Magic Leap Patent | Systems And Methods For Augmented Reality
Publication Number: 20200098191
Publication Date: 20200326
Applicants: Magic Leap
Examples of the disclosure describe systems and methods for sharing perspective views of virtual content. In an example method, a virtual object is presented, via a display, to a first user. A first perspective view of the virtual object is determined, wherein the first perspective view is based on a position of the virtual object and a first position of the first user. The virtual object is presented, via a display, to a second user, wherein the virtual object is presented to the second user according to the first perspective view. An input is received from the first user. A second perspective view of the virtual object is determined, wherein the second perspective view is based on the input from the first user. The virtual object is presented, via a display, to the second user, wherein presenting the virtual object to the second user comprises presenting a transition from the first perspective view to the second perspective view.
CROSS-REFERENCE TO RELATED APPLICATIONS
 This application claims priority to U.S. Provisional Application No. 62/736,432, filed on Sep. 25, 2018, the contents of which are incorporated by reference herein in their entirety.
 This disclosure relates in general to systems and methods for sharing and presenting visual signals, and in particular to systems and methods for sharing and presenting visual signals corresponding content in a mixed reality environment.
 Modern computing and display technologies have facilitated the development of systems for so called “virtual reality” or “augmented reality” experiences, wherein digitally reproduced images or portions thereof are presented to a user in a manner wherein they seem to be, or may be perceived as, real. A virtual reality, or “VR”, scenario typically involves presentation of digital or virtual image information without transparency to other actual real-world visual input; an augmented reality, or “AR”, scenario typically involves presentation of digital or virtual image information as an augmentation to visualization of the actual world around the user.
 For example, referring to FIG. 1, an augmented reality scene (4) is depicted wherein a user of an AR technology sees a real-world park-like setting (6) featuring people, trees, buildings in the background, and a concrete platform (1120). In addition to these items, the user of the AR technology also perceives that he “sees” a robot statue (1110) standing upon the real-world platform (1120), and a cartoon-like avatar character (2) flying by which seems to be a personification of a bumble bee, even though these elements (2, 1110) do not exist in the real world.
 Correct placement of this virtual imagery in the real world for life-like augmented reality (or “mixed reality”) requires a series of intercoupled coordinate frameworks.
 The human visual perception system is very complex, and producing a VR or AR technology that facilitates a comfortable, natural-feeling, rich presentation of virtual image elements amongst other virtual or real-world imagery elements is challenging.
 For instance, head-worn AR displays (or helmet-mounted displays, or smart glasses) typically are at least loosely coupled to a user’s head, and thus move when the user’s head moves. Display components, such as eyepieces for a head-mounted display, may be asymmetrically positioned to a user’s eyes. For example, a binocular system may place one eyepiece closer or farther to a given eye (e.g., as compared to a complementary eyepiece and eye). In a monocular system, alignment of the monolithic eyepiece may be at an angle, such that a left/right eye is not similarly positioned to the other eye.
 Complicating the variation in fit as described above is the motion of the user’s head or changes to the user’s position otherwise.
 As an example, if a user wearing a head-worn display views a virtual representation of a three-dimensional (3D) object on the display and walks around the area where the 3D object appears, that 3D object may be re-rendered for each viewpoint, giving the user the perception that he or she is walking around an object that occupies real space. If the head-worn display is used to present multiple objects within a virtual space (for instance, a rich virtual world), measurements of head pose (i.e., the location and orientation of the user’s head) can be used to re-render the scene to match the user’s dynamically changing head location and orientation and provide an increased sense of immersion in the virtual space.
 In AR systems, detection or calculation of head pose can facilitate the display system to render virtual objects such that they appear to occupy a space in the real world in a manner that makes sense to the user.
 In some augmented reality technology such as Google Glass.RTM., virtual content is displayed in a fixed position. In such examples, the virtual content and the device share a common coordinate frame, as any motion of the device will similarly change the position of the virtual content.
 In some augmented reality or mixed reality systems, a series of coordinate frames ensures the virtual content appears fixed to the real world or environment the device is in, rather than fixed to the device itself.
 Examples of the disclosure describe systems and methods for sharing perspective views of virtual content. In an example method, a virtual object is presented, via a display, to a first user. A first perspective view of the virtual object is determined, wherein the first perspective view is based on a position of the virtual object and a first position of the first user. The virtual object is presented, via a display, to a second user, wherein the virtual object is presented to the second user according to the first perspective view. An input is received from the first user. A second perspective view of the virtual object is determined, wherein the second perspective view is based on the input from the first user. The virtual object is presented, via a display, to the second user, wherein presenting the virtual object to the second user comprises presenting a transition from the first perspective view to the second perspective view.
BRIEF DESCRIPTION OF THE DRAWINGS
 FIG. 1 illustrates an augmented reality scenario with certain virtual reality object according to some embodiments.
 FIGS. 2A-2C illustrate various configurations of components comprising a visual display system according to some embodiments.
 FIG. 3 illustrates remote interaction with cloud computing assets according to some embodiments.
 FIG. 4 illustrates a single user coordinate frame system with virtual content according to some embodiments.
 FIG. 5 illustrates a user device coordinate frame to binocular render cameras according to some embodiments.
 FIG. 6 illustrates a multi-user coordinate frame system with virtual content according to some embodiments.
 FIG. 7 illustrates a multi-user sharing coordinate frame system with virtual content according to some embodiments.
 FIGS. 8A-8C illustrate world frame selection protocols among users according to some embodiments.
 FIGS. 9A-9B illustrate device to render camera coordinate frame transform options according to some embodiments.
 FIGS. 10A-10B illustrate angular relationships between viewers and resultant virtual content displays, according to some embodiments.
