Patent Publication Number: US-11660536-B2

Title: Display control program, display control apparatus and display control method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/784,338, accorded a filing date of Feb. 7, 2020 (allowed), which is a continuation of U.S. patent application Ser. No. 15/547,736, accorded a filing date of Jul. 31, 2017 (U.S. Pat. No. 10,596,464, issued Mar. 24, 2020), which is a National Stage application claiming priority to International Application No.: PCT/JP2016/055391, filed on Feb. 24, 2016, which claims priority to JP 2015-039077, filed Feb. 27, 2015, JP 2015-119033, filed Jun. 12, 2015, and JP 2015-182762, filed Sep. 16, 2015, the entire disclosures of which are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a display control technology and, more particularly, to a display control program, a display control apparatus, and a display control method that are configured to control display on a head mounted display. 
     BACKGROUND ART 
     Game playing is practiced in which, with a head mounted display that is connected to a game machine worn on the head of a user, the user operates a controller, for example, while looking at a screen displayed on the head mounted display. With an ordinary stationary display connected to a game machine, the user&#39;s visual field range extends also to the outside of a display screen, so that the user may not concentrate on the screen or lose the sense of absorption in the game being played. On the contrary, wearing a head mounted display makes the user look at only the video shown on the display, thereby providing effects of the increased sense or absorption and enhanced game entertainment. 
     SUMMARY 
     Technical Problem 
     The inventors hereof recognized that, in order to allow more and more users to enjoy games in which head mounted displays are used, display control technologies of higher convenience are required. 
     Solution to Problem 
     In order to solve the problem described above, there is provided a display control program in one aspect of the present invention, the program causing a computer to function as an instruction input acquisition block configured to acquire information indicative of an entered instruction from a first input apparatus used by a first user whose head wearing a head mounted display on and information indicative of entered instruction from a second input apparatus used by a second user enabled to view a display apparatus; a control block configured to control, in a virtual three-dimensional space, an event on the basis of an instruction acquired by the instruction input acquisition block; a first image generation block configured to generate a first image of the virtual three-dimensional space to be displayed on the head mounted display; and a second image generation block configured to generate a second image of the virtual three-dimensional space to be displayed on the display apparatus. 
     It should be noted that any combinations of the components described above and those obtained by translating the expressions of the present invention between method, apparatus, and system are also valid as embodiments of the present invention. 
     Advantageous Effect of Invention 
     As described and according to the present invention, user convenience of a head mounted display is enhanced. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective views illustrating a usage environment of a game system practiced as one embodiment of the present invention. 
         FIG.  2    is an external perspective view illustrating a head mounted display practiced as another embodiment of the present invention. 
         FIG.  3    is a functional configuration diagram illustrating the head mounted display. 
         FIG.  4    is a diagram illustrating external views of an input apparatus. 
         FIG.  5    is a diagram illustrating a configuration of a game machine. 
         FIG.  6    is a functional configuration diagram illustrating the game machine. 
         FIG.  7    is a diagram illustrating one example of a first game image that is displayed on the head mounted display. 
         FIG.  8    is a diagram illustrating another example of the first game image that is displayed on the head mounted display. 
         FIG.  9    is a diagram illustrating still another example of a first game image that is displayed on the head mounted display. 
         FIG.  10    is a diagram illustrating still another example of a first game image that is displayed on the head mounted display. 
         FIG.  11    is a diagram illustrating still another example of a first game image that is displayed on the head mounted display. 
         FIG.  12    is a diagram illustrating still another example of a first game image that is displayed on the head mounted display. 
         FIG.  13    is a diagram illustrating still another example of a first game image that is displayed on the head mounted display. 
         FIG.  14    is a diagram illustrating still another example of a first game image that is displayed on the head mounted display. 
         FIG.  15    is a diagram illustrating still another example of a first game image that is displayed on the head mounted display. 
         FIG.  16    is a diagram illustrating one example of a second game image that is displayed on a display apparatus. 
         FIG.  17    is a diagram illustrating still another example of a first game image that is displayed on the head mounted display. 
         FIG.  18    is a diagram illustrating another example of a second game image that is displayed on the display apparatus. 
         FIG.  19    is a diagram illustrating still another example of the first game image that is displayed on the head mounted display. 
         FIG.  20    is a diagram illustrating still another example of the second game image that is displayed on the display apparatus. 
         FIG.  21    is a diagram illustrating still another example of the first game image that is displayed on the head mounted display. 
         FIG.  22    is a diagram illustrating still another example of the second game image that is displayed on the display apparatus. 
         FIG.  23    is a diagram illustrating still another example of the second game image that is displayed on the display apparatus. 
         FIG.  24    is a diagram illustrating still another example of the first game image that is displayed on the head mounted display. 
         FIG.  25    is a flowchart indicative of a procedure of a display control method practiced as an embodiment of the present invention. 
         FIG.  26    is a flowchart indicative of a procedure of the display control method practiced as an embodiment of the present invention. 
         FIG.  27    is a flowchart indicative of a procedure of the display control method practiced as an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     The following describes a display technology based on a head mounted display (HMD). A head mounted display is a display apparatus that are mounted on the head of a user such that the eyes of the user are covered, thereby allowing the user to view still images and moving images displayed on a display screen arranged in front of the user&#39;s eyes. The subjects to be displayed on the head mounted display may be such content as movies or television programs; in the present embodiment, an example is described in which a head mounted display is used as a display apparatus that displays game images. 
     Now, referring to  FIG.  1   , there is shown an environment in which a game system  1  practiced as one embodiment of the present invention is used. The game system  1  includes a game apparatus  10  for executing a game program, an input apparatus  6  through which user instructions are entered in the game apparatus  10 , an imaging apparatus  14  for taking pictures of a real space around a user, a head mounted display  100  for displaying a first game image generated by the game apparatus  10 , and a display apparatus  12  for displaying a second game image generated by the game apparatus  10 . 
     The game apparatus  10  executes a game program on the basis of instruction input entered from the input apparatus  6  or the head mounted display  100  and the position or attitude of the input apparatus  6  or the head mounted display  100 , and generates a first game image to transmit the generated first game image to the head mounted display  100  and generates a second game image to transmit the generated second image to the display apparatus  12 . 
     The head mounted display  100  displays the first game image generated in the game apparatus  10 . Further, the head mounted display  100  transmits information related with a user input operation done through an input apparatus arranged on the head mounted display  100  to the game apparatus  10 . The head mounted display  100  may be connected to the game apparatus  10  with a wired cable or in a wireless manner such as wireless local area network (LAN). 
     The display apparatus  12  displays the second game image generated in the game apparatus  10 . The display apparatus  12  may be a television having a display and a speaker or a computer display. 
     The input apparatus  6  has a function of transmitting a user instruction input to the game apparatus  10 ; in the present embodiment, the input apparatus  6  is configured as a wireless controller that provides wireless communication with the game apparatus  10 . The input apparatus  6  and the game apparatus  10  may establish wireless connection by use of a Bluetooth (trademark) protocol. It should be noted that the input apparatus  6  may also be a wired controller connected to the game apparatus  10  with a cable, in addition to a wireless controller. 
