Creation of an Augmented Reality Session Using Skeletal Tracking

Abstract

Methods and systems for creating a shared augmented reality (AR) session are disclosed. The methods and systems perform operations including: receiving (502), by a second device, a request to join an AR session initialized (501) by a first device; in response to receiving the request, detecting (503) a body corresponding to a user of the first device in one or more images captured by a camera of the second device; identifying (504) body parts of the detected body corresponding to the user of the first device; determining (505), by the second device, a transformation between the first device and the second device in the AR session using the identified body parts; and causing (506) the second device to display the AR session based on the determined transformation.

Description

[0001] Priority Claim

[0002] This application claims priority to U.S. Patent Application No. 16 / 782,874, filed on February 5, 2020, which is hereby incorporated by reference in its entirety. Background Art

[0003] Augmented reality (AR) is a modification of the virtual environment. For example, in virtual reality (VR), a user is fully immersed in a virtual world, while in AR, a user is immersed in a world that combines virtual objects with the real world or superimposes virtual objects on the real world. AR systems are designed to generate and present virtual objects that interact authentically with the real-world environment and with each other. Examples of AR applications can include single-player or multi-player video games, instant messaging systems, and the like. Brief Description of the Drawings

[0004] In the drawings, like reference numerals may describe similar components in different views, and the drawings are not necessarily drawn to scale. Like reference numerals with different alphabetic suffixes may represent different instances of similar components. Some embodiments are illustrated in the drawings by way of example and not limitation, in which:

[0005] Figure 1 is a graphical representation of a networked environment in which the present disclosure may be deployed, according to some example embodiments.

[0006] Figure 2 is a graphical representation of a messaging client application, according to some example embodiments.

[0007] Figure 3 is a graphical representation of a data structure maintained in a database, according to some example embodiments.

[0008] Figure 4 is a graphical representation of a message, according to some example embodiments.

[0009] Figure 5 is a flowchart of a process for creating an AR session using skeleton tracking, according to some example embodiments.

[0010] Figure 6 is a block diagram showing a software architecture in which the present disclosure may be implemented, according to some example embodiments.

[0011] Figure 7 is a graphical representation of a machine in the form of a computer system within which a set of instructions may be executed to cause the machine to perform any one or more of the methods discussed herein.

[0012] Figure 8 is a graphical representation of a processing environment in accordance with some example embodiments. DETAILED DESCRIPTION

[0013] The following description includes systems, methods, techniques, instruction sequences, and computer program products that embody illustrative embodiments of the present disclosure. In the following description, numerous specific details are set forth for purposes of explanation to provide an understanding of the various embodiments of the inventive subject matter. It will be apparent, however, to those skilled in the art that embodiments of the inventive subject matter may be practiced without these specific details. Generally, well-known instruction instances, protocols, structures, and techniques need not be shown in detail.

[0014] In addition, embodiments of the present disclosure improve the functionality of AR creation software and systems by establishing a common coordinate system for a shared AR session based on skeletal positions and tracking. In one embodiment, the system hosts a shared AR session, which is a session that multiple users can participate in via client devices. Each user in the shared AR session can see the same AR objects located in a real-world scene from each user's own perspective. The shared AR session can be, for example, an AR racing game where each user controls a different car. Each user views the same shared AR scene, which includes real-world objects that are simultaneously displayed on the client devices. In the shared AR scene, a common AR object or a collection of AR objects, such as AR cars, is displayed on each client device. In this way, users are able to view the AR scene from different orientations, positions, and perspectives while still being able to see the common AR object or collection of AR objects. The experience can be synchronized and shared among all users. In this example, the actions of one user in the shared AR session can be synchronized and broadcast to all other users. Thus, the shared AR session is a shared virtual space, but in AR. As another example, two users can point their devices at a real-world scene that includes a table. The two users can be adjacent to each other or across the table from each other. An AR object, such as a virtual piece of paper, can be placed on the real-world table and viewed by each user on their respective devices. When one user modifies the paper by writing with virtual ink on the virtual paper, the other user can simultaneously see the virtual paper being modified.

[0015] One challenge in generating a shared AR session is establishing the origin of the shared AR scene and how to align the shared AR scene relative to the surrounding environment. For example, when a user is tracking a shared AR scene, each of the client devices can detect its position in space and its movement within the shared AR scene. However, the client devices may not detect or determine the same origin position or how the AR scene is aligned relative to the surrounding environment of the respective devices in the shared AR scene. Thus, although each of the client devices in the client devices presents the same virtual content (e.g., a car, a race track), etc., the virtual content may not appear at the same position within the shared AR scene on each device. For example, the virtual content may not be rotated on each of the display screens of the client devices so as to be aligned in the same way.

[0016] In some cases, predefined markers can be used to synchronize the shared AR scene. For example, one device can display a barcode or other suitable predefined image for another device to scan and determine the appropriate transformation for the AR scene. That is, the second device can use the following orientation of the first device to determine information about the coordinate system of the first device: the orientation is the orientation of the first device when the second device scans the marker displayed on the first device. An example of such a system is described in further detail in co-owned, co-assigned U.S. Patent Application No. 16 / 729,078, filed on December 27, 2019, which is incorporated herein by reference in its entirety. Although such systems are generally suitable for synchronizing AR scenes, generating the markers introduces some inefficiencies due to the need to store and agree on the images of the markers before participating in the shared AR session.

[0017] In one embodiment, the system implements a method for aligning all client devices in a shared AR session to the origin center of the shared AR scene (or world) and rotating the shared AR scene in a specific orientation. In one embodiment, the system uses skeleton tracking to establish the origin center of the shared AR scene to create a shared AR session. In particular, the disclosed embodiment improves systems that use markers to create a shared AR session by avoiding the need to predefine and store markers. This reduces the number of steps required to create a shared AR session, reduces overall processing and storage resources, and thus improves the overall functionality of the electronic device. Also, by using skeleton tracking, errors in the AR session caused by drift of the common coordinate system can be corrected during the AR session. In particular, whenever a body is detected in the scene, the error can be corrected continuously or periodically without having to re-scan the markers presented by other devices.

[0018] Figure 1FIG. 0 is a block diagram illustrating an example system 100 for exchanging data (e.g., messages and associated content) over a network. System 100 includes multiple instances of client devices 102, each instance hosting multiple applications including a messaging client application 104 and an AR session client controller 124. Each messaging client application 104 is communicatively coupled via a network 106 (e.g., the Internet) to other instances of the messaging client application 104 and a messaging server system 108. Each AR session client controller 124 is communicatively coupled via the network 106 to other instances of the AR session client controller 124 and an AR session server controller 126 in the messaging server system 108.

[0019] The messaging client application 104 is capable of communicating and exchanging data with another messaging client application 104 and the messaging server system 108 via the network 106. The data exchanged between the messaging client applications 104 and between the messaging client application 104 and the messaging server system 108 includes functionality (e.g., commands to activate functions) and payload data (e.g., text, audio, video, or other multimedia data).

[0020] The messaging server system 108 provides server-side functionality to a particular messaging client application 104 via the network 106. While certain functions of system 100 are described herein as being performed by the messaging client application 104 or by the messaging server system 108, the location of certain functions within the messaging client application 104 or within the messaging server system 108 is a design choice. For example, it may be technically preferable to initially deploy certain technologies and functions within the messaging server system 108 but later migrate the technologies and functions to the messaging client application 104 when the client device 102 has sufficient processing power.