 FIGS. 11A-11C illustrate additional angular relationships between viewers with distance variations and resultant virtual content displays, according to some embodiments.
 FIGS. 11D-11E illustrate resultant virtual content perception based on angular differences among users according to some embodiments.
 FIGS. 12A-12C illustrate an example mixed reality environment.
 FIGS. 13A-13D illustrate components of an example mixed reality system that can be used to generate and interact with a mixed reality environment.
 FIG. 14A illustrates an example mixed reality handheld controller that can be used to provide input to a mixed reality environment.
 FIG. 14B illustrates an example auxiliary unit that can be used with an example mixed reality system.
 FIG. 15 illustrates an example functional block diagram for an example mixed reality system.
 The present invention relates to systems and methods to create a plurality of coordinate frames for determining relative position of virtual content, a head mounted display (HMD) for presenting AR content to at least one user, and a user’s eye positions.
 Additional embodiments, advantages, and details are described in greater detail below with specific reference to the figures as appropriate.
* Mixed Reality Environment*
 Like all people, a user of a mixed reality system exists in a real environment–that is, a three-dimensional portion of the “real world,” and all of its contents, that are perceptible by the user. For example, a user perceives a real environment using one’s ordinary human senses–sight, sound, touch, taste, smell–and interacts with the real environment by moving one’s own body in the real environment. Locations in a real environment can be described as coordinates in a coordinate space; for example, a coordinate can comprise latitude, longitude, and elevation with respect to sea level; distances in three orthogonal dimensions from a reference point; or other suitable values. Likewise, a vector can describe a quantity having a direction and a magnitude in the coordinate space.
 A computing device can maintain, for example in a memory associated with the device, a representation of a virtual environment. As used herein, a virtual environment is a computational representation of a three-dimensional space. A virtual environment can include representations of any object, action, signal, parameter, coordinate, vector, or other characteristic associated with that space. In some examples, circuitry (e.g., a processor) of a computing device can maintain and update a state of a virtual environment; that is, a processor can determine at a first time t0, based on data associated with the virtual environment and/or input provided by a user, a state of the virtual environment at a second time t1. For instance, if an object in the virtual environment is located at a first coordinate at time t0, and has certain programmed physical parameters (e.g., mass, coefficient of friction); and an input received from user indicates that a force should be applied to the object in a direction vector; the processor can apply laws of kinematics to determine a location of the object at time t1 using basic mechanics. The processor can use any suitable information known about the virtual environment, and/or any suitable input (e.g., real world parameters), to determine a state of the virtual environment at a time t1. In maintaining and updating a state of a virtual environment, the processor can execute any suitable software, including software relating to the creation and deletion of virtual objects in the virtual environment; software (e.g., scripts) for defining behavior of virtual objects or characters in the virtual environment; software for defining the behavior of signals (e.g., audio signals) in the virtual environment; software for creating and updating parameters associated with the virtual environment; software for generating audio signals in the virtual environment; software for handling input and output; software for implementing network operations; software for applying asset data (e.g., animation data to move a virtual object over time); or many other possibilities.
 Output devices, such as a display or a speaker, can present any or all aspects of a virtual environment to a user. For example, a virtual environment may include virtual objects (which may include representations of inanimate objects; people; animals; lights; etc.) that may be presented to a user. A processor can determine a view of the virtual environment (for example, corresponding to a “camera” with an origin coordinate, a view axis, and a frustum); and render, to a display, a viewable scene of the virtual environment corresponding to that view. Any suitable rendering technology may be used for this purpose. In some examples, the viewable scene may include only some virtual objects in the virtual environment, and exclude certain other virtual objects. Similarly, a virtual environment may include audio aspects that may be presented to a user as one or more audio signals. For instance, a virtual object in the virtual environment may generate a sound originating from a location coordinate of the object (e.g., a virtual character may speak or cause a sound effect); or the virtual environment may be associated with musical cues or ambient sounds that may or may not be associated with a particular location. A processor can determine an audio signal corresponding to a “listener” coordinate–for instance, an audio signal corresponding to a composite of sounds in the virtual environment, and mixed and processed to simulate an audio signal that would be heard by a listener at the listener coordinate–and present the audio signal to a user via one or more speakers.
 Because a virtual environment exists only as a computational structure, a user cannot direct1y perceive a virtual environment using one’s ordinary senses. Instead, a user can perceive a virtual environment only indirect1y, as presented to the user, for example by a display, speakers, haptic output devices, etc. Similarly, a user cannot direct1y touch, manipulate, or otherwise interact with a virtual environment; but can provide input data, via input devices or sensors, to a processor that can use the device or sensor data to update the virtual environment. For example, a camera sensor can provide optical data indicating that a user is trying to move an object in a virtual environment, and a processor can use that data to cause the object to respond accordingly in the virtual environment.
 A mixed reality system can present to the user, for example using a transmissive display and/or one or more speakers (which may, for example, be incorporated into a wearable head device), a mixed reality (“MR”) environment that combines aspects of a real environment and a virtual environment. In some embodiments, the one or more speakers may be external to the head-mounted wearable unit. As used herein, an MR environment is a simultaneous representation of a real environment and a corresponding virtual environment. In some examples, the corresponding real and virtual environments share a single coordinate space; in some examples, a real coordinate space and one or more corresponding virtual coordinate spaces are related to each other by a transformation matrix (or other suitable representation). Accordingly, in some embodiments, a single coordinate (along with, in some examples, a transformation matrix) can define a first location in the real environment, and also a second, corresponding, location in the virtual environment; and vice versa.