     The input apparatus  6 , driven by a battery, is configured by having two or more buttons for performing instruction input operations for making a game progress. When the user operates a button of the input apparatus  6 , an instruction input done by this operation is transmitted to the game apparatus  10  through wireless communication. 
     The imaging apparatus  14  is a video camera configured by a charge coupled device (CCD) imaging device or a complementary metal-oxide semiconductor (CMOS) imaging device, for example, and takes pictures of a real space with a predetermined period, thereby generating a frame image for each period. The imaging apparatus  14  is connected to the game apparatus  10  through an interface such as universal serial bus (USB) or the like. In image captured by the imaging apparatus  14  is used to derive the positions and attitudes of the input apparatus  6  and the head mounted display  100  in the game apparatus  10 . The imaging apparatus  14  may be a ranging camera for obtaining distance or a stereo camera. In this case, the imaging apparatus  14  allows the acquisition of distances between the imaging apparatus  14  and the input apparatus  6  or the head mounted display  100 , for example. 
     In the game system  1  of the present embodiment, the input apparatus  6  and the head mounted display  100  each have a light emission block that emits a light of two or more colors. During a game, the light emission block emits light in color indicated by the game apparatus  10  which is imaged by the imaging apparatus  14 . The imaging apparatus  14  takes a picture of the input apparatus  6  and generates a frame image, supplying the generated frame image to the game apparatus  10 . Acquiring the frame image, the game apparatus  10  derives the positional information about the light emission block in the real space from the position and size of the image of the light emission block in the frame image. The game apparatus  10  handles the positional information as a game operation instruction, thereby reflecting the game operation instruction onto such processing of the game as controlling the operation of a player&#39;s character. 
     In addition, the input apparatus  6  and the head mounted display  100  each has an acceleration sensor and a gyro sensor. The sensor detection values are transmitted to the game apparatus  10  with a predetermined period. Receiving the sensor detection values, the game apparatus  10  acquires the attitude information of the input apparatus  6  and the head mounted display  100  in the real space. The game apparatus  10  handles the attitude information as an operation instruction for a game and reflects the attitude information onto the processing of the game. 
     Referring to  FIG.  2   , there is shown an external view of the head mounted display  100  practiced as one embodiment of the present invention. The head mounted display  100  has a main body section  110 , a head contact section  112 , and a light emission section  114 . 
     Arranged on the main body section  110  are a display, a global positioning system (GPS) unit for acquiring positional information, an attitude sensor, and a communication apparatus. The head contact section  112  may include a biometric information acquisition sensor for detecting biometric information such as user&#39;s body temperature, heartbeat, blood composition, perspiration, brainwave, and brain blood flow. The light emission selection  114  emits light in a color indicated by the game apparatus  10  as described above and functions as the standard for computing the position of the head mounted display  100  in an image taken by the imaging apparatus  14 . 
     The head mounted display  100  may further include a camera for taking pictures of user&#39;s eyes. The camera arranged on the head mounted display  100  allows detection of field of view, pupil movement, and blink of the eyes of the user. 
     In the present embodiment, the head mounted display  100  is described; however, the display control technology of the present embodiment is also applicable not only to the head mounted display  100  in a limited sense but also a head mounted display having eye glasses, a spectacle-type display, a spectacle-type camera, a headphone, a headset (a headphone with a microphone), an earphone, an earring, an ear-hooked camera, a hat, a hat with camera, or a hair band, for example. 
     Referring to  FIG.  3   , there is shown a functional diagram of the head mounted display  100 . The head mounted display  100  has an input interface  122 , an output interface  130 , a backlight  132 , a communication control block  140 , a network adaptor  142 , an antenna  144 , a storage block  150 , a GPS unit  161 , a wireless unit  162 , an attitude sensor  164 , an external input/output terminal interface  170 , an external memory  172 , a clock block  180 , a display apparatus  90 , and a control block  160 . These functional blocks are also realized by only hardware, only software, or a combination thereof. 
     The control block  160  is a main processor that processes signals such as an image signal and a sensor signal, instructions, and data and outputs the results of the processing. The input interface  122  receives an operation signal and a setting signal from an input button or the like and supplies the received signals to the control block  160 . The output interface  130  receives an image signal from the control block  160  and makes the display apparatus  90  display the received image signal. The backlight  132  supplies backlight to a liquid crystal display that makes up the display apparatus  90 . 
     The communication control block  140  transmits data entered from the control block  160  to the outside in a wired or wireless manner through the network adaptor  142  or the antenna  144 . Also, the communication control block  140  receives data from the outside in a wired or wireless manner through the network adaptor  142  or the antenna  144  and outputs the received data to the control block  160 . 
     The storage block  150  temporarily stores data, parameters, and operation signals that are processed by the control block  160 . 
     The GPS unit  161  receives positional information from a GPS satellite by following an operation signal from the control block  160  and supplies the received positional information to the control block  160 . The wireless unit  162  receives positional information from a wireless base station by following an operation signal from the control block  160  and supplies the received positional information to the control block  160 . 
     The attitude sensor  164  detects attitude information such as the direction and tilt of the main body section  110  of the head mounted display  100 . The attitude sensor  164  can be realized by appropriately combining a gyro sensor, an acceleration sensor, and an angular acceleration sensor. 
     The external input/output terminal interface  170  is an interface for the connection of peripheral devices such as a USB controller. The external memory  172  is an external memory such as a flash memory. 
     The clock block  180  sets time information on the basis of a setting signal received from the control block  160  and supplies time data to the control block  160 . 
     Referring to  FIG.  4   , there is shown an external view of an input apparatus.  FIG.  4 ( a )  shows an external configuration of the top view of the input apparatus. The user holds a left-side hold section  78   b  by the left hand and a right-side hold section  78   a  by the right hand and operates the input apparatus  6 . Arranged on top of the housing of the input apparatus  6  are a direction key  71 , analog sticks  77   a  and  77   b  and four-types of operation buttons  76  that make up the input block. Four-types of buttons  72  through  75  are identified by different colors and different symbols. Namely, the circle button  72  has a red circle, the cross button  73  has a blue cross, the square button  74  has a purple square, and a triangle button  75  has a green triangle. On top of the housing, a touch pad  79  is arranged on a flat area between the direction key  71  and the operation button  76 . The touch pad  79  sinks when the user presses the panel and returns to the original position when the user releases the panel, thus functioning also as a press button. 
     A function button  80  is arranged between the two analog sticks  77   a  and  77   b . The function button  80  is used to power on the input apparatus  6  and, at the same time, activate the communication function for interconnecting the input apparatus  6  and the game apparatus  10 . After connection of the input apparatus  6  with the game apparatus  10 , the function button  80  is also used to display a menu screen on the game apparatus  10 . 
     A SHARE button  81  is arranged between the touch pad  79  and the direction key  71 . The SHARE button  81  is used to enter a user instruction for an operating system (OS) or the system software of the game apparatus  10 . An OPTIONS button  82  is arranged between the touch pad  79  and the operation button  76 . The OPTIONS button  82  is used to enter a user instruction for an application (a game) that is executed on the game apparatus  10 . The SHARE button  81  and the OPTIONS button  82  may be formed as push buttons. 
