Patent Publication Number: US-10319346-B2

Title: Method for communicating via virtual space and system for executing the method

Description:
RELATED APPLICATIONS 
     The present application claims priority to Japanese Patent Application No. 2016-250989 filed Dec. 26, 2016, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     TECHNICAL FIELD 
     This disclosure relates to communication, and more particularly, to communication via a virtual space. 
     BACKGROUND 
     There is known a technology for communicating by using a virtual space. For example, in Japanese Patent Application Laid-open No. 2016-152619 (Patent Document 1), there is described a “system enabling a user to experience special communication to/from a specific user” (see “Abstract”). 
     PATENT DOCUMENTS 
     
         
         [Patent Document 1] JP 2016-152619 A 
       
    
     SUMMARY 
     According to at least one embodiment of this disclosure, there is provided a method including defining a virtual space to be associated with a first user. The virtual space includes a second avatar associated with a second user. The virtual space is associated with a first head-mounted device (HMD) to be connected to a first computer. The second user is associated with a second HMD associated with a second computer communicably connected to the first computer. The method further includes receiving a signal transmitted from the second computer. The method further includes detecting a communication quality between the first computer and the second computer based on the signal. The method further includes determining a display mode of the second avatar in the virtual space in accordance with the communication quality. The method further includes displaying the second avatar in the virtual space based on the display mode. 
     The above-mentioned and other objects, features, aspects, and advantages of the disclosure may be made clear from the following detailed description of this disclosure, which is to be understood in association with the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  A diagram of a system including a head-mounted device (HMD) according to at least one embodiment of this disclosure. 
         FIG. 2  A block diagram of a hardware configuration of a computer according to at least one embodiment of this disclosure. 
         FIG. 3  A diagram of a uvw visual-field coordinate system to be set for an HMD according to at least one embodiment of this disclosure. 
         FIG. 4  A diagram of a mode of expressing a virtual space according to at least one embodiment of this disclosure. 
         FIG. 5  A diagram of a plan view of a head of a user wearing the HMD according to at least one embodiment of this disclosure. 
         FIG. 6  A diagram of a YZ cross section obtained by viewing a field-of-view region from an X direction in the virtual space according to at least one embodiment of this disclosure. 
         FIG. 7  A diagram of an XZ cross section obtained by viewing the field-of-view region from a Y direction in the virtual space according to at least one embodiment of this disclosure. 
         FIG. 8A  A diagram of a schematic configuration of a controller according to at least one embodiment of this disclosure. 
         FIG. 8B  A diagram of an example of a yaw direction, a roll direction, and a pitch direction that are defined with respect to a right hand of the user according to at least one embodiment of this disclosure. 
         FIG. 9  A block diagram of a hardware configuration of a server according to at least one embodiment of this disclosure. 
         FIG. 10  A block diagram of a computer according to at least one embodiment of this disclosure. 
         FIG. 11  A sequence chart of processing to be executed by a system including an HMD set according to at least one embodiment of this disclosure. 
         FIG. 12A  A schematic diagram of HMD systems of several users sharing the virtual space interact using a network according to at least one embodiment of this disclosure. 
         FIG. 12B  A diagram of a field-of-view image of a user  5 A in  FIG. 12A  according to at least one embodiment of this disclosure. 
         FIG. 13  A sequence diagram of processing to be executed by a system including an HMD interacting in a network according to at least one embodiment of this disclosure. 
         FIG. 14  A block diagram of a detailed configuration of modules of the computer according to at least one embodiment of this disclosure. 
         FIG. 15  A flowchart of processing to be executed according to at least one embodiment of this disclosure. 
         FIG. 16  A flowchart of processing to be executed according to at least one embodiment of this disclosure. 
         FIG. 17  A flowchart of processing to be executed according to at least one embodiment of this disclosure. 
         FIG. 18  A diagram of an example of an image that is visually recognizable by the user as the field-of-view image according to at least one embodiment of this disclosure. 
         FIG. 19  A diagram of an example of another display mode of avatar objects to be included in the field-of-view image when a user having a poor communication state is included as a chat partner according to at least one embodiment of this disclosure. 
         FIG. 20  A diagram of the field-of-view image to be presented by the HMD worn by the user of a computer having a poor communication speed according to at least one embodiment of this disclosure. 
         FIG. 21  A diagram of an example of an image that is visually recognizable by the user as the field-of-view image according to at least one embodiment of this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Now, with reference to the drawings, embodiments of this technical idea are described in detail. In the following description, like components are denoted by like reference symbols. The same applies to the names and functions of those components. Therefore, detailed description of those components is not repeated. In one or more embodiments described in this disclosure, components of respective embodiments can be combined with each other, and the combination also serves as a part of the embodiments described in this disclosure. 
     [Configuration of HMD System] 
     With reference to  FIG. 1 , a configuration of a head-mounted device (HMD) system  100  is described.  FIG. 1  is a diagram of a system  100  including a head-mounted display (HMD) according to at least one embodiment of this disclosure. The system  100  is usable for household use or for professional use. 
     The system  100  includes a server  600 , HMD sets  110 A,  110 B,  110 C, and  110 D, an external device  700 , and a network  2 . Each of the HMD sets  110 A,  110 B,  110 C, and  110 D is capable of independently communicating to/from the server  600  or the external device  700  via the network  2 . In some instances, the HMD sets  110 A,  110 B,  110 C, and  110 D are also collectively referred to as “HMD set  110 ”. The number of HMD sets  110  constructing the HMD system  100  is not limited to four, but may be three or less, or five or more. The HMD set  110  includes an HMD  120 , a computer  200 , an HMD sensor  410 , a display  430 , and a controller  300 . The HMD  120  includes a monitor  130 , an eye gaze sensor  140 , a first camera  150 , a second camera  160 , a microphone  170 , and a speaker  180 . In at least one embodiment, the controller  300  includes a motion sensor  420 . 
     In at least one aspect, the computer  200  is connected to the network  2 , for example, the Internet, and is able to communicate to/from the server  600  or other computers connected to the network  2  in a wired or wireless manner. Examples of the other computers include a computer of another HMD set  110  or the external device  700 . In at least one aspect, the HMD  120  includes a sensor  190  instead of the HMD sensor  410 . In at least one aspect, the HMD  120  includes both sensor  190  and the HMD sensor  410 . 
     The HMD  120  is wearable on a head of a user  5  to display a virtual space to the user  5  during operation. More specifically, in at least one embodiment, the HMD  120  displays each of a right-eye image and a left-eye image on the monitor  130 . Each eye of the user  5  is able to visually recognize a corresponding image from the right-eye image and the left-eye image so that the user  5  may recognize a three-dimensional image based on the parallax of both of the user&#39;s the eyes. In at least one embodiment, the HMD  120  includes any one of a so-called head-mounted display including a monitor or a head-mounted device capable of mounting a smartphone or other terminals including a monitor. 
     The monitor  130  is implemented as, for example, a non-transmissive display device. In at least one aspect, the monitor  130  is arranged on a main body of the HMD  120  so as to be positioned in front of both the eyes of the user  5 . Therefore, when the user  5  is able to visually recognize the three-dimensional image displayed by the monitor  130 , the user  5  is immersed in the virtual space. In at least one aspect, the virtual space includes, for example, a background, objects that are operable by the user  5 , or menu images that are selectable by the user  5 . In at least one aspect, the monitor  130  is implemented as a liquid crystal monitor or an organic electroluminescence (EL) monitor included in a so-called smartphone or other information display terminals. 
     In at least one aspect, the monitor  130  is implemented as a transmissive display device. In this case, the user  5  is able to see through the HMD  120  covering the eyes of the user  5 , for example, smartglasses. In at least one embodiment, the transmissive monitor  130  is configured as a temporarily non-transmissive display device through adjustment of a transmittance thereof. In at least one embodiment, the monitor  130  is configured to display a real space and a part of an image constructing the virtual space simultaneously. For example, in at least one embodiment, the monitor  130  displays an image of the real space captured by a camera mounted on the HMD  120 , or may enable recognition of the real space by setting the transmittance of a part the monitor  130  sufficiently high to permit the user  5  to see through the HMD  120 . 
     In at least one aspect, the monitor  130  includes a sub-monitor for displaying a right-eye image and a sub-monitor for displaying a left-eye image. In at least one aspect, the monitor  130  is configured to integrally display the right-eye image and the left-eye image. In this case, the monitor  130  includes a high-speed shutter. The high-speed shutter operates so as to alternately display the right-eye image to the right of the user  5  and the left-eye image to the left eye of the user  5 , so that only one of the user&#39;s  5  eyes is able to recognize the image at any single point in time. 
     In at least one aspect, the HMD  120  includes a plurality of light sources (not shown). Each light source is implemented by, for example, a light emitting diode (LED) configured to emit an infrared ray. The HMD sensor  410  has a position tracking function for detecting the motion of the HMD  120 . More specifically, the HMD sensor  410  reads a plurality of infrared rays emitted by the HMD  120  to detect the position and the inclination of the HMD  120  in the real space. 
     In at least one aspect, the HMD sensor  410  is implemented by a camera. In at least one aspect, the HMD sensor  410  uses image information of the HMD  120  output from the camera to execute image analysis processing, to thereby enable detection of the position and the inclination of the HMD  120 . 
     In at least one aspect, the HMD  120  includes the sensor  190  instead of, or in addition to, the HMD sensor  410  as a position detector. In at least one aspect, the HMD  120  uses the sensor  190  to detect the position and the inclination of the HMD  120 . For example, in at least one embodiment, when the sensor  190  is an angular velocity sensor, a geomagnetic sensor, or an acceleration sensor, the HMD  120  uses any or all of those sensors instead of (or in addition to) the HMD sensor  410  to detect the position and the inclination of the HMD  120 . As an example, when the sensor  190  is an angular velocity sensor, the angular velocity sensor detects over time the angular velocity about each of three axes of the HMD  120  in the real space. The HMD  120  calculates a temporal change of the angle about each of the three axes of the HMD  120  based on each angular velocity, and further calculates an inclination of the HMD  120  based on the temporal change of the angles. 