[0021] The messaging server system 108 supports various services and operations provided to the messaging client application 104. Such operations include sending data to the messaging client application 104, receiving data from the messaging client application 104, and processing data generated by the messaging client application 104. As an example, the data may include message content, client device information, geographical location information, media annotations and overlays, message content persistence conditions, social network information, and live event information. The data exchange within the messaging system 100 is invoked and controlled via functions available through the user interface (UI) of the messaging client application 104.

[0022] The AR session client controller 124 can communicate with and exchange data with another AR session client controller 124 and an AR session server controller 126 via the network 106. The data exchanged between AR session client controllers 124 and between the AR session client controller 124 and the AR session server controller 126 can include: a session identifier identifying a shared AR session; a transformation between a first device and a second device (e.g., multiple client devices 102, including the first device and the second device), which is used to align the shared AR session to a common origin; a common coordinate system; functions (e.g., commands for activation functions) and other payload data (e.g., text, audio, video, or other multimedia data). In some cases, the AR session client controller 124 calculates the transformation between the two devices based on the position and orientation of the body parts of the body depicted in one or more images captured by one of the two devices. For example, the first device of the two devices can include a camera of a user pointing at the second device of the two devices. The first device can send one or more images together with the position and orientation information of the first device to the AR session server controller 126. As an example, the first device can send the origin and coordinate system (coordinate system or frame) of the first device. The AR session server controller 126 can process one or more images to identify the skeletal joint positions of the body depicted in the images. The AR session server controller 126 can identify body parts, such as the wrist joint position in the skeletal joint positions.

[0023] The AR session server controller 126 can calculate a transformation (e.g., a common coordinate system) based on the identified body part, which represents how the identified body part is positioned in the AR scene relative to the position and orientation of the first device. That is, the transformation represents how the body part corresponding to the origin of the second device (e.g., the wrist position) appears relative to the first device. As an example, the second device may be held in the right hand of the user of the second device, which means that the right wrist position is the origin based on which the second device generates AR content. By determining the position of this origin relative to the first device and providing this information to the second device in the form of a transformation, the second device can determine the offset by which the AR content presented by the second device is to be shifted. The AR session server controller 126 sends the transformation to the second device so that the second device can adjust the AR coordinate system based on this transformation. In this way, the first device and the second device synchronize their coordinate systems (coordinate systems and frames) to display the content in the AR session. Specifically, the AR session server controller 126 calculates the origin of the second device in the coordinate system of the first device. Then, the AR session server controller 126 can determine the offset in the coordinate system of the second device based on the position of the origin in the coordinate system of the second device from the perspective of the second device. A transformation is generated using this offset so that the second device generates AR content according to a common coordinate system (coordinate system or frame) shared with the first device.

[0024] Specifically, turning now to the messaging server system 108, the application programming interface (API) server 110 is coupled to the application server 112 and provides a programming interface to the application server 112. The application server 112 is communicatively coupled to the database server 118, which facilitates access to the database 120 in which data associated with the messages processed by the application server 112 is stored.

[0025] The Application Programming Interface (API) Server 110 receives and sends message data (e.g., commands and message payloads) between the client device 102 and the application server 112. Specifically, the Application Programming Interface (API) Server 110 provides a set of interfaces (e.g., routines and protocols) that the messaging client application 104 can call or query to invoke the functions of the application server 112. The Application Programming Interface (API) Server 110 exposes various functions supported by the application server 112, including account registration, login functionality, sending a message from a specific messaging client application 104 to another messaging client application 104 via the application server 112, sending media files (e.g., images or videos) from the messaging client application 104 to the messaging server application 114, setting up a collection of media data (e.g., a story) for possible access by another messaging client application 104, retrieving the friend list of the user of the client device 102, retrieving such collections, retrieving messages and content, adding and deleting friends to and from the social graph, the location of friends within the social graph, and opening application events (e.g., involving the messaging client application 104).

[0026] The application server 112 hosts multiple applications and subsystems, including the messaging server application 114, the image processing system 116, the social networking system 122, and the AR session server controller 126. The messaging server application 114 implements multiple message processing techniques and functions, particularly those related to the aggregation and other processing of content (e.g., text and multimedia content) included in messages received from multiple instances of the messaging client application 104. As will be described in further detail, text and media content from multiple sources can be aggregated into collections of content (e.g., referred to as a story or a gallery). The messaging server application 114 then makes these collections available to the messaging client application 104. Given the hardware requirements for such processing, other processor and memory-intensive data processing may also be performed by the messaging server application 114 on the server side.

[0027] The application server 112 also includes an image processing system 116 dedicated to performing various image processing operations, typically on images or videos received within the payload of messages at the messaging server application 114.

[0028] The social networking system 122 supports various social networking function services and makes these functions and services available to the messaging server application 114. To this end, the social networking system 122 maintains and accesses the entity graph 304 within the database 120, as Figure 3as shown). Examples of functions and services supported by the social networking system 122 include identifying other users of the messaging system 100 with whom a particular user has a relationship or whom the particular user "follows", and also identifying the interests of the particular user and other entities.

[0029] The application server 112 also includes an AR session server controller 126 that can communicate with an AR session client controller 124 in the client device 102 to establish a separate or shared AR session. The AR session server controller 126 can also be coupled to the messaging server application 114 to establish an electronic group communication session (e.g., group chat, instant messaging) for the client device in the shared AR session. The electronic group communication session can be associated with a session identifier provided by the client device 102 to obtain access to the electronic group communication session and the shared AR session. In one embodiment, the client device first obtains access to the electronic group communication session and then obtains a session identifier in the electronic group communication session that enables the client device to access the shared AR session. In some embodiments, the client device 102 is able to access the shared AR session without the help of or without communicating with the AR session server controller 126 in the application server 112.

[0030] The application server 112 is communicatively coupled to a database server 118, which facilitates access to a database 120 that stores data associated with messages processed by the messaging server application 114.

[0031] Figure 2 is a block diagram showing additional details regarding the system 100 according to an example embodiment. Specifically, the system 100 is shown to include a messaging client application 104 and an application server 112, which in turn includes a plurality of subsystems, namely a transient timer system 202, a collection management system 204, and an annotation system 206.

[0032] The transient timer system 202 is responsible for implementing transient access to the content allowed by the messaging client application 104 and the messaging server application 114. To this end, the transient timer system 202 incorporates a plurality of timers that selectively display messages and associated content and enable access to messages and associated content via the messaging client application 104 based on the duration and display parameters associated with a message or a collection of messages (e.g., a story). Additional details regarding the operation of the transient timer system 202 are provided below.

[0033] The collection management system 204 is responsible for managing collections of media (e.g., collections of text, image, video, and audio data). In some examples, collections of content (e.g., messages, including images, videos, text, and audio) can be organized into "event libraries" or "event stories". Such collections can be made available for a specified period of time (e.g., the duration of the event to which the content pertains). For example, content related to a concert can be made available as a "story" during the duration of that concert. The collection management system 204 may also be responsible for publishing an icon that notifies the user interface of the messaging client application 104 of the existence of a particular collection.