       FIG.  4 ( b )  shows an external configuration of a side of the rear section of the input apparatus. On top of the side of the rear section of the housing of the input apparatus  6 , the touch pad  79  extends from the top of the housing; below the side of the rear section of the housing, a light-emitting block  85  that is long sideways is arranged. The light-emitting block  85  has red (R), green (G), and blue (B) light-emitting diodes (LEDs) that are turned on according to emitted light color information transmitted from the game apparatus  10 . 
     On the side of the rear section of the housing, an upper button  83   a  and an upper button  83   b  are arranged symmetrically along longitudinal direction, and a lower button  84   a  and a lower button  84   b  are arranged symmetrically along longitudinal direction. The upper button  83   a  and the lower button  84   a  are operated by the index finger and the middle finger of the right hand of the user, respectively; the upper button  83   b  and the lower button  84   b  are operated by the index finger and the middle finger of the left hand of the user, respectively. As shown, arranging the light-emitting block  85  between the line of the upper button  83   a  and the lower button  84   a  of the right side and the line of the upper button  83   b  and the lower button  84   b  of the left side makes the light-emitting block  85  visible without being hidden by the index finger or the middle finger that operates these buttons, thereby allowing the imaging apparatus  14  to suitably image the turned-on light-emitting block  85 . The upper buttons  83  may be configured as a push button and the lower buttons  84  may be configured as a pivotally supported trigger button. 
     Referring to  FIG.  5   , there is shown a configuration of the game apparatus  10 . The game apparatus  10  has a main power supply button  20 , a power supply ON LED  21 , a standby LED  22 , a system controller  24 , a clock  26 , a device controller  30 , a media drive  32 , a USB module  34 , a flash memory  36 , a wireless communication module  38 , a wired communication module  40 , a sub system  50 , and a main system  60 . 
     The main system  60  has a main central processing unit (CPU), a memory and a memory controller that form a main storage unit, and a graphics processing unit (GPU) and so forth. The GPU is mainly used for computational processing of game programs. These functions are configured as system-on-chips which may be formed on a single chip. The main CPU has a function of executing game programs recorded to an auxiliary storage apparatus  2 . 
     The sub system  50  has a sub CPU and a memory and a memory controller that form a main storage apparatus and so forth, but does not have either a GPU or a function of executing game programs. The number of circuit gates of the sub CPU is lower than the number of circuit gates of the main CPU and the operation power dissipation of the sub CPU is lower than that of the main CPU. The sub CPU also operates while the main CPU is in a standby state and the processing function of the sub CPU is restricted to lower the power dissipation. 
     The main power supply button  20  that is arranged on the front side of the housing of the game apparatus  10  and is an input block through which user operation input is executed, is operated to power on/off the main system  60  of the game apparatus  10 . The power supply ON LED  21  is turned on when the main power supply button  20  is turned on and the standby LED  22  is turned on when the main power supply button  20  is turned off. 
     The system controller  24  detects the pressing of the main power supply button  20  by the user. When the main power supply button  20  is pressed with the main power supply being off, the system controller  24  acquires this pressing operation as “on instruction,” while, when the main power supply button  20  is pressed with the main power supply being on, the system controller  24  acquires this pressing operation as “off instruction.” 
     The clock  26  is a realtime clock that generates current date and time information and supplies the generated current date and time information to the system controller  24 , the sub system  50 , and the main system  60 . 
     The device controller  30  is configured as a large-scale integrated circuit (LSI) that executes transfer of information between devices like a south bridge. As shown, the device controller  30  is connected to devices such as the system controller  24 , the media drive  32 , the USB module  34 , the flash memory  36 , the wireless communication module  38 , the wired communication module  40 , the sub system  50 , and the main system  60 . The device controller  30  absorbs the difference in electric properties and data transfer speeds between the devices and controls the timing of data transfer. 
     The media drive  32  is a drive apparatus which is loaded with a read only memory (ROM) medium  44  recording application software such as games and license information to drive the ROM medium  44 , thereby reading programs and data from the ROM medium  44 . The ROM medium  44  is a read-only recording medium such as an optical disc, a magneto-optical disc, or a Blu-ray disc, for example. 
     The USB module  34  is a module for providing connection with external devices through a USB cable. The USB module  34  may provide connection to the auxiliary storage apparatus and the imaging apparatus  14  through a USB cable. The flash memory  36  is an auxiliary storage apparatus that configures an internal storage. The wireless communication module  38  provides wireless communication with the input apparatus  6 , for example, on the basis of a communication protocol such as Bluetooth (trademark) protocol or Institute of Electrical and Electronics Engineers (IEEE) 802.11 protocol. It should be noted that the wireless communication module  38  may be compliant with the third-generation digital mobile phone scheme based on the international mobile telecommunication 2000 (IMT-2000) specified by International Telecommunication Union (ITU) or, further, may be compliant with digital mobile phone schemes of other generations. The wired communication module  40  provides wired communication with external devices, an external network via an access point (AP)  8 , for example. 
     Referring to  FIG.  6   , there is shown a functional configuration of the game apparatus  10 . The main system  60  of the game apparatus  10  has a control portion  310  and a data hold portion  360 . The control portion  310  has a game control block  311 , an instruction input acquisition block  312 , a taken image analysis block  313 , an HMD information acquisition block  314 , an input apparatus information acquisition block  315 , a first image generation block  316 , and a second image generation block  317 . 
     The data hold portion  360  holds program data of games that are executed on the game apparatus  10  and various kinds of data that are used by game programs. 
     The instruction input acquisition block  312  acquires, from the input apparatus  6  or the head mounted display  100 , information associated with user instruction input accepted by the input apparatus  6  or the head mounted display  100 . 
     The taken image analysis block  313  acquires an image taken by the imaging apparatus  14  and analyzes the acquired image, thereby computing the positions and attitudes of the input apparatus  6  and the head mounted display  100 . The taken image analysis block  313  acquires frame images from the imaging apparatus  14  at a predetermined imaging speed (30 frames/second, for example) and extracts the images of the light emission blocks of the input apparatus  6  and the head mounted display  100  from the frame images, thereby identifying the positions and sizes of the light emission blocks in the frame images. For example, the taken image analysis block  313  identifies the gravity center coordinates and radius of the image of an emitting body in the frame images. When the user turns on the light emission block in a color seldom used in an environment where the user uses the game system  1 , the precision images of the light emission blocks can be extracted from the frame images. 
     The taken image analysis block  313  derives the positional information of the input apparatus  6  and the head mounted display  100  as viewed from the imaging apparatus  14  from the position and size of the image of an identified light emitting body. The taken image analysis block  313  derives the positional coordinates in a camera coordinates from the gravity center coordinates of the image of the light emitting body and the information about distance from the imaging apparatus  14  from the radius of the image of the light emitting body. These positional coordinates and distance information form the positional information of the input apparatus  6  and the head mounted display  100 . 