     The eye gaze sensor  140  detects a direction in which the lines of sight of the right eye and the left eye of the user  5  are directed. That is, the eye gaze sensor  140  detects the line of sight of the user  5 . The direction of the line of sight is detected by, for example, a known eye tracking function. The eye gaze sensor  140  is implemented by a sensor having the eye tracking function. In at least one aspect, the eye gaze sensor  140  includes a right-eye sensor and a left-eye sensor. In at least one embodiment, the eye gaze sensor  140  is, for example, a sensor configured to irradiate the right eye and the left eye of the user  5  with an infrared ray, and to receive reflection light from the cornea and the iris with respect to the irradiation light, to thereby detect a rotational angle of each of the user&#39;s  5  eyeballs. In at least one embodiment, the eye gaze sensor  140  detects the line of sight of the user  5  based on each detected rotational angle. 
     The first camera  150  photographs a lower part of a face of the user  5 . More specifically, the first camera  150  photographs, for example, the nose or mouth of the user  5 . The second camera  160  photographs, for example, the eyes and eyebrows of the user  5 . A side of a casing of the HMD  120  on the user  5  side is defined as an interior side of the HMD  120 , and a side of the casing of the HMD  120  on a side opposite to the user  5  side is defined as an exterior side of the HMD  120 . In at least one aspect, the first camera  150  is arranged on an exterior side of the HMD  120 , and the second camera  160  is arranged on an interior side of the HMD  120 . Images generated by the first camera  150  and the second camera  160  are input to the computer  200 . In at least one aspect, the first camera  150  and the second camera  160  are implemented as a single camera, and the face of the user  5  is photographed with this single camera. 
     The microphone  170  converts an utterance of the user  5  into a voice signal (electric signal) for output to the computer  200 . The speaker  180  converts the voice signal into a voice for output to the user  5 . In at least one embodiment, the speaker  180  converts other signals into audio information provided to the user  5 . In at least one aspect, the HMD  120  includes earphones in place of the speaker  180 . 
     The controller  300  is connected to the computer  200  through wired or wireless communication. The controller  300  receives input of a command from the user  5  to the computer  200 . In at least one aspect, the controller  300  is held by the user  5 . In at least one aspect, the controller  300  is mountable to the body or a part of the clothes of the user  5 . In at least one aspect, the controller  300  is configured to output at least any one of a vibration, a sound, or light based on the signal transmitted from the computer  200 . In at least one aspect, the controller  300  receives from the user  5  an operation for controlling the position and the motion of an object arranged in the virtual space. 
     In at least one aspect, the controller  300  includes a plurality of light sources. Each light source is implemented by, for example, an LED configured to emit an infrared ray. The HMD sensor  410  has a position tracking function. In this case, the HMD sensor  410  reads a plurality of infrared rays emitted by the controller  300  to detect the position and the inclination of the controller  300  in the real space. In at least one aspect, the HMD sensor  410  is implemented by a camera. In this case, the HMD sensor  410  uses image information of the controller  300  output from the camera to execute image analysis processing, to thereby enable detection of the position and the inclination of the controller  300 . 
     In at least one aspect, the motion sensor  420  is mountable on the hand of the user  5  to detect the motion of the hand of the user  5 . For example, the motion sensor  420  detects a rotational speed, a rotation angle, and the number of rotations of the hand. The detected signal is transmitted to the computer  200 . The motion sensor  420  is provided to, for example, the controller  300 . In at least one aspect, the motion sensor  420  is provided to, for example, the controller  300  capable of being held by the user  5 . In at least one aspect, to help prevent accidently release of the controller  300  in the real space, the controller  300  is mountable on an object like a glove-type object that does not easily fly away by being worn on a hand of the user  5 . In at least one aspect, a sensor that is not mountable on the user  5  detects the motion of the hand of the user  5 . For example, a signal of a camera that photographs the user  5  may be input to the computer  200  as a signal representing the motion of the user  5 . As at least one example, the motion sensor  420  and the computer  200  are connected to each other through wired or wireless communication. In the case of wireless communication, the communication mode is not particularly limited, and for example, Bluetooth (trademark) or other known communication methods are usable. 
     The display  430  displays an image similar to an image displayed on the monitor  130 . With this, a user other than the user  5  wearing the HMD  120  can also view an image similar to that of the user  5 . An image to be displayed on the display  430  is not required to be a three-dimensional image, but may be a right-eye image or a left-eye image. For example, a liquid crystal display or an organic EL monitor may be used as the display  430 . 
     In at least one embodiment, the server  600  transmits a program to the computer  200 . In at least one aspect, the server  600  communicates to/from another computer  200  for providing virtual reality to the HMD  120  used by another user. For example, when a plurality of users play a participatory game, for example, in an amusement facility, each computer  200  communicates to/from another computer  200  via the server  600  with a signal that is based on the motion of each user, to thereby enable the plurality of users to enjoy a common game in the same virtual space. Each computer  200  may communicate to/from another computer  200  with the signal that is based on the motion of each user without intervention of the server  600 . 
     The external device  700  is any suitable device as long as the external device  700  is capable of communicating to/from the computer  200 . The external device  700  is, for example, a device capable of communicating to/from the computer  200  via the network  2 , or is a device capable of directly communicating to/from the computer  200  by near field communication or wired communication. Peripheral devices such as a smart device, a personal computer (PC), or the computer  200  are usable as the external device  700 , in at least one embodiment, but the external device  700  is not limited thereto. 
     [Hardware Configuration of Computer] 
     With reference to  FIG. 2 , the computer  200  in at least one embodiment is described.  FIG. 2  is a block diagram of a hardware configuration of the computer  200  according to at least one embodiment. The computer  200  includes, a processor  210 , a memory  220 , a storage  230 , an input/output interface  240 , and a communication interface  250 . Each component is connected to a bus  260 . In at least one embodiment, at least one of the processor  210 , the memory  220 , the storage  230 , the input/output interface  240  or the communication interface  250  is part of a separate structure and communicates with other components of computer  200  through a communication path other than the bus  260 . 
     The processor  210  executes a series of commands included in a program stored in the memory  220  or the storage  230  based on a signal transmitted to the computer  200  or in response to a condition determined in advance. In at least one aspect, the processor  210  is implemented as a central processing unit (CPU), a graphics processing unit (GPU), a micro-processor unit (MPU), a field-programmable gate array (FPGA), or other devices. 
     The memory  220  temporarily stores programs and data. The programs are loaded from, for example, the storage  230 . The data includes data input to the computer  200  and data generated by the processor  210 . In at least one aspect, the memory  220  is implemented as a random access memory (RAM) or other volatile memories. 
     The storage  230  permanently stores programs and data. In at least one embodiment, the storage  230  stores programs and data for a period of time longer than the memory  220 , but not permanently. The storage  230  is implemented as, for example, a read-only memory (ROM), a hard disk device, a flash memory, or other non-volatile storage devices. The programs stored in the storage  230  include programs for providing a virtual space in the system  100 , simulation programs, game programs, user authentication programs, and programs for implementing communication to/from other computers  200 . The data stored in the storage  230  includes data and objects for defining the virtual space. 
     In at least one aspect, the storage  230  is implemented as a removable storage device like a memory card. In at least one aspect, a configuration that uses programs and data stored in an external storage device is used instead of the storage  230  built into the computer  200 . With such a configuration, for example, in a situation in which a plurality of HMD systems  100  are used, for example in an amusement facility, the programs and the data are collectively updated. 
     The input/output interface  240  allows communication of signals among the HMD  120 , the HMD sensor  410 , the motion sensor  420 , and the display  430 . The monitor  130 , the eye gaze sensor  140 , the first camera  150 , the second camera  160 , the microphone  170 , and the speaker  180  included in the HMD  120  may communicate to/from the computer  200  via the input/output interface  240  of the HMD  120 . In at least one aspect, the input/output interface  240  is implemented with use of a universal serial bus (USB), a digital visual interface (DVI), a high-definition multimedia interface (HDMI) (trademark), or other terminals. The input/output interface  240  is not limited to the specific examples described above. 
     In at least one aspect, the input/output interface  240  further communicates to/from the controller  300 . For example, the input/output interface  240  receives input of a signal output from the controller  300  and the motion sensor  420 . In at least one aspect, the input/output interface  240  transmits a command output from the processor  210  to the controller  300 . The command instructs the controller  300  to, for example, vibrate, output a sound, or emit light. When the controller  300  receives the command, the controller  300  executes anyone of vibration, sound output, and light emission in accordance with the command. 
     The communication interface  250  is connected to the network  2  to communicate to/from other computers (e.g., server  600 ) connected to the network  2 . In at least one aspect, the communication interface  250  is implemented as, for example, a local area network (LAN), other wired communication interfaces, wireless fidelity (Wi-Fi), Bluetooth®, near field communication (NFC), or other wireless communication interfaces. The communication interface  250  is not limited to the specific examples described above. 
     In at least one aspect, the processor  210  accesses the storage  230  and loads one or more programs stored in the storage  230  to the memory  220  to execute a series of commands included in the program. In at least one embodiment, the one or more programs includes an operating system of the computer  200 , an application program for providing a virtual space, and/or game software that is executable in the virtual space. The processor  210  transmits a signal for providing a virtual space to the HMD  120  via the input/output interface  240 . The HMD  120  displays a video on the monitor  130  based on the signal. 
     In  FIG. 2 , the computer  200  is outside of the HMD  120 , but in at least one aspect, the computer  200  is integral with the HMD  120 . As an example, a portable information communication terminal (e.g., smartphone) including the monitor  130  functions as the computer  200  in at least one embodiment. 
     In at least one embodiment, the computer  200  is used in common with a plurality of HMDs  120 . With such a configuration, for example, the computer  200  is able to provide the same virtual space to a plurality of users, and hence each user can enjoy the same application with other users in the same virtual space. 
     According to at least one embodiment of this disclosure, in the system  100 , a real coordinate system is set in advance. The real coordinate system is a coordinate system in the real space. The real coordinate system has three reference directions (axes) that are respectively parallel to a vertical direction, a horizontal direction orthogonal to the vertical direction, and a front-rear direction orthogonal to both of the vertical direction and the horizontal direction in the real space. The horizontal direction, the vertical direction (up-down direction), and the front-rear direction in the real coordinate system are defined as an x axis, a y axis, and a z axis, respectively. More specifically, the x axis of the real coordinate system is parallel to the horizontal direction of the real space, the y axis thereof is parallel to the vertical direction of the real space, and the z axis thereof is parallel to the front-rear direction of the real space. 