[0034] The collection management system 204 also includes a curation interface 208 that allows a collection manager to manage and curate a particular collection of content. For example, the curation interface 208 enables an event organizer to curate a collection of content related to a particular event (e.g., delete inappropriate content or redundant messages). Additionally, the collection management system 204 employs machine vision (or image recognition technology) and content rules to automatically curate content collections. In certain implementations, compensation may be paid to users to include user-generated content in a collection. In such cases, the curation interface 208 operates to automatically pay such users for the use of their content.

[0035] The annotation system 206 provides various functions that enable a user to annotate or otherwise modify or edit media content associated with a message. For example, the annotation system 206 provides functions related to generating and publishing a media overlay for a message processed by the system 100. The annotation system 206 operably supplies a media overlay or supplement (e.g., an image filter) to the messaging client application 104 based on the geographical location of the client device 102. In another example, the annotation system 206 operably supplies a media overlay to the messaging client application 104 based on other information (e.g., social network information of the user of the client device 102). The media overlay can include audio and visual content as well as visual effects. Examples of audio and visual content include pictures, text, logos, animations, and sound effects. Examples of visual effects include color overlays. The audio and visual content or visual effects can be applied to a media content item (e.g., a photo) at the client device 102. For example, the media overlay can include text that can be overlaid on a photo taken by the client device 102. In another example, the media overlay includes a location identifier (e.g., Venice Beach) overlay, a name of a live event, or a business name (e.g., Beach Café) overlay. In another example, the annotation system 206 uses the geographical location of the client device 102 to identify a media overlay that includes the name of a business at the geographical location of the client device 102. The media overlay can include other markers associated with the business. The media overlay can be stored in the database 120 and accessed via the database server 118.

[0036] In one example implementation, the annotation system 206 provides a user-based publishing platform that enables a user to select a geographical location on a map and upload content associated with the selected geographical location. The user can also specify the circumstances under which a particular media overlay should be provided to other users. The annotation system 206 generates a media overlay that includes the uploaded content and associates the uploaded content with the selected geographical location.

[0037] In another example implementation, the annotation system 206 provides a business-based publishing platform that enables a business to select a particular media overlay associated with a geographical location via a bidding process. For example, the annotation system 206 associates the media overlay of the highest-bidding business with the corresponding geographical location for a predefined amount of time.

[0038] Figure 3 is a schematic diagram showing a data structure 300 that can be stored in the database 120 of the messaging server system 108 according to certain example implementations. Although the content of the database 120 is shown as including multiple tables, it will be understood that the data can be stored in other types of data structures (e.g., as an object-oriented database).

[0039] The database 120 includes message data stored in a message table 314. An entity table 302 stores entity data, including an entity graph 304. Entities whose records are maintained in the entity table 302 can include individuals, corporate entities, organizations, objects, locations, events, etc. Regardless of the type, any entity about which the messaging server system 108 stores data can be an identified entity. Each entity is set with a unique identifier and an entity type identifier (not shown).

[0040] The entity graph 304 also stores information about the relationships and associations between entities. By way of example only, such relationships can be social relationships based on interests or activities, professional relationships (e.g., working in the same company or organization).

[0041] The database 120 also stores annotation data in an annotation table 312 in the form of examples of filters. The filters whose data is stored in the annotation table 312 are associated with videos (whose data is stored in a video table 310) and / or images (whose data is stored in an image table 308) and are applied to the videos and / or images. In one example, a filter is an overlay that is displayed as being overlaid on an image or video during presentation to a recipient user. Filters can be of various types, including user-selected filters from a library of filters presented to a sending user by the messaging client application 104 when the sending user is composing a message. Other types of filters include geolocation filters (also known as geo-filters), which can be presented to the sending user based on a geographical location. For example, based on geographical location information determined by the GPS unit of the client device 102, the messaging client application 104 can present geographical location filters specific to a neighborhood or a particular location within a user interface. Another type of filter is a data filter, which can be selectively presented to the sending user by the messaging client application 104 based on other input or information collected by the client device 102 during the message creation process. Examples of data filters include the current temperature at a particular location, the current speed at which the sending user is traveling, the battery life of the client device 102, or the current time.

[0042] Other annotation data that can be stored in the image table 308 is so-called "LENS" data. A "LENS" can be a real-time special effect and sound that can be added to an image or video.

[0043] As mentioned above, the video table 310 stores video data which, in one embodiment, is associated with messages whose records are maintained in the message table 314. Similarly, the image table 308 stores image data associated with messages whose message data is stored in the entity table 302. The entity table 302 may associate various annotations from the annotation table 312 with the various images and videos stored in the image table 308 and the video table 310.

[0044] The story table 306 stores data about a collection of messages and associated image, video, or audio data, where the messages and associated image, video, or audio data are compiled into a collection (e.g., a story or a gallery). The creation of a particular collection may be initiated by a particular user (e.g., each user whose records are maintained in the entity table 302). A user may create a "personal story" in the form of a collection of content that has already been created and sent / broadcast by that user. To this end, the user interface of the messaging client application 104 may include icons that a user can select to enable the sending user to add specific content to his or her personal story.

[0045] Collections may also constitute "Live Stories", which are collections of content from multiple users created manually, automatically, or using a combination of manual and automated techniques. For example, a "Live Story" may constitute a curated stream of user-submitted content from different locations and events. Options may be presented, for example, via the user interface of the messaging client application 104 to users whose client device's location service is enabled and who are at a common location event at a particular time to contribute content to a particular Live Story. The messaging client application 104 may identify Live Stories to users based on the users' locations. The end result is a "Live Story" told from a community perspective.

[0046] Another type of content collection is called a "Location Story", which enables users whose client devices 102 are located within a particular geographical location (e.g., on a college or university campus) to contribute to a particular collection. In some embodiments, contributing to a Location Story may require a second level of authentication to verify that the end user belongs to a particular organization or other entity (e.g., is a student on a university campus).

[0047] The database 120 can also store data related to individual and shared AR sessions in the AR session table 316. The data in the AR session table 316 can include data transmitted between the AR session client controller 124 and another AR session client controller 124, as well as data transmitted between the AR session client controller 124 and the AR session server controller 126. The data can include data for establishing a common coordinate system for a shared AR scene, transformations between devices, session identifiers, images depicting the body, skeletal joint positions, wrist joint positions, and the like.

[0048] Figure 4 FIG. 4 is a schematic diagram showing the structure of a message 400 according to some embodiments. The message 400 is generated by the messaging client application 104 for transmission to another messaging client application 104 or the messaging server application 114. The content of a particular message 400 is used to populate a message table 314 stored in a database 120 accessible by the messaging server application 114. Similarly, the content of the message 400 is stored in memory as "in-transit" or "in-flight" data of the client device 102 or the application server 112. The message 400 is shown as including the following components:

[0049] ● Message identifier 402: A unique identifier that identifies the message 400.

[0050] ● Message text payload 404: Text to be generated by the user via the user interface of the client device 102 and included in the message 400.

[0051] ● Message image payload 406: Image data captured by the camera component of the client device 102 or retrieved from the memory component of the client device 102 and included in the message 400.

[0052] ● Message video payload 408: Video data captured by the camera component or retrieved from the memory component of the client device 102 and included in the message 400.

