JP7762413B2 - Computer program, and image display method and image display system using the same - Google Patents

Description

The present invention relates to a computer program for causing hologram sheet-like changes in the representation of an image of a card-like object.

Attempts have been made to render card-like objects displayed on a game screen with hologram-sheet-like color changes, similar to those seen on physical cards in the real world. For example, Patent Document 1 discloses a technology in which multiple sheets with white areas that simulate light reflection are prepared in advance so that their display modes are differentiated, and a sheet is appropriately selected based on the detected tilt of the user's terminal device. The selected sheet is then overlaid on an image of a character or the like, thereby rendering a color change that corresponds to the tilt of the terminal device. Patent Document 2 discloses a technology in which the color of a color-changing image overlaid on the background of a card-like object is changed according to a trigonometric function whose parameters include the orientation (tilt) of the terminal device and the display position within the image, thereby changing the rendering of the background of the card to resemble a hologram sheet.

Patent No. 5661835 Patent No. 6723895

Conventional technology only produces certain changes in the representation of background areas, etc., in response to changes in the device's orientation. Meanwhile, the appearance of the hologram sheet portion of a real card changes not only depending on the direction from which the user views it, but also on the amount of light hitting it. Conventional technology does not necessarily adequately represent changes that occur in response to the amount of light hitting it, and there is room for improvement.

The present invention therefore aims to provide a computer program or the like that is suitable for changing the representation of at least a partial area of a card-like object into a hologram sheet-like representation.

A computer program according to one aspect of the present invention is a computer program for causing a specified computer to execute a process for displaying an image of a card-like object on a user device. The computer program is configured to cause the computer to execute the following steps: detect a reference direction required for determining color information of a target area included in the object based on output from a sensor on the user device; and determine the color information of the target area in association with the reference direction so that the representation of the target area changes in the form of a hologram sheet as the detected reference direction changes. In the step of determining the color information, the color information is determined by changing at least one of the incident direction of light incident on the target area and the line of sight direction of the user of the user device relative to the target area in association with the reference direction, while the incident direction and the line of sight direction are referenced.

A computer program according to another aspect of the present invention is a computer program that causes a specified computer to execute a process for displaying an image of a card-like object on a user device. The computer is configured to cause the computer to execute the following steps: detect a reference direction required for determining color information of a target area included in the object based on output from a sensor on the user device; and determine the color information of the target area in association with the reference direction so that the representation of the target area changes in the form of a hologram sheet as the detected reference direction changes. In the step of determining the color information, the incident direction of light incident on the target area is changed in association with the reference direction, and the color information is determined by referring to the incident direction.

An image display method according to one aspect of the present invention is an image display method that causes a predetermined computer to execute processing to display an image of a card-like object on a user device, and causes the computer to execute the steps of detecting the reference direction based on the output of a sensor on the user device and determining color information for the target area in accordance with the computer program of the above aspect.

An image display system according to one aspect of the present invention is an image display system that causes a predetermined computer to execute a process for displaying an image of a card-like object on a user device, and causes the computer to execute the steps of detecting the reference direction based on the output of a sensor on the user device and determining color information for the target area in accordance with the computer program of the above aspect.

1 is a diagram showing an example of a game system including a game machine to which a computer program according to an embodiment of the present invention is applied; FIG. 10 is a diagram showing an example of cards displayed on a game screen. 3A and 3B are diagrams showing an example of a change in the background image of the card in FIG. 2 . FIG. 10 is a diagram showing an example of the relationship between a card and the line of sight and the incident direction of ambient light in a virtual three-dimensional space. FIG. 10 is a diagram showing an example of changing the incident direction in response to a change in the attitude of the game machine. FIG. 10 is a diagram showing an example of changing the line of sight direction in response to a change in the attitude of the game console. 10A and 10B are diagrams showing an example of a case where the incident direction and the line of sight direction are changed in response to a change in the attitude of the game machine. FIG. 10 is a diagram showing an example of changing the orientation of a card in a virtual three-dimensional space in response to a change in the attitude of the gaming machine. FIG. 10 is a diagram illustrating an example of a method for expressing a background image in the form of a hologram sheet. FIG. 2 is a diagram showing an example of the configuration of a control system of a game machine. 11 is a flowchart showing an example of a process executed by the control unit of FIG. 10 to draw a background image. FIG. 10 is a diagram showing an example of detecting the incident direction of ambient light in the real world using a camera in a game console. FIG. 10 is a diagram showing an example of detecting the gaze direction of a user in the real world using a camera on a game console. 10A and 10B are diagrams showing an example of bending and deforming a card in a virtual three-dimensional space in response to a user operation.

Figure 1 shows an example of a game system according to one embodiment of the present invention. The game system 1 in Figure 1 is an example of an image display system, configured as a network system including a game machine 2 and a server 3 that can communicate with the game machine 2 via a predetermined network NT. The game machine 2 is an example of a user device to which the present invention is applied. The game machine 2 functions as a terminal device for the server 3, and allows users to play a predetermined game by communicating with the server 3 or with other game machines 2 via the server 3. However, the game machine 2 may also be a standalone game machine that does not communicate with the server 3. In that case, the game machine 2 alone constitutes the game system.