     The HMD information acquisition block  314  acquires information associated with the attitude of the head mounted display from the head mounted display  100 . In addition, the HMD information acquisition block  314  acquires the information associated with the position of the head mounted display  100  from the taken image analysis block  313 . These pieces of information are transmitted to the game control block  311 . The information associated with the attitude of the head mounted display  100  may be obtained by the analysis by the taken image analysis block  313  of the taken image of the head mounted display  100 . 
     The input apparatus information acquisition block  315  acquires the information associated with the attitude of the input apparatus  6  from the input apparatus  6 . In addition, the input apparatus information acquisition block  315  acquires the information associated with the position of the input apparatus  6  from the taken image analysis block  313 . These pieces of information are transmitted to the game control block  311 . The information associated with the attitude of the input apparatus  6  may be obtained by the analysis by the taken image analysis block  313  of the taken image of the input apparatus  6 . 
     If the input apparatus  6  is not imaged by the imaging apparatus  14  because the input apparatus  6  gets out of the imaging range of the imaging apparatus  14  or hidden by the user body or some obstacle, then the input apparatus information acquisition block  315  computes the position of the input apparatus  6  on the basis of the information about the position of the input apparatus  6  obtained last and the attitude of the input apparatus  6  obtained subsequent to that moment. For example, on the basis of the data of translational acceleration obtained from an acceleration sensor of the input apparatus  6 , a shift from the position of the input apparatus  6  obtained last may be computed, thereby computing the current position of the input apparatus  6 . While the input apparatus  6  is not imaged by the imaging apparatus  14 , the positions of the input apparatus  6  are sequentially computed in the same manner. If the input apparatus  6  is imaged by the imaging apparatus  14  again, the positions of the input apparatus  6  sequentially computed by the acceleration data may not indicate the correct position due to the accumulated drift errors, so that the position of the input apparatus  6  newly computed by the taken image analysis block  313  may be used as the current position of the input apparatus  6 . This holds the same with the position of the head mounted display  100 . 
     The game control block  311  executes game programs and makes a game progress on the basis of the user instruction input acquired by the instruction input acquisition block  312  and the information associated with the positions or attitudes of the input apparatus  6  or the head mounted display  100 . In a game field configured by a virtual three-dimensional space, the game control block  311  changes the positions of player&#39;s characters subject to operation on the basis of inputs through the direction key  71  and the analog sticks  77   a  and  77   b  of the input apparatus  6  and changes in the position of the input apparatus  6  or the head mounted display  100 . 
     The first image generation block  316  generates an image to be displayed on the head mounted display  100 . The first image generation block  316  sets a viewpoint position on the basis of the position of a subject of operation that is controlled by the game control block  311 , sets a sightline direction on the basis of the attitude of the head mounted display  100 , and renders a virtual three-dimensional space, thereby generating the image of a game field. The first image generation block  316  relates the attitude of the head mounted display  100  with the sightline direction in the game field with a predetermined timing and, subsequently, changes the sightline direction as the attitude of the head mounted display  100  changes. Consequently, the user can look out over the game field by actually moving his or her head, thereby experiencing as if the user actually existed in the game field. The first image generation block  316  adds game-related information and an image or the like to be displayed on the head mounted display  100  to the generated game field image, thereby generating a first image. The first image generated by the first image generation block  316  is transmitted to the head mounted display  100  through the wireless communication module  38  or the wired communication module  40 . 
     The second image generation block  317  generates an image to be displayed on the display apparatus  12 . If the same image as an image to be displayed on the head mounted display  100  is displayed on the display apparatus  12 , the first image generated by the first image generation block  316  is also transmitted to the display apparatus  12 . If an image different from an image to be displayed on the head mounted display  100  is displayed on the display apparatus  12 , if a user wearing the head mounted display  100  and a user viewing the display apparatus  12  execute a match game, for example, then the second image generation block  317  sets a viewpoint position and a sightline direction that are different from those with the first image generation block  316  and executes rendering of a virtual three-dimensional space, thereby generating an image of a game field. The second image generation block  317  adds game-related information and an image to be displayed on the display apparatus  12  to the generated game field image so as to generate a second image. The second image generated by the second image generation block  317  is transmitted to the display apparatus  12  through the wireless communication module  38  and the wired communication module  40 . 
     On the basis of a relative position between the input apparatus  6  and the head mounted display  100 , the first image generation block  316  can display an image of the input apparatus  6  for the first image. The user wearing the head mounted display  100  cannot view surrounding situations in the real world; however, displaying an image of the input apparatus  6  at a position in the first image where the input apparatus  6  would be visible unless the user wears the head mounted display  100  allows the user to have a feeling as if he or she were viewing a real world, thereby enhancing the reality of the first image and providing a deeper immersive sense to the user. 
     When the game control block  311  changes the positions of a subject of operation in a game field, the first image generation block  316  can change viewpoint position setting methods in accordance with the position of a game field. For example, the first image generation block  316  may set a viewpoint position at a predetermined position in the rear of a subject of operation in an area of a game field and makes the viewpoint position follow as the subject of operation moves; on another area, the first image generation block  316  may fix a viewpoint position at a predetermined position regardless of the change in the position of a subject of operation. Consequently, a game field image can be generated by appropriately setting a viewpoint position in accordance with game field positions, thereby providing a user interface of easy operation so as to enhance user convenience. 
     The first image generation block can generate a first game image for a first user who views the head mounted display  100  and the second image generation block can generate a second game image for a second user who views the display apparatus  12 . The first user is unable to view the second game image displayed on the display apparatus  12  and the second user is unable to view the first game image displayed on the head mounted display  100 , so that use of this game system allows the execution of a match game while hiding own information from the play mate. 
     The following describes the above-mentioned features by way of examples of various games. 
     Shooting Game: 
     Referring to  FIG.  7   , there is shown an example of the first game image that is displayed on the head mounted display.  FIG.  7    shows an image of a game in which targets are shot down with throwing knives thrown from the input apparatus displayed a first game image. In a game field where two or more targets  502  are arranged, the game control block  311  moves the arranged targets  502  in a predetermined manner. The first image generation block  316  sets a viewpoint position at a predetermined position in the game field and, on the basis of the attitude of the head mounted display, sets a sightline direction, thereby rendering the game field so as to generate the first game image. At this moment, on the basis of a relative position between the input apparatus  6  and the head mounted display  100 , the first image generation block  316  arranges the input apparatus  6  in the game field and displays an image  500  of the input apparatus  6  in the first image. The image  500  of the input apparatus  6  is generated on the basis of the real input apparatus  6  and displayed with a precision of a degree at which the input apparatus  6  is recognizable by the user to be a real one. When a change occurs in the position and attitude of the input apparatus  6 , the first image generation block  316  also changes the position and attitude of the image  500  of the input apparatus  6  in the first game image. Consequently, the reality of the image of the input apparatus  6  that is displayed in the first game image can be enhanced. 