[0053] ● Message audio payload 410: Audio data captured by the microphone or retrieved from the memory component of the client device 102 and included in the message 400.

[0054] ● Message annotation 412: Annotation data (e.g., filters, stickers, or other enhancements) representing an annotation to be applied to the message image payload 406, the message video payload 408, or the message audio payload 410 of the message 400.

[0055] ● Message duration parameter 414: A parameter value that indicates, in seconds, the amount of time that the content of the message (e.g., message image payload 406, message video payload 408, message audio payload 410) will be presented or made accessible to the user via the messaging client application 104.

[0056] ● Message geographic location parameter 416: Geographic location data (e.g., latitude and longitude coordinates) associated with the content payload of the message. Multiple message geographic location parameter 416 values can be included in the payload, with each of these parameter values associated with a content item included in the content (e.g., a specific image within message image payload 406 or a specific video within message video payload 408).

[0057] ● Message story identifier 418: An identifier value that identifies one or more content collections (e.g., “stories”) associated with a specific content item within the message image payload 406 of message 400. For example, multiple images within message image payload 406 can each be associated with multiple content collections using identifier values.

[0058] ● Message tag 420: Each message 400 can be tagged with multiple tags, with each tag within the multiple tags indicating a theme of the content included in the message payload. For example, in the case where a specific image included in message image payload 406 depicts an animal (e.g., a lion), a tag value indicating the relevant animal can be included within message tag 420. The tag value can be manually generated based on user input or can be automatically generated using, for example, image recognition.

[0059] ● Message sender identifier 422: An identifier (e.g., a messaging system identifier, an email address, or a device identifier) that indicates the user of the client device 102 on which message 400 was generated and from which message 400 was sent.

[0060] ● Message recipient identifier 424: An identifier (e.g., a messaging system identifier, an email address, or a device identifier) that indicates the user of the client device 102 to which message 400 is addressed.

[0061] The content (e.g., value) of each component of the message 400 can be a pointer to a location in a table where content data values are stored. For example, the image value in the message image payload 406 can be a pointer to a location (or address) within the image table 308. Similarly, the value within the message video payload 408 can point to data stored within the video table 310, the value stored within the message annotation 412 can point to data stored within the annotation table 312, the value stored within the message story identifier 418 can point to data stored within the story table 306, and the values stored within the message sender identifier 422 and the message recipient identifier 424 can point to user records stored within the entity table 302.

[0062] Figure 5 is a flowchart of a process for an AR session based on skeleton tracking according to some example embodiments. Although the flowchart may depict the operations as a sequential process, many of these operations can be performed in parallel or simultaneously. Additionally, the order of the operations can be rearranged. The process terminates when its operations are complete. The process can correspond to a method, a program, etc. The steps of the method can be performed wholly or partially, can be combined with some or all of the steps in other methods, and can be executed by any number of different systems (e.g., Figure 1 , Figure 7 and / or Figure 8 as described in) or any part thereof (e.g., a processor included in any of the said systems).

[0063] At operation 501, the AR session is initialized (e.g., as a result of a first device initiating the AR session, by the first device, by the second device, and / or on the server). For example, the AR session client controller 124 in the first client device (e.g., client device 102) can initialize the shared AR session.

[0064] At operation 502, the second device receives a request to join the AR session of the first device. In response to receiving the request, the second device activates the AR session and initializes the AR session on the second device. In one embodiment, during the initialization of the shared AR session, the first device and the second device can be in independent, active Simultaneous Localization And Mapping (SLAM) sessions with respect to each other, and these SLAM sessions need to be aligned with each other to establish the shared AR session. In one example, the second device receives a message with an AR session identifier from the first device via the messaging client application 104. The second device can receive a user selection (e.g., on-screen button or link) to join the AR session identified in the message. In response to receiving the user selection of the on-screen button, the second device uses the AR session identifier to join the shared AR session with the first device such that the first device and the second device are synchronized and display the same AR content with respect to the real-world scene displayed on each device.

[0065] In some embodiments, initializing the shared AR session includes the first device determining a first device transformation (e.g., referred to as transformation T A ). The first device transformation can be based on the first device's current pose and the first device's origin. The first device's current pose can be the position and orientation of the first device with respect to the real world along the x, y, and z axes. The first device origin is the origin of the coordinate system tracked by the first device. In some cases, transformation T A can represent the transformation from the first device origin to the user's hand. Similarly, initializing the shared AR session can also include the second device determining a second device transformation (e.g., referred to as transformation T B ). The second device transformation can be based on the second device's current pose and the second device's origin. The second device's current pose can be the position and orientation of the second device with respect to the real world along the x, y, and z axes. The second device origin is the origin of the coordinate system tracked by the second device. The origin of the coordinate system tracked by the first device can be different from the origin of the coordinate system tracked by the second device. Thus, a common transformation is calculated to synchronize the coordinate systems of the first device and the second device such that the AR content is presented consistently on the first device and the second device.

[0066] At operation 503, in response to receiving a request to join an AR session of a first device, a body corresponding to a user of the first device is detected in one or more images captured by a camera of a second device. For example, in response to receiving the request, the second device displays a prompt to the user indicating that the user should point the camera of the second device at the user of the first device, where the user of the first device is the user with whom the user of the second device wishes to join an AR session. When the user of the second device points the camera at the user of the first device, the second device captures one or more images. The second device detects a body (e.g., a human pose) in the one or more images. For example, the second device detects a body in the one or more images by performing image processing and employing human recognition and classification processing (e.g., using machine learning, such as a trained neural network).

[0067] At operation 504, the second device identifies body parts of the detected body corresponding to the user of the first device. For example, a second user of the second device can point the second device at a first user of the first device such that the body of the first user is within the field of view of the camera included in the second device. Then, the second device can find the wrist position or the wrist bone joint position corresponding to the hand of the first user holding the first device. The AR session client controller 124 in the second device detects the wrist bone joint position or transformation by analyzing one or more images within the field of view of the camera. The bone joint transformation includes the positioning of the bone joint in 3D space and the rotation information of the bone joint position. In one embodiment, the AR session client controller 124 implements a bone joint detection algorithm to detect the wrist bone joint position and transformation. Specifically, once a body is recognized in one or more images captured by the second device, the second device generates a bone joint representation of the body. The bone joint representation identifies a set of points corresponding to different bone joints of the body (e.g., head joint, shoulder joint, arm joint, wrist joint, leg joint, foot joint, etc.).

[0068] In some embodiments, the second device analyzes the body depicted in one or more images to identify which hand (left or right) is holding the first device. The second device selects the skeletal joint of the wrist corresponding to the hand holding the first device. In particular, the origin of the coordinate system of the first device is a fixed point in the 3D space of the device. The first device can calculate a transformation relative to this fixed point to represent the movement of the first device over time relative to the fixed origin. In one embodiment, the transformation represents the position of the hand holding the first device relative to the origin of the first device. Thus, by identifying the position of the wrist skeletal joint of the hand holding the first device and the transformation, the second device can determine the position of the first device in the 3D space in the coordinate system of the second device. In some embodiments, the first device may be a head-mounted device. In such a case, the second device analyzes the body depicted in one or more images to identify the head wearing the first device. The second device selects the skeletal joint of the head. In particular, the transformation of the first device is based on the position of the head wearing the first device in the 3D space relative to the origin of the first device. Thus, by identifying the position of the head skeletal joint of the head wearing the first device and the transformation, the second device can determine the position of the first device in the 3D space in the coordinate system of the second device.

