Patent Publication Number: US-11663738-B2

Title: AR data simulation with gaitprint imitation

Description:
RELATED APPLICATION 
     The present application claims priority to U.S. Provisional Patent Application Ser. No. 63/190,113, filed May 18, 2021, which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The subject matter disclosed herein generally relates to a visual tracking system. Specifically, the present disclosure addresses systems and methods for generating a motion database of visual tracking systems based on gaitprint. 
     BACKGROUND 
     An augmented reality (AR) device enables a user to observe a scene while simultaneously seeing relevant virtual content that may be aligned to items, images, objects, or environments in the field of view of the device. A virtual reality (VR) device provides a more immersive experience than an AR device. The VR device blocks out the field of view of the user with virtual content that is displayed based on a position and orientation of the VR device. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced. 
         FIG.  1    is a block diagram illustrating an environment for operating a visual tracking system in accordance with one example embodiment. 
         FIG.  2    is a block diagram illustrating a display device in accordance with one example embodiment. 
         FIG.  3    is a block diagram illustrating a visual tracking system in accordance with one example embodiment. 
         FIG.  4    is a block diagram illustrating a gait abstraction module in accordance with one example embodiment. 
         FIG.  5    is a block diagram illustrating a content simulation application in accordance with one example embodiment. 
         FIG.  6    is a block diagram illustrating a process in accordance with one example embodiment. 
         FIG.  7    is a flow diagram illustrating a method for generating ground truth data in accordance with one example embodiment. 
         FIG.  8    is block diagram showing a software architecture within which the present disclosure may be implemented, according to an example embodiment. 
         FIG.  9    is a diagrammatic representation of a machine in the form of a computer system within which a set of instructions may be executed for causing the machine to perform any one or more of the methodologies discussed herein, according to one example embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The description that follows describes systems, methods, techniques, instruction sequences, and computing machine program products that illustrate example embodiments of the present subject matter. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide an understanding of various embodiments of the present subject matter. It will be evident, however, to those skilled in the art, that embodiments of the present subject matter may be practiced without some or other of these specific details. Examples merely typify possible variations. Unless explicitly stated otherwise, structures (e.g., structural Components, such as modules) are optional and may be combined or subdivided, and operations (e.g., in a procedure, algorithm, or other function) may vary in sequence or be combined or subdivided. 
     The term “augmented reality” (AR) is used herein to refer to an interactive experience of a real-world environment where physical objects that reside in the real-world are “augmented” or enhanced by computer-generated digital content (also referred to as virtual content or synthetic content). AR can also refer to a system that enables a combination of real and virtual worlds, real-time interaction, and 3D registration of virtual and real objects. A user of an AR system perceives virtual content that appear to be attached or interact with a real-world physical object. 
     The term “virtual reality” (VR) is used herein to refer to a simulation experience of a virtual world environment that is completely distinct from the real-world environment. Computer-generated digital content is displayed in the virtual world environment. VR also refers to a system that enables a user of a VR system to be completely immersed in the virtual world environment and to interact with virtual objects presented in the virtual world environment. 
     The term “AR application” is used herein to refer to a computer-operated application that enables an AR experience. The term “VR application” is used herein to refer to a computer-operated application that enables a VR experience. The term “AR/VR application” refers to a computer-operated application that enables a combination of an AR experience or a VR experience. 
     The “visual tracking system” is used herein to refer to a computer-operated application or system that enables a system to track visual features identified in images captured by one or more cameras of the visual tracking system, and build a model of a real-world environment based on the tracked visual features. Non-limiting examples of the visual tracking system include: a visual Simultaneous Localization and Mapping system (VSLAM), and Visual Odometry Inertial (VIO) system. VSLAM can be used to build a target from an environment or a scene based on one or more cameras of the visual tracking system. VIO (also referred to as a visual-inertial tracking system, and visual odometry system) determines a latest position or pose of a device based on data acquired from multiple sensors (e.g., depth cameras, inertial sensors) of the device. 
     The term “gait” (also referred to as “gait print”) is herein to refer to a movement pattern of a user. For example, the gait identifies a biometric modality that identifies a user based on the way the user walk, runs, or jumps among some examples of movements. 
     AR/VR applications enable a user to access information, such as in the form of virtual content rendered in a display of an AR/VR display device (also referred to as a display device). The rendering of the virtual content may be based on a position of the display device relative to a physical object or relative to a frame of reference (external to the display device) so that the virtual content correctly appears in the display. For AR, the virtual content appears aligned with a physical object as perceived by the user and a camera of the AR display device. The virtual content appears to be attached to a physical object of interest. In order to do this, the AR display device detects the physical object and tracks a pose of the AR display device relative to a position of the physical object. A pose identifies a position and orientation of the display device relative to a frame of reference or relative to another object. For VR, the virtual object appears at a location (in the virtual environment) based on the pose of the VR display device. The virtual content is therefore refreshed based on a latest position of the device. 