 In an MR environment, a virtual object (e.g., in a virtual environment associated with the MR environment) can correspond to a real object (e.g., in a real environment associated with the MR environment). For instance, if the real environment of an MR environment comprises a real lamp post (a real object) at a location coordinate, the virtual environment of the MR environment may comprise a corresponding virtual lamp post (a virtual object) at a corresponding location coordinate. As used herein, the real object in combination with its corresponding virtual object together constitute a “mixed reality object.” It is not necessary for a virtual object to perfect1y match or align with a corresponding real object. In some examples, a virtual object can be a simplified version of a corresponding real object. For instance, if a real environment includes a real lamp post, a corresponding virtual object may comprise a cylinder of roughly the same height and radius as the real lamp post (reflecting that lamp posts may be roughly cylindrical in shape). Simplifying virtual objects in this manner can allow computational efficiencies, and can simplify calculations to be performed on such virtual objects. Further, in some examples of an MR environment, not all real objects in a real environment may be associated with a corresponding virtual object. Likewise, in some examples of an MR environment, not all virtual objects in a virtual environment may be associated with a corresponding real object. That is, some virtual objects may solely in a virtual environment of an MR environment, without any real-world counterpart. In some examples, not all real objects may be associated with a corresponding real object.
 In some examples, virtual objects may have characteristics that differ, sometimes drastically, from those of corresponding real objects. For instance, while a real environment in an MR environment may comprise a green, two-armed cactus–a prickly inanimate object–a corresponding virtual object in the MR environment may have the characteristics of a green, two-armed virtual character with human facial features and a surly demeanor. In this example, the virtual object resembles its corresponding real object in certain characteristics (color, number of arms); but differs from the real object in other characteristics (facial features, personality). In this way, virtual objects have the potential to represent real objects in a creative, abstract, exaggerated, or fanciful manner; or to impart behaviors (e.g., human personalities) to otherwise inanimate real objects. In some examples, virtual objects may be purely fanciful creations with no real-world counterpart (e.g., a virtual monster in a virtual environment, perhaps at a location corresponding to an empty space in a real environment).
 Compared to VR systems, which present the user with a virtual environment while obscuring the real environment, a mixed reality system presenting an MR environment affords the advantage that the real environment remains perceptible while the virtual environment is presented. Accordingly, the user of the mixed reality system is able to use visual and audio cues associated with the real environment to experience and interact with the corresponding virtual environment. As an example, while a user of VR systems may struggle to perceive or interact with a virtual object displayed in a virtual environment–because, as noted above, a user cannot direct1y perceive or interact with a virtual environment–a user of an MR system may find it intuitive and natural to interact with a virtual object by seeing, hearing, and touching a corresponding real object in his or her own real environment. This level of interactivity can heighten a user’s feelings of immersion, connection, and engagement with a virtual environment. Similarly, by simultaneously presenting a real environment and a virtual environment, mixed reality systems can reduce negative psychological feelings (e.g., cognitive dissonance) and negative physical feelings (e.g., motion sickness) associated with VR systems. Mixed reality systems further offer many possibilities for applications that may augment or alter our experiences of the real world.
 FIG. 12A illustrates an example real environment 1200 in which a user 1210 uses a mixed reality system 1212. Mixed reality system 1212 may comprise a display (e.g., a transmissive display) and one or more speakers, and one or more sensors (e.g., a camera), for example as described below. The real environment 1200 shown comprises a rectangular room 1204A, in which user 1210 is standing; and real objects 1222A (a lamp), 1224A (a table), 1226A (a sofa), and 1228A (a painting). Room 1204A further comprises a location coordinate 1206, which may be considered an origin of the real environment 1200. As shown in FIG. 12A, an environment/world coordinate system 1208 (comprising an x-axis 1208X, a y-axis 1208Y, and a z-axis 1208Z) with its origin at point 1206 (a world coordinate), can define a coordinate space for real environment 1200. In some embodiments, the origin point 1206 of the environment/world coordinate system 1208 may correspond to where the mixed reality system 1212 was powered on. In some embodiments, the origin point 1206 of the environment/world coordinate system 1208 may be reset during operation. In some examples, user 1210 may be considered a real object in real environment 1200; similarly, user 1210’s body parts (e.g., hands, feet) may be considered real objects in real environment 1200. In some examples, a user/listener/head coordinate system 1214 (comprising an x-axis 1214X, a y-axis 1214Y, and a z-axis 1214Z) with its origin at point 1215 (e.g., user/listener/head coordinate) can define a coordinate space for the user/listener/head on which the mixed reality system 1212 is located. The origin point 1215 of the user/listener/head coordinate system 1214 may be defined relative to one or more components of the mixed reality system 1212. For example, the origin point 1215 of the user/listener/head coordinate system 1214 may be defined relative to the display of the mixed reality system 1212 such as during initial calibration of the mixed reality system 1212. A matrix (which may include a translation matrix and a Quaternion matrix or other rotation matrix), or other suitable representation can characterize a transformation between the user/listener/head coordinate system 1214 space and the environment/world coordinate system 1208 space. In some embodiments, a left ear coordinate 1216 and a right ear coordinate 1217 may be defined relative to the origin point 1215 of the user/listener/head coordinate system 1214. A matrix (which may include a translation matrix and a Quaternion matrix or other rotation matrix), or other suitable representation can characterize a transformation between the left ear coordinate 1216 and the right ear coordinate 1217, and user/listener/head coordinate system 1214 space. The user/listener/head coordinate system 1214 can simplify the representation of locations relative to the user’s head, or to a head-mounted device, for example, relative to the environment/world coordinate system 1208. Using Simultaneous Localization and Mapping (SLAM), visual odometry, or other techniques, a transformation between user coordinate system 1214 and environment coordinate system 1208 can be determined and updated in real-time.