The game console 2 includes a main unit 4 and a pair of controllers 5A and 5B. The main unit 4 executes various processes for providing a game, and the controllers 5A and 5B function as an example of input means that detects user operations and provides operation information to the main unit 4. A monitor 6 is integrally provided on the main unit 4 and serves as an example of output means or display means. Instead of, or in addition to, the monitor 6, a monitor separate from the game console 2 may be used to display the game screen. Each of the controllers 5A and 5B is provided integrally or detachably with the main unit 4, and functions as an example of input means for the game console 2 by being connected to the main unit 4 via a wired or wireless connection. Hereinafter, the controllers 5A and 5B will be collectively referred to as "controllers 5," and the two will sometimes be referred to separately as the first controller 5A and the second controller 5B.

Each controller 5 is provided with an operation unit 7, such as a push button switch 7a and directional indicator keys 7b, that can be operated by the user. Each controller 5 outputs a signal corresponding to the operation state of the operation unit 7 to the main unit 4. Each controller 5 incorporates a gyro sensor 8, an example of a sensor that outputs a signal corresponding to the attitude (tilt) of the controller 5. The gyro sensor 8 outputs a signal corresponding to rotational movement (e.g., angular acceleration) around three orthogonal axes (Gx-axis, Gy-axis, and Gz-axis) established with respect to the game console 2, as a signal indicating the attitude of the controller 5. The directions of the detection axes Gx, Gy, and Gz may be determined appropriately as long as they can detect changes in attitude in real space. As an example, the normal direction to the screen of the monitor 6 may be set as the Gz-axis, and the directions of the short and long sides of the screen may be set as the Gx-axis and Gy-axis, respectively. In this case, from the perspective of a user facing the game console 2, rotation around the Gx-axis corresponds to roll, rotation around the Gy-axis corresponds to pitch, and rotation around the Gz-axis corresponds to yaw.

The game machine 2 provides the user with a card-based game. Figure 2 shows an example of a game screen displayed on the monitor 6 in this game. The game screen 10 in Figure 2 is an example of a screen displayed when the user is allowed to view cards such as characters and items that they have acquired, like an illustrated book. The game screen 10 includes a list display section 12 in which icon images 11 symbolizing card characters, etc. are displayed in a matrix, and a card display section 15 in which a card image 14 of a character, etc. corresponding to an icon image 11 selected with a cursor 13 is displayed. In the list display section 12, the display manner of the icon images 11 may be differentiated depending on whether or not the user has acquired a character, such as by highlighting icon images 11 of characters, etc. that the user has already acquired, while graying out icon images 11 of characters, etc. that the user has not yet acquired. Alternatively, only icon images 11 corresponding to characters, etc. that the user has acquired may be displayed.

As shown enlarged in FIG. 3, the card image 14 further includes a main image 16 showing the appearance of the character, a frame image 17 decorating the card, and a background image 18. The frame image 17 further includes text and other information 17a indicating the name of the character, the rank of the card, etc. The background image 18 enhances the decorativeness and dramatic effect of the card image 14. In this embodiment, the card image 14 is rendered so that the appearance of the background image 18 changes like a hologram sheet in association with changes in posture detected by the gyro sensor 8. Therefore, the background image 18 corresponds to an example of a target area. Due to limitations in the representation of the drawing, FIG. 3(a) illustrates an example in which the background image 18 is rendered relatively bright, and FIG. 3(b) illustrates an example in which the background image 18 is rendered relatively dark. The change in the background image 18 is not limited to two stages, as shown in FIGS. 3(a) and 3(b), but occurs continuously or steplessly in response to changes in the posture of the controller 5.

Changes in the background image 18 take into account the direction from which the user views the image (the line of sight) and the direction from which light strikes the image (the incident direction), just as with a physical hologram sheet. In other words, the background image 18 is rendered by regarding at least one of the line of sight and the incident direction as having changed in relation to the orientation of the controller 5. Because each of the two controllers 5A and 5B has a built-in gyro sensor 8, the output of the gyro sensor 8 of either controller 5, for example, the first controller 5A, may be used as the reference for rendering the background image 18. When the controllers 5 are integrated with or attached to the main unit 4, the output of the gyro sensor 8 of either controller 5 indicates the orientation of the game console 2. When the controllers 5 are separated from the main unit 4, the output signal of the gyro sensor 8 of either controller 5 may be used as the output signal representative of the orientation of the game console 2. In other words, even if the attitude of the main body 4 remains unchanged, a change in the attitude of one of the controllers 5 is considered to be a change in the attitude of the game console 2. If the main body 4 has a built-in gyro sensor, the representation of the background image 18 may be changed in association with the output signal of that gyro sensor. In either case, the gyro sensor that detects changes in direction that serve as a reference for changing the representation of the background image 18 may be determined appropriately. In the following explanation, the output of the gyro sensor 8 of one of the controllers 5 is considered to be an output that represents a change in the attitude of the game console 2.