     The present application describes a method for transferring one human gait to another to simulate AR content in the virtual simulation world. This “impersonation” or transfer of one human gait to another user&#39;s trajectory generates large numbers of training/testing data that are based on one person&#39;s unique gait print. This training data can help personalize and further customize tuning of computer vision algorithms of visual tracking systems. As such, gait pattern for simulation of virtual environments enlarges the diversity of simulation trajectories (e.g., pose over time). 
     In one example embodiment, the present application describes a method for transferring a gait pattern of a first user to a second user to simulate augmented reality content in a virtual simulation environment. In one aspect, the method includes identifying a gait pattern of a first user operating a first visual tracking system in a first physical environment, identifying a trajectory from a second visual tracking system operated by a second user in a second physical environment, the trajectory based on poses of the second visual tracking system over time, modifying the trajectory from the second visual tracking system based on the gait pattern of the first user, applying the modified trajectory in a plurality of virtual environments, and generating simulated ground truth data based on the modified trajectory in the plurality of virtual environments. 
     As a result, one or more of the methodologies described herein facilitate solving the technical problem of calibrating camera intrinsic parameters based on operating conditions that are different from factory conditions. The presently described method provides an improvement to an operation of the functioning of a computer by providing further accurate calibration computation to enhance a VSLAM pose estimation. Furthermore, one or more of the methodologies described herein may obviate a need for certain efforts or computing resources. Examples of such computing resources include Processor cycles, network traffic, memory usage, data storage capacity, power consumption, network bandwidth, and cooling capacity. 
       FIG.  1    is a network diagram illustrating an environment  100  suitable for operating an AR device  118 , an AR device  122 , and a server  110 , according to some example embodiments. The environment  100  includes a user B  120 , an AR device  118 , and a physical object  102 . The user A  116  operates the AR device  118  in real world environment A  104 . The user A  116  may be a human user (e.g., a human being), a machine user (e.g., a computer configured by a software program to interact with the user A  116 ), or any suitable combination thereof (e.g., a human assisted by a machine or a machine supervised by a human). The user A  116  is associated with the AR device  118 . The user B  120  operates the user B  120  in real world environment B  114 . The user B  120  is associated with the AR device  122 . 
     The AR device  118  includes a computing device having a display such as a smartphone, a tablet computer, or a wearable computing device (e.g., watch or glasses). The computing device may be hand-held or may be removable mounted to a head of the user B  120 . In one example, the display includes a screen that displays images captured with the cameras of the AR device  118 . In another example, the display of the device may be transparent such as in lenses of wearable computing glasses. In other examples, the display may be non-transparent, partially transparent, or partially opaque. In yet other examples, the display may be wearable by the user A  116  to completely or partially cover the field of vision of the user A  116 . 
     The AR device  118  includes an AR application (not shown) that causes a display of virtual content based on images detected with the cameras of the AR device  118 . For example, the user B  120  may point multiple cameras of the AR device  118  to capture an image of the physical object  102 . The physical object  102  is within a field of view  106  of a first camera (not shown) of the AR device  118  and within a field of view  108  of a second camera (not shown) of the AR device  118 . The AR application generates virtual content corresponding to an identified object (e.g., physical object  102 ) in the image and presents the virtual content in a display (not shown) of the AR device  118 . 
     The AR device  118  includes a visual tracking system (not shown) that tracks the pose (e.g., 6DOF pose, position and orientation) of the AR device  118  relative to the real world environment A  104  using, for example, optical sensors (e.g., depth-enabled 3D camera, image camera), inertia sensors (e.g., gyroscope, accelerometer), magnetometer, wireless sensors (Bluetooth, Wi-Fi), GPS sensor, and audio sensor. In one example, the AR device  118  includes a visual Simultaneous Localization and Mapping system (VSLAM) that operates with multiple cameras of the AR device  118 . The AR device  118  displays virtual content based on the 3DFO pose of the AR device  118  relative to the real world environment A  104  and/or the physical object  102  (as determined by the visual tracking system). 
     In one example, the AR device  118  determines a gait print based on a motion of the user A  116 . The AR device  118  sends the user A  116  gait print and the trajectory data (e.g., 6DOF over time) of the AR device  118  in the real world environment A  104  to a content simulation application  112  of the server  110  for further simulation and training of computer vision algorithms. The AR device  122  determines a gait print based on a motion of the user B  120 . The AR device  122  sends the user B  120  gait print and the trajectory data (e.g., 6DOF over time) of the AR device  122  in the real world environment B  114  to the content simulation application  112  for further simulation and training of computer vision algorithms. The content simulation application  112  is described further below with respect to  FIG.  5   . 