[0069] At operation 505, the second device uses the identified body part to determine the transformation between the first device and the second device in the AR session. For example, the AR session client controller 124 of the second device uses the wrist skeletal joint position or transformation (e.g., the skeletal joint transformation representing the origin in the coordinate system of the first device and including rotation information) to determine the transformation (T C ) between the origin of the first device and the origin of the second device. The transformation (T C ) can be a transformation matrix describing the transformation between the origin of the first device and the origin of the second device. Specifically, the second device calculates the offset or transformation from the origin of the first device in the coordinate system of the first device to the position of that origin in the coordinate system of the second device. As an example, the first device determines the transformation based on the origin of the first device at a first position in the 3D space in the coordinate system of the first device. The second device identifies the origin of the first device (e.g., the position and transformation of the skeletal wrist joint) as being at a second position in the 3D space of the coordinate system of the second device. The second device receives the coordinate system or transformation of the first device determined by the first device and compares the position of the second position in the 3D space of the coordinate system of the second device with the first position in the coordinate system of the first device. As an example, the second device determines that the second position is offset 5 degrees and 3 centimeters relative to the first position. In response, the second device calculates the transformation representing this offset between the origins of the two devices and may send this transformation to the first device. Then, the first device shifts all the AR content displayed by the first device based on the offset indicated in the transformation.

[0070] In one embodiment, the second device receives a first device transformation (T A ) from the first device and also uses the first device transformation (T A ) to determine a transformation (T C ) between the origin of the first device and the origin of the second device. In this embodiment, the transformation (T C ) can be a transformation matrix that describes the transformation between the first device transformation (T A ) (determined based on the origin of the first device) and the second device transformation (T B ) (determined based on the origin of the second device). The AR session client controller 124 of the second device can also determine a second offset based on the first device transformation (T A ). The second offset can be the offset of the current pose of the second device from the origin of the first device. In this embodiment, the second offset is in daisy chain with the offsets calculated by other devices in the shared AR session to ensure that the devices in the shared AR session can be aligned with each other at the same origin (e.g., the shared AR world origin) of the AR shared session.

[0071] In one embodiment, the AR session client controller 124 of the second device determines a transformation (T C ) between the origin of the first device and the origin of the second device by using the position or transformation of the wrist bone joint positions in one or more images, the scale of the position or transformation of the wrist bone joint positions in one or more images, or the rotation of the position or transformation of the wrist bone joint positions in one or more images or any combination thereof. For example, to determine the transformation (T C ), the AR session client controller 124 of the second device can use basic computer vision, manipulation of images, geometry, translation, visual representation, angles, distances, etc.

[0072] In one embodiment, the AR session client controller 124 of the second device sends the transformation (T C ) to the AR session client controller 124 and / or the AR session server controller 126 of the first device. The AR session client controller 124 of the second device can also send the transformation (T C ) in a (group) communication session, for example, via the messaging client application 104. In some embodiments, the AR session client controller 124 of the second device uses the transformation (T C ) to determine a common coordinate system. In some embodiments, the AR session client controller 124 of the first device uses the transformation (T C ) received from the second device to determine a common coordinate system.

[0073] At operation 506, based on the determined transformation, the AR session client controller 124 in the first device causes a shared AR session to be displayed via the first device, and the AR session client controller 124 in the second device causes a shared AR session to be displayed via the second device. In one embodiment, a shared AR scene included in the shared AR session is caused to be displayed via the first device and the second device.

[0074] In one embodiment, the AR session client controller 124 of the second device may filter out the wrist joint position or the image of the transformation that results in a transformation (T C ) opposite to gravity. Although the captured wrist joint position or frames of the transformation are rotationally offset in position along the ground plane, both the first device and the second device may be aligned with each other with respect to the position where the ground is located (e.g., which direction is up and which direction is down). The AR session client controller 124 of the second device performs a gravity check by determining whether the observed first current pose (or the image of the captured wrist joint position) is opposite to gravity.

[0075] In this embodiment, the AR session client controller 124 of the second device receives information including the angle of the gravity axis and uses this information to compare with the tracking data of the wrist joint position (e.g., the frames of the markers captured by the camera in the second device). Then, the AR session client controller 124 of the second device checks whether the first device and the second device match in terms of how to orient the pose of the first device with respect to the gravity position. Then, the AR session client controller 124 of the second device may filter out the data (or the frames of the captured markers) that are in disagreement in terms of the orientation with respect to the gravity position (e.g., the lower quality data).

[0076] As an example, after the transformation is provided to the first device, the first device and the second device synchronize the display of the AR content. Specifically, the respective cameras of the first device and the second device may point at the real-world table from different angles. The AR session may cause an AR paper object (e.g., a virtual paper) to be displayed on top of the real-world table. In such a case, the first device displays the AR paper object on top of the real-world table on the screen of the first device, while the second device displays the same common AR paper object on top of the same real-world table on the screen of the second device. To synchronize the position of the AR paper, the first device shifts or changes the placement position of the AR paper object relative to the origin of the coordinate system of the first device based on the transformation received from the second device.

[0077] In some embodiments, when the body of the user of the first device is detected in one or more images captured by the second device, the second device recalculates or recomputes the transformation between the coordinate system of the first device and the coordinate system of the second device. For example, the first device and the second device use the initially computed transformation to start participating in a shared AR session. The transformation can be computed or determined by the second device using markers displayed by the first device and / or by identifying the skeletal wrist joint position or transformation of the user of the first device. At a later time (e.g., five minutes later) when the first device and the second device are participating in the shared AR session, the second device can again identify the body and corresponding body parts (e.g., wrist skeletal joint position) in the real-world images captured by the second device. In response to identifying the body, the second device performs the above process to compute a second transformation between the first device and the second device in the AR session using the identified body parts. In some embodiments, the second transformation is computed each time the body is identified in one or more images captured by the second device. In some embodiments, the second transformation is computed periodically at a predetermined time interval (e.g., every five minutes after entering the shared AR session). In such a case, after the predetermined time interval has elapsed, the second device then begins processing the images captured by the second device to identify the body of the user of the first device. In some implementations, the body of the user of the first device may not appear until several minutes or hours after the predetermined time interval has been reached. However, once the body is identified several minutes or hours after the predetermined time interval has been reached, the second transformation is computed based on the identified body. In some cases, an image of the body of the user of the first device is captured before the predetermined time interval has been reached, but the image is cached and processed after the predetermined time interval has been reached to compute the second transformation.

[0078] In some embodiments, the second device compares the most recently computed second transformation with the previously computed and determined transformation. The second device computes an error based on comparing the second transformation with the previously computed and determined transformation. The second device determines whether to update the transformation used by the first device with the second transformation based on the value of the error relative to a threshold. Specifically, if the second device determines that the error is less than the threshold, the second device prevents updating the transformation used by the first device with the second transformation. That is, the first device maintains presenting the shared AR session content based on the previously determined transformation rather than based on the most recently computed second transformation.