     In at least one aspect, the HMD sensor  410  includes an infrared sensor. When the infrared sensor detects the infrared ray emitted from each light source of the HMD  120 , the infrared sensor detects the presence of the HMD  120 . The HMD sensor  410  further detects the position and the inclination (direction) of the HMD  120  in the real space, which corresponds to the motion of the user  5  wearing the HMD  120 , based on the value of each point (each coordinate value in the real coordinate system). In more detail, the HMD sensor  410  is able to detect the temporal change of the position and the inclination of the HMD  120  with use of each value detected over time. 
     Each inclination of the HMD  120  detected by the HMD sensor  410  corresponds to an inclination about each of the three axes of the HMD  120  in the real coordinate system. The HMD sensor  410  sets a uvw visual-field coordinate system to the HMD  120  based on the inclination of the HMD  120  in the real coordinate system. The uvw visual-field coordinate system set to the HMD  120  corresponds to a point-of-view coordinate system used when the user  5  wearing the HMD  120  views an object in the virtual space. 
     [Uvw Visual-Field Coordinate System] 
     With reference to  FIG. 3 , the uvw visual-field coordinate system is described.  FIG. 3  is a diagram of a uvw visual-field coordinate system to be set for the HMD  120  according to at least one embodiment of this disclosure. The HMD sensor  410  detects the position and the inclination of the HMD  120  in the real coordinate system when the HMD  120  is activated. The processor  210  sets the uvw visual-field coordinate system to the HMD  120  based on the detected values. 
     In  FIG. 3 , the HMD  120  sets the three-dimensional uvw visual-field coordinate system defining the head of the user  5  wearing the HMD  120  as a center (origin). More specifically, the HMD  120  sets three directions newly obtained by inclining the horizontal direction, the vertical direction, and the front-rear direction (x axis, y axis, and z axis), which define the real coordinate system, about the respective axes by the inclinations about the respective axes of the HMD  120  in the real coordinate system, as a pitch axis (u axis), a yaw axis (v axis), and a roll axis (w axis) of the uvw visual-field coordinate system in the HMD  120 . 
     In at least one aspect, when the user  5  wearing the HMD  120  is standing (or sitting) upright and is visually recognizing the front side, the processor  210  sets the uvw visual-field coordinate system that is parallel to the real coordinate system to the HMD  120 . In this case, the horizontal direction (x axis), the vertical direction (y axis), and the front-rear direction (z axis) of the real coordinate system directly match the pitch axis (u axis), the yaw axis (v axis), and the roll axis (w axis) of the uvw visual-field coordinate system in the HMD  120 , respectively. 
     After the uvw visual-field coordinate system is set to the HMD  120 , the HMD sensor  410  is able to detect the inclination of the HMD  120  in the set uvw visual-field coordinate system based on the motion of the HMD  120 . In this case, the HMD sensor  410  detects, as the inclination of the HMD  120 , each of a pitch angle (θu), a yaw angle (θv), and a roll angle (θw) of the HMD  120  in the uvw visual-field coordinate system. The pitch angle (θu) represents an inclination angle of the HMD  120  about the pitch axis in the uvw visual-field coordinate system. The yaw angle (θv) represents an inclination angle of the HMD  120  about the yaw axis in the uvw visual-field coordinate system. The roll angle (θw) represents an inclination angle of the HMD  120  about the roll axis in the uvw visual-field coordinate system. 
     The HMD sensor  410  sets, to the HMD  120 , the uvw visual-field coordinate system of the HMD  120  obtained after the movement of the HMD  120  based on the detected inclination angle of the HMD  120 . The relationship between the HMD  120  and the uvw visual-field coordinate system of the HMD  120  is constant regardless of the position and the inclination of the HMD  120 . When the position and the inclination of the HMD  120  change, the position and the inclination of the uvw visual-field coordinate system of the HMD  120  in the real coordinate system change in synchronization with the change of the position and the inclination. 
     In at least one aspect, the HMD sensor  410  identifies the position of the HMD  120  in the real space as a position relative to the HMD sensor  410  based on the light intensity of the infrared ray or a relative positional relationship between a plurality of points (e.g., distance between points), which is acquired based on output from the infrared sensor. In at least one aspect, the processor  210  determines the origin of the uvw visual-field coordinate system of the HMD  120  in the real space (real coordinate system) based on the identified relative position. 
     [Virtual Space] 
     With reference to  FIG. 4 , the virtual space is further described.  FIG. 4  is a diagram of a mode of expressing a virtual space  11  according to at least one embodiment of this disclosure. The virtual space  11  has a structure with an entire celestial sphere shape covering a center  12  in all 360-degree directions. In  FIG. 4 , for the sake of clarity, only the upper-half celestial sphere of the virtual space  11  is included. Each mesh section is defined in the virtual space  11 . The position of each mesh section is defined in advance as coordinate values in an XYZ coordinate system, which is a global coordinate system defined in the virtual space  11 . The computer  200  associates each partial image forming a panorama image  13  (e.g., still image or moving image) that is developed in the virtual space  11  with each corresponding mesh section in the virtual space  11 . 
     In at least one aspect, in the virtual space  11 , the XYZ coordinate system having the center  12  as the origin is defined. The XYZ coordinate system is, for example, parallel to the real coordinate system. The horizontal direction, the vertical direction (up-down direction), and the front-rear direction of the XYZ coordinate system are defined as an X axis, a Y axis, and a Z axis, respectively. Thus, the X axis (horizontal direction) of the XYZ coordinate system is parallel to the x axis of the real coordinate system, the Y axis (vertical direction) of the XYZ coordinate system is parallel to the y axis of the real coordinate system, and the Z axis (front-rear direction) of the XYZ coordinate system is parallel to the z axis of the real coordinate system. 
     When the HMD  120  is activated, that is, when the HMD  120  is in an initial state, a virtual camera  14  is arranged at the center  12  of the virtual space  11 . In at least one embodiment, the virtual camera  14  is offset from the center  12  in the initial state. In at least one aspect, the processor  210  displays on the monitor  130  of the HMD  120  an image photographed by the virtual camera  14 . In synchronization with the motion of the HMD  120  in the real space, the virtual camera  14  similarly moves in the virtual space  11 . With this, the change in position and direction of the HMD  120  in the real space is reproduced similarly in the virtual space  11 . 
     The uvw visual-field coordinate system is defined in the virtual camera  14  similarly to the case of the HMD  120 . The uvw visual-field coordinate system of the virtual camera  14  in the virtual space  11  is defined to be synchronized with the uvw visual-field coordinate system of the HMD  120  in the real space (real coordinate system). Therefore, when the inclination of the HMD  120  changes, the inclination of the virtual camera  14  also changes in synchronization therewith. The virtual camera  14  can also move in the virtual space  11  in synchronization with the movement of the user  5  wearing the HMD  120  in the real space. 
     The processor  210  of the computer  200  defines a field-of-view region  15  in the virtual space  11  based on the position and inclination (reference line of sight  16 ) of the virtual camera  14 . The field-of-view region  15  corresponds to, of the virtual space  11 , the region that is visually recognized by the user  5  wearing the HMD  120 . That is, the position of the virtual camera  14  determines a point of view of the user  5  in the virtual space  11 . 
     The line of sight of the user  5  detected by the eye gaze sensor  140  is a direction in the point-of-view coordinate system obtained when the user  5  visually recognizes an object. The uvw visual-field coordinate system of the HMD  120  is equal to the point-of-view coordinate system used when the user  5  visually recognizes the monitor  130 . The uvw visual-field coordinate system of the virtual camera  14  is synchronized with the uvw visual-field coordinate system of the HMD  120 . Therefore, in the system  100  in at least one aspect, the line of sight of the user  5  detected by the eye gaze sensor  140  can be regarded as the line of sight of the user  5  in the uvw visual-field coordinate system of the virtual camera  14 . 
     [User&#39;s Line of Sight] 
     With reference to  FIG. 5 , determination of the line of sight of the user  5  is described.  FIG. 5  is a plan view diagram of the head of the user  5  wearing the HMD  120  according to at least one embodiment of this disclosure. 
     In at least one aspect, the eye gaze sensor  140  detects lines of sight of the right eye and the left eye of the user  5 . In at least one aspect, when the user  5  is looking at a near place, the eye gaze sensor  140  detects lines of sight R 1  and L 1 . In at least one aspect, when the user  5  is looking at a far place, the eye gaze sensor  140  detects lines of sight R 2  and L 2 . In this case, the angles formed by the lines of sight R 2  and L 2  with respect to the roll axis w are smaller than the angles formed by the lines of sight R 1  and L 1  with respect to the roll axis w. The eye gaze sensor  140  transmits the detection results to the computer  200 . 
     When the computer  200  receives the detection values of the lines of sight R 1  and L 1  from the eye gaze sensor  140  as the detection results of the lines of sight, the computer  200  identifies a point of gaze N 1  being an intersection of both the lines of sight R 1  and L 1  based on the detection values. Meanwhile, when the computer  200  receives the detection values of the lines of sight R 2  and L 2  from the eye gaze sensor  140 , the computer  200  identifies an intersection of both the lines of sight R 2  and L 2  as the point of gaze. The computer  200  identifies a line of sight N 0  of the user  5  based on the identified point of gaze N 1 . The computer  200  detects, for example, an extension direction of a straight line that passes through the point of gaze N 1  and a midpoint of a straight line connecting a right eye R and a left eye L of the user  5  to each other as the line of sight N 0 . The line of sight N 0  is a direction in which the user  5  actually directs his or her lines of sight with both eyes. The line of sight NO corresponds to a direction in which the user  5  actually directs his or her lines of sight with respect to the field-of-view region  15 . 
     In at least one aspect, the system  100  includes a television broadcast reception tuner. With such a configuration, the system  100  is able to display a television program in the virtual space  11 . 
     In at least one aspect, the HMD system  100  includes a communication circuit for connecting to the Internet or has a verbal communication function for connecting to a telephone line or a cellular service. 
     [Field-of-View Region] 
     With reference to  FIG. 6  and  FIG. 7 , the field-of-view region  15  is described.  FIG. 6  is a diagram of a YZ cross section obtained by viewing the field-of-view region  15  from an X direction in the virtual space  11 .  FIG. 7  is a diagram of an XZ cross section obtained by viewing the field-of-view region  15  from a Y direction in the virtual space  11 . 
     In  FIG. 6 , the field-of-view region  15  in the YZ cross section includes a region  18 . The region  18  is defined by the position of the virtual camera  14 , the reference line of sight  16 , and the YZ cross section of the virtual space  11 . The processor  210  defines a range of a polar angle α from the reference line of sight  16  serving as the center in the virtual space as the region  18 . 