     In another example, the content simulation application  112  receives sensor data from the AR device  118  and the AR device  122 . The content simulation application  112  determines the gait print of the user A  116  and the user B  120  based on the second data. 
     In one example, the AR device  118  and the AR device  122  communicate with server  110  via a computer network (not shown). The computer network may be any network that enables communication between or among machines, databases, and devices. Accordingly, the computer network may be a wired network, a wireless network (e.g., a mobile or cellular network), or any suitable combination thereof. The computer network may include one or more portions that constitute a private network, a public network (e.g., the Internet), or any suitable combination thereof. 
     Any of the machines, databases, or devices shown in  FIG.  1    may be implemented in a general-purpose computer modified (e.g., configured or programmed) by software to be a special-purpose computer to perform one or more of the functions described herein for that machine, database, or device. For example, a computer system able to implement any one or more of the methodologies described herein is discussed below with respect to  FIG.  7   . As used herein, a “database” is a data storage resource and may store data structured as a text file, a table, a spreadsheet, a relational database (e.g., an object-relational database), a triple store, a hierarchical data store, or any suitable combination thereof. Moreover, any two or more of the machines, databases, or devices illustrated in  FIG.  1    may be combined into a single machine, and the functions described herein for any single machine, database, or device may be subdivided among multiple machines, databases, or devices. 
       FIG.  2    is a block diagram illustrating modules (e.g., components) of the AR device  118 , according to some example embodiments. The AR device  118  includes sensors  202 , a display  204 , a processor  208 , and a storage device  206 . Examples of AR device  118  include a wearable computing device, a mobile computing device (such as a smart phone or smart table), a navigational device, a portable media device. 
     The sensors  202  include, for example, optical sensor  214  (e.g., camera such as a color camera, a thermal camera, a depth sensor and one or multiple grayscale, global shutter tracking cameras), an inertial sensor  216  (e.g., gyroscope, accelerometer, magnetometer). In one example, the optical sensor  214  include one or more cameras. 
     Other examples of sensors  202  include a proximity or location sensor (e.g., near field communication, GPS, Bluetooth, Wifi), an audio sensor (e.g., a microphone), a temperature sensor, or any suitable combination thereof. It is noted that the sensors  202  described herein are for illustration purposes and the sensors  202  are thus not limited to the ones described above. 
     The display  204  includes a screen or monitor configured to display images generated by the processor  208 . In one example embodiment, the display  204  may be transparent or semi-opaque so that the user B  120  can see through the display  204  (in AR use case). In another example, the display  204  includes a touchscreen display configured to receive a user input via a contact on the touchscreen display. 
     The processor  208  includes an AR application  212 , a visual tracking system  210 , and a gaitprint abstraction module  222 . The AR application  212  detects the physical object  102  using computer vision based on the detected features of the environment processed by the visual tracking system  210 . The AR application  212  retrieves virtual content (e.g., 3D object model) based on the identified physical object  102  or physical environment. The AR application  212  renders the virtual object in the display  204 . In one example embodiment, the AR application  212  includes a local rendering engine that generates a visualization of virtual content overlaid (e.g., superimposed upon, or otherwise displayed in tandem with) on an image of the physical object  102  captured by the optical sensor  214 . A visualization of the virtual content may be manipulated by adjusting a position of the physical object  102  (e.g., its physical location, orientation, or both) relative to the optical sensor  214 . Similarly, the visualization of the virtual content may be manipulated by adjusting a pose of the AR device  118  relative to the physical object  102 . For a VR application, the AR application  212  displays the virtual content in an immersive virtual world displayed in the display  204  at a location (in the display  204 ) determined based on a pose of the AR device  118 . 
     The visual tracking system  210  estimates a 6DOF pose of the AR device  118  and generate trajectory data (e.g., 6DOF poses over time). For example, the visual tracking system  210  uses image data and corresponding inertial data from the optical sensor  214  and the inertial sensor  216  to track a location and pose of the AR device  118  relative to a frame of reference (e.g., detected features in the real world environment A  104 ). Example components of the visual tracking system  210  are described in more detail below with respect to  FIG.  3   . 
     The gaitprint abstraction module  222  uses the 6DOF poses over time and the IMU data from the inertial sensor  216  to identify a gait print that is unique to the user A  116 . 
     The storage device  206  stores virtual content  218 , landmark map  220 , and gaitprint dataset  224 . The virtual content  218  includes, for example, a database of visual references (e.g., images of physical objects) and corresponding experiences (e.g., two-dimensional or three-dimensional virtual object models). The landmark map  220  stores trajectories data and a map of an environment based on features detected by the visual tracking system  210 . The gaitprint dataset  224  stores the biometric gait print pattern of the user A  116  (as determined by the gaitprint abstraction module  222 ). 