Next, with reference to Figures 4 to 8, an example of processing for changing the representation of the background image 18 into a hologram sheet will be described. In the processing for drawing the card image 14, the area of the background image 18 and other areas (in the example of Figure 3, the areas of the main image 16 and frame image 17) are identified separately. The background image 18 is drawn using a predetermined shader program for image processing, while other areas are drawn using a predetermined texture image as is. As an example, the drawing of the main image 16, etc. may be processed so that the color information of the texture image of the shader program is used directly in the shader program. Alternatively, the main image 16 may be drawn in a separate process on a layer different from the drawing of the background image 18, and then overlaid on the background image 18. The processing for drawing the background image 18 will be mainly described below.

As shown in Figure 4, assume that a card 20, which serves as an object corresponding to a card image 14, and a virtual camera 21 that photographs the card 20 are placed within a predetermined virtual three-dimensional space VS. A world coordinate system (Wx-Wy-Wz) is set as a three-axis Cartesian coordinate system in the virtual three-dimensional space VS, and an object coordinate system (Ox-Oy-Oz) is set as a three-axis Cartesian coordinate system for the card 20. The origin of each coordinate system and the direction of each axis may be determined as appropriate. In Figure 4, as an example, the object coordinate system is set with the Z axis normal to the card 20, and the X and Y axes in the directions of the short and long sides of the card 20, respectively.

The virtual camera 21 can be set in any position and orientation. However, the card image 14 shown in Figures 2 and 3 is always displayed facing the user, regardless of the attitude of the game machine 2, as an image with a constant shape and size. Therefore, in the example of Figure 4, the virtual camera 21 is set to photograph the card 20 from a fixed angle of view from the normal direction. In other words, the photographing direction C of the card 20 by the virtual camera 21 coincides with the normal direction of the card 20. As an example, the photographing optical axis of the virtual camera 21 is set to pass through the center of the card 20. The photographing optical axis does not necessarily have to be set to pass through the center of the card 20, as long as it is possible to include the entire surface of the card 20 in the photographing range.

In the virtual three-dimensional space VS, the incident direction L of ambient light relative to the card 20 is also set. For example, assuming that light is irradiated toward the card 20 from a specific light source 22, the direction of that light is set as the incident direction L. Ambient light is light that strikes the card 20 and may be either natural light or illumination light. The light source 22 in Figure 4 is depicted to indicate the direction of ambient light; it is not necessary for the light source 22 to be placed as a virtual object within the virtual three-dimensional space VS. For example, if the ambient light is parallel light such as sunlight, the light source 22 may be considered to be located at infinity in a specific direction. In this case, it is sufficient to set the incident direction L of the ambient light; it is not necessary to place the light source 22 itself in the virtual three-dimensional space VS. This also applies to the light sources 22 shown in Figures 5 to 8 and 14 described below. On the other hand, a lighting device that irradiates parallel light may be set as the light source 22 at a specific position within the virtual three-dimensional space VS. If ambient light is set to spread uniformly, such as illumination light from a point light source, the position of the light source 22 must be determined. When setting the ambient light, various characteristics such as intensity (brightness), color temperature, and wavelength distribution may be set in addition to the direction. These characteristics may be reflected appropriately in the rendering of the background image 18.

Next, referring to Figure 5, an example of the relationship between the attitude of the game machine 2 and the line of sight and incident direction relative to the card 20 will be described. Figure 5 shows an example of changing the incident direction L of ambient light in response to changes in the attitude of the game machine 2. In this example, it is assumed that the light source 22 changes direction in virtual three-dimensional space in response to changes in the attitude of the game machine 2, and that the light source 22 moves from the position indicated by the imaginary line to the position indicated by the solid line, as shown by arrow A. The card 20 is stationary. On the game screen 10 of Figure 2, the card image 14 is always displayed facing forward, i.e., with the card 20 observed from the front, so the virtual camera 21, like the card 20, is also stationary. In other words, the relative positional relationship between the card 20 and the virtual camera 21 is unchanged.

In addition, in Figure 5, the user is assumed to observe the card 20 from the same direction as the shooting direction C of the virtual camera 21. For example, assume that the user's eye 23 is located at the position of the virtual camera 21 (position of the imaging plane). Therefore, the user's line of sight E with respect to the card 20 coincides with the shooting direction C of the virtual camera 21, and the line of sight E with respect to the card 20 remains constant regardless of changes in the attitude of the game device 2. Therefore, the relationship between the card 20 and the incident direction L changes depending on the attitude of the game device 2.

The shader program for rendering the background image 18 determines the color information for each pixel of the background image 18 using the user's line of sight E and the direction of incident ambient light L as parameters. In the example of Figure 5, the line of sight E remains constant relative to the card 20, while the direction of incident ambient light L changes relative to the card 20. Therefore, while the monitor 6 displays the card image 14 as if the card 20 were observed from the front, it is possible to change the representation of the background image 18 in the same way as if the way the light hits the card 20 changes. The appearance of a real hologram sheet varies in a variety of ways depending on the direction from which it is observed and the direction from which the light hits it; even if the direction from which it is observed remains the same, the appearance changes if the direction from which the light hits it changes. In the example of Figure 5, such changes can be reproduced.