     In  FIG. 7 , the field-of-view region  15  in the XZ cross section includes a region  19 . The region  19  is defined by the position of the virtual camera  14 , the reference line of sight  16 , and the XZ cross section of the virtual space  11 . The processor  210  defines a range of an azimuth β from the reference line of sight  16  serving as the center in the virtual space  11  as the region  19 . The polar angle α and β are determined in accordance with the position of the virtual camera  14  and the inclination (direction) of the virtual camera  14 . 
     In at least one aspect, the system  100  causes the monitor  130  to display a field-of-view image  17  based on the signal from the computer  200 , to thereby provide the field of view in the virtual space  11  to the user  5 . The field-of-view image  17  corresponds to a part of the panorama image  13 , which corresponds to the field-of-view region  15 . When the user  5  moves the HMD  120  worn on his or her head, the virtual camera  14  is also moved in synchronization with the movement. As a result, the position of the field-of-view region  15  in the virtual space  11  is changed. With this, the field-of-view image  17  displayed on the monitor  130  is updated to an image of the panorama image  13 , which is superimposed on the field-of-view region  15  synchronized with a direction in which the user  5  faces in the virtual space  11 . The user  5  can visually recognize a desired direction in the virtual space  11 . 
     In this way, the inclination of the virtual camera  14  corresponds to the line of sight of the user  5  (reference line of sight  16 ) in the virtual space  11 , and the position at which the virtual camera  14  is arranged corresponds to the point of view of the user  5  in the virtual space  11 . Therefore, through the change of the position or inclination of the virtual camera  14 , the image to be displayed on the monitor  130  is updated, and the field of view of the user  5  is moved. 
     While the user  5  is wearing the HMD  120  (having a non-transmissive monitor  130 ), the user  5  can visually recognize only the panorama image  13  developed in the virtual space  11  without visually recognizing the real world. Therefore, the system  100  provides a high sense of immersion in the virtual space  11  to the user  5 . 
     In at least one aspect, the processor  210  moves the virtual camera  14  in the virtual space  11  in synchronization with the movement in the real space of the user  5  wearing the HMD  120 . In this case, the processor  210  identifies an image region to be projected on the monitor  130  of the HMD  120  (field-of-view region  15 ) based on the position and the direction of the virtual camera  14  in the virtual space  11 . 
     In at least one aspect, the virtual camera  14  includes two virtual cameras, that is, a virtual camera for providing a right-eye image and a virtual camera for providing a left-eye image. An appropriate parallax is set for the two virtual cameras so that the user  5  is able to recognize the three-dimensional virtual space  11 . In at least one aspect, the virtual camera  14  is implemented by a single virtual camera. In this case, a right-eye image and a left-eye image may be generated from an image acquired by the single virtual camera. In at least one embodiment, the virtual camera  14  is assumed to include two virtual cameras, and the roll axes of the two virtual cameras are synthesized so that the generated roll axis (w) is adapted to the roll axis (w) of the HMD  120 . 
     [Controller] 
     An example of the controller  300  is described with reference to  FIG. 8A  and  FIG. 8B .  FIG. 8A  is a diagram of a schematic configuration of a controller according to at least one embodiment of this disclosure.  FIG. 8B  is a diagram of a coordinate system to be set for a hand of a user holding the controller according to at least one embodiment of this disclosure. 
     In at least one aspect, the controller  300  includes a right controller  300 R and a left controller (not shown). In  FIG. 8A  only right controller  300 R is shown for the sake of clarity. The right controller  300 R is operable by the right hand of the user  5 . The left controller is operable by the left hand of the user  5 . In at least one aspect, the right controller  300 R and the left controller are symmetrically configured as separate devices. Therefore, the user  5  can freely move his or her right hand holding the right controller  300 R and his or her left hand holding the left controller. In at least one aspect, the controller  300  may be an integrated controller configured to receive an operation performed by both the right and left hands of the user  5 . The right controller  300 R is now described. 
     The right controller  300 R includes a grip  310 , a frame  320 , and a top surface  330 . The grip  310  is configured so as to be held by the right hand of the user  5 . For example, the grip  310  may be held by the palm and three fingers (e.g., middle finger, ring finger, and small finger) of the right hand of the user  5 . 
     The grip  310  includes buttons  340  and  350  and the motion sensor  420 . The button  340  is arranged on a side surface of the grip  310 , and receives an operation performed by, for example, the middle finger of the right hand. The button  350  is arranged on a front surface of the grip  310 , and receives an operation performed by, for example, the index finger of the right hand. In at least one aspect, the buttons  340  and  350  are configured as trigger type buttons. The motion sensor  420  is built into the casing of the grip  310 . When a motion of the user  5  can be detected from the surroundings of the user  5  by a camera or other device. In at least one embodiment, the grip  310  does not include the motion sensor  420 . 
     The frame  320  includes a plurality of infrared LEDs  360  arranged in a circumferential direction of the frame  320 . The infrared LEDs  360  emit, during execution of a program using the controller  300 , infrared rays in accordance with progress of the program. The infrared rays emitted from the infrared LEDs  360  are usable to independently detect the position and the posture (inclination and direction) of each of the right controller  300 R and the left controller. In  FIG. 8A , the infrared LEDs  360  are shown as being arranged in two rows, but the number of arrangement rows is not limited to that illustrated in  FIG. 8 . In at least one embodiment, the infrared LEDs  360  are arranged in one row or in three or more rows. In at least one embodiment, the infrared LEDs  360  are arranged in a pattern other than rows. 
     The top surface  330  includes buttons  370  and  380  and an analog stick  390 . The buttons  370  and  380  are configured as push type buttons. The buttons  370  and  380  receive an operation performed by the thumb of the right hand of the user  5 . In at least one aspect, the analog stick  390  receives an operation performed in any direction of 360 degrees from an initial position (neutral position). The operation includes, for example, an operation for moving an object arranged in the virtual space  11 . 
     In at least one aspect, each of the right controller  300 R and the left controller includes a battery for driving the infrared ray LEDs  360  and other members. The battery includes, for example, a rechargeable battery, a button battery, a dry battery, but the battery is not limited thereto. In at least one aspect, the right controller  300 R and the left controller are connectable to, for example, a USB interface of the computer  200 . In at least one embodiment, the right controller  300 R and the left controller do not include a battery. 
     In  FIG. 8A  and  FIG. 8B , for example, a yaw direction, a roll direction, and a pitch direction are defined with respect to the right hand of the user  5 . A direction of an extended thumb is defined as the yaw direction, a direction of an extended index finger is defined as the roll direction, and a direction perpendicular to a plane defined by the yaw-direction axis and the roll-direction axis when the user  5  extends his or her thumb and index finger is defined as the pitch direction. 
     [Hardware Configuration of Server] 
     With reference to  FIG. 9 , the server  600  in at least one embodiment is described.  FIG. 9  is a block diagram of a hardware configuration of the server  600  according to at least one embodiment of this disclosure. The server  600  includes a processor  610 , a memory  620 , a storage  630 , an input/output interface  640 , and a communication interface  650 . Each component is connected to a bus  660 . In at least one embodiment, at least one of the processor  610 , the memory  620 , the storage  630 , the input/output interface  640  or the communication interface  650  is part of a separate structure and communicates with other components of server  600  through a communication path other than the bus  660 . 
     The processor  610  executes a series of commands included in a program stored in the memory  620  or the storage  630  based on a signal transmitted to the server  600  or on satisfaction of a condition determined in advance. In at least one aspect, the processor  610  is implemented as a central processing unit (CPU), a graphics processing unit (GPU), a micro processing unit (MPU), a field-programmable gate array (FPGA), or other devices. 
     The memory  620  temporarily stores programs and data. The programs are loaded from, for example, the storage  630 . The data includes data input to the server  600  and data generated by the processor  610 . In at least one aspect, the memory  620  is implemented as a random access memory (RAM) or other volatile memories. 
     The storage  630  permanently stores programs and data. In at least one embodiment, the storage  630  stores programs and data for a period of time longer than the memory  620 , but not permanently. The storage  630  is implemented as, for example, a read-only memory (ROM), a hard disk device, a flash memory, or other non-volatile storage devices. The programs stored in the storage  630  include programs for providing a virtual space in the system  100 , simulation programs, game programs, user authentication programs, and programs for implementing communication to/from other computers  200  or servers  600 . The data stored in the storage  630  may include, for example, data and objects for defining the virtual space. 
     In at least one aspect, the storage  630  is implemented as a removable storage device like a memory card. In at least one aspect, a configuration that uses programs and data stored in an external storage device is used instead of the storage  630  built into the server  600 . With such a configuration, for example, in a situation in which a plurality of HMD systems  100  are used, for example, as in an amusement facility, the programs and the data are collectively updated. 
     The input/output interface  640  allows communication of signals to/from an input/output device. In at least one aspect, the input/output interface  640  is implemented with use of a USB, a DVI, an HDMI, or other terminals. The input/output interface  640  is not limited to the specific examples described above. 
     The communication interface  650  is connected to the network  2  to communicate to/from the computer  200  connected to the network  2 . In at least one aspect, the communication interface  650  is implemented as, for example, a LAN, other wired communication interfaces, Wi-Fi, Bluetooth, NFC, or other wireless communication interfaces. The communication interface  650  is not limited to the specific examples described above. 
     In at least one aspect, the processor  610  accesses the storage  630  and loads one or more programs stored in the storage  630  to the memory  620  to execute a series of commands included in the program. In at least one embodiment, the one or more programs include, for example, an operating system of the server  600 , an application program for providing a virtual space, and game software that can be executed in the virtual space. In at least one embodiment, the processor  610  transmits a signal for providing a virtual space to the HMD device  110  to the computer  200  via the input/output interface  640 . 
     [Control Device of HMD] 
     With reference to  FIG. 10 , the control device of the HMD  120  is described. According to at least one embodiment of this disclosure, the control device is implemented by the computer  200  having a known configuration.  FIG. 10  is a block diagram of the computer  200  according to at least one embodiment of this disclosure.  FIG. 10  includes a module configuration of the computer  200 . 