 FIG. 12B illustrates an example virtual environment 1230 that corresponds to real environment 1200. The virtual environment 1230 shown comprises a virtual rectangular room 1204B corresponding to real rectangular room 1204A; a virtual object 1222B corresponding to real object 1222A; a virtual object 1224B corresponding to real object 1224A; and a virtual object 1226B corresponding to real object 1226A. Metadata associated with the virtual objects 1222B, 1224B, 1226B can include information derived from the corresponding real objects 1222A, 1224A, 1226A. Virtual environment 1230 additionally comprises a virtual monster 1232, which does not correspond to any real object in real environment 1200. Real object 1228A in real environment 1200 does not correspond to any virtual object in virtual environment 1230. A persistent coordinate system 1233 (comprising an x-axis 1233X, a y-axis 1233Y, and a z-axis 1233Z) with its origin at point 1234 (persistent coordinate), can define a coordinate space for virtual content. The origin point 1234 of the persistent coordinate system 1233 may be defined relative/with respect to one or more real objects, such as the real object 1226A. A matrix (which may include a translation matrix and a Quaternion matrix or other rotation matrix), or other suitable representation can characterize a transformation between the persistent coordinate system 1233 space and the environment/world coordinate system 1208 space. In some embodiments, each of the virtual objects 1222B, 1224B, 1226B, and 1232 may have their own persistent coordinate point relative to the origin point 1234 of the persistent coordinate system 1233. In some embodiments, there may be multiple persistent coordinate systems and each of the virtual objects 1222B, 1224B, 1226B, and 1232 may have their own persistent coordinate point relative to one or more persistent coordinate systems.
 With respect to FIGS. 12A and 12B, environment/world coordinate system 1208 defines a shared coordinate space for both real environment 1200 and virtual environment 1230. In the example shown, the coordinate space has its origin at point 1206. Further, the coordinate space is defined by the same three orthogonal axes (1208X, 1208Y, 1208Z). Accordingly, a first location in real environment 1200, and a second, corresponding location in virtual environment 1230, can be described with respect to the same coordinate space. This simplifies identifying and displaying corresponding locations in real and virtual environments, because the same coordinates can be used to identify both locations. However, in some examples, corresponding real and virtual environments need not use a shared coordinate space. For instance, in some examples (not shown), a matrix (which may include a translation matrix and a Quaternion matrix or other rotation matrix), or other suitable representation can characterize a transformation between a real environment coordinate space and a virtual environment coordinate space.
 FIG. 12C illustrates an example MR environment 1250 that simultaneously presents aspects of real environment 1200 and virtual environment 1230 to user 1210 via mixed reality system 1212. In the example shown, MR environment 1250 simultaneously presents user 1210 with real objects 1222A, 1224A, 1226A, and 1228A from real environment 1200 (e.g., via a transmissive portion of a display of mixed reality system 1212); and virtual objects 1222B, 1224B, 1226B, and 1232 from virtual environment 1230 (e.g., via an active display portion of the display of mixed reality system 1212). As above, origin point 1206 acts as an origin for a coordinate space corresponding to MR environment 1250, and coordinate system 1208 defines an x-axis, y-axis, and z-axis for the coordinate space.
 In the example shown, mixed reality objects comprise corresponding pairs of real objects and virtual objects (i.e., 1222A/1222B, 1224A/1224B, 1226A/1226B) that occupy corresponding locations in coordinate space 1208. In some examples, both the real objects and the virtual objects may be simultaneously visible to user 1210. This may be desirable in, for example, instances where the virtual object presents information designed to augment a view of the corresponding real object (such as in a museum application where a virtual object presents the missing pieces of an ancient damaged sculpture). In some examples, the virtual objects (1222B, 1224B, and/or 1226B) may be displayed (e.g., via active pixelated occlusion using a pixelated occlusion shutter) so as to occlude the corresponding real objects (1222A, 1224A, and/or 1226A). This may be desirable in, for example, instances where the virtual object acts as a visual replacement for the corresponding real object (such as in an interactive storytelling application where an inanimate real object becomes a “living” character).
 In some examples, real objects (e.g., 1222A, 1224A, 1226A) may be associated with virtual content or helper data that may not necessarily constitute virtual objects. Virtual content or helper data can facilitate processing or handling of virtual objects in the mixed reality environment. For example, such virtual content could include two-dimensional representations of corresponding real objects; custom asset types associated with corresponding real objects; or statistical data associated with corresponding real objects. This information can enable or facilitate calculations involving a real object without incurring unnecessary computational overhead.
 In some examples, the presentation described above may also incorporate audio aspects. For instance, in MR environment 1250, virtual monster 1232 could be associated with one or more audio signals, such as a footstep sound effect that is generated as the monster walks around MR environment 1250. As described further below, a processor of mixed reality system 1212 can compute an audio signal corresponding to a mixed and processed composite of all such sounds in MR environment 1250, and present the audio signal to user 1210 via one or more speakers included in mixed reality system 1212 and/or one or more external speakers.
* Example Mixed Reality System*
 Referring to FIGS. 2A-2D, some general componentry options are illustrated. In the portions of the detailed description which follow the discussion of FIGS. 2A-2D, various systems, subsystems, and components are presented for addressing the objectives of providing a high-quality, comfortably-perceived display system for human VR and/or AR.