In the example of Figure 5, the light source 22, i.e., the incident direction L, changes in response to changes in the attitude of the game machine 2. However, the incident direction L relative to the card 20 can be changed by moving the card 20 and virtual camera 21 together in response to changes in the attitude of the game machine 2 while keeping the light source 22 stationary. In other words, whether the light source 22 is moved while the card 20 and virtual camera 21 are kept stationary, or the card 20 and virtual camera 21 are moved together in a unified manner while keeping the light source 22 stationary, the relative positional relationship between the card 20 and virtual camera 21 and the light source 22 changes, and the incident direction L relative to the card 20 changes. Note that in the example of Figure 5, even if the card 20 and virtual camera 21 are rotated relative to the light source 22 around an axis normal to the card 20, the incident direction L changes, and the appearance of the background image 18 changes. For example, if the gyro axis Gz in FIG. 1 is the normal direction of the monitor 6 and yaw motion around the gyro axis Gz corresponds to rotational motion around the normal direction of the card 20 in virtual three-dimensional space, even if the gyro sensor 8 detects only yaw motion around the gyro axis Gz and not roll motion or pitch motion around the gyro axes Gx and Gy, the incident direction L relative to the card 20 will change, and the appearance of the background image 18 will change accordingly. A method for causing a hologram sheet-like change in the background image 18 depending on the line of sight E and the incident direction L may be similar to processing using an existing shader program, and an example of this method will be described later. The shooting direction C and the line of sight E strictly differ depending on the position of the card 20. However, if the difference is negligible, the shooting direction C and the line of sight E may be considered to be constant throughout the entire card 20. However, the shooting direction C and the line of sight E may also be changed depending on the position of the card 20.

Figure 6 shows an example in which the line of sight direction E changes in response to changes in the attitude of the game machine 2. In the example of Figure 6, the card 20 remains stationary regardless of changes in the attitude of the game machine 2, and the virtual camera 21 also remains stationary. Furthermore, while in the example of Figure 5 the light source 22 moves within the virtual three-dimensional space, in the example of Figure 6 the light source 22 also remains stationary, and the incident direction L of the ambient light relative to the card 20 remains constant.

In the example of Figure 6, on the other hand, it is assumed that the user's eyes 23 move within virtual three-dimensional space as the attitude of the game console 2 changes. That is, a card image 14 captured by the virtual camera 21 from the normal direction of the card 20 is displayed on the monitor 6, but the direction from which the user views the card image 14 displayed on the monitor 6 changes depending on the attitude of the game console 2. For example, it is assumed that the eyes 23 move from the imaginary line position to the solid line position as indicated by arrow A. Therefore, the line of sight E that should be considered when rendering the background image 18 does not coincide with the shooting direction C captured by the virtual camera 21, but rather changes relative to the card 20. This change in line of sight E is reflected in the background image 18. In this example, it is possible to reproduce the change in appearance of a real hologram sheet when the direction of light incidence is constant and the viewing direction changes. Note that in the example of Figure 6, even if the position of the eyes 23 remains unchanged and the card 20, virtual camera 21, and light source 22 move together as the attitude of the game console 2 changes, it is possible to change the line of sight E relative to the card 20.

Figure 7 shows an example in which both the line of sight E and the incident direction L relative to the card 20 change as the attitude of the game machine 2 changes. In this example, the card 20 and virtual camera 21 remain stationary regardless of changes in the attitude of the game machine 2. Meanwhile, it is assumed that the light source 22 and the user's eye 23 move within the virtual three-dimensional space in response to changes in the attitude of the game machine 2. For example, assume that the light source 22 and the eye 23 move from the imaginary line position to the solid line position as indicated by arrow A. In this case, the relationship between the line of sight E and the incident direction L remains constant regardless of changes in the attitude of the game machine 2, but both the line of sight E and the incident direction L change together with respect to the card 20. Therefore, changes in both the line of sight E and the incident direction L can be reflected in the representation of the background image 18.

Figure 8 shows yet another example of the relationship between the attitude of the game machine 2 and the line of sight and incident direction relative to the card 20. In the example of Figure 8, the card 20 changes its orientation in the virtual three-dimensional space in response to changes in the attitude of the game machine 2, and the orientation of the card 20 as seen from the virtual camera 21 also changes accordingly. As an example, an example of the card 20 before the change is shown by imaginary lines, and an example of the card 20 after the orientation has changed as indicated by arrow A is shown by solid lines. Meanwhile, in the example of Figure 8, the virtual camera 21 and light source 22 are assumed to be positioned in a fixed position and in a fixed orientation in the virtual three-dimensional space, regardless of the attitude of the game machine 2. The user's eyes 23 are also assumed to be located at the position of the virtual camera 21. Therefore, if the orientation of the card 20 changes, both the line of sight E relative to the card 20 and the incident direction L of the ambient light change accordingly.