     In  FIG. 10 , the computer  200  includes a control module  510 , a rendering module  520 , a memory module  530 , and a communication control module  540 . In at least one aspect, the control module  510  and the rendering module  520  are implemented by the processor  210 . In at least one aspect, a plurality of processors  210  function as the control module  510  and the rendering module  520 . The memory module  530  is implemented by the memory  220  or the storage  230 . The communication control module  540  is implemented by the communication interface  250 . 
     The control module  510  controls the virtual space  11  provided to the user  5 . The control module  510  defines the virtual space  11  in the HMD system  100  using virtual space data representing the virtual space  11 . The virtual space data is stored in, for example, the memory module  530 . In at least one embodiment, the control module  510  generates virtual space data. In at least one embodiment, the control module  510  acquires virtual space data from, for example, the server  600 . 
     The control module  510  arranges objects in the virtual space  11  using object data representing objects. The object data is stored in, for example, the memory module  530 . In at least one embodiment, the control module  510  generates virtual space data. In at least one embodiment, the control module  510  acquires virtual space data from, for example, the server  600 . In at least one embodiment, the objects include, for example, an avatar object of the user  5 , character objects, operation objects, for example, a virtual hand to be operated by the controller  300 , and forests, mountains, other landscapes, streetscapes, or animals to be arranged in accordance with the progression of the story of the game. 
     The control module  510  arranges an avatar object of the user  5  of another computer  200 , which is connected via the network  2 , in the virtual space  11 . In at least one aspect, the control module  510  arranges an avatar object of the user  5  in the virtual space  11 . In at least one aspect, the control module  510  arranges an avatar object simulating the user  5  in the virtual space  11  based on an image including the user  5 . In at least one aspect, the control module  510  arranges an avatar object in the virtual space  11 , which is selected by the user  5  from among a plurality of types of avatar objects (e.g., objects simulating animals or objects of deformed humans). 
     The control module  510  identifies an inclination of the HMD  120  based on output of the HMD sensor  410 . In at least one aspect, the control module  510  identifies an inclination of the HMD  120  based on output of the sensor  190  functioning as a motion sensor. The control module  510  detects parts (e.g., mouth, eyes, and eyebrows) forming the face of the user  5  from a face image of the user  5  generated by the first camera  150  and the second camera  160 . The control module  510  detects a motion (shape) of each detected part. 
     The control module  510  detects a line of sight of the user  5  in the virtual space  11  based on a signal from the eye gaze sensor  140 . The control module  510  detects a point-of-view position (coordinate values in the XYZ coordinate system) at which the detected line of sight of the user  5  and the celestial sphere of the virtual space  11  intersect with each other. More specifically, the control module  510  detects the point-of-view position based on the line of sight of the user  5  defined in the uvw coordinate system and the position and the inclination of the virtual camera  14 . The control module  510  transmits the detected point-of-view position to the server  600 . In at least one aspect, the control module  510  is configured to transmit line-of-sight information representing the line of sight of the user  5  to the server  600 . In such a case, the control module  510  may calculate the point-of-view position based on the line-of-sight information received by the server  600 . 
     The control module  510  translates a motion of the HMD  120 , which is detected by the HMD sensor  410 , in an avatar object. For example, the control module  510  detects inclination of the HMD  120 , and arranges the avatar object in an inclined manner. The control module  510  translates the detected motion of face parts in a face of the avatar object arranged in the virtual space  11 . The control module  510  receives line-of-sight information of another user  5  from the server  600 , and translates the line-of-sight information in the line of sight of the avatar object of another user  5 . In at least one aspect, the control module  510  translates a motion of the controller  300  in an avatar object and an operation object. In this case, the controller  300  includes, for example, a motion sensor, an acceleration sensor, or a plurality of light emitting elements (e.g., infrared LEDs) for detecting a motion of the controller  300 . 
     The control module  510  arranges, in the virtual space  11 , an operation object for receiving an operation by the user  5  in the virtual space  11 . The user  5  operates the operation object to, for example, operate an object arranged in the virtual space  11 . In at least one aspect, the operation object includes, for example, a hand object serving as a virtual hand corresponding to a hand of the user  5 . In at least one aspect, the control module  510  moves the hand object in the virtual space  11  so that the hand object moves in association with a motion of the hand of the user  5  in the real space based on output of the motion sensor  420 . In at least one aspect, the operation object may correspond to a hand part of an avatar object. 
     When one object arranged in the virtual space  11  collides with another object, the control module  510  detects the collision. The control module  510  is able to detect, for example, a timing at which a collision area of one object and a collision area of another object have touched with each other, and performs predetermined processing in response to the detected timing. In at least one embodiment, the control module  510  detects a timing at which an object and another object, which have been in contact with each other, have moved away from each other, and performs predetermined processing in response to the detected timing. In at least one embodiment, the control module  510  detects a state in which an object and another object are in contact with each other. For example, when an operation object touches another object, the control module  510  detects the fact that the operation object has touched the other object, and performs predetermined processing. 
     In at least one aspect, the control module  510  controls image display of the HMD  120  on the monitor  130 . For example, the control module  510  arranges the virtual camera  14  in the virtual space  11 . The control module  510  controls the position of the virtual camera  14  and the inclination (direction) of the virtual camera  14  in the virtual space  11 . The control module  510  defines the field-of-view region  15  depending on an inclination of the head of the user  5  wearing the HMD  120  and the position of the virtual camera  14 . The rendering module  520  generates the field-of-view region  17  to be displayed on the monitor  130  based on the determined field-of-view region  15 . The communication control module  540  outputs the field-of-view region  17  generated by the rendering module  520  to the HMD  120 . 
     The control module  510 , which has detected an utterance of the user  5  using the microphone  170  from the HMD  120 , identifies the computer  200  to which voice data corresponding to the utterance is to be transmitted. The voice data is transmitted to the computer  200  identified by the control module  510 . The control module  510 , which has received voice data from the computer  200  of another user via the network  2 , outputs audio information (utterances) corresponding to the voice data from the speaker  180 . 
     The memory module  530  holds data to be used to provide the virtual space  11  to the user  5  by the computer  200 . In at least one aspect, the memory module  530  stores space information, object information, and user information. 
     The space information stores one or more templates defined to provide the virtual space  11 . 
     The object information stores a plurality of panorama images  13  forming the virtual space  11  and object data for arranging objects in the virtual space  11 . In at least one embodiment, the panorama image  13  contains a still image and/or a moving image. In at least one embodiment, the panorama image  13  contains an image in a non-real space and/or an image in the real space. An example of the image in a non-real space is an image generated by computer graphics. 
     The user information stores a user ID for identifying the user  5 . The user ID is, for example, an internet protocol (IP) address or a media access control (MAC) address set to the computer  200  used by the user. In at least one aspect, the user ID is set by the user. The user information stores, for example, a program for causing the computer  200  to function as the control device of the HMD system  100 . 
     The data and programs stored in the memory module  530  are input by the user  5  of the HMD  120 . Alternatively, the processor  210  downloads the programs or data from a computer (e.g., server  600 ) that is managed by a business operator providing the content, and stores the downloaded programs or data in the memory module  530 . 
     In at least one embodiment, the communication control module  540  communicates to/from the server  600  or other information communication devices via the network  2 . 
     In at least one aspect, the control module  510  and the rendering module  520  are implemented with use of, for example, Unity® provided by Unity Technologies. In at least one aspect, the control module  510  and the rendering module  520  are implemented by combining the circuit elements for implementing each step of processing. 
     The processing performed in the computer  200  is implemented by hardware and software executed by the processor  410 . In at least one embodiment, the software is stored in advance on a hard disk or other memory module  530 . In at least one embodiment, the software is stored on a CD-ROM or other computer-readable non-volatile data recording media, and distributed as a program product. In at least one embodiment, the software may is provided as a program product that is downloadable by an information provider connected to the Internet or other networks. Such software is read from the data recording medium by an optical disc drive device or other data reading devices, or is downloaded from the server  600  or other computers via the communication control module  540  and then temporarily stored in a storage module. The software is read from the storage module by the processor  210 , and is stored in a RAM in a format of an executable program. The processor  210  executes the program. 
     [Control Structure of HMD System] 
     With reference to  FIG. 11 , the control structure of the HMD set  110  is described.  FIG. 11  is a sequence chart of processing to be executed by the system  100  according to at least one embodiment of this disclosure. 
     In  FIG. 11 , in Step S 1110 , the processor  210  of the computer  200  serves as the control module  510  to identify virtual space data and define the virtual space  11 . 
     In Step S 1120 , the processor  210  initializes the virtual camera  14 . For example, in a work area of the memory, the processor  210  arranges the virtual camera  14  at the center  12  defined in advance in the virtual space  11 , and matches the line of sight of the virtual camera  14  with the direction in which the user  5  faces. 
     In Step S 1130 , the processor  210  serves as the rendering module  520  to generate field-of-view image data for displaying an initial field-of-view image. The generated field-of-view image data is output to the HMD  120  by the communication control module  540 . 
     In Step S 1132 , the monitor  130  of the HMD  120  displays the field-of-view image based on the field-of-view image data received from the computer  200 . The user  5  wearing the HMD  120  is able to recognize the virtual space  11  through visual recognition of the field-of-view image. 
     In Step S 1134 , the HMD sensor  410  detects the position and the inclination of the HMD  120  based on a plurality of infrared rays emitted from the HMD  120 . The detection results are output to the computer  200  as motion detection data. 
     In Step S 1140 , the processor  210  identifies a field-of-view direction of the user  5  wearing the HMD  120  based on the position and inclination contained in the motion detection data of the HMD  120 . 
     In Step S 1150 , the processor  210  executes an application program, and arranges an object in the virtual space  11  based on a command contained in the application program. 
     In Step S 1160 , the controller  300  detects an operation by the user  5  based on a signal output from the motion sensor  420 , and outputs detection data representing the detected operation to the computer  200 . In at least one aspect, an operation of the controller  300  by the user  5  is detected based on an image from a camera arranged around the user  5 . 
     In Step S 1170 , the processor  210  detects an operation of the controller  300  by the user  5  based on the detection data acquired from the controller  300 . 
     In Step S 1180 , the processor  210  generates field-of-view image data based on the operation of the controller  300  by the user  5 . The communication control module  540  outputs the generated field-of-view image data to the HMD  120 . 
     In Step S 1190 , the HMD  120  updates a field-of-view image based on the received field-of-view image data, and displays the updated field-of-view image on the monitor  130 . 