     Any one or more of the modules described herein may be implemented using hardware (e.g., a processor of a machine) or a combination of hardware and software. For example, any module described herein may configure a processor to perform the operations described herein for that module. Moreover, any two or more of these modules may be combined into a single module, and the functions described herein for a single module may be subdivided among multiple modules. Furthermore, according to various example embodiments, modules described herein as being implemented within a single machine, database, or device may be distributed across multiple machines, databases, or devices. 
       FIG.  3    illustrates the visual tracking system  210  in accordance with one example embodiment. The visual tracking system  210  includes, for example, an inertial module  302 , an optical module  304 , a SLAM application  306 . The inertial module  302  accesses inertial sensor data from the inertial sensor  216 . The optical module  304  accesses optical sensor data from the optical sensor  214 . 
     The SLAM application  306  determines a 3DOF pose (e.g., location, position, orientation) of the AR device  118  relative to a frame of reference (e.g., real world environment A  104 ). In one example embodiment, the SLAM application  306  includes a visual odometry system that estimates the pose of the AR device  118  based on 3D maps of feature points from images captured with the optical sensor  214  and the inertial sensor data captured with the inertial sensor  216 . The SLAM application  306  is capable of operating as a stereo VSLAM and monocular VSLAM. In other words, the SLAM application  306  can toggle its operation between the monocular and stereo V-SLAM without the interruption of localization and mapping. The SLAM application  306  provides the pose information to the gaitprint abstraction module  222  so that the gaitprint abstraction module  222  can identify a gait print of the user A  116  based on the pose data and IMU data from the inertial sensor  216 . 
       FIG.  4    is a block diagram illustrating a gaitprint abstraction module  222  in accordance with one example embodiment. The unsupervised training program  402  abstracts the movement of the AR device  118  (worn by the user A  116 ) to identify a gait pattern of the user A  116 . The unsupervised training program  402  includes, for example, an unsupervised training program  402  and a trained machine-learning model  404 . 
     The unsupervised training program  402  accesses inertial sensor data from the inertial sensor  216  and pose data from the visual tracking system  210 . The unsupervised training program  402  operates an unsupervised training algorithm that learn patterns from untagged dataset (IMU data and pose data). The trained machine-learning model  404  trains a gait model based on the identified patterns from the unsupervised training program  402 . The gait model identifies the user A  116  gait print. The trained machine-learning model  404  provides the user A  116  gait print to the content simulation application  112 . In another example, the content simulation application  112  also receives the trajectories data from the visual tracking system  210 . 
       FIG.  5    is a block diagram illustrating the content simulation application  112  in accordance with one example embodiment. The content simulation application  112  includes a trajectory adaptation module  502 , a virtual world environment database  508 , a ground truth data  504 , and a cv training module  506 . 
     The trajectory adaptation module  502  adapts the gait print of a user to another user&#39;s trajectory in another physical environment. The trajectory adaptation module  502  receives the gait print of the user A  116  and trajectories data of the AR device  118 . The trajectory adaptation module  502  also receives the gait print of the user B  120  and trajectories data of the AR device  122 . In one example, the trajectory adaptation module  502  includes a gait modified trajectory module  510  and a virtual environment gait modified trajectory application  512 . 
     The ground truth data  504  stores simulated ground truth data for SLAM and computer vision algorithm. 
     The cv training module  506  retrains a computer vision algorithm at the AR device  118 /AR device  122 . 
       FIG.  6    is a block diagram illustrating an example process in accordance with one example embodiment. The sensors  202  provides sensor data to the visual tracking system  210  and the gaitprint abstraction module  222 . 
     The visual tracking system  210  determines a 6DOF pose of the AR device  118  based on the sensor data. The visual tracking system  210  provides the pose data to the gaitprint abstraction module  222  and the AR application  212 . The visual tracking system  210  provides trajectories data (e.g., 6DOF poses over time) to the content simulation application  112 . In one example, the computer vision algorithm in the visual tracking system  210  is retuned or retrained based on the tuned computer vision algorithm received from the content simulation application  112 . 
     The gaitprint abstraction module  222  identifies a gait print of the user A  116  based on the IMU data from sensors  202  and the pose data from visual tracking system  210 . The gaitprint abstraction module  222  provides the gait print to the content simulation application  112  and to the storage device  206 . 
     The AR application  212  retrieves virtual content from the virtual content  218 . The AR application  212  instructs the display  204  to display the virtual content  218  at a location based on the geometric model (e.g., pose data) of the AR device  118 . 
     The storage device  206  stores the gaitprint dataset  224  and the virtual content  218 . 
       FIG.  7    is a flow diagram illustrating a method  700  for generating ground truth data in accordance with one example embodiment. Operations in the method  700  may be performed by the server  110 , using components (e.g., modules, engines) described above with respect to  FIG.  5   . Accordingly, the method  700  is described by way of example with reference to the server  110 . However, it shall be appreciated that at least some of the operations of the method  700  may be deployed on various other hardware configurations or be performed by similar components residing elsewhere. For example, part of the method  700  may be operated at the AR device  118  or AR device  122 . 