 As shown in FIG. 2A, an AR system user (60) is depicted wearing an exemplary head mounted component (58) featuring a frame (64) structure coupled to a display system (62) positioned in front of the eyes of the user. A speaker (66) can be coupled to the frame (64) in the depicted configuration and positioned adjacent the ear canal of the user. (In one embodiment, another speaker, not shown, can be positioned adjacent the other ear canal of the user to provide for stereo/shapeable sound control). The display (62) can be operatively coupled (68), such as by a wired lead or wireless connectivity, to a local processing and data module (70) which may be mounted in a variety of configurations, such as fixedly attached to the frame (64), fixedly attached to a helmet or hat (80) as shown in the embodiment of FIG. 2B, embedded in headphones, removably attached to the torso of the user (60) in a backpack-style configuration, or removably attached to the hip (84) of the user (60) in a belt-coupling style configuration as shown in the embodiment of FIG. 2C.
 The local processing and data module (70) may comprise a power-efficient processor or controller, as well as digital memory, such as flash memory, both of which may be utilized to assist in the processing, caching, and storage of data captured from sensors which may be operatively coupled to the frame (64), such as image capture devices (such as cameras), microphones, inertial measurement units, accelerometers, compasses, GPS units, radio devices, and/or gyros; and/or data acquired and/or processed using the remote processing module (72) and/or remote data repository (74), possibly for passage to the display (62) after such processing or retrieval.
 The local processing and data module (70) may be operatively coupled (76, 78), such as via a wired or wireless communication links, to the remote processing module (72) and remote data repository (74) such that these remote modules (72, 74) are operatively coupled to each other and available as resources to the local processing and data module (70).
 In one embodiment, the remote processing module (72) may comprise one or more relatively powerful processors or controllers configured to analyze and process data and/or image information. In one embodiment, the remote data repository (74) may comprise a relatively large-scale digital data storage facility, which may be available through the internet or other networking configuration in a “cloud” resource configuration. In one embodiment, all data can be stored and all computation can be performed in the local processing and data module, allowing fully autonomous use from any remote modules.
* Example Mixed Reality System*
 Example mixed reality system 1212–which can correspond to the example AR system depicted in FIGS. 2A-2D–can include a wearable head device (e.g., a wearable augmented reality or mixed reality head device) comprising a display (which may comprise left and right transmissive displays, which may be near-eye displays, and associated components for coupling light from the displays to the user’s eyes); left and right speakers (e.g., positioned adjacent to the user’s left and right ears, respectively); an inertial measurement unit (IMU) (e.g., mounted to a temple arm of the head device); an orthogonal coil electromagnetic receiver (e.g., mounted to the left temple piece); left and right cameras (e.g., depth (time-of-flight) cameras) oriented away from the user; and left and right eye cameras oriented toward the user (e.g., for detecting the user’s eye movements). However, a mixed reality system 1212 can incorporate any suitable display technology, and any suitable sensors (e.g., optical, infrared, acoustic, LIDAR, EOG, GPS, magnetic). In addition, mixed reality system 1212 may incorporate networking features (e.g., Wi-Fi capability) to communicate with other devices and systems, including other mixed reality systems. Mixed reality system 1212 may further include a battery (which may be mounted in an auxiliary unit, such as a belt pack designed to be worn around a user’s waist), a processor, and a memory. The wearable head device of mixed reality system 1212 may include tracking components, such as an IMU or other suitable sensors, configured to output a set of coordinates of the wearable head device relative to the user’s environment. In some examples, tracking components may provide input to a processor performing a Simultaneous Localization and Mapping (SLAM) and/or visual odometry algorithm. In some examples, mixed reality system 1212 may also include a handheld controller 1400, and/or an auxiliary unit 1420, which may be a wearable beltpack, as described further below.
 FIGS. 13A-13D illustrate components of an example mixed reality system 1300 (which may correspond to mixed reality system 1212) that may be used to present an MRE (which may correspond to MRE 1250), or other virtual environment, to a user. FIG. 13A illustrates a perspective view of a wearable head device 2102 included in example mixed reality system 1300. FIG. 13B illustrates a top view of wearable head device 2102 worn on a user’s head 2202. FIG. 13C illustrates a front view of wearable head device 2102. FIG. 13D illustrates an edge view of example eyepiece 2110 of wearable head device 2102. As shown in FIGS. 13A-13C, the example wearable head device 2102 includes an example left eyepiece (e.g., a left transparent waveguide set eyepiece) 2108 and an example right eyepiece (e.g., a right transparent waveguide set eyepiece) 2110. Each eyepiece 2108 and 2110 can include transmissive elements through which a real environment can be visible, as well as display elements for presenting a display (e.g., via imagewise modulated light) overlapping the real environment. In some examples, such display elements can include surface diffractive optical elements for controlling the flow of imagewise modulated light. For instance, the left eyepiece 2108 can include a left incoupling grating set 2112, a left orthogonal pupil expansion (OPE) grating set 2120, and a left exit (output) pupil expansion (EPE) grating set 2122. Similarly, the right eyepiece 2110 can include a right incoupling grating set 2118, a right OPE grating set 2114 and a right EPE grating set 2116. Imagewise modulated light can be transferred to a user’s eye via the incoupling gratings 2112 and 2118, OPEs 2114 and 2120, and EPE 2116 and 2122. Each incoupling grating set 2112, 2118 can be configured to deflect light toward its corresponding OPE grating set 2120, 2114. Each OPE grating set 2120, 2114 can be designed to incrementally deflect light down toward its associated EPE 2122, 2116, thereby horizontally extending an exit pupil being formed. Each EPE 2122, 2116 can be configured to incrementally redirect at least a portion of light received from its corresponding OPE grating set 2120, 2114 outward to a user eyebox position (not shown) defined behind the eyepieces 2108, 2110, vertically extending the exit pupil that is formed at the eyebox. Alternatively, in lieu of the incoupling grating sets 2112 and 2118, OPE grating sets 2114 and 2120, and EPE grating sets 2116 and 2122, the eyepieces 2108 and 2110 can include other arrangements of gratings and/or refractive and reflective features for controlling the coupling of imagewise modulated light to the user’s eyes.
