters InternationalIndustryManufacturingFounded1994 (1994)HeadquartersSunbury, Pennsylvania, U.S.Area servedWorldwideProductsWooden roller coastersWebsitegreatcoasters.com Great Coasters International, Inc. (GCI or GCII) is a Sunbury, Pennsylvania-based roller coaster manufacturer which has created several award-winning rides since its formation in 1994. Starting in 2006 with Thunderbird at PowerPark in Finland, the company expanded be…
Structure of the flyover complex Fe2(C4H4CO)(CO)6, which has idealized C2-symmetry. In organometallic chemistry, a flyover complex features two metals bridged by the fragment OC(RC=CR)2. Some flyover complexes are symmetrical and some are not. Structure of an asymmetrical flyover complex (C5H5)2Fe2[(CCF3)4CO]CO. The Fe-Fe bond length is 258.8 picometers.[1] Common examples are the iron carbonyl derivatives, which are typically air-stable, soluble in nonpolar solvents, and red-orange in c…
Mossel Bay CommandoMossel Bay Commando emblemActiveFebruary 14, 1969 (54 years ago) (1969-02-14)–April 1, 1997 (26 years ago) (1997-04-01)Country South AfricaAllegiance Republic of South Africa Republic of South Africa Branch South African Army South African Army TypeInfantryRoleLight InfantrySizeOne BattalionPart ofSouth African Infantry CorpsArmy Territorial ReserveGarrison/HQMossel BayMilitary unit Mossel Bay Commando was a light…
Ilocano rebel against Spain (1731-63) This article includes a list of general references, but it lacks sufficient corresponding inline citations. Please help to improve this article by introducing more precise citations. (November 2013) (Learn how and when to remove this template message) Gabriela SilangGabriela Silang on a 1974 stamp of the PhilippinesBornMaría Josefa Gabriela Cariño(1731-03-19)March 19, 1731Santa, Ilocos Sur, Captaincy General of the Philippines, Spanish EmpireDiedSeptember …
Ківальські ДеталіНосій КівальськіЗатверджений 17 листопада 1768 рокуВикористання 1 рід Ківальські (пол. Kiwalski) − шляхетський герб, визнаний Альфредом Знамієровським[1] за різновид герба Леліва. Зміст 1 Опис герба 2 Історія 3 Гербовий рід 4 Бібліографія 5 Примітки Опис гер…
Tennis tournamentMiddlesex ChampionshipsDefunct tennis tournamentTourPre open eraFounded1884Abolished1949LocationChiswick Park, Chiswick, Middlesex, Great BritainVenueChiswick Park Lawn Tennis ClubSurfaceGrass The Middlesex Championships.[1] or Middlesex Lawn Tennis Championships[2] and also known as the Middlesex Open Tennis Championships was a men's and women's grass court tennis founded at the Chiswick Park Lawn Tennis Club,Chiswick Park, Chiswick, Middlesex, Great Britain in …
Pakistani literary personality (1925–2019) This article is an orphan, as no other articles link to it. Please introduce links to this page from related articles; try the Find link tool for suggestions. (January 2018) Siddiqa BegumBegum in 2012BornSiddiqa Begum1925Died15 December 2019 (aged 93-94)[1]OccupationEditor of Adbe LatifNationalityPakistani Siddiqa Begum (Urdu: صدیقہ بیگم) was a literary personality of the city of Lahore. She has been the editor of Urdu magazine Adbe L…
Pertempuran Perlintasan CiaterBagian dari Pertempuran Jawa dalam kampanye Hindia BelandaSebuah benteng pengintai Belanda di perlintasan CiaterTanggal5–7 Maret 1942LokasiPerlintasan Ciater, Jawa BaratHasil Kemenangan Jepang Hindia Belanda menyerahPihak terlibat Belanda Hindia Belanda Britania Raya JepangTokoh dan pemimpin Jacob Pesman W.J. de Veer † Toshinari ShōjiKekuatan 9.00027 pesawat 3.00039 pesawat lbsPertempuran Jawa Kalijati Leuwiliang Perlintasan Ciater Pertem…
2001 novel by Mick Lewis The topic of this article may not meet Wikipedia's notability guideline for books. Please help to demonstrate the notability of the topic by citing reliable secondary sources that are independent of the topic and provide significant coverage of it beyond a mere trivial mention. If notability cannot be shown, the article is likely to be merged, redirected, or deleted.Find sources: Rags novel – news · newspapers · books · scholar…
MaduraiCityPeriyar Bus stand, Teppakulam Mariyamman tank, Madurai Corporation, River Vaigai, Thirumalai Nayak Palace, Meenakshi Amman Temple, Madurai city,CountryIndiaStateTamil NaduDistrictMadurai districtPemerintahan • MayorV. V. Rajan ChellappaLuas • Total51,96 km2 (2,006 sq mi)Ketinggian101 m (331 ft)Populasi (2001) • Total928.869 • Kepadatan0,18/km2 (0,46/sq mi) [1]Languages • Officia…
Lokasi Pengunjung: 3.144.108.113