[0079] In some implementations, if the second device determines that the error is equal to or greater than the threshold, the second device causes the AR session to be displayed based on the second transformation. Specifically, the second device sends the second transformation to the first device along with an instruction to replace the currently used transformation with the second transformation. References to skeletal joint positions above or below should be understood to include the position of the skeletal joint position in 3D space as well as the rotational information about the skeletal joint position.

[0080] In some embodiments, the second device stores or accesses multiple thresholds. Based on the positioning of the content within the shared AR session, a threshold is selected from the multiple thresholds against which the second device compares the error between two transforms. As an example, a first threshold among the multiple thresholds may correspond to AR content positioned relative to one or more real-world objects. Specifically, the first threshold may correspond to the display of a virtual object above, below, to the side of, or at some other position relative to a real-world object. For example, the first threshold may correspond to a virtual paper object placed on a table. Such a threshold may be a very small value because the precision of the placement of the virtual object may need to be high. In such a case, the first device and the second device may need to place the virtual object very accurately relative to the real-world object. As another example, a second threshold greater than the first threshold may correspond to AR content positioned independent of any real-world object. Specifically, the second threshold may correspond to the display of a virtual object anywhere in the real-world scene, such as a floating virtual paper or a virtual graphic. The positioning of such a virtual object does not depend on the positioning of real-world objects, and thus, the precision level of the placement of the virtual object can be kept low. As another example, a third threshold may correspond to the type of virtual content presented in the AR session. Specifically, when the virtual content corresponds to a first object size, the third threshold may be a relatively large value, while when the virtual content corresponds to a second object size smaller than the first object size, the third threshold may be a relatively small value. When the virtual content corresponds to a static object, the third threshold may be a relatively large value, while when the virtual content corresponds to an animated object, the third threshold may be a relatively small value.

[0081] In some embodiments, the second device determines the type of virtual content displayed in the shared AR session between the first device and the second device, and whether the virtual content is placed relative to a real-world object. The second device selects one of the multiple thresholds to compare with the error between the transforms based on the type of the virtual content and whether the virtual content is positioned or placed relative to a real-world object. In some cases, multiple AR objects are displayed in the shared AR session. In such a case, the second device retrieves the multiple thresholds corresponding to each AR object and selects the threshold with the minimum value among the multiple thresholds. The second device uses the selected threshold to compare with the error calculated between a second transform and a previously calculated current transform used to generate the shared AR session.

[0082] In some embodiments, a second device can join a shared AR session with a first device by adjusting a transformation determined by the second device. In such a case, each device joining the AR session may not need to send back the shared transformation. For example, the second device can identify skeletal joint positions corresponding to the first device (e.g., the hand holding the first device or the head wearing the first device). The second device can calculate a transformation of a coordinate system determined by the second device based on points in 3D space corresponding to the identified skeletal joint positions. The second device can adjust the coordinate system of the second device based on this transformation. In this way, the placement and positioning of virtual content presented by the second device are adjusted relative to the origin of the second device and the identified skeletal joint positions corresponding to the first device. The placement and positioning of the virtual content are synchronized with the way the same content is presented on the first device based on the transformation calculated by the second device. In this implementation, the device joining the shared AR session (e.g., the second device) rather than the device initiating the AR session (e.g., the first device) adjusts its own coordinate system used for presenting AR content. In this case, the first device continues to present the content in the AR session based on the coordinate system of the first device without adjusting the coordinate system based on the calculated transformation. The second device adjusts the coordinate system of the second device based on the calculated transformation to synchronize the display of the content on the second device with the skeletal joint positions corresponding to the first device and based on the determined position of the first device in 3D space.

[0083] Figure 6 FIG. 600 is a block diagram showing a software architecture 604 that may be installed on any one or more of the devices described herein. The software architecture 604 is supported by hardware such as a machine 602 including a processor 620, a memory 626, and I / O components 638. In this example, the software architecture 604 can be conceptualized as a stack of layers, where each layer provides a specific function. The software architecture 604 includes layers such as an operating system 612, libraries 610, frameworks 608, and applications 606. In operation, an application 606 activates an API call 650 through the software stack and receives a message 652 in response to the API call 650.

[0084] The operating system 612 manages hardware resources and provides common services. The operating system 612 includes, for example, a kernel 614, services 616, and drivers 622. The kernel 614 acts as an abstraction layer between the hardware layer and other software layers. For example, the kernel 614 provides memory management, processor management (e.g., scheduling), component management, network and security settings, and other functions. The services 616 can provide other common services for other software layers. The drivers 622 are responsible for controlling or interfacing with the underlying hardware. For example, the drivers 622 can include a display driver, a camera driver, or Low-power drivers, flash drives, serial communication drivers (e.g., Universal Serial Bus (USB) drivers), drivers, audio drivers, power management drivers, etc.

[0085] The library 610 provides low-level common infrastructure used by the application 606. The library 610 may include a system library 618 (e.g., C standard library), and the system library 618 provides functions such as memory allocation functions, string operation functions, mathematical functions, etc. In addition, the library 610 may include an API library 624, such as a media library (e.g., a library for supporting the presentation and operation of various media formats, the various media formats such as Moving Picture Experts Group-4 (MPEG4), Advanced Video Coding (H.264 or AVC), Moving Picture Experts Group-3 (MP3), Advanced Audio Coding (AAC), Adaptive Multi-Rate (AMR) audio codec, Joint Photographic Experts Group (JPEG or JPG) or Portable Network Graphics (PNG)), a graphics library (e.g., the OpenGL framework for presenting in two-dimensional (2D) and three-dimensional (3D) in graphical content on a display), a database library (e.g., SQLite that provides various relational database functions), a web library (e.g., WebKit that provides web browsing functions), etc. The library 610 may also include a variety of other libraries 628 to provide many other APIs to the application 606.

[0086] The framework 608 provides high-level common infrastructure used by the application 606. For example, the framework 608 provides various Graphical User Interface (GUI) functions, advanced resource management, and advanced location services. The framework 608 may provide a wide range of other APIs that can be used by the application 606, and some of these APIs may be specific to a particular operating system or platform.

[0087] In an example embodiment, the application 606 may include a home application 636, a contacts application 630, a browser application 632, an e-book reader application 634, a location application 642, a media application 644, a messaging application 646, a gaming application 648, and a wide variety of other applications such as third-party applications 640. The application 606 is a program that executes functions defined in the program. One or more of the applications 606 can be created using various programming languages, the programming languages such as object-oriented programming languages (e.g., Objective-C, Java, or C++) or procedural programming languages (e.g., C or assembly language). In a particular example, the third-party application 640 (e.g., an application developed using an ANDROID TM or IOS TM software development kit (SDK) by an entity other than the vendor of a particular platform) can be a mobile operating system such as IOS TM, ANDROID TM , or mobile software running on other mobile operating systems. In this example, third-party application 640 may activate API call 650 provided by operating system 612 to facilitate the functions described herein.