 In some examples, wearable head device 2102 can include a left temple arm 2130 and a right temple arm 2132, where the left temple arm 2130 includes a left speaker 2134 and the right temple arm 2132 includes a right speaker 2136. An orthogonal coil electromagnetic receiver 2138 can be located in the left temple piece, or in another suitable location in the wearable head unit 2102. An Inertial Measurement Unit (IMU) 2140 can be located in the right temple arm 2132, or in another suitable location in the wearable head device 2102. The wearable head device 2102 can also include a left depth (e.g., time-of-flight) camera 2142 and a right depth camera 2144. The depth cameras 2142, 2144 can be suitably oriented in different directions so as to together cover a wider field of view.
 In the example shown in FIGS. 13A-13D, a left source of imagewise modulated light 2124 can be optically coupled into the left eyepiece 2108 through the left incoupling grating set 2112, and a right source of imagewise modulated light 2126 can be optically coupled into the right eyepiece 2110 through the right incoupling grating set 2118. Sources of imagewise modulated light 2124, 2126 can include, for example, optical fiber scanners; projectors including electronic light modulators such as Digital Light Processing (DLP) chips or Liquid Crystal on Silicon (LCoS) modulators; or emissive displays, such as micro Light Emitting Diode (.mu.LED) or micro Organic Light Emitting Diode (.mu.OLED) panels coupled into the incoupling grating sets 2112, 2118 using one or more lenses per side. The input coupling grating sets 2112, 2118 can deflect light from the sources of imagewise modulated light 2124, 2126 to angles above the critical angle for Total Internal Reflection (TIR) for the eyepieces 2108, 2110. The OPE grating sets 2114, 2120 incrementally deflect light propagating by TIR down toward the EPE grating sets 2116, 2122. The EPE grating sets 2116, 2122 incrementally couple light toward the user’s face, including the pupils of the user’s eyes.
 In some examples, as shown in FIG. 13D, each of the left eyepiece 2108 and the right eyepiece 2110 includes a plurality of waveguides 2402. For example, each eyepiece 2108, 2110 can include multiple individual waveguides, each dedicated to a respective color channel (e.g., red, blue and green). In some examples, each eyepiece 2108, 2110 can include multiple sets of such waveguides, with each set configured to impart different wavefront curvature to emitted light. The wavefront curvature may be convex with respect to the user’s eyes, for example to present a virtual object positioned a distance in front of the user (e.g., by a distance corresponding to the reciprocal of wavefront curvature). In some examples, EPE grating sets 2116, 2122 can include curved grating grooves to effect convex wavefront curvature by altering the Poynting vector of exiting light across each EPE.
 In some examples, to create a perception that displayed content is three-dimensional, stereoscopically-adjusted left and right eye imagery can be presented to the user through the imagewise light modulators 2124, 2126 and the eyepieces 2108, 2110. The perceived realism of a presentation of a three-dimensional virtual object can be enhanced by selecting waveguides (and thus corresponding the wavefront curvatures) such that the virtual object is displayed at a distance approximating a distance indicated by the stereoscopic left and right images. This technique may also reduce motion sickness experienced by some users, which may be caused by differences between the depth perception cues provided by stereoscopic left and right eye imagery, and the autonomic accommodation (e.g., object distance-dependent focus) of the human eye.
 FIG. 13D illustrates an edge-facing view from the top of the right eyepiece 2110 of example wearable head device 2102. As shown in FIG. 13D, the plurality of waveguides 2402 can include a first subset of three waveguides 2404 and a second subset of three waveguides 2406. The two subsets of waveguides 2404, 2406 can be differentiated by different EPE gratings featuring different grating line curvatures to impart different wavefront curvatures to exiting light. Within each of the subsets of waveguides 2404, 2406 each waveguide can be used to couple a different spectral channel (e.g., one of red, green and blue spectral channels) to the user’s right eye 2206. (Although not shown in FIG. 13D, the structure of the left eyepiece 2108 is analogous to the structure of the right eyepiece 2110.)
 FIG. 14A illustrates an example handheld controller component 1400 of a mixed reality system 1300. In some examples, handheld controller 1400 includes a grip portion 1446 and one or more buttons 1450 disposed along a top surface 1448. In some examples, buttons 1450 may be configured for use as an optical tracking target, e.g., for tracking six-degree-of-freedom (6DOF) motion of the handheld controller 1400, in conjunction with a camera or other optical sensor (which may be mounted in a head unit (e.g., wearable head device 2102) of mixed reality system 1300). In some examples, handheld controller 1400 includes tracking components (e.g., an IMU or other suitable sensors) for detecting position or orientation, such as position or orientation relative to wearable head device 2102. In some examples, such tracking components may be positioned in a handle of handheld controller 1400, and/or may be mechanically coupled to the handheld controller. Handheld controller 1400 can be configured to provide one or more output signals corresponding to one or more of a pressed state of the buttons; or a position, orientation, and/or motion of the handheld controller 1400 (e.g., via an IMU). Such output signals may be used as input to a processor of mixed reality system 1300. Such input may correspond to a position, orientation, and/or movement of the handheld controller (and, by extension, to a position, orientation, and/or movement of a hand of a user holding the controller). Such input may also correspond to a user pressing buttons 1450.