In the example of Figure 8, it is not possible to display a card image 14 in which the card 20 is always viewed facing forward, as is the case with the game screen 10 of Figure 2. When the attitude of the game device 2 is changed, an image is displayed in which the card 20 changes orientation accordingly. Even in this case, because the line of sight direction E and incident direction L relative to the card 20 change, it is possible to change the representation of the background image 18 in the form of a hologram sheet in accordance with these changes.

Next, referring to Figure 9, an example of a method for changing the representation of the background image 18 in the form of a hologram sheet in association with the line of sight and incident direction will be described. Figure 9 shows an example of information used to render the background image 18. As an example, a bump map 30 and color information 31 corresponding to the bump map 30 are used to render the background image 18.

The bump map 30 is information that specifies the normal direction at each pixel of the background image 18. For example, the normal direction at any pixel Pij on the background image 18 is specified as a normal vector Nij (Xij, Yij, Zij) using values in an appropriate coordinate system. The normal vector may be defined as a unit vector, for example, and the normal direction may be expressed synonymously with the normal vector N below. The normal vector N may be expressed according to the object coordinate system, for example, but may also be defined in other coordinate systems that are uniquely or inherently determined for the card 20. While Figure 9 conveniently illustrates the differences in normal direction specified in the bump map 30 as a periodic shading pattern, the bump map 30 may be set as appropriate, as long as a normal vector appropriate for generating a hologram sheet-like change in the background image 18 is set for each pixel. As an example, the normal vectors of each pixel in the bump map 30 are differentiated by assuming that the surface of the card 20 has minute irregularities similar to those of a hologram sheet. In other words, the bump map 30 artificially imparts minute irregularities to the card 20 similar to those of an actual hologram sheet.

Color information 31 is information for specifying the initial value of color information to be assigned to each pixel of background image 18. Color information 31 includes, as an example, a specular map 32, a diffuse map 33, and an emission map 34. Specular map 32 is information that specifies, on a pixel-by-pixel basis, color information for imparting a specular reflection effect to background image 18, diffuse map 33 is information that specifies color information for imparting a diffuse reflection effect to background image 18, and emission map 34 is information that specifies color information for imparting an emission effect to background image 18. For example, in specular map 32, the RGB values Rij, Gij, and Bij to be assigned to any pixel Pij are specified as color information Cij for that pixel Pij. Color information may be specified in the other maps 33 and 4 in a similar manner.

As is clear from the relationship between the normal vector Nij at pixel Pij and the line of sight E and incident direction L shown in Figure 9, even if the line of sight E and incident direction L are constant relative to the card 20, the line of sight E and incident direction L, when based on the direction of the normal vector N of each pixel, differ for each pixel. The shader that renders the background image 18 corrects the color information specified in the color information 31 for each pixel according to a calculation rule (function) that incorporates the normal vector N, line of sight E, and incident direction L for each pixel as parameters, and determines the final color information for each pixel based on the calculation results. Through this processing, the color information for each pixel of the background image 18 varies in various ways depending on the normal vector N, line of sight E, and incident direction L, relative to the initial value specified in the color information 31. This allows the background image 18 to be displayed in a hologram sheet-like manner. Furthermore, at least one of the line of sight E and incident direction L changes depending on the orientation of the game console 2, as illustrated above. Therefore, when the attitude of the game console 2 is changed, the representation of the background image 18 also changes, as if the line of sight or the direction of incident light had changed. This makes it possible to change the representation of the background image 18 in the same way as with an actual hologram sheet.

Next, an example of the control system of the game machine 2 and its processing will be described, focusing on the portion related to drawing the card image 14. Figure 10 shows an example of the schematic configuration of the control system of the game machine 2. The game machine 2 comprises a control unit 50 and a storage unit 51. The control unit 50 is configured as a computer including a CPU and GPU as microprocessors, and internal storage devices required for their operation, such as cache memory, RAM, and frame memory. The storage unit 51 is a storage device that uses non-volatile storage media such as magnetic storage media and flash memory, and functions as an external storage device for the control unit 50. The operation units 7, gyro sensors 8, and monitor 6 of the controllers 5A and 5B are connected to the control unit 50. The control unit 50 may further include a sound source control unit, a network control unit, etc.

The storage unit 51 stores a game program Pg, game data Dg, and play data Dp for providing a game. The game program Pg is an application program that causes the control unit 50 to execute various arithmetic processes and operational controls required for the game, in cooperation with an operating system that controls the basic operations of the control unit 50, or an image rendering program pre-installed in the control unit 50 to cause the GPU to execute image rendering processes. The game program Pg further includes a game processing program Pg1 and an image processing program Pg2. The game processing program Pg1 is a computer program that causes the control unit 50 to execute various processes required to progress the game provided by the game machine 2 in accordance with the user's selections. The image processing program Pg2 is a computer program that draws images corresponding to the game's progress and displays them on the monitor 6. The shader program for drawing the card images 14 described above also constitutes part of the image processing program Pg2.