     [Avatar Object] 
     With reference to  FIG. 12A  and  FIG. 12B , an avatar object according to at least one embodiment is described.  FIG. 12  and  FIG. 12B  are diagrams of avatar objects of respective users  5  of the HMD sets  110 A and  110 B. In the following, the user of the HMD set  110 A, the user of the HMD set  110 B, the user of the HMD set  110 C, and the user of the HMD set  110 D are referred to as “user  5 A”, “user  5 B”, “user  5 C”, and “user  5 D”, respectively. A reference numeral of each component related to the HMD set  110 A, a reference numeral of each component related to the HMD set  110 B, a reference numeral of each component related to the HMD set  110 C, and a reference numeral of each component related to the HMD set  110 D are appended by A, B, C, and D, respectively. For example, the HMD  120 A is included in the HMD set  110 A. 
       FIG. 12A  is a schematic diagram of HMD systems of several users sharing the virtual space interact using a network according to at least one embodiment of this disclosure. Each HMD  120  provides the user  5  with the virtual space  11 . Computers  200 A to  200 D provide the users  5 A to  5 D with virtual spaces  11 A to  11 D via HMDs  120 A to  120 D, respectively. In  FIG. 12A , the virtual space  11 A and the virtual space  11 B are formed by the same data. In other words, the computer  200 A and the computer  200 B share the same virtual space. An avatar object  6 A of the user  5 A and an avatar object  6 B of the user  5 B are present in the virtual space  11 A and the virtual space  11 B. The avatar object  6 A in the virtual space  11 A and the avatar object  6 B in the virtual space  11 B each wear the HMD  120 . However, the inclusion of the HMD  120 A and HMD  120 B is only for the sake of simplicity of description, and the avatars do not wear the HMD  120 A and HMD  120 B in the virtual spaces  11 A and  11 B, respectively. 
     In at least one aspect, the processor  210 A arranges a virtual camera  14 A for photographing a field-of-view region  17 A of the user  5 A at the position of eyes of the avatar object  6 A. 
       FIG. 12B  is a diagram of a field of view of a HMD according to at least one embodiment of this disclosure.  FIG. 12(B)  corresponds to the field-of-view region  17 A of the user  5 A in  FIG. 12A . The field-of-view region  17 A is an image displayed on a monitor  130 A of the HMD  120 A. This field-of-view region  17 A is an image generated by the virtual camera  14 A. The avatar object  6 B of the user  5 B is displayed in the field-of-view region  17 A. Although not included in  FIG. 12B , the avatar object  6 A of the user  5 A is displayed in the field-of-view image of the user  5 B. 
     In the arrangement in  FIG. 12B , the user  5 A can communicate to/from the user  5 B via the virtual space  11 A through conversation. More specifically, voices of the user  5 A acquired by a microphone  170 A are transmitted to the HMD  120 B of the user  5 B via the server  600  and output from a speaker  180 B provided on the HMD  120 B. Voices of the user  5 B are transmitted to the HMD  120 A of the user  5 A via the server  600 , and output from a speaker  180 A provided on the HMD  120 A. 
     The processor  210 A translates an operation by the user  5 B (operation of HMD  120 B and operation of controller  300 B) in the avatar object  6 B arranged in the virtual space  11 A. With this, the user  5 A is able to recognize the operation by the user  5 B through the avatar object  6 B. 
       FIG. 13  is a sequence chart of processing to be executed by the system  100  according to at least one embodiment of this disclosure. In  FIG. 13 , although the HMD set  110 D is not included, the HMD set  110 D operates in a similar manner as the HMD sets  110 A,  110 B, and  110 C. Also in the following description, a reference numeral of each component related to the HMD set  110 A, a reference numeral of each component related to the HMD set  110 B, a reference numeral of each component related to the HMD set  110 C, and a reference numeral of each component related to the HMD set  110 D are appended by A, B, C, and D, respectively. 
     In Step S 1310 A, the processor  210 A of the HMD set  110 A acquires avatar information for determining a motion of the avatar object  6 A in the virtual space  11 A. This avatar information contains information on an avatar such as motion information, face tracking data, and sound data. The motion information contains, for example, information on a temporal change in position and inclination of the HMD  120 A and information on a motion of the hand of the user  5 A, which is detected by, for example, a motion sensor  420 A. An example of the face tracking data is data identifying the position and size of each part of the face of the user  5 A. Another example of the face tracking data is data representing motions of parts forming the face of the user  5 A and line-of-sight data. An example of the sound data is data representing sounds of the user  5 A acquired by the microphone  170 A of the HMD  120 A. In at least one embodiment, the avatar information contains information identifying the avatar object  6 A or the user  5 A associated with the avatar object  6 A or information identifying the virtual space  11 A accommodating the avatar object  6 A. An example of the information identifying the avatar object  6 A or the user  5 A is a user ID. An example of the information identifying the virtual space  11 A accommodating the avatar object  6 A is a room ID. The processor  210 A transmits the avatar information acquired as described above to the server  600  via the network  2 . 
     In Step S 1310 B, the processor  210 B of the HMD set  110 B acquires avatar information for determining a motion of the avatar object  6 B in the virtual space  11 B, and transmits the avatar information to the server  600 , similarly to the processing of Step S 1310 A. Similarly, in Step S 1310 C, the processor  210 C of the HMD set  110 C acquires avatar information for determining a motion of the avatar object  6 C in the virtual space  11 C, and transmits the avatar information to the server  600 . 
     In Step S 1320 , the server  600  temporarily stores pieces of player information received from the HMD set  110 A, the HMD set  110 B, and the HMD set  110 C, respectively. The server  600  integrates pieces of avatar information of all the users (in this example, users  5 A to  5 C) associated with the common virtual space  11  based on, for example, the user IDs and room IDs contained in respective pieces of avatar information. Then, the server  600  transmits the integrated pieces of avatar information to all the users associated with the virtual space  11  at a timing determined in advance. In this manner, synchronization processing is executed. Such synchronization processing enables the HMD set  110 A, the HMD set  110 B, and the HMD  120 C to share mutual avatar information at substantially the same timing. 
     Next, the HMD sets  110 A to  110 C execute processing of Step S 1330 A to Step S 1330 C, respectively, based on the integrated pieces of avatar information transmitted from the server  600  to the HMD sets  110 A to  110 C. The processing of Step S 1330 A corresponds to the processing of Step S 1180  of  FIG. 11 . 
     In Step S 1330 A, the processor  210 A of the HMD set  110 A updates information on the avatar object  6 B and the avatar object  6 C of the other users  5 B and  5 C in the virtual space  11 A. Specifically, the processor  210 A updates, for example, the position and direction of the avatar object  6 B in the virtual space  11  based on motion information contained in the avatar information transmitted from the HMD set  110 B. For example, the processor  210 A updates the information (e.g., position and direction) on the avatar object  6 B contained in the object information stored in the memory module  530 . Similarly, the processor  210 A updates the information (e.g., position and direction) on the avatar object  6 C in the virtual space  11  based on motion information contained in the avatar information transmitted from the HMD set  110 C. 
     In Step S 1330 B, similarly to the processing of Step S 1330 A, the processor  210 B of the HMD set  110 B updates information on the avatar object  6 A and the avatar object  6 C of the users  5 A and  5 C in the virtual space  11 B. Similarly, in Step S 1330 C, the processor  210 C of the HMD set  110 C updates information on the avatar object  6 A and the avatar object  6 B of the users  5 A and  5 B in the virtual space  11 C. 
     [Detailed Configuration of Modules] 
     Now, with reference to  FIG. 14 , a description is given of a detailed configuration of modules of the computer  200 .  FIG. 14  is a block diagram of the detailed configuration of modules of the computer  200  according to at least one embodiment of this disclosure. 
     In  FIG. 14 , the control module  510  includes a virtual camera control module  1421 , a field-of-view region determination module  1422 , a reference-line-of-sight identification module  1423 , a virtual space definition module  1424 , a virtual object generation module  1425 , an avatar object control module  1426 , a sound control module  1427 , and a communication environment detection module  1428 . The rendering module  520  includes a field-of-view image generation module  1429 . The memory module  530  stores space information  1431 , object information  1432 , and user information  1433 . 
     In at least one aspect, the control module  510  controls display of an image on the monitor  130  of the HMD  120 . The virtual camera control module  1421  arranges the virtual camera  14  in the virtual space  11 , and controls, for example, the behavior and direction of the virtual camera  14 . The field-of-view region determination module  1422  defines the field-of-view region  15  in accordance with the direction of the head of the user  5  wearing the HMD  120 . The field-of-view image generation module  1429  generates a field-of-view image to be displayed on the monitor  130  based on the determined field-of-view region  15 . Further, the field-of-view image generation module  1429  generates a field-of-view image based on data received from the control module  510 . Data on the field-of-view image (also referred to as “field-of-view image data”) generated by the field-of-view image generation module  1429  is output to the HMD  120  by the communication control module  540 . The reference-line-of-sight identification module  1423  identifies the line of sight of the user  5  based on the signal from the eye gaze sensor  140 . 
     When the sound control module  1427  detects from the HMD  120  an utterance using the microphone  170  of the user  5 , the sound control module  1427  identifies the computer  200  to which sound data corresponding to the utterance is to be transmitted. The sound data is transmitted to the computer  200  identified by the sound control module  1427 . When the sound control module  1427  receives the sound data from the computer  200  of another user via the network  2 , the sound control module  1427  outputs a sound (utterance) corresponding to that sound data from the speaker  180 . 
     The control module  510  controls the virtual space  11  to be provided to the user  5 . First, the virtual space definition module  1424  generates virtual space data representing the virtual space  11 , to thereby define the virtual space  11  in the HMD set  110 . 
     The virtual object generation module  1425  generates data on objects to be arranged in the virtual space  11 . The objects may include, for example, another avatar object and a virtual vehicle. Data generated by the virtual object generation module  1425  is output to the field-of-view image generation module  1429 . 
     The avatar object control module  1426  generates avatar objects of the users communicating via the virtual space  11 , and presents the generated avatar objects in the virtual space  11 . In at least one aspect, the avatar object control module  1426  generates data for displaying the avatar object of the user having the worst communication environment among a plurality of communication partners in a mode different from the display mode of the avatar objects of the other users. For example, the avatar object control module  1426  presents the avatar object corresponding to a user of the HMD  120  having a communication environment that is lower than a standard determined in advance in a display mode different from the display mode of the avatar object corresponding to a user of an HMD having a communication environment equal to or higher than the standard determined in advance. 