 FIG. 14B illustrates an example auxiliary unit 1420 of a mixed reality system 1300. The auxiliary unit 1420 can include a battery to provide energy to operate the system 1300, and can include a processor for executing programs to operate the system 1300. As shown, the example auxiliary unit 1420 includes a clip 2128, such as for attaching the auxiliary unit 1420 to a user’s belt. Other form factors are suitable for auxiliary unit 1420 and will be apparent, including form factors that do not involve mounting the unit to a user’s belt. In some examples, auxiliary unit 1420 is coupled to the wearable head device 2102 through a multiconduit cable that can include, for example, electrical wires and fiber optics. Wireless connections between the auxiliary unit 1420 and the wearable head device 2102 can also be used.
 In some examples, mixed reality system 1300 can include one or more microphones to detect sound and provide corresponding signals to the mixed reality system. In some examples, a microphone may be attached to, or integrated with, wearable head device 2102, and may be configured to detect a user’s voice. In some examples, a microphone may be attached to, or integrated with, handheld controller 1400 and/or auxiliary unit 1420. Such a microphone may be configured to detect environmental sounds, ambient noise, voices of a user or a third party, or other sounds.
* Example Mixed Reality Network Architecture*
 Referring now to FIG. 3, a schematic illustrates coordination between the cloud computing assets (46) and local processing assets, which may, for example reside in head mounted componentry (58) coupled to the user’s head (120) and a local processing and data module (70), coupled to the user’s belt (308). Component 70 may also be termed a “belt pack” 70. In one embodiment, the cloud (46) assets, such as one or more server systems (110) can be operatively coupled (115), such as via wired or wireless networking (wireless being preferred for mobility, wired being preferred for certain high-bandwidth or high-data-volume transfers that may be desired), direct1y to (40, 42) one or both of the local computing assets, such as processor and memory configurations, coupled to the user’s head (120) and belt (308) as described above. These computing assets local to the user may be operatively coupled to each other as well, via wired and/or wireless connectivity configurations (44), such as the wired coupling (68) discussed below in reference to FIG. 8. In one embodiment, to maintain a low-inertia and small-size subsystem mounted to the user’s head (120), primary transfer between the user and the cloud (46) may be via the link between the subsystem mounted at the belt (308) and the cloud. The head mounted (120) subsystem can be primarily data-tethered to the belt-based (308) subsystem using wireless connectivity, such as ultra-wideband (“UWB”) connectivity, which can be employed in personal computing peripheral connectivity applications.
 With efficient local and remote processing coordination, and an appropriate display device for a user, such as the user interface or user display system (62) shown in FIG. 2A, or variations thereof, aspects of one world pertinent to a user’s current actual or virtual location may be transferred or “passed” to the user and updated in an efficient fashion. In other words, a map of the world may be continually updated at a storage location which may partially reside on the user’s AR system and partially reside in the cloud resources. The map (also referred to as a “passable world model”) may be a large database comprising raster imagery, 3D and 2D points, parametric information and other information about the real world. As more and more AR users continually capture information about their real environment (e.g., through cameras, sensors, IMUs, etc.), the map can become more and more accurate and complete.
 With a configuration as described above, wherein there is one world model that can reside on cloud computing resources and be distributed from there, such world can be “passable” to one or more users in a relatively low bandwidth form, which can be preferable to passing around real-time video data or the like. The augmented experience of the person standing near the statue (i.e., as shown in FIG. 1) may be informed by the cloud-based world model, a subset of which may be passed down to them and their local display device to complete the view. A person sitting at a remote display device, which may be as simple as a personal computer sitting on a desk, can efficient1y download that same section of information from the cloud and have it rendered on their display. Indeed, one person actually present in the park near the statue may take a remotely-located friend for a walk in that park, with the friend joining through virtual and augmented reality. The system may need to know where the street is, where the trees are, where the statue is. In some embodiments, such information can be stored on the cloud, and the joining friend can download from the cloud aspects of the scenario, and then start walking along as an augmented reality local relative to the person who is actually in the park.
 3D points may be captured from the environment, and the pose (i.e., vector and/or origin position information relative to the world) of the cameras that capture those images or points may be determined, so that these points or images may be “tagged”, or associated, with this pose information. Points captured by a second camera may be utilized to determine the pose of the second camera. In other words, one can orient and/or localize a second camera based upon comparisons with tagged images from a first camera. This knowledge may be utilized to extract textures, make maps, and create a virtual copy of the real world (because then there are two cameras around that are registered).
 So at the base level, in one embodiment a person-worn system can be utilized to capture both 3D points and the 2D images that produced the points, and these points and images may be sent out to a cloud storage and processing resource. They may also be cached locally with embedded pose information (i.e., cache the tagged images); so the cloud may have on the ready (i.e., in available cache) tagged 2D images (i.e., tagged with a 3D pose), along with 3D points. If a user is observing something dynamic, additional information may be sent up to the cloud pertinent to the motion (for example, if looking at another person’s face, a texture map of the face can be taken and pushed up at an optimized frequency even though the surrounding world is otherwise basically static). More information on object recognizers and the passable world model may be found in U.S. patent application Ser. No. 14/205,126, entit1ed “System and method for augmented and virtual reality”, which is incorporated by reference in its entirety herein.
* Mixed Reality Coordinate Frames*
 FIG. 4 illustrates an exemplary environment of a user wearing a HMD AR device having a “head” coordinate frame. The HMD can create a “world” coordinate frame, such as by passable world creation and mapping described above, wherein the user’s head position and orientation can be measured relative to the world coordinate frame. The environment can also comprise virtual content having its own “local” coordinate frame. Placement of the virtual content may be processed by the HMD by applying a transform from the local to world coordinate frames.