The game data Dg is data that should be referenced as appropriate when controlling the game. The game data Dg may include various data necessary to render the card image 14, such as the bump map 30 and color information 31 shown in FIG. 9, as well as various texture data such as the main image 16 and frame image 17 that should be expressed in the card image 14. The play data Dp is data for each user associated with the user's game play on the game machine 2. For example, information such as the user's play history and status may be included in the play data Dp. The game program Pg and game data Dg are distributed from the server 3 to the game machine 2 as appropriate and stored in the storage unit 51. However, these data may also be provided via a storage medium readable by the game machine 2.

When the control unit 50 reads the game program Pg, the control unit 50 is provided with a game processing unit 52 and an image processing unit 53. The game processing unit 52 is a logical device realized by the control unit 50's CPU and the game processing program Pg1 working together, and the image processing unit 53 is a logical device realized by the control unit 50's GPU and the image processing program Pg2 working together. The game processing unit 52 controls the game in accordance with the game processing program Pg1. The image processing unit 53 performs processing to draw images according to the progress of the game played by the game processing unit 52 and display them on the monitor 6. Note that if a computer program for causing the control unit 50's GPU to execute general-purpose image processing for drawing images of three-dimensional objects, such as a general-purpose shader program, is pre-installed in the game console 2, the image processing program Pg2 may be configured to implement the image processing unit 53 in conjunction with that general-purpose computer program.

11 shows an example of a processing procedure executed by the control unit 50 of the game machine 2 to draw the background image 18. This example is an example of processing in which the incident direction L is changed in response to changes in the attitude of the game machine 2, as shown in FIG. 5, and the background image 18 is drawn while the line of sight direction E remains unchanged relative to the card 20. When the game being played on the game machine 2 is in a state in which a card image 14 is being displayed, the processing of FIG. 11 is initiated to draw the background image 18. When the processing of FIG. 11 is initiated, the game processing unit 52 first detects and sets the current attitude of the game machine 2 based on the output of the gyro sensor 8 (step S11). The attitude of the game machine 2 may be detected as the difference between the output of the gyro sensor 8 in the initial attitude, with the state in which the game machine 2 is in a specific attitude being defined as the initial attitude, and the current output of the gyro sensor 8. The initial attitude may be the attitude of the game machine 2 at the time when display of the card image 14 begins, for example, but is not limited thereto. Alternatively, the initial attitude may be the attitude of the game machine 2 at the time when the game is started or when the game transitions to a specific mode. The orientation detected in step S11 indicates the orientation of the game console 2, and this orientation corresponds to an example of the reference direction required to determine the color information of the background image 18.

Next, the game processing unit 52 sets the card 20 in the virtual three-dimensional space (step S12). As an example, the game processing unit 52 places the card 20 as a polygon model at a predetermined position within the virtual three-dimensional space. Furthermore, the game processing unit 52 sets textures such as a bump map 30 and color information 31 prepared for rendering the background image 18 (step S13), and then sets a shader for rendering the background image 18 (step S14). In this case, the shader may be a programmable shader programmed for rendering the background image 18, and may be provided to the control unit 50 as part of the image processing program Pg2. After completing the processing of step S14, the game processing unit 52 passes the information set in steps S11 to S14 to the image processing unit 53 as information for rendering the background image 18, and starts rendering the background image 18 (step S15). Thereafter, the game processing unit 52 completes the processing of FIG. 11.

Meanwhile, the image processing unit 53 initiates the processing of FIG. 11 in response to the processing of step S15. Based on information provided by the game processing unit 52, the image processing unit 53 first sequentially executes vertex shader processing in step S21, pixel shader processing in step S22, and post-effect processing in step S23 to draw the background image 18. It then adds other images from the game screen 10 to draw a final image and displays it on the monitor 6. The vertex shader processing converts the coordinates of each vertex of the polygons constituting the card 20 in the virtual three-dimensional space into a two-dimensional screen coordinate system. The pixel shader processing determines the color information of each pixel in the screen coordinate system. The post-effect processing further corrects the color information of each pixel in accordance with predetermined conditions. These processes may be performed in the same manner as a typical shader program. However, the processing of the background image 18 includes processing based on the normal direction of each pixel, the viewing direction, and the incident direction of ambient light, and the incident direction reflects changes in the attitude of the game console 2. An example of these processes is shown in FIG. 11, but the main points are explained below.

First, in the vertex shader processing of step S21, the incident direction of ambient light relative to the card 20 is determined according to the orientation of the game console 2 set in step S11, in other words, the reference orientation detected based on the output of the gyro sensor 8. However, the quantitative (angular) correspondence between changes in the reference orientation and changes in the incident orientation does not necessarily need to be set one-to-one. For example, if the rotation angle detected by the gyro sensor 8 around a specific gyro axis is X°, the angle by which the incident orientation changes around the same axis is doubled to 2X°. The amount of change in the incident orientation may be increased by a fixed ratio relative to the amount of change in the reference orientation. In this case, the degree of change in the background image 18 relative to changes in the orientation of the game console 2 is increased, making it possible to more strongly impress the user with the changes in the hologram sheet. However, the amount of change in the incident orientation may also be reduced by a fixed ratio relative to the amount of change in the reference orientation. Such a reduction relationship may be set when, for example, a one-to-one relationship would result in an unnaturally large change in the background image 18 relative to changes in the orientation of the game console 2.