     In block  702 , the server  110  records sensor data of AR device a of user A  116 . In block  704 , the server  110  computes trajectories of AR device a on user A  116 . In block  706 , the server  110  determines gait print of user a based on poses and imu data. In block  708 , the server  110  record sensors data of AR device b of user b. In block  710 , the server  110  computes trajectories of AR device b on user b. In block  712 , the server  110  modifies trajectories of AR device b to adapt to gaitprint of user a. In block  714 , the server  110  applies modified trajectories in virtual environments. In block  716 , the server  110  captures simulated ground truth data. In block  718 , the server  110  retrains CV algorithms with the simulated ground truth data for user a motion pattern. In block  720 , the server  110  retrains CV algorithms with the simulated ground truth data for other real-world environment. In block  722 , the server  110  provides retrained cv algorithms to AR device a. 
     It is to be noted that other embodiments may use different sequencing, additional or fewer operations, and different nomenclature or terminology to accomplish similar functions. In some embodiments, various operations may be performed in parallel with other operations, either in a synchronous or asynchronous manner. The operations described herein were chosen to illustrate some principles of operations in a simplified form. 
       FIG.  8    is block diagram  800  showing a software architecture within which the present disclosure may be implemented, according to an example embodiment. The software architecture  804  is supported by hardware such as a machine  802  that includes Processors  820 , memory  826 , and I/O Components  838 . In this example, the software architecture  804  can be conceptualized as a stack of layers, where each layer provides a particular functionality. The software architecture  804  includes layers such as an operating system  812 , libraries  810 , frameworks  808 , and applications  806 . Operationally, the applications  806  invoke API calls  850  through the software stack and receive messages  852  in response to the API calls  850 . 
     The operating system  812  manages hardware resources and provides common services. The operating system  812  includes, for example, a kernel  814 , services  816 , and drivers  822 . The kernel  814  acts as an abstraction layer between the hardware and the other software layers. For example, the kernel  814  provides memory management, Processor management (e.g., scheduling), Component management, networking, and security settings, among other functionalities. The services  816  can provide other common services for the other software layers. The drivers  822  are responsible for controlling or interfacing with the underlying hardware. For instance, the drivers  822  can include display drivers, camera drivers, BLUETOOTH® or BLUETOOTH® Low Energy drivers, flash memory drivers, serial communication drivers (e.g., Universal Serial Bus (USB) drivers), WI-FI® drivers, audio drivers, power management drivers, and so forth. 
     The libraries  810  provide a low-level common infrastructure used by the applications  806 . The libraries  810  can include system libraries  818  (e.g., C standard library) that provide functions such as memory allocation functions, string manipulation functions, mathematic functions, and the like. In addition, the libraries  810  can include API libraries  824  such as media libraries (e.g., libraries to support presentation and manipulation of various media formats such as Moving Picture Experts Group-4 (MPEG4), Advanced Video Coding (H.264 or AVC), Moving Picture Experts Group Layer-3 (MP3), Advanced Audio Coding (AAC), Adaptive Multi-Rate (AMR) audio codec, Joint Photographic Experts Group (JPEG or JPG), or Portable Network Graphics (PNG)), graphics libraries (e.g., an OpenGL framework used to render in two dimensions (2D) and three dimensions (3D) in a graphic content on a display), database libraries (e.g., SQLite to provide various relational database functions), web libraries (e.g., WebKit to provide web browsing functionality), and the like. The libraries  810  can also include a wide variety of other libraries  828  to provide many other APIs to the applications  806 . 
     The frameworks  808  provide a high-level common infrastructure that is used by the applications  806 . For example, the frameworks  808  provide various graphical user interface (GUI) functions, high-level resource management, and high-level location services. The frameworks  808  can provide a broad spectrum of other APIs that can be used by the applications  806 , some of which may be specific to a particular operating system or platform. 
     In an example embodiment, the applications  806  may include a home application  836 , a contacts application  830 , a browser application  832 , a book reader application  834 , a location application  842 , a media application  844 , a messaging application  846 , a game application  848 , and a broad assortment of other applications such as a third-party application  840 . The applications  806  are programs that execute functions defined in the programs. Various programming languages can be employed to create one or more of the applications  806 , structured in a variety of manners, 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 specific example, the third-party application  840  (e.g., an application developed using the ANDROID™ or IOS™ software development kit (SDK) by an entity other than the vendor of the particular platform) may be mobile software running on a mobile operating system such as IOS™, ANDROID™, WINDOWS® Phone, or another mobile operating system. In this example, the third-party application  840  can invoke the API calls  850  provided by the operating system  812  to facilitate functionality described herein. 