     The communication environment includes, for example, the speed of the network, the resolution of a monitor incorporated in the HMD  120  or a monitor included in an information processing terminal mounted to the HMD  120 , and the like. In at least one embodiment of this disclosure, the avatar object control module  1426  generates data for presenting each avatar object in a mode that depends on the worst communication environment among respective communication environments of one or more other HMDs. In at least one embodiment of this disclosure, the avatar object control module  1426  generates data for presenting in the virtual space an avatar object in accordance with the image quality of the monitor. In at least one embodiment of this disclosure, when the speed of communication to/from each HMD is lower than a speed determined in advance or when there is an HMD having a slower communication speed than the communication speed of the other HMDs, the avatar object control module  1426  generates data for presenting the avatar object in the virtual space at a lower resolution than the resolution determined in advance. 
     For example, in at least one embodiment, in response to a detection that the communication environment of any one of the computers  200 B and  200 C that the computer  200 A communicates to/from is worse than the communication environment of another one of the computers  200 B and  200 C, the avatar object control module  1426  displays the avatar object of the user who is using the computer having that worse communication environment in a mode different from the avatar object of the user who is using the other of those computers. In at least one aspect, in response to a detection that the communication environment of the computer  200 A is worse than the communication environments of the other computers  200 B and  200 C, the avatar object control module  1426  generates data for presenting in the virtual space  11  an object or a message notifying that fact, and outputs the generated data to the HMD  120 . The HMD  120  displays the object or message on the monitor  130  based on that data. The user  5 A is able to recognize that his/her own communication environment is worse than the communication environment of each of the other users  5 B and  5 C. 
     In at least one aspect, when the user  5 A enters into the computer  200 A via the controller  300  an input for selecting the avatar object presented in the virtual space  11 , the avatar object control module  1426  generates data for presenting the avatar object selected based on the input in a mode different from the mode of the other avatar objects. In this case, because the user  5 A designates the avatar object of the user having a poor communication environment based on his/her own judgment, the user  5  is put on notice to pay more attention to conversation and chat under conditions (e.g., speaking slowly) different from the conversation and chat utilized by other users having a better communication environment. 
     The communication environment detection module  1428  detects the communication environment between the computer  200 A and each of the other computers  200 B and  200 C. For example, in at least one aspect, the communication environment detection module  1428  detects the network speed. The speed is detected by, for example, detection using a ping command, detection using an ftp command, detection using a ttcp command, and the like. 
     In at least one aspect, the communication environment detection module  1428  detects the resolution of a monitor displaying images based on data from the other computers  200 B and  200 C that the computer  200 A communicates to/from. This monitor may be, for example, the monitor  130  incorporated in the HMD  120 , or a monitor incorporated in a smartphone or some other information communication terminal mounted to the HMD  120 . For example, the communication environment detection module  1428  acquires the resolution and other specifications of each monitor from the monitor itself or from the HMD  120  or information communication terminal including the monitor. In at least one aspect, the communication environment detection module  1428  acquires the specifications from the server  600  or some other information management apparatus that possesses the specifications of each monitor. 
     The space information  1431  stores one or more templates defined to provide the virtual space  11 . 
     The object information  1432  stores content to be reproduced in the virtual space  11  and information for arranging an object to be used in the content. The content may include, for example, game content and content representing landscapes that resemble those of the real world. 
     The user information  1433  stores, for example, a program for causing the computer  200 A to function as a control device for the HMD set  110  and an application program that uses each piece of content stored in the object information  1432 . 
     [Control Structure] 
     The control structure of the computer  200 A is now described with reference to  FIG. 15 .  FIG. 15  is a flowchart of a part of processing to be executed by the computer  200 A according to at least one embodiment of this disclosure. The computer  200 A is connected to the other computers  200 B and  200 C via the network  2 . The computer  200 B is connected to the HMD  120 B worn by another user  5 B. The computer  200 C is connected to the HMD  120 C worn by another user  5 C. 
     In Step S 1510 , the processor  210  detects that the HMD  120  is being worn on the head of the user  5  based on a signal sent from the HMD  120 . In Step S 1520 , the processor  210  defines in the memory  220  the virtual space  11  to be presented by the HMD  120 . 
     In Step S 1530 , the processor  210  detects, based on the data received from the server  600 , the communication environments of the other computers  200 B and  200 C communicating to/from the computer  200 A. The communication environment may be, for example, the transmission speed of sound data, the transmission speed of image data, a difference between those transmission speeds, the resolution of the monitor of the HMD used by those other users, and the like. 
     In Step S 1540 , the processor  210  generates data for displaying in the virtual space  11  the avatar object corresponding to each of the other users  5 B and  5 C in a mode that depends on the communication environment. For example, when the communication speed between the computer  200 A and computer  200 B is slower than the communication speed between the computer  200 A and computer  200 C, the processor  210  changes the color of the avatar object of the user  5 B to a color different from the color of the avatar object of the another user  5 C. In at least one aspect, the processor  210  presents the avatar object of the user  5 B fainter than the avatar object of the user  5 C. For example, the processor  210  may present a transparent object as the avatar object of the user  5 B. In at least one aspect, when the resolution of the monitor  130  of the HMD  120 C is lower than the resolution of the monitor  130  of the HMD  120 , the processor  210  sets the resolution of the avatar object of the user  5 B to be lower than the resolution of the avatar object of the user  5 C so that the image quality of the avatar object of the user  5 B is lower than the image quality of the avatar object of the user  5 C. 
     In Step S 1550 , the processor  210  outputs the generated data to the HMD  120 . Based on that data, the monitor  130  of the HMD  120  presents in the virtual space  11  an avatar object representing each of the users  5 B and  5 C. When the user  5  wearing the HMD  120  visually recognizes each avatar object, the user  5  may recognize the avatar object (e.g., avatar object of user  5 B) displayed in a different mode from the display mode of the other avatar objects. This enables the user  5  to recognize that the communication environment of the user  5 B has reduced quality, and hence the user  5  is able to perform an operation in accordance with the communication environment of that user. For example, when communicating (e.g., chatting) to/from the user  5 B, the user  5  may talk more slowly than in the case of transmitting a message to the other user  5 B or perform an operation in the virtual space  11  more slowly than usually used in communications with users having a better quality communication environment. 
     The control structure of the server  600  is now described with reference to  FIG. 16 .  FIG. 16  is a flowchart of a part of processing to be executed by the processor  610  of the server  600  according to at least one embodiment of this disclosure. In at least one aspect, the server  600  is managed by a provider that provides a communication service via a virtual space. The processing in  FIG. 16  is executed when at least two of the computers  200 A,  200 B, and  200 C are able to communicate to/from each other. In the following, the processing is described based on the assumption that the computers  200 ,  200 B, and  200 C are in a mutually communicable state. 
     In Step S 1610 , the processor  610  receives a signal from each of the computers  200 A,  200 B, and  200 C, and detects the speed of the communication of each computer to/from the other computers. In Step S 1620 , the processor  610  refers to the detected result, and identifies the computer having the slowest communication speed. In Step S 1630 , the processor  610  transmits to each of the computers other than the computer having the slowest communication speed a signal containing information indicating the computer having the slowest communication speed. 
     For example, in a given communication session, when the communication speed of the computer  200 B is the slowest, the processor  610  transmits to the other computers  200 A and  200 C a signal including an identification number of the computer  200 B and a symbol representing that the communication speed is the slowest. When that signal is received from the server  600 , the processor  210  of each of the computers  200 A and  200 C associates and stores in the memory  220  the identification number of the session, the identification number of the computer  200 B, and the symbol. 
     When the computer  200 A receives the signal from the computer  200 B, the processor  210  of the computer  200 A creates an avatar object of the user  5 B of the computer  200 B based on the signal. At this time, the processor  210  refers to the memory  220  and confirms whether or not a computer having a slow communication speed is registered. For example, when information (identification number and symbol) on the computer  200 B as a computer having a slow communication speed is stored in the memory  220 , the processor  210  displays, in the case in which the avatar object of the user  5 B is to be generated based on the data received from the computer  200 B, the avatar object of the user  5 B in a mode different from the display mode of the avatar object of the user  5 C of the another computer  200 C. 
     Yet another mode of detecting the communication environment is now described with reference to  FIG. 17 .  FIG. 17  is a flowchart of processing to be executed according to at least one embodiment of this disclosure. Detection of the communication speed of each computer and other communication environments is not limited to the server  600  and each computer. For example, when the HMD  120  has an arithmetic function, the HMD  120  may also detect a computer having a slow communication speed. The control structure of the HMD  120  is now described with reference to  FIG. 17 . 
     In Step S 1710 , the processor of the HMD  120  receives, via the server  600  and the computer  200 A, a signal transmitted from each of the computers  200 B and  200 C connected to the HMDs  120 B and  120 C, respectively. In Step S 1720 , the processor identifies the computer having the slowest communication speed based on the signal received from each computer. In Step S 1730 , the processor displays the avatar object based on the signal received from the computer having the slowest communication speed in a mode different from the display mode of the other avatar objects. 
     For example, the HMD  120  connected to the computer  200 A identifies the computer having the slowest communication speed based on the signal transmitted from each of the computers  200 B and  200 C. The HMD  120  generates data for displaying the avatar object of the user of the identified computer in a mode different from avatar objects of the users of the other computers. The HMD  120  also displays an image on the monitor  130  based on the generated data. 
     Next, display modes of the avatar objects are described with reference to with  FIG. 18  to  FIG. 21 .  FIG. 18  to  FIG. 21  are diagrams of examples of an image that is visually recognizable by the user as a field-of-view image according to at least one embodiment of this disclosure. 
     For example, when the user  5 A operates the controller  300  to activate a chat application and instructs the start of chat in the virtual space  11 , communication is established to/from the computers  200 B and  200 C used by the other users  5 B and  5 C who have executed the chat application and are in an online state at that time. Then, the avatar object of each communicable user is presented on each HMD  120 . When communication is established, each computer  200 A,  200 B, and  200 C, or the server  600  providing a chat service, detects the communication environment between each computer. The communication environment may be, for example, the communication speed, the image resolution, and the like. 