The vertex shader process also places the polygon model of card 20 set in step S12 in virtual three-dimensional space and converts the vertex coordinates of each polygon in virtual three-dimensional space into coordinate values in a two-dimensional screen coordinate system corresponding to the imaging plane of the virtual camera. In the example of Figure 5, virtual camera 21 is positioned to photograph card 20 from the normal direction, and the positional relationship between card 20 and virtual camera 21 remains unchanged. Therefore, regardless of the position and orientation of card 20 in virtual three-dimensional space, the vertex coordinates of each polygon in the screen coordinate system after coordinate conversion remain constant.

As described above, if the ambient light incident on the card 20 is parallel light, the incident direction can be uniquely determined from the reference direction determined based on the output of the gyro sensor 8, without having to place a light source 22 in virtual three-dimensional space to determine the incident direction. Furthermore, the correspondence between the card 20 and the virtual camera 21 is also constant. Therefore, it is possible to omit the vertex shader processing and directly determine the vertex coordinates of each polygon in the screen coordinate system, thereby determining the coordinates in the bump map 30 and color information 31. However, shader programs are generally configured to place a polygon model in virtual three-dimensional space, perform vertex shader processing to convert the three-dimensional coordinates of each polygon vertex into two-dimensional coordinates in the screen coordinate system, and then use the results of this processing to perform pixel shader processing. Therefore, by first placing the polygon model of the card 20 in virtual three-dimensional space and then employing a procedure to determine the vertex coordinates in the screen coordinate system, existing programmable shaders can be applied, which is convenient. As shown in Figure 8, when changing the positional relationship between the card 20 and the virtual camera 21 in the virtual three-dimensional space, coordinate transformation processing using vertex shader processing is required.

In the pixel shader processing of step S22, as an example, the final color of each pixel on the background image 18 is determined through specular processing, diffuse processing, and emission processing. In this processing, calculations are performed using the normal vector N of each pixel specified in the bump map 30, the incident direction L of ambient light on the card 20, and the line of sight E as parameters. Note that the incident direction L and line of sight E are expressed as unit vectors having those directions and incorporated into the calculations. In the following, the incident direction L and line of sight E will both refer to vectors.

Specular processing calculates the effect of specular reflection on the card 20 on the color information of each pixel in the background image 18. For example, the incident direction L and the line of sight E are added together to obtain a half vector H. Next, the strength of specular reflection at each pixel is calculated by raising a predetermined multiplier a to the inner product (N·H) of each pixel's normal vector N and half vector H. Furthermore, specular Sp, which is color information that takes into account the specular (specular reflection) of each pixel, is calculated by multiplying the specular color and intensity. For example, the specular color may be the color information of each pixel specified by the specular map 32. In this process, the smaller the deviation between the line of sight E and the incident direction L, and the smaller the deviation between these directions and the normal vector N, the greater the strength of specular reflection. As a result, the specular Sp shifts toward white, or in other words, becomes brighter. If the direction in which card 20 is observed from the front is considered to be the normal direction of card 20 as a whole, the smaller the deviation of the incident direction L and viewing direction E from that normal direction, the brighter the specular reflection of background image 18 will be, while the intensity of the specular reflection will vary depending on the deviation of the incident direction L and viewing direction E from the normal vector N of each pixel.

Diffuse processing is a process that calculates the effect that diffuse light generated by reflection on the card 20 has on the color information of each pixel in the background image 18. For example, the intensity of diffuse light at each pixel is calculated by taking the dot product of the incident direction L and the normal vector N of each pixel. Next, diffuse Df, which is color information that takes into account the diffusion (diffuse reflection) of each pixel, is calculated by multiplying the diffuse color and intensity. As an example, the diffuse color may be the color information of each pixel specified by the diffuse map 33. In this process, the smaller the deviation between the incident direction L and the normal vector N, the greater the intensity of diffuse reflection, and as a result, the diffuse Df changes toward white, or in other words, becomes brighter. In other words, the intensity of diffuse reflection varies depending on the deviation between the incident direction L and the normal vector N of each pixel.

Emission processing is a process for further correcting the color information of the background image 18. When appropriate color information correction is required, such as uniformly increasing the brightness of at least a portion of the background image 18 relative to the color information obtained by specular processing and diffuse processing, the emission color specified in the emission map 34 is set as the amount of correction as emission Em. For example, when specular processing and diffuse processing are used to reproduce a situation in which the card 20 is backlit, that is, where ambient light is shining from behind the card 20, reflection from the card 20 is almost nonexistent, and the background image 18 may be rendered uniformly as black or a dark color close to black. In such cases, emission Em may be set to increase overall brightness. Other processes may be applied, such as correcting color information so that the brightness of the background image 18 does not exceed an upper or lower limit. However, emission Em may be omitted.