       FIG.  9    is a diagrammatic representation of the machine  900  within which instructions  908  (e.g., software, a program, an application, an applet, an app, or other executable code) for causing the machine  900  to perform any one or more of the methodologies discussed herein may be executed. For example, the instructions  908  may cause the machine  900  to execute any one or more of the methods described herein. The instructions  908  transform the general, non-programmed machine  900  into a particular machine  900  programmed to carry out the described and illustrated functions in the manner described. The machine  900  may operate as a standalone device or may be coupled (e.g., networked) to other machines. In a networked deployment, the machine  900  may operate in the capacity of 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. The machine  900  may comprise, but not be 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 telephone, a smart phone, 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 executing the instructions  908 , sequentially or otherwise, that specify actions to be taken by the machine  900 . Further, while only a single machine  900  is illustrated, the term “machine” shall also be taken to include a collection of machines that individually or jointly execute the instructions  908  to perform any one or more of the methodologies discussed herein. 
     The machine  900  may include Processors  902 , memory  904 , and I/O Components  942 , which may be configured to communicate with each other via a bus  944 . In an example embodiment, the Processors  902  (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 ASIC, a Radio-Frequency Integrated Circuit (RFIC), another Processor, or any suitable combination thereof) may include, for example, a Processor  906  and a Processor  910  that execute the instructions  908 . The term “Processor” is intended to include multi-core Processors that may comprise two or more independent Processors (sometimes referred to as “cores”) that may execute instructions contemporaneously. Although  FIG.  9    shows multiple Processors  902 , the machine  900  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 multiples cores, or any combination thereof. 
     The memory  904  includes a main memory  912 , a static memory  914 , and a storage unit  916 , both accessible to the Processors  902  via the bus  944 . The main memory  904 , the static memory  914 , and storage unit  916  store the instructions  908  embodying any one or more of the methodologies or functions described herein. The instructions  908  may also reside, completely or partially, within the main memory  912 , within the static memory  914 , within machine-readable medium  918  within the storage unit  916 , within at least one of the Processors  902  (e.g., within the Processor&#39;s cache memory), or any suitable combination thereof, during execution thereof by the machine  900 . 
     The I/O Components  942  may include a wide variety of Components to receive input, provide output, produce output, transmit information, exchange information, capture measurements, and so on. The specific I/O Components  942  that are included in a particular machine will depend on the type of machine. For example, portable machines such as mobile phones may include a touch input device or other such input mechanisms, while a headless server machine will likely not include such a touch input device. It will be appreciated that the I/O Components  942  may include many other Components that are not shown in  FIG.  9   . In various example embodiments, the I/O Components  942  may include output Components  928  and input Components  930 . The output Components  928  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 vibratory motor, resistance mechanisms), other signal generators, and so forth. The input Components  930  may include alphanumeric input Components (e.g., a keyboard, a touch screen configured to receive alphanumeric input, a photo-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 another pointing instrument), tactile input Components (e.g., a physical button, a touch screen that provides location and/or force of touches or touch gestures, or other tactile input Components), audio input Components (e.g., a microphone), and the like. 
     In further example embodiments, the I/O Components  942  may include biometric Components  932 , motion Components  934 , environmental Components  936 , or position Components  938 , among a wide array of other Components. For example, the biometric Components  932  include Components to detect expressions (e.g., hand expressions, facial expressions, vocal expressions, body gestures, or eye tracking), measure biosignals (e.g., blood pressure, heart rate, body temperature, perspiration, or brain waves), identify a person (e.g., voice identification, retinal identification, facial identification, fingerprint identification, or electroencephalogram-based identification), and the like. The motion Components  934  include acceleration sensor Components (e.g., accelerometer), gravitation sensor Components, rotation sensor Components (e.g., gyroscope), and so forth. The environmental Components  936  include, for example, illumination sensor Components (e.g., photometer), temperature sensor Components (e.g., one or more thermometers that detect ambient temperature), humidity sensor Components, pressure sensor Components (e.g., barometer), acoustic sensor Components (e.g., one or more microphones that detect background noise), proximity sensor Components (e.g., infrared sensors that detect nearby objects), gas sensors (e.g., gas detection sensors to detection concentrations of hazardous gases for safety or to measure pollutants in the atmosphere), or other Components that may provide indications, measurements, or signals corresponding to a surrounding physical environment. The position Components  938  include location sensor Components (e.g., a GPS receiver Component), altitude sensor Components (e.g., altimeters or barometers that detect air pressure from which altitude may be derived), orientation sensor Components (e.g., magnetometers), and the like. 