 By giving the virtual content its own coordinate frame, as opposed to being measured direct1y to the world coordinate frame as the user’s head can be, the virtual content may choose a more persistent frame position. For example, if a virtual lamp is placed on a table, there could be a plurality of data points on the table to provide placement input for relative positioning of the virtual lamp that do not substantially change over time. By contrast, if a world map is created as a function of a certain orientation and position, and the user changes position or orientation thus necessitating a new world coordinate frame, the virtual lamp may continue to utilize the same local coordinate frame rather than adjust to a new world framework which may introduce jitter or positional shifts in the appearance of the lamp.
 In some embodiments, a coordinate frame can be established by using sensors of a mixed reality system (e.g., mixed reality system 1212 or 1300). For example, a world coordinate frame can be created using depth sensors, time-of-flight cameras, LIDAR sensors, and/or RGB cameras to identify placement of physical objects in relation to each other. A mixed reality system used in a room can identify physical features of a room and identify placement of those features. For example, a mixed reality system can determine the placement of a desk relative to a chair relative to a cabinet relative to the floor relative to the walls. As a user walks around the room, a world coordinate frame can be refined as physical objects are viewed from different angles and/or different distances to more accurately determine relative positions. A mixed reality system can also establish a local coordinate frame using more localized features as compared to a world coordinate frame. For example, a local coordinate frame can be established for a desk by identifying features of the desk and identifying relative placement of those features. Corners of a desk can be identified and placed in relation to each other such that a virtual object can be displayed as sitting on the desk as if it were a real object. The virtual object can be placed using a local coordinate frame (e.g., the virtual object’s position is determined relative to the corners of the desk). A local coordinate frame (e.g., of the desk) can then be transformed to the world coordinate frame that can place the desk relative to other physical objects in the room.
 FIG. 5 depicts a further coordinate frame transform between the head coordinate frame and render cameras for either display unit (i.e. a left/right in a binocular system or a single system in a monocular field of view). As display mediums may vary in position to a user’s eyes, where virtual content is rendered relative to that position may require further coordinate frame analysis. Position for a render camera to a head coordinate frame may be provided by calibration level intrinsics. If content were projected to a display irrespective of a render camera, then changes in eye position may warp the intended position of the content. Further discussion of a render camera transform is provided below.
 FIG. 6 displays a multi-user system wherein User 1 and User 2 are observing the same virtual content. As depicted, world coordinate frames may have been created relative to each user’s own device, and the virtual content can have a local coordinate frame that then transforms to either world coordinate frame (e.g., world 1 and world 2).
 In some embodiments, and as shown in FIG. 7, the Users 1 and 2 can share a world coordinate frame. This can prevent minor variations in world coordinate frame quality and system noise from giving disparate views of the common content.
 For example, in FIG. 8A, User 1 and User 2 are inside a room, but User 2 is closer to a wall on the left side, and as a result as User 2 looks towards content near that wall has fewer data points to collect and create a reliable long term world coordinate frame. By contrast, as User 1 looks at the virtual content, there are more objects in the line of sight from which to create a reliable world coordinate frame. User 2 can utilize the world coordinate frame as created by User 1. Map quality analysis and world coordinate frame suitability is enabled further in conjunction with U.S. Patent Application No. 62/702829, “Methods and Apparatuses for Determining and/or Evaluating Localization Maps of Head-Worn Image Display Devices,” the contents of which is hereby incorporated by reference in its entirety.
 If User 2 moves closer the wall, as in FIG. 8B, it is possible that the world coordinate frame of User 1 is no longer visible by User 2. User 2 may not be able to measure headpose and therefore virtual content could begin to float or shift with User 2 movement. Instead, as depicted in FIG. 8C, a new world 2 coordinate frame may be created, despite lower reliability in the world.
 In some embodiments, a mixed reality system (e.g., mixed reality system 1212 or 1300) can receive a world coordinate frame from a server. For example, a room may have been mapped by a previous mixed reality system, and an established world coordinate frame can be uploaded to a server. When a new user enters the same room, a mixed reality system can recognize that the room has been previously mapped and receive an appropriate world coordinate frame from the server. A mixed reality system can identify a room using location tracking (e.g., GPS coordinates or Wi-Fi triangulation) and/or using computer vision (e.g., recognizing features in the room and matching those features with features of previously mapped rooms). In some embodiments, a world coordinate frame received from a server can be more reliable than a world coordinate frame established by User 1 or User 2. For example, each mixed reality system that maps the room can upload additional information to a server, thereby increasing the reliability of a cumulative world coordinate frame stored in a server. Upon recognizing that a room has a previously-established world coordinate frame, a mixed reality system or a server can determine which one of several world coordinate frames is more reliable, and a mixed reality system can utilize the most reliable world coordinate frame.
 FIG. 9A depicts a first render camera protocol for transforming to a display unit from a head coordinate. As depicted, a user’s pupil for a single eye moves from position A to B. For an optical eyepiece displaying a virtual object, given an optical power, a virtual object that is meant to appear stationary can project in 3D at one of two positions based on the pupil position (assuming the render camera is configured to use a pupil as the coordinate frame). In other words, using a pupil coordinate transformed to a head coordinate can cause jitter in a stationary virtual content as the user’s eyes move. This is referred to as a view dependent display or projection system.
 In some embodiments, as depicted in FIG. 9B, a Camera Render frame is positioned that encompasses all pupil positions, for example at the center of rotation of the eyeball. An object projection CR area can be consistent regardless of the pupil position A and B. The head coordinate can transform to the Camera Render frame, which is referred to as a view independent display or projection system. In some embodiments, an image warp is applied to the virtual content to account for a change in eye position, but as this still renders at the same position, jitter can be minimized.