In pixel shader processing, the specular Sp, diffuse Df, and emission Em calculated as described above are added together to calculate the final color information for each pixel. The resulting color information is obtained by modifying the color information for each pixel of the background image 18 using parameters such as specular reflection and diffuse reflection, which correspond to the relationship between the incident direction L and the line of sight E relative to the normal vector N at each pixel. Therefore, by modifying the normal vector N of each pixel specified in the bump map 30 in accordance with the minute irregularities of an actual hologram sheet, it is possible to express a color distribution similar to that of a hologram sheet. Furthermore, by changing the incident direction L in response to changes in the attitude of the game console 2, it is possible to express the way the background image 18 changes depending on the direction of light, in a manner similar to that of a hologram sheet.

The post-effect processing in step S23 is performed to add further visual effects to the final color of each pixel of the background image 18 determined by the pixel shader processing. As an example, pixels that meet certain conditions, such as pixels with a luminance equal to or greater than a predetermined brightness, may be extracted, and the color information of the extracted pixels may be corrected to create a blurring effect. However, the post-effect processing may also be omitted as appropriate.

In the above, the processing of FIG. 11 is applied to the example of FIG. 5, i.e., when the incident direction L is changed in response to a change in the attitude of the game machine 2. However, the processing of FIG. 11 may also be applied to the examples of FIG. 6, FIG. 7, or FIG. 8. That is, the example of FIG. 6 can be realized by changing the line of sight E in response to a change in the attitude of the game machine 2, and the example of FIG. 7 can be realized by changing both the line of sight E and the incident direction L. Furthermore, the example of FIG. 8 can be realized by moving the card 20 and virtual camera 21 within virtual three-dimensional space in response to a change in the attitude of the game machine 2.

The present invention is not limited to the above-described embodiment and may be implemented in various modified or altered forms. For example, when displaying an image of the card 20 photographed while always facing forward as the card image 14 as described above, it is not necessarily necessary to place the card 20 as a polygon model in a virtual three-dimensional space and convert the three-dimensional vertex coordinates of each polygon into the screen coordinate system of the virtual camera 21. Furthermore, the coordinates of each position of the card 20 projected onto the screen coordinate system can be identified without such coordinate conversion, and the correspondence with the coordinates of the bump map 30 and color information 31 is also uniquely determined. Furthermore, the correspondence between changes in the attitude of the game machine 2 and the incident direction L or the line of sight E can also be identified without necessarily constructing a scene in a virtual three-dimensional space. Therefore, it is also possible to place the card 20 in a two-dimensional screen coordinate system and perform the processing from step S22 onwards.

On the other hand, the processing in Figure 11 shows only the processing required to draw the background image 18 portion of the card image 14, and other images such as the main image 16 may be drawn using any appropriate method. When performing processing such as shading at least a portion of the main image 16 or frame image 17, an appropriate shader program may be prepared, and the processing may be performed in any appropriate order before or after the processing in Figure 11. Furthermore, when a portion of the main image 16, etc. is to be transformed into a hologram sheet like the background image 18, the processing in Figure 11 may also be applied to that portion. Even when the main image 16, frame image 17, and background image 18 are drawn using separate processes, the order of processing does not matter as long as a Z-buffer is used, and it is not necessary to process the images in the background first.

The processing content of the image processing unit 53 shown in Figure 11 is one example, and may be modified as appropriate as long as at least one of the incident direction L and the line of sight direction E is changed in accordance with a change in the attitude of the game device 2, and the change results in a hologram sheet-like change in the representation of the background image 18.

In the process of Figure 11, color information was determined by taking into account both the incident direction L and the line of sight direction E as parameters in the pixel shader process. However, as long as changes in the incident direction L are reflected in the representation of the background image 18, a simpler process may be applied in which the line of sight direction E is not considered as a parameter and the color information of each pixel is determined from the relationship between the incident direction L and the normal vector N. Even in this case, it is possible to reflect changes in the relationship between the normal vector N and the incident direction L in the representation of the background image 18, thereby representing changes in the background image 18 corresponding to changes in the direction in which light strikes. In other words, the reference direction required to determine the color information of the background image 18 may be detected based on the output of a sensor in the game console 2, and the incident direction L may be changed in relation to the detected reference direction, while the incident direction may be referenced as a parameter to determine the color information of each pixel so that the representation of the background image 18 changes like a hologram sheet.

In the above embodiment, the reference direction was detected using the output of the gyro sensor 8, and at least one of the incident direction L and the line of sight direction E was changed in response to changes in the reference direction. However, the sensor used to detect the reference direction is not limited to the example using the gyro sensor 8. Any sensor that can output a signal containing directional information can be used appropriately to detect the reference direction. Furthermore, the reference direction is not limited to the example in which it is set in association with the attitude of the game console 2. The reference direction is a direction that changes so as to change the representation of the background image 18, and can serve as a reference for identifying the incident direction L and the line of sight direction E, and does not necessarily have to be a direction that represents the attitude of the game console 2.

For example, as shown in FIG. 12, a camera 60 provided on the game machine 2 may be used to capture an image of the external environment surrounding the user, and the incident direction Lr of ambient light from a light source (including the sun) 61 in the real world may be detected from the obtained image, and the