     Communication may be implemented using a wide variety of technologies. The I/O Components  942  further include communication Components  940  operable to couple the machine  900  to a network  920  or devices  922  via a coupling  924  and a coupling  926 , respectively. For example, the communication Components  940  may include a network interface Component or another suitable device to interface with the network  920 . In further examples, the communication Components  940  may include wired communication Components, wireless communication Components, cellular communication Components, Near Field Communication (NFC) Components, Bluetooth® Components (e.g., Bluetooth® Low Energy), WiFi® Components, and other communication Components to provide communication via other modalities. The devices  922  may be another machine or any of a wide variety of peripheral devices (e.g., a peripheral device coupled via a USB). 
     Moreover, the communication Components  940  may detect identifiers or include Components operable to detect identifiers. For example, the communication Components  940  may include Radio Frequency Identification (RFID) tag reader Components, NFC smart tag detection Components, optical reader Components (e.g., an optical sensor to detect one-dimensional bar codes such as Universal Product Code (UPC) bar code, multi-dimensional bar codes such as Quick Response (QR) code, Aztec code, Data Matrix, Dataglyph, MaxiCode, PDF417, Ultra Code, UCC RSS-2D bar code, and other optical codes), or acoustic detection Components (e.g., microphones to identify tagged audio signals). In addition, a variety of information may be derived via the communication Components  940 , such as location via Internet Protocol (IP) geolocation, location via Wi-Fi® signal triangulation, location via detecting an NFC beacon signal that may indicate a particular location, and so forth. 
     The various memories (e.g., memory  904 , main memory  912 , static memory  914 , and/or memory of the Processors  902 ) and/or storage unit  916  may store one or more sets of instructions and data structures (e.g., software) embodying or used by any one or more of the methodologies or functions described herein. These instructions (e.g., the instructions  908 ), when executed by Processors  902 , cause various operations to implement the disclosed embodiments. 
     The instructions  908  may be transmitted or received over the network  920 , using a transmission medium, via a network interface device (e.g., a network interface Component included in the communication Components  940 ) and using any one of a number of well-known transfer protocols (e.g., hypertext transfer protocol (HTTP)). Similarly, the instructions  908  may be transmitted or received using a transmission medium via the coupling  926  (e.g., a peer-to-peer coupling) to the devices  922 . 
     As used herein, the terms “Machine-Storage Medium,” “device-storage medium,” and “computer-storage medium” mean the same thing and may be used interchangeably in this disclosure. The terms refer to a single or multiple storage devices and/or media (e.g., a centralized or distributed database, and/or associated caches and servers) that store executable instructions and/or data. The terms shall accordingly be taken to include, but not be limited to, solid-state memories, and optical and magnetic media, including memory internal or external to processors. Specific examples of Machine-Storage Media, computer-storage media, and/or device-storage media include non-volatile memory, including by way of example semiconductor memory devices, e.g., erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), field-programmable gate arrays (FPGAs), and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The terms “Machine-Storage Media,” “computer-storage media,” and “device-storage media” specifically exclude carrier waves, modulated data signals, and other such media, at least some of which are covered under the term “signal medium” discussed below. 
     The terms “transmission medium” and “signal medium” mean the same thing and may be used interchangeably in this disclosure. The terms “transmission medium” and “signal medium” shall be taken to include any intangible medium that is capable of storing, encoding, or carrying the instructions  1416  for execution by the machine  1400 , and include digital or analog communications signals or other intangible media to facilitate communication of such software. Hence, the terms “transmission medium” and “signal medium” shall be taken to include any form of modulated data signal, carrier wave, and so forth. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. 
     The terms “machine-readable medium,” “Computer-Readable Medium,” and “device-readable medium” mean the same thing and may be used interchangeably in this disclosure. The terms are defined to include both Machine-Storage Media and transmission media. Thus, the terms include both storage devices/media and carrier waves/modulated data signals. 
     Although an embodiment has been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader scope of the present disclosure. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. The accompanying drawings that form a part hereof, show by way of illustration, and not of limitation, specific embodiments in which the subject matter may be practiced. The embodiments illustrated are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other embodiments may be utilized and derived therefrom, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. This Detailed Description, therefore, is not to be taken in a limiting sense, and the scope of various embodiments is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled. 
     Such embodiments of the inventive subject matter may be referred to herein, individually and/or collectively, by the term “invention” merely for convenience and without intending to voluntarily limit the scope of this application to any single invention or inventive concept if more than one is in fact disclosed. Thus, although specific embodiments have been illustrated and described herein, it should be appreciated that any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the above description. 
     The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment. 
     EXAMPLES 
     Described implementations of the subject matter can include one or more features, alone or in combination as illustrated below by way of example. 
     Example 1 is a method comprising: identifying a gait pattern of a first user operating a first visual tracking system in a first physical environment; identifying a trajectory from a second visual tracking system operated by a second user in a second physical environment, the trajectory based on poses of the second visual tracking system over time; modifying the trajectory from the second visual tracking system based on the gait pattern of the first user; applying the modified trajectory in a plurality of virtual environments; and generating simulated ground truth data based on the modified trajectory in the plurality of virtual environments. 