     Referring to  FIG.  8   , there is shown an example of the first game image that is displayed on the head mounted display. When the user shakes his or her head horizontally or vertically to change the attitude of the head mounted display  100 , the first image generation block  316  changes the sightline direction in accordance with the attitude of the head mounted display  100 . When a target  502  enters a predetermined range  504  at the center of the first game image, the game control block  311  locks on this target  502  as a target and displays on the target  502  a  FIG.  506    indicative that the target  502  is locked on. Namely, when the user views the target  502  by directing his or her head in the direction of target  502  displayed in the first game image, the target  502  in the direction of a predetermined range from that direction is locked on. Thus, setting a character or an object in the direction in which the user is viewing as a subject of operation allows the determination or change of subjects of operation with ease without use of the input apparatus  6 , for example, thereby enhancing the user convenience. 
     Referring to  FIG.  9   , there is shown an example of the first game image that is displayed on the head mounted display. When the user executes a flick operation on the touch pad  79  of the input apparatus  6 , the first image generation block  316  displays a manner in which a throwing knife  508  is thrown from the position of the touch pad  79  in the image  500  of the input apparatus  6  displayed in the first game image in accordance with a moving distance of the flick operation. At this moment, a user&#39;s hand may be displayed in the first image or, so as to enhance the visibility of the throwing knife, the user&#39;s hand may be not displayed. Thus, changing the image  500  of the input apparatus  6  displayed in the first game image in accordance with instruction input entered in the input apparatus  6  allows the feedback of the instruction entered by the user in the first game image so as to indicate the reflection of the instruction in an easy-to-understand manner. Further, this setup gives a feeling to the user that a throwing knife comes out of the input apparatus  6  actually held by the user, so that the user can experience a unique feeling in which a real world and a virtual world melt together. 
     Referring to  FIG.  10   , there is shown an example of the first game image that is displayed on the head mounted display. When the moving distance of a flick operation done by the user on the touch pad  79  of the input apparatus  6  exceeds a predetermined value, the game control block  311  throws a throwing knife  508  in a direction determined on the basis of the attitude of the input apparatus  6  from a virtual position of the input apparatus  6  at a speed corresponding to the speed of the flick operation, in a game field. The first image generation block  316  generates a first game image indicative of a manner in which the throwing knife  508  is thrown. The game control block  311  computes a locus  509  of the throwing knife  508  on the basis of physical computation and moves the throwing knife  508  in accordance with the computed locus  509 . If the throwing knife  508  hits one of the targets  502 , the game control block  311  drops the hit target  502 . As described above, if a target is locked on, the game control block  311  does not move the throwing knife along the computed locus, but recalculates the locus so as to the throwing knife travels toward the target, thereby moving the throwing knife along the recalculated locus. In this case, the throwing knife hits the locked-on target, thereby dropping this target. 
     Racing Game: 
     Referring to  FIG.  11   , there is shown an example of the first game image that is displayed on the head mounted display. This diagram shows an image of a racing game in which players ride bicycles and runs along a predetermined course, thereby competing for the time required to reach a goal. The game control block  311  makes the bicycles run in accordance with the input entered through buttons and the like on the input apparatus  6  in a game field where a predetermined course is arranged and controls the travel direction of the bicycles in accordance with the attitude of the input apparatus  6 . In addition, the game control block  311  executes control such that, when the position of the head mounted display  100  gets lower, the air resistance to the body of the user pedaling the bicycle gets smaller, so that the speed of the bicycle is increased; conversely, when the position of the head mounted display  100  gets higher, the air resistance gets greater, so that the speed of the bicycle is decreased. In this game too, the image  500  of the input apparatus  6  is displayed in the first game image and the front image of the bicycle is displayed such that the image  500  of the input apparatus  6  comes to the center of a handle  510 . As the position and attitude of the input apparatus  6  change, the first image generation block  316  changes the position and attitude of the image  500  of the input apparatus  6  in the first game image and then changes the position and attitude of the front image of the bicycle. 
     In this racing game, the input apparatus  6  is regarded as the handle of the bicycle; however, if the position of the input apparatus  6  largely deviates from the initial position, the position of the handle gets to an unnatural position, thereby canceling the premise that the handle be operated as the input apparatus  6 . Therefore, if the position of the input apparatus  6  deviates from a predetermined range with the position of the input apparatus  6  at a predetermined timing used as standard before a race begins or during a race, the game control block  311  notifies the user of that fact by displaying thereof in the first game image, outputting sound, or vibrating the input apparatus  6 , for example, thereby prompting the user to return the position of the input apparatus  6  to the correct position. At this moment, the game control block  311  may stop accepting the instruction input associated with bicycle travel or stop the bicycle. By deleting the front image of the bicycle from the first game image or displaying a manner in which the input apparatus  6  is shifted from the center of the handle of the bicycle, the first image generation block  316  may notify the user that the input apparatus  6  is no more functioning as the handle of the bicycle. If the position of the input apparatus  6  deviates from the reference position by more than a first range, then the game control block  311  may notify the user thereof; if the position of the input apparatus  6  deviates from the reference position by more than the second range greater than the first range, then the game control block  311  may display a manner in which the input apparatus  6  gets out of the bicycle without accepting the instruction input from the input apparatus  6 . Consequently, the input apparatus  6  can be operated within a proper range, thereby preventing the deviation from the imaging range of the imaging apparatus  14  or the inability of displaying the image of the input apparatus  6  into the first game image. 
     Referring to  FIG.  12   , there is shown an example of the first game image that is displayed on the head mounted display. The first image generation block  316  displays current speed  512  of the bicycle at the position of the touch pad  79  of the image  500  of the input apparatus  6  displayed in the first game image. This setup allows displaying as if a display apparatus were arranged although there is no display apparatus arranged on the touch pad  79  of the real input apparatus  6 . In addition, this setup allows displaying of information to be presented to the user in the game, in a novel form. 
     Action Game: 
     Referring to  FIG.  13   , there is shown an example of the first game image that is displayed on the head mounted display. This diagram shows an image of a game in which a player&#39;s character is operated and moved inside a game field, thereby leading the player&#39;s character to a predetermined goal. In a game field where obstacles and undulations are arranged, the game control block  311  moves the player&#39;s character  516  in accordance with the input from the direction key or analog sticks or the like of the input apparatus  6  and makes the player&#39;s character  516  jump in accordance with the input from a button or the like. 
     In such an action game, depending on the position of a game field, different methods are applied to the setting of the viewpoint position of the camera used by the first image generation block  316  when generating the first game image. In the example of this diagram, the viewpoint position is set at a predetermined position in the rear and above the player&#39;s character  516  and the viewpoint position is moved as the player&#39;s character  516  moves. The sightline direction is changed in accordance with the attitude of the head mounted display  100 . Namely, an image is generated in which the user feels as if he or she were viewing the game field riding a vehicle following the player&#39;s character  516  from behind. 
     Referring to  FIG.  14   , there is shown an example of the first game image that is displayed on the head mounted display. In the example of this diagram, the viewpoint position is fixed to a predetermined position in a game field and only the sightline direction is changed in accordance with the attitude of the head mounted display  100 . Namely, an image is generated in which the user feels as if he or she were viewing the game field without moving after getting down from a vehicle. 