[0088] Figure 7 is a graphical representation of a machine 700 in which instructions 708 (e.g., software, program, application, applet, app, or other executable code) can be executed to cause the machine 700 to perform any one or more of the methods discussed herein. For example, instructions 708 may cause machine 700 to perform any one or more of the methods described herein. Instructions 708 transform a general purpose, unprogrammed machine 700 into a particular machine 700 programmed to perform the described and shown functions in the described manner. Machine 700 may operate as a stand-alone device or may be coupled (e.g., networked) to other machines. In a network deployment, machine 700 may operate as a server machine or a client machine in a server-client network environment, or as a peer machine in a peer-to-peer (or distributed) network environment. Machine 700 may include, but is not limited to, a server computer, a client computer, a personal computer (PC), a tablet computer, a laptop computer, a netbook, a set-top box (STB), a PDA, an entertainment media system, a cellular phone, a smartphone, a mobile device, a wearable device (e.g., a smart watch), a smart home device (e.g., a smart appliance), other smart devices, a web appliance, a network router, a network switch, a network bridge, or any machine capable of sequentially or otherwise executing instructions 708 specifying actions to be taken by machine 700. Further, although only a single machine 700 is shown, the term "machine" shall also be taken to include a collection of machines that individually or jointly execute instructions 708 to perform any one or more of the methods discussed herein.

[0089] Machine 700 may include a processor 702, a memory 704, and I / O components 742, which may be configured to communicate with each other via a bus 744. In an example embodiment, processor 702 (e.g., a central processing unit (CPU), a reduced instruction set computing (RISC) processor, a complex instruction set computing (CISC) processor, a graphics processing unit (GPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a radio frequency integrated circuit (RFIC), other processors, or any suitable combination thereof) may include, for example, a processor 706 and a processor 710 that execute instructions 708. The term "processor" is intended to include multi-core processors, which may include two or more independent processors (sometimes referred to as "cores") that may execute instructions simultaneously. Although Figure 7A number of processors 702 are shown, but machine 700 may include a single processor with a single core, a single processor with multiple cores (e.g., a multi-core processor), multiple processors with a single core, multiple processors with multiple cores, or any combination thereof.

[0090] Memory 704 includes main memory 712, static memory 714, and storage unit 716 that are accessible by processor 702 via bus 744. Main memory 704, static memory 714, and storage unit 716 store instructions 708 that implement any one or more of the methods or functions described herein. The instructions 708 may also reside, completely or partially, within machine-readable medium 718 within main memory 712, within static memory 714, within storage unit 716, within at least one of processors 702 (e.g., within a cache memory of the processor), or in any suitable combination thereof during execution by machine 700.

[0091] I / O components 742 may include various components for receiving input, providing output, generating output, transmitting information, exchanging information, capturing measurement results, etc. The specific I / O components 742 included in a particular machine will depend on the type of the machine. For example, a portable machine such as a mobile phone may include a touch input device or other such input mechanism, while a headless server machine will unlikely include such a touch input device. It will be understood that I / O components 742 may include Figure 7 many other components not shown in. In various example embodiments, I / O components 742 may include output components 728 and input components 730. Output components 728 may include visual components (e.g., a display such as a plasma display panel (PDP), a light emitting diode (LED) display, a liquid crystal display (LCD), a projector, or a cathode ray tube (CRT)), acoustic components (e.g., speakers), haptic components (e.g., a vibration motor, a resistance mechanism), other signal generators, etc. Input components 730 may include alphanumeric input components (e.g., a keyboard, a touch screen configured to receive alphanumeric input, an optical keyboard, or other alphanumeric input components), point-based input components (e.g., a mouse, a touchpad, a trackball, a joystick, a motion sensor, or other pointing instrument), haptic input components (e.g., physical buttons, a touch screen that provides the location and / or force of a touch or touch gesture, or other haptic input components), audio input components (e.g., a microphone), etc.

[0092] In additional example embodiments, the I / O component 742 may include a biometric component 732, a motion component 734, an environmental component 736, or a positioning component 738, as well as a variety of other components. For example, the biometric component 732 includes components for detecting expressions (e.g., hand expressions, facial expressions, voice expressions, body postures, or eye tracking), measuring biometric signals (e.g., blood pressure, heart rate, body temperature, perspiration, or brain waves), identifying people (e.g., voice recognition, retina recognition, facial recognition, fingerprint recognition, or electroencephalogram-based recognition), and so on. The motion component 734 includes acceleration sensor components (e.g., accelerometers), gravity sensor components, rotational sensor components (e.g., gyroscopes), and so on. The environmental component 736 includes, for example, lighting sensor components (e.g., photometers), temperature sensor components (e.g., one or more thermometers for detecting ambient temperature), humidity sensor components, pressure sensor components (e.g., barometers), acoustic sensor components (e.g., one or more microphones for detecting background noise), proximity sensor components (e.g., infrared sensors for detecting nearby objects), gas sensors (e.g., gas detection sensors for detecting the concentration of hazardous gases for safety reasons or for measuring pollutants in the atmosphere), or other components that can provide indications, measurements, or signals corresponding to the surrounding physical environment. The positioning component 738 includes position sensor components (e.g., GPS receiver components), altitude sensor components (e.g., altimeters or barometers that detect the air pressure from which altitude can be obtained), orientation sensor components (e.g., magnetometers), and so on.

[0093] Various techniques can be used to implement communication. The I / O component 742 also includes a communication component 740 that is operable to couple the machine 700 to the network 720 or the device 722 via the coupler 724 and the coupler 726, respectively. For example, the communication component 740 may include a network interface component or another suitable device to interface with the network 720. In additional examples, the communication component 740 may include a wired communication component, a wireless communication component, a cellular communication component, a near field communication (NFC) component, components (e.g., low power), components, and other communication components that provide communication via other forms. The device 722 may be another machine or any of a variety of peripheral devices (e.g., a peripheral device coupled via USB).

[0094] In addition, the communication component 740 may detect an identifier or include components operable to detect an identifier. For example, the communication component 740 may include a radio frequency identification (RFID) tag reader component, an NFC smart tag detection component, an optical reader component (e.g., an optical sensor for detecting: one-dimensional barcodes, such as Universal Product Code (UPC) barcodes; multi-dimensional barcodes, such as Quick Response (QR) codes, Aztec codes, Data Matrix, Dataglyph, MaxiCode, PDF417, Ultra Code, UCC RSS-2D barcodes; and other optical codes), or an acoustic detection component (e.g., a microphone for identifying tagged audio signals). Additionally, various information may be derived via the communication component 740, such as a location via Internet Protocol (IP) geolocation, a location via signal triangulation, a location via detecting an NFC beacon signal that may indicate a specific location, etc.

[0095] Various memories (e.g., memory 704, main memory 712, static memory 714, and / or the memory of the processor 702) and / or storage unit 716 may store one or more sets of instructions and data structures (e.g., software) that embody or are used by any one or more of the methods or functions described herein. When executed by the processor 702, these instructions (e.g., instructions 708) cause various operations to implement the disclosed embodiments.

[0096] The instructions 708 may be sent or received over the network 720 using a transmission medium, via a network interface device (e.g., the network interface component included in the communication component 740), and using any one of a plurality of well-known transmission protocols (e.g., Hypertext Transfer Protocol (HTTP)). Similarly, the instructions 708 may be sent or received using a transmission medium via a coupling 726 (e.g., a peer-to-peer coupling) to the device 722.