     Example 2 includes example 1, further comprising: retraining a computer vision algorithm with the simulated ground truth data, the retrained computer vision algorithm configured for a motion pattern of the first user. 
     Example 3 includes example 2, further comprising: providing the retrained computer vision algorithm to the first visual tracking system, wherein the first visual tracking system is re-configured for the motion pattern of the first user based on the retrained computer vision algorithm. 
     Example 4 includes example 1, further comprising: retraining a computer vision algorithm with the simulated ground truth data, the retrained computer vision algorithm configured for one of the plurality of virtual environments. 
     Example 5 includes example 4, further comprising: providing the retrained computer vision algorithm to the first visual tracking system, wherein the first visual tracking system is located in a third physical environment, the third physical environment corresponding to the one of the plurality of virtual environments. 
     Example 6 includes example 1, wherein the ground truth data comprises a combination of color images, depth images, surface normals, and camera poses. 
     Example 7 includes example 1, further comprising: accessing sensor data from the first visual tracking system of the first user in the first physical environment; and determining the gait pattern of the first user based on the sensor data of the first user in the first environment. 
     Example 8 includes example 7, wherein the sensor data comprises 6DOF poses of the first visual tracking system over time in the first physical environment. 
     Example 9 includes example 1, further comprising: accessing sensor data from the second visual tracking system of the second user in the second physical environment; and determining the trajectory based on the sensor data from the second visual tracking system. 
     Example 10 includes example 1, further comprising: accessing sensor data from a first visual tracking system of a first user in a first environment; accessing pose data from a second visual tracking system of a second user in a second environment; determining a gait pattern of the first user based on the pose data of the first user in the first environment; modify a trajectory of the second virtual tracking system to adapt to the gait pattern of the first user; apply the modified trajectory in a plurality of virtual environments; accessing pose data from a second visual tracking system of a second user in a second environment; and generating a simulation of the first user trajectory in the second environment based on the first gait pattern of the first user in the first environment and the pose data of the second user in the second environment. 
     Example 11 is a computing apparatus comprising: a processor; and a memory storing instructions that, when executed by the processor, configure the apparatus to: identify a gait pattern of a first user operating a first visual tracking system in a first physical environment; identify a trajectory from a second visual tracking system operated by a second user in a second physical environment, the trajectory based on poses of the second visual tracking system over time; modify the trajectory from the second visual tracking system based on the gait pattern of the first user; apply the modified trajectory in a plurality of virtual environments; and generate simulated ground truth data based on the modified trajectory in the plurality of virtual environments. 
     Example 12 includes the computing apparatus of example 11, wherein the instructions further configure the apparatus to: retrain a computer vision algorithm with the simulated ground truth data, the retrained computer vision algorithm configured for a motion pattern of the first user. 
     Example 13 includes the computing apparatus of example 12, wherein the instructions further configure the apparatus to: provide the retrained computer vision algorithm to the first visual tracking system, wherein the first visual tracking system is re-configured for the motion pattern of the first user based on the retrained computer vision algorithm. 
     Example 14 includes the computing apparatus of example 11, wherein the instructions further configure the apparatus to: retrain a computer vision algorithm with the simulated ground truth data, the retrained computer vision algorithm configured for one of the plurality of virtual environments. 
     Example 15 includes the computing apparatus of example 14, wherein the instructions further configure the apparatus to: provide the retrained computer vision algorithm to the first visual tracking system, wherein the first visual tracking system is located in a third physical environment, the third physical environment corresponding to the one of the plurality of virtual environments. 
     Example 16 includes the computing apparatus of example 11, wherein the ground truth data comprises a combination of color images, depth images, surface normals, and camera poses. 
     Example 17 includes the computing apparatus of example 11, wherein the instructions further configure the apparatus to: access sensor data from the first visual tracking system of the first user in the first physical environment; and determine the gait pattern of the first user based on the sensor data of the first user in the first environment. 
     Example 18 includes the computing apparatus of example 17, wherein the sensor data comprises 6DOF poses of the first visual tracking system over time in the first physical environment. 
     Example 19 includes the computing apparatus of example 11, wherein the instructions further configure the apparatus to: access sensor data from the second visual tracking system of the second user in the second physical environment; and determine the trajectory based on the sensor data from the second visual tracking system. 
     Example 20 is a non-transitory computer-readable storage medium, the computer-readable storage medium including instructions that when executed by a computer, cause the computer to: identify a gait pattern of a first user operating a first visual tracking system in a first physical environment; identify a trajectory from a second visual tracking system operated by a second user in a second physical environment, the trajectory based on poses of the second visual tracking system over time; modify the trajectory from the second visual tracking system based on the gait pattern of the first user; apply the modified trajectory in a plurality of virtual environments; and generate simulated ground truth data based on the modified trajectory in the plurality of virtual environments.