     For the data of a game field, data for specifying rules of determining a viewpoint position is set in addition to contour data such as geological features and the data of arranged characters and items. These pieces of data may be set for each area obtained by dividing the game field into two or more areas. Updating the position of the player&#39;s character in accordance with the instruction input by the user, the game control block  311  transmits the rules of determining the viewpoint position specified at the updated position to the first image generation block  316 . The first image generation block  316  determines the viewpoint position in accordance with the rules transmitted from the game control block  311 , thereby rendering the game field. For example, in the example shown in  FIG.  14   , the viewpoint position remains fixed while the player&#39;s character is inside the predetermined area; however, when the position of the player&#39;s character deviates from the predetermined area and enters another area, the first image generation block  316  determines the viewpoint position in accordance with the rules specified in the new area, thereby setting the viewpoint position at a predetermined position in the rear of the player&#39;s character, for example. 
     Consequently, a game producer can flexibly set how to suitably generate game images by appropriately setting a viewpoint position in accordance with the geological features of a game field, the types of arranged items, gimmicks, and characters, and the actions to be executed by a player&#39;s character. Further, since appropriate game images can be generated in match with the situations of a game field, user convenience is enhanced. 
     The rules of determining a viewpoint position may be dynamically set in accordance with situations of a game field. For example, in the case where the geological features of the game field change, an algorithm for determining rules from the geological features of the game field may be specified in advance, thereby first determining the rules from the geological features of the game field and then determining a viewpoint position in accordance with the determined rules. Consequently, an appropriate viewpoint position can be set in conformity with the situations of the game field, thereby enhancing user convenience. 
     Match Game 1: 
     Referring to  FIG.  15   , there is shown an example of the first game image that is displayed on the head mounted display. This diagram shows an image of a game in which a first user wearing the head mounted display  100  and a second user viewing the display apparatus  12  fight each other. In this match game, while throwing a bomb  522  to the second character  520  of the second user by the input in the input apparatus  6 , the first user moves the head mounted display  100  to move a first character, thereby avoiding a bomb  524  thrown by the second character  520 . While throwing the bomb  524  to the first character by the input in the input apparatus  6 , the second user enters the input in the input apparatus  6  to move the second character  520 , thereby avoiding the bomb  522  thrown by the first character. Two or more second users may participate in a match game; in this case, two or more second characters may attack the first character. 
     The first image generation block  316  sets a viewpoint position at a position of the first character in a game field and then sets the sightline direction in the direction to which the head mounted display  100  faces, thereby generating the first image. Therefore, in the example shown in this diagram, a game image of first-person viewpoint is displayed on the head mounted display  100 . The bomb  524  thrown by the second character  520  looks like it is flying to the user, so that a game high in reality can be provided. 
     The game control block  311  changes the position of the first character as the attitude of the head mounted display  100  changes. In addition, the game control block  311  throws the bomb  522  in the direction indicated by the first character in accordance with the instruction input to the input apparatus  6  and computes a locus by physical computation or the like, thereby moving the bomb  522 . If the bomb  522  thrown by the first character hits the second character  520 , then the physical strength value of the second character  520  is decreased by a predetermined value. The bomb  524  thrown by the second character  520  hits the first character, then the physical strength value of the first character is decreased by a predetermined value. If the physical strength of any one of the characters reaches zero, the game ends at that moment. 
     Referring to  FIG.  16   , there is shown an example of the second game image that is displayed on the display apparatus  12 . The second image generation block  317  fixes the viewpoint position and the sightline direction so as to allow the view over the entire game field and the displaying of a first character  526  and the second character  520  in the game image, thereby generating the second image. If there are a single second user and a single second character  520 , then the second image generation block  317  may set the viewpoint position at the position of the second character  520  or a predetermined position in the rear of the second character  520  to set the sightline direction in the moving direction of the second character  520 , thereby generating the second image; if there are two or more second users and two or more second characters  520 , then it is desirable for the second image generation block  317  to generate the second image fixed such that the entire game field can be viewed, thereby facilitating all second users to view the game image. 
     In accordance with the instruction input to the input apparatus  6 , the game control block  311  changes the position of the second character  520 . In addition, in accordance with the instruction input to the input apparatus  6 , the game control block  311  throws the bomb  524  in the direction indicated by the second character  520  and computes a locus by physical computation or the like, thereby moving the bomb. 
     As described above, in a game where the first user and the second user share the same virtual three-dimensional space and both the users interact with each other in this virtual three-dimensional space, game images with the same virtual three-dimensional space viewed from separate viewpoints can be provided to each of the users. 
     Referring to  FIG.  17   , there is shown an example of a first game image that is displayed on the head mounted display. In this diagram, the first game image is the first game image that is shown on the head mounted display  100  of the first user in the match game described above like the first game image shown in  FIG.  15   , a first character display area  530  being arranged for displaying the first character in the game field. The first game image shown in  FIG.  15    is generated from a first-person viewpoint, so that the first character is not displayed in the first image, making the first user be unable to see the first character, namely the avatar of the first user. Therefore, in the example of this diagram, the image of a first character  532  is displayed in the first character display area  530 . This setup allows the first user to play the game while looking at the first character  532 , thereby sharing the contents of the same game between the first user and the second user. 
     Further, in the first game image shown in this diagram, an imaging character  534  holding a camera  536  is displayed in the proximity of the first character display area  530 . Displaying, in the first game image, a manner in which the imaging character  534  is taking an image in the direction thereof by use of the camera  536  allows the first user to understand that an image of the first character that is the own avatar is being displayed in the first character display area  530 . 
     Referring to  FIG.  18   , there is shown an example of the second game image that is displayed on the display apparatus  12 . Like the second game image shown in  FIG.  16   , the second game image in this diagram is displayed on the display apparatus  12  that the second user views in the match game described above. In the first game image shown in  FIG.  17   , the imaging character  534  was displayed; however, since the imaging character  534  does not participate in the match game, the imaging character  534  is not displayed in the second game image shown in this diagram. 
     When the first user moves his or her head to the left side in order to ward off the bomb  524 , the game control block  311  receives information that the head mounted display  100  has moved to the left side and moves the first character  526  to the left side. At this moment, in the second game image generated by the second image generation block  317 , a manner in which the first character  526  moves to the right side is displayed. Further, when the first user tilts his or her head to the left side in order to ward off the bomb  524 , the game control block  311  receives information that the head mounted display  100  has tilted to the left side and tilts the head of the first character  526  to the left side. At this moment, in the second game image generated by the second image generation block  317 , a manner in which the head of the first character  526  tilts to the right side is displayed. 
     The first image generation block  316  arranges the first character display area  530  at a predetermined position of the game field and displays the image of the first character in the first character display area  530 . In addition, the first image generation block  316  displays the imaging character  534  having the camera  536  at a predetermined position of the game field. In the first character display area  530 , an image obtained by left-right reversing all or part of a second game image generated by the second image generation block  317  may be displayed. This setup allows a manner in which the position and attitude of the first character  532  changes with the movement of the first user to be displayed in the first game image. Further, since the first character display area  530  can be shown as if it were a mirror, the first user is able to fully become the first character  532 , thereby immersing in the game world. 