[0097] Now turning to Figure 8 , Figure 8 a graphical representation of a processing environment 800 is shown, which includes processors 806, 808, and 802 (e.g., a GPU, a CPU, or a combination thereof).

[0098] The processor 802 is shown coupled to a power supply 804 and includes (permanently configured or temporarily instantiated) modules, namely the AR session client component 810. The AR session client component 810 is operable to, for example, initialize a shared AR session, cause markers to be displayed, capture images of the markers using a camera, generate a transformation (T C) and a common coordinate system and cause the shared AR session to be displayed. Although not shown, the processor 802 can alternatively include an AR session server controller component that can perform the operations of the AR session server controller 126. As shown, the processor 802 is communicatively coupled to both the processor 806 and the processor 808.

[0099] When using phrases similar to “at least one of A, B, or C,” “at least one of A, B, and C,” “one or more of A, B, or C,” or “one or more of A, B, or C,” it is intended that the phrase be interpreted to mean that in an embodiment, A can exist alone, in an embodiment, B can exist alone, in an embodiment, C can exist alone, or in a single embodiment, any combination of elements A, B, and C can exist; for example, A and B, A and C, B and C, or A and B and C.

[0100] Changes and modifications can be made to the disclosed embodiments without departing from the scope of the present disclosure. These and other changes or modifications are intended to be included within the scope of the present disclosure as expressed in the appended claims.

Claims

1. A method for an AR session based on skeleton tracking, comprising: receiving, by a second device, a request to join an AR session initialized by a first device; in response to receiving the request, detecting, in one or more images captured by a camera of the second device, a body corresponding to a user of the first device; identifying body parts of the detected body, the body parts including a hand holding the first device and a wrist corresponding to the hand; using, by the second device, the identified body parts to determine a transformation between the first device and the second device in the AR session; and causing the second device to display the AR session based on the determined transformation; the method further comprising: receiving, at the second device, information including an angle of a gravity axis for the one or more images; comparing, at the second device, the angle of the gravity axis with tracking data of a wrist joint position of the wrist; and filtering, based on the comparison, at the second device, an image of the wrist joint position or a determined transformation in a case where there is a disagreement in the orientation of the first device relative to the gravity axis.

2. The method according to claim 1, further comprising: using the transformation to determine a common coordinate system; and using the common coordinate system to generate the AR session.

3. The method according to claim 1 or 2, wherein the first device initializes the AR session by: determining, by the first device, a first device transformation based on a current pose of the first device and a first device origin, where the first device origin is a first origin of a first coordinate system tracked by the first device.

4. The method according to claim 3, further comprising: determining, by the second device in response to receiving a request to join the AR session of the first device, a second device transformation based on a current pose of the second device and a second device origin, where the second device origin is a second origin of a second coordinate system tracked by the second device.

5. The method according to claim 3, further comprising: sending, from the second device to the first device, the transformation representing coordinates of AR content on the second device relative to a position of the first device.

6. The method according to claim 5, wherein determining, by the second device, the transformation between the first device and the second device includes: determining, by the second device, an offset based on a current pose of the second device and the origin of the first device, based on the first device transformation.

7. The method according to claim 1 or 2, wherein identifying the body parts further includes: processing the one or more images to identify a plurality of skeletal positions of the body; and identifying, from the plurality of skeletal positions, skeletal positions corresponding to the body parts.

8. The method according to claim 7, wherein the body part is a wrist, and the skeletal position corresponding to the body part includes a wrist joint.

9. The method according to claim 8, further comprising: Search for an image of the first device in the one or more images; Determine that the first device is held by a first user in the right hand of the first user; And Based on determining that the first device is held by the first user in the right hand of the first user, select the wrist corresponding to the right hand as the body part.

10. The method according to claim 1 or 2, Wherein, The first device uses a first coordinate system to display an AR object, wherein the second device uses a second coordinate system to display an AR object, and wherein causing the first device and the second device to display the AR session includes: Displaying a common AR object in the AR session on the second device based on the second coordinate system; Causing the first device to adjust the first coordinate system of the first device based on a transformation between the first device and the second device in the AR session; and Causing the first device to display the common AR object in the AR session on the first device based on the adjustment of the first coordinate system.

11. The method according to claim 1 or 2, Wherein, The transformation is a first transformation, and the method further includes: Calculating a second transformation during the AR session when the body is detected in additional images captured after the one or more images.

12. The method according to claim 11, further Including: Calculating the second transformation whenever the body is detected during the AR session.

13. The method according to claim 11, Wherein, Calculating the second transformation at a predetermined time interval.

14. The method according to claim 11, further Including: Comparing the first transformation with the second transformation; Calculating an error based on the comparison of the first transformation and the second transformation; In response to determining that the error is less than a threshold, maintaining the display of the AR session based on the first transformation.

15. The method according to claim 14, further Including: In response to determining that the error is equal to or greater than the threshold, causing the first device and the second device to display the AR session based on the second transformation.

16. The method according to claim 14 or 15, selecting the threshold from a plurality of thresholds based on the positioning of content within the AR session.

17. The method according to claim 16, Wherein, A first threshold among the plurality of thresholds corresponds to AR content positioned relative to one or more real-world objects, a second threshold among the plurality of thresholds corresponds to AR content positioned independently of any real-world object, and the first threshold is less than the second threshold.

18. The method according to claim 1 or 2, further Including: Initializing the AR session using a given transformation between the first device and the second device, the given transformation being calculated based on a marker displayed on the first device; And Updating the given transformation using the AR session based on a transformation determined using the identified body part.

19. A system for an AR session based on skeleton tracking, Including: A processor; And A memory component having instructions stored thereon, which when executed by the processor cause the processor to perform operations including the following operations: Receiving, by a second device, a request to join an AR session initialized by a first device; In response to receiving the request, detecting a body corresponding to the user of the first device in one or more images captured by a camera of the second device; Identifying body parts of the detected body, the body parts including the hand holding the first device and the wrist corresponding to the hand; Using, by the second device, the identified body parts to determine a transformation between the first device and the second device in the AR session; And Causing the second device to display the AR session based on the determined transformation; The operations further include: Receiving, at the second device, information including an angle of a gravity axis for the one or more images; Comparing, at the second device, the angle of the gravity axis with tracking data of a wrist joint position of the wrist; and Based on the comparison, filtering, at the second device, an image of the wrist joint position or a determined transformation in a case where there is a disagreement in the orientation of the first device relative to the gravity axis.

20. A non-transitory computer-readable storage medium having instructions stored thereon, which when executed by a processor cause the processor to perform operations including the following operations: Receiving, by a second device, a request to join an AR session initialized by a first device; In response to receiving the request, detecting a body corresponding to the user of the first device in one or more images captured by a camera of the second device; Identifying body parts of the detected body, the body parts including the hand holding the first device and the wrist corresponding to the hand; Using, by the second device, the identified body parts to determine a transformation between the first device and the second device in the AR session; And Causing the second device to display the AR session based on the determined transformation; The operations further include: Receiving, at the second device, information including an angle of a gravity axis for the one or more images; Comparing, at the second device, the angle of the gravity axis with tracking data of a wrist joint position of the wrist; and Based on the comparison, filtering, at the second device, an image of the wrist joint position or a determined transformation in a case where there is a disagreement in the orientation of the first device relative to the gravity axis.

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