     In  FIG. 18 , in at least one aspect, the user  5  visually recognizes a field-of-view image  1817 - 1  presented by the HMD  120  connected to the computer  200 A. The field-of-view image  1817 - 1  includes avatar objects  1820  and  1810  of the other computers  200 B and  200 C that the computer  200 A is communicating with. The computer  200 A may then detect that the communication state to/from the computer  200 B is worse than the communication state to/from the computer  200 C. Examples of the communication state being worse may include the communication speed to/from the computer  200 B being slower than the communication speed to/from the computer  200 C, the resolution of the monitor  130  of the HMD  120  connected to the computer  200 B being lower than the resolution of the monitor  130  of the HMD  120  connected to the computer  200 C, and the like. 
     In response to a determination that the communication state is worse, the avatar object  1820  is displayed in a mode different from the display mode of the avatar object  1810 , in a field-of-view image  1817 - 2 . For example, as indicated by the dotted line of the field-of-view image  1817 - 2 , the avatar object  1820  is presented in the field-of-view image  1817 - 2  at a lower resolution than the resolution of the avatar object  1810 . 
     Further, in at least one aspect, an object  1840  indicating that a user having a poor communication state is included as a chat partner is displayed in the field-of-view image  1817 - 2 . Displaying the object  1840  enables the user  5  to easily recognize that such a user is present, and hence, for example, adjusting the speed of subsequent conversation is easier. 
       FIG. 19  is a diagram of another display mode of the avatar objects to be included in the field-of-view image when a user having a poor communication state is included as a chat partner according to at least one embodiment of this disclosure. 
     When the computer  200 A establishes communication with the computers  200 B and  200 C, as an initial state, a field-of-view image  1917 - 1  presents avatar objects  1920  and  1910  corresponding to the user of each of the computers  200 B and  200 C. 
     In the field-of-view image  1917 - 2 , in response to a detection that the communication state to/from the computer  200 B is poor, the size of the avatar object  1920  is decreased compared with the size of the avatar object  1910 . The avatar object  1920  may be presented in a position separated from the avatar object  1910 . The object  1840  may also be presented. When the user  5 A recognizes a change in the display mode of the avatar object  1920 , the user  5 A is able to know that the communication environment of the computer  200 B of the user  5 B using the avatar object  1920  is worse than the communication environment of the computer  200 C used by the user  5 C. As a result, when the user  5 A talks slowly, the user  5 B is able to handle the utterances of the user  5 , which allows each user to enjoy chatting via the virtual space  11  without feeling stress. 
       FIG. 20  is a diagram of the field-of-view image to be presented by the HMD  120 B worn by the user  5 B of the computer  200 B having a poor communication speed according to at least one embodiment of this disclosure. 
     In a field-of-view image  2017 - 1 , when communication is established between the user  5 B and the other users  5 A and  5 C, the monitor  130  of the HMD  120 B displays, as initial images, avatar objects  2010  and  2020  corresponding to the users  5 A and  5 C, respectively. Then, the computer  200 B detects that its own communication environment is worse than the communication environment (e.g., communication speed and resolution of the monitor  130 ) of the other computers  200 A and  200 C. This detection is performed, for example, based on a measurement result of a known communication speed or based on a result notified from the server  600  as the detection result of the communication environment. 
     As a result of the detection, in a field-of-view image  2017 - 2 , the avatar objects  2010  and  2020  may be presented at a more distant place than the initially presented place. The size of the avatar objects  2010  and  2020  may be decreased compared with when those avatar objects were initially presented. An object  2040  indicating that the communication environment of the computer  200 B is worse than the communication environment of each of the other computers  200  and  200 C for which communication is currently established is presented in the field-of-view image  2017 - 2 . The user  5 B recognizes that the communication environment of the computer  200 B is not good by visually recognizing the object  2040  or a display mode like that described above of the avatar objects  2010  and  2020  included in the field-of-view image  2017 - 2 . The user  5 B is able to then proceed with chatting with other users  5 A and  5 C by, for example, reducing the amount of his/her utterances or transmitting a character-based message. As a result, stress caused by an inconsistent communication environment can be reduced. 
       FIG. 21  is a diagram of another example of the field-of-view image to be presented by the HMD  120 B worn by the user  5 B of the computer  200 B having a poor communication speed according to at least one embodiment of this disclosure. 
     A field-of-view image  2117 - 1  represents an image of an initial state after communication to/from each computer is established. At this time, similar to the field-of-view image  2017 - 1  in  FIG. 20 , the field-of-view image  2117 - 1  includes avatar objects  2010  and  2020  shown in a normal display mode determined in advance. The computer  200 B is then capable of detecting that that communication environment is worse than the communication environment of each of the other computers  200 A and  200 C. 
     In a field-of-view image  2117 - 2 , the visibility of the field-of-view image  2117 - 1  may be reduced in response to this detection. For example, a blurring process is performed on the field-of-view image  2117 - 1 , or the brightness of the screen is reduced. In this way, the user  5 B is able to easily recognize that the communication environment of the computer  200 B used by the user  5 B is worse than the communication environment of the computer  200  or the computer  200 C used by the chat partner. Therefore, in a subsequent chat, the user  5 B takes an appropriate measure, such as adjusting his/her utterance speed, or increasing the frequency of using text messages that are less likely to be affected by deterioration in the communication environment. As a result, the stress of communicating via the virtual space  11  may be reduced. 
     As described above, in at least one embodiment of this disclosure, in a case in which two or more users  5 A,  5 B,  5 C chat or communicate in some other way via the virtual space  11 , when the communication environment of any one of the users is worse than the other users, the fact that the communication environment of that user is poor is notified to the relevant user, or that fact is notified to all the users who are communicating via the virtual space  11 . For example, a message or an icon notifying that fact is displayed on the monitor of the HMD worn by the relevant user or the monitor of the computer used by the relevant user. In this way, that user is able to talk to the other users more slowly, or is able to inform the other users of the fact that his/her communication environment is poor and ask the other users to talk more slowly. As a result, each user is able to communicate in consideration of the other users, and hence stress may be reduced. 
     In at least one embodiment described above, there is described an example in which the fact that the communication environment of a given user is worse than the communication environment of each of the other users is notified to that given user. However, the notification destination is not limited to the given user. In at least one aspect, the notification is also notified to the other users. Exemplary modes of notifying may be the same as the mode in  FIG. 18  to  FIG. 21 . In this way, the other users are able to easily recognize that a user having a poor communication environment is included as a communication partner. Proposing to the communication partners, including the user having a poor communication environment, measures such as talking more slowly, or employing text communication in place of talking is easier. As a result, communication is performed more smoothly. 
     The above-mentioned technical features of at least one embodiment are summarized as follows, for example. 
     (Configuration 1) 
     According to at least one embodiment of this disclosure, there is provided a method to be executed on a computer (e.g.,  200 A,  200 B, or  200 C) to communicate via a virtual space  11 , or a non-transitory computer-readable data recording medium having stored thereon a command for causing a computer to implement the method. The method includes defining the virtual space  11  to be provided by an HMD  120  connected to the computer  200 A. The method further includes detecting, based on signals transmitted from other apparatus (e.g., computers  200 B and  200 C, HMDs  120 B and  120 C, and server  600 ) communicably connected to the computer  200 , communication environments of the other apparatus. The method further includes presenting in the virtual space  11  an avatar object corresponding to each of users  5 B and  5 C of the other HMDs  120 B and  120 C in a mode that depends on the communication environments. 
     (Configuration 2) 
     According to at least one embodiment of this disclosure, the presenting of the avatar object in the virtual space  11  includes presenting the avatar object corresponding to a user (e.g., any one of HMD  120 B or  120 C) of the HMD  120  having a communication environment that is lower than a standard determined in advance in a display mode different from a display mode of an avatar object corresponding to a user of an HMD having a communication environment equal to or higher than the standard determined in advance. 
     (Configuration 3) 
     According to at least one embodiment of this disclosure, the presenting of the avatar object in the virtual space  11  includes presenting each avatar object in a mode that depends on the worst communication environment among respective communication environments of one or more other HMDs. 
     (Configuration 4) 
     According to at least one embodiment of this disclosure, the detecting of the communication environments includes receiving information representing an image quality of the head-mounted device, and the presenting of the avatar object in the virtual space  11  includes presenting in the virtual space  11  the avatar object in accordance with the image quality. 
     (Configuration 5) 
     According to at least one embodiment of this disclosure, the detecting of the communication environments includes detecting a speed of communication to/from the other HMDs  120 B and  120 C, and the presenting of the avatar object in the virtual space  11  includes presenting, when the communication speed is lower than a speed determined in advance or when the speed of communication to/from anyone of the HMDs is lower than the speed of communication to/from the other HMDs, the avatar object in the virtual space  11  at a lower resolution than a resolution determined in advance. 
     (Configuration 6) 
     According to at least one embodiment of this disclosure, the method further includes receiving user input for selecting an avatar object presented in the virtual space  11 , and the presenting of the avatar object in the virtual space  11  includes presenting the avatar object selected based on the user input in a mode different from a mode of other avatar objects. 
     (Configuration 7) 
     According to at least one embodiment of this disclosure, there is provided a system for executing any one of the methods described above on the computers  200 A,  200 B, and  200 C. 
     (Configuration 8) 
     According to at least one embodiment of this disclosure, there is provided a computer  200  including: a memory  220  having stored thereon the program described above; and a processor  210  for executing the program. 
     It is to be understood that the embodiments disclosed herein are merely examples in all aspects and in no way intended to limit this disclosure. The scope of this disclosure is defined by the appended claims and not by the above description, and it is intended that this disclosure encompasses all modifications made within the scope and spirit equivalent to those of the appended claims. 
     In the at least one embodiment described above, the description is given by exemplifying the virtual space (VR space) in which the user is immersed using an HMD. However, a see-through HMD may be adopted as the HMD. In this case, the user may be provided with a virtual experience in an augmented reality (AR) space or a mixed reality (MR) space through output of a field-of-view image that is a combination of the real space visually recognized by the user via the see-through HMD and a part of an image forming the virtual space. In this case, action may be exerted on a target object in the virtual space based on motion of a hand of the user instead of the operation object. Specifically, the processor may identify coordinate information on the position of the hand of the user in the real space, and define the position of the target object in the virtual space in connection with the coordinate information in the real space. With this, the processor can grasp the positional relationship between the hand of the user in the real space and the target object in the virtual space, and execute processing corresponding to, for example, the above-mentioned collision control between the hand of the user and the target object. As a result, it is possible to exert action on the target object based on motion of the hand of the user.