     Of the second game images generated by the second image generation block  317 , the first image generation block  316  may display an image of a predetermined area at a fixed position into the first character display area  530  or display an image of a predetermined area into the first character display area  530  by changing the position of the predetermined area with the movement of the first character  532  so as for the first character  532  to be displayed in the first character display area  530 . In the former case, the first character display area  530  can be shown as if it were a mirror; in the latter case, the imaging character  534  can be shown as if it pursued the first character  532  for taking an image. In the former case, the imaging character  534  may not be displayed in the first game image. In accordance with the position of the first character  532  and a game situation, the first image generation block  316  may enlarge or reduce part of the second game image and display a resultant image in the first character display area  530 . Further, in accordance with an instruction from the first user, it may be determined whether or not to display the image of the first character  532  in the first character display area  530 . 
     Match Game 2: 
     Referring to  FIG.  19   , there is shown an example of the first game image displayed on a head mounted display. This diagram shows an image of a game in which the first user wearing the head mounted display  100  and the second user viewing the display apparatus  12  play a match. In this match game, the first user manipulates a cat character and the second user manipulates a character of a mouse  540 . In the game field, a cheese  542  that is a favorite food of the mouse is arranged. The second user manipulates the mouse  540  by an input through the input apparatus  6  in order to get the cheese  542  while the cat is not watching. The first user manipulates the cat by moving the head mounted display  100  and changing the attitude of the head mounted display  100  in order to observe the mouse  540  not to get the cheese  542 . The first game image shown in this diagram is the first game image that is displayed before the game is started. The cheese  542  is put on a plate and the mouse  540  cannot get it yet. 
     The first image generation block  316  sets a viewpoint position at the position of the head of the cat in the game field and sets the line-of-sight direction in the direction in which the head mounted display  100  is directed, thereby generating the first image. Consequently, the first game image of first-person viewpoint is displayed on the head mounted display  100 . As the position and attitude of the head mounted display  100  change, the game control block  311  changes the a cat&#39;s position and a head direction and, at the same time, changes the viewpoint position and the line-of-sight direction for generating the first game image. 
     Referring to  FIG.  20   , there is shown an example of a second game image that is displayed on the display apparatus  12 . The second game image shown in this diagram is also a second game image that is displayed before a game is started. Before a game is started, the character of a cat  550  to be manipulated by the first user hides behind a curtain  552  and is indicated by dashed lines. When the first user moves his or her head forward, the game control block  311  opens the curtain  552  to move the cat  550  forward, displaying the cat  550  in solid lines. The game control block  311  sets the position of the head mounted display  100  for opening or closing the curtain with reference to the position of the head mounted display  100  at a predetermined timing before the game is started; when the head mounted display  100  is moved beyond the preset position, the curtain  552  is opened and, when the head mounted display  100  is moved short of the preset position, the curtain  552  is closed. 
     When the first user directs his or her face toward the mouse  540  and the eyes of the cat  550  meet the eyes of the mouse  540  with the curtain  552  being open, the game starts. Upon entering of the mouse  540  into a predetermined range in the center of the first game image, the game control block  311  determines that the eyes of the cat  550  have met with the eyes of the mouse  540 , thereby starting the game. While the first user is not looking in the direction of the mouse  540  because the first user is looking sideways, for examples, the game does not start. When the game starts, the game control block  311  displays a manner in which the cheeses  542  on the plate are scattered in the game field and accepts an instruction input for moving the cat  550  and the mouse  540 . 
     In the example shown in this diagram, the character of the cat  550  wears a pair of goggles  554  made after the external view of the head mounted display  100 . This setup allows easy visual recognition that the character of the cat  550  is a character to be manipulated by the first user wearing the head mounted display  100 . 
     Referring to  FIG.  21   , there is shown an example of the first game image that is displayed on the head mounted display. In the game field, there are arranged an obstacle such as a can  544  and an object such as a vegetable  546  in addition to the scattered cheeses  542 . The second user manipulates the mouse  540  to move it inside the game field and gets the cheese  542  by avoiding the obstacles. 
     Referring to  FIG.  22   , there is shown an example of the second game image that is displayed on the display apparatus  12 . When the first user moves the head mounted display  100  forward during a game, the game control block  311  opens the curtain  552  and moves the cat  550  forward. When the cat  550  finds out the mouse  540  while the curtain  552  is open, the game control block  311  may give damages to the found mouse  540 . In this case, the game control block  311  gives damages to the mouse upon entering by this mouse  540  in a predetermined range in the center of the first game image. The game control block  311  manages a physical power value of the mouse  540  and may reduce the physical power value of the found mouse  540  by a predetermined value, thereby making game-over on the second user manipulating the mouse  540  whose physical power value has reached zero. Further, the cheese  542  obtained by the found mouse  540  may be returned to the game field again. Still further, the found mouse  540  may be forcibly moved to a den  548 . When the cat  550  finds out the mouse  540 , the game control block  311  may make the mouse  540  immobile. In this case, the game control block  311  prohibits the movement of the mouse  540  while the mouse  540  is inside a predetermined range in the center of the first game image. The game control block  311  may allow the cat  550  to throw an obstacle such as the can  544  to the mouse  540 . In this case, the game control block  311  throws the can  544  from the position of the cat  550  in accordance with an instruction input by the first user through the input apparatus  6 . When the can  544  hits the mouse  540 , the physical power value of that mouse  540  may be reduced by a predetermined value. 
     Turning his or her head up and down and left and right, the first user searches for the mouse  540  inside the game field. When the mouse  540  is displayed on the head mounted display  100 , that mouse  540  may be supposed to have been found out by the cat  550 ; alternatively, as described above, when the mouse  540  enters a center predetermined range, that mouse  540  may be supposed to have been found out by the cat  550 . In the latter case, the first user himself or herself finds out the mouse  540  when the mouse  540  is displayed on the head mounted display  100 ; in order to suppose that the cat  550  has found out that mouse  540 , it is required for the mouse  540  to enter the center predetermined range by directing the face in the direction of that mouse  540 . 
     While the curtain  552  is open and the cat  550  comes out, the second user moves the mouse  540  behind a vegetable  546  or inside the den  548  so as to prevent the detection by the cat  550 . When the cat  550  recedes and the curtain  552  is shut, the second user moves the mouse  540  again so as to get the cheese  542 . If the mouse  540  can get all cheeses  542  arranged in the game field within a time limit, the second user wins the game; otherwise, the first user wins the game. 
     When the first user looks down, a floor is displayed in the first game image; when the user moves the head mounted display  100  up and down in this state, the viewpoint position is moved up and down, thereby enlarging and reducing the image of the floor. Here, when the viewpoint position approaches the floor at or beyond a predetermined position, the first image generation block  316  displays the image of the floor in a blurred manner. This setup allows the expression of a manner in which too close approach to the floor causes an out-of-focus state, thereby preventing the difficulty in seeing the floor or an object put thereon due to too much enlargement. In addition, this setup allows the indication to the first user a relation between the position of a floor in a game world and the position of the head mounted display  100  in the real world, thereby preventing the movement of the viewpoint position downward beyond the floor when the first user further moves the position of the head mounted display  100 . 
     Referring to  FIG.  23   , there is shown an example of a second game image that is displayed on the display apparatus  12 . In this match game, the mouse  540  cannot take the cheese  542  while the cat  550  comes forward from the curtain  552 , so that, if the cat  550  remains coming out in front of the curtain  552 , the game does not progress. Therefore, if a first state in which the cat comes forward from the curtain  552  and is able to find out the mouse  540  continues for not shorter than a predetermined period of time, the first state is forcibly switched to a second state in which the cat  550  cannot find out the mouse  540 . In the example shown in this diagram, the game control block  311  counts a first elapsed time starting from the opening of the curtain  552  and, when the first elapsed time reaches a first predetermined time, closes the goggles  554  worn by the cat  550 , thereby preventing the cat  550  from finding out the mouse  540 . At this moment, as shown in  FIG.  24   , in the first game image displayed on the head mounted display  100 , a totally dark image or an image low in transmittance is displayed, thereby indicating to the first user that the goggles  554  has been closed. When the first user moves the head mounted display  100  backward and the curtain  552  is closed, the game control block  311  returns the first elapsed time to zero. 
     An arrangement may also be provided in which the cat  550  cannot come out forward by opening the curtain  552  immediately after the curtain  552  has been closed. In this case, the game control block  311  counts a second elapsed time starting from the closing of the curtain  552  and does not open the curtain  552  if the head mounted display  100  is moved forward until the second elapsed time reaches a second predetermined time. The game control block  311  may make the second predetermined time in the case where the curtain  552  is closed after the closing of the goggle  554  when the first elapsed time has reached the first predetermined time longer than the second predetermined time in the case where the curtain  552  is closed by moving the head mounted display  100  backward by the first user before the first elapsed time reaches the first predetermined time. This setup allows to give a penalty that, if the curtain  552  is left open until the first elapsed time reaches the first predetermined time, the curtain  552  cannot be opened in a longer period of time, so that the first user is made consider to close the curtain  552  before the first elapsed time reaches the first predetermined time, thereby providing a game in which tactics are enjoyed between the first user with the timing of opening and closing the curtain  552  and the second user with the timing of moving the mouse  540 . 
     In the example shown in this diagram, the cat  550  is disabled to find out the mouse  540  by closing the goggles  554  worn by the cat  550 ; in another example, a manner may be displayed in which, when the first elapsed time reaches the first predetermined time, a character such as a dog appears and blocks the field of vision of the cat  550  or the cat  550  is forcibly returned to the backward and the curtain  552  is closed. 
     As described above, in switching event states between the first state in which the cat  550  can find out the mouse  540  and the second state in which the cat  550  cannot find out the mouse  540  in accordance with the position of the head mounted display  100 , if the first state continues for not shorter than a predetermined time, then, regardless of the position of the head mounted display  100 , changing the states to the second state allows the provision of a game property that also has a temporal element. 
     Referring to  FIG.  25   , there is shown a flowchart indicative of a procedure of a display control method practiced as one embodiment of the present invention. The HMD information acquisition block  314  acquires the positional information of the head mounted display  100  obtained from a taken image of the head mounted display  100  (S 100 ) and the input apparatus information acquisition block  315  acquires the positional information of the input apparatus  6  acquired from a taken image of the input apparatus  6  (S 102 ). The instruction input acquisition block  312  acquires the information associated with the instruction input from the input apparatus  6  (S 104 ). The game control block  311  controls the game on the basis of the position of the head mounted display  100 , the position of the input apparatus  6 , and instruction input from the input apparatus  6  (S 106 ). The first image generation block  316  generates an image of the game to be controlled by the game control block  311 , the image being to be displayed on the head mounted display  100  (S 108 ). At this moment, the first image generation block  316  displays the image of the input apparatus  6  in the generated image on the basis of a relative position between the head mounted display  100  and the input apparatus  6  (S 110 ). The generated image is transmitted to the head mounted display  100  (S 112 ). 
     Referring to  FIG.  26   , there is shown a flowchart indicative of a procedure of the display control method practiced as one embodiment of the present invention. The instruction input acquisition block  312  acquires the information associated with an instruction input from the input apparatus  6  (S 120 ). The game control block  311  updates the position subject to operation on the basis of an input instruction (S 122 ) and acquires rules for determining a viewpoint position specified at the updated position (S 124 ). The first image generation block  316  determines the viewpoint position in accordance with the rules for determining a viewpoint position (S 126 ). The HMD information acquisition block  314  acquires the information associated with the attitude of the head mounted display  100  from the head mounted display  100  (S 128 ). The first image generation block  316  generates an image to be displayed on the head mounted display  100  by use of the determined viewpoint position and the sightline direction determined on the basis of the attitude of the head mounted display  100  (S 130 ). The generated image is transmitted to the head mounted display  100  (S 132 ). 
     Referring to  FIG.  27   , there is shown a flowchart indicative of a procedure of the display control method practiced as one embodiment of the present invention. The instruction input acquisition block  312  acquires the information associated with an instruction input from the input apparatus  6  of the first user (S 140 ) and, at the same time, acquires the information associated with an instruction input from the input apparatus  6  of the second user (S 142 ). The HMD information acquisition block  314  acquires the information associated with position and attitude of the head mounted display  100  (S 144 ) and the input apparatus information acquisition block  315  acquires the information associated with the position and attitude of the input apparatus  6  (S 146 ). The game control block  311  controls the game on the basis of the input instruction, the position and attitude of the head mounted display  100 , and the position and attitude of the input apparatus  6  (S 148 ). The first image generation block  316  generates the first image to be displayed on the head mounted display  100  by use of the viewpoint position and sightline direction of the first user (S 150 ), the generated first image being transmitted to the head mounted display  100  (S 152 ). The second image generation block  317  generates the second image to be displayed on the display apparatus  12  by use of the viewpoint position and sightline direction of the second user (S 154 ), the generated second image being transmitted to the display apparatus  12  (S 156 ). 
     While preferred embodiments of the present invention have been described using specific terms, such description is for illustrative purpose only, and it is to be understood by those skilled in the art that changes and variations may be made without departing from the spirit or scope of the following claims. 
     In the examples described above, an image for monocular vision is displayed on the display apparatus  90  of the head mounted display  100 ; it is also practicable to display an image for binocular vision. 
     In the examples described above, the head mounted display  100  is used in a game system; the technologies described in the embodiments of the present invention are also applicable to display content other than games. 
     REFERENCE SIGNS LIST 
       10  Game apparatus,  90  Display apparatus,  100  Head mounted display,  311  Game control block,  312  Instruction input acquisition block,  313  Taken image analysis block,  314  HMD information acquisition block,  315  Input apparatus information acquisition block,  316  First image generation block,  317  Second image generation block 
     INDUSTRIAL APPLICABILITY 
     The present invention is applicable to a display control apparatus configured to control displaying onto a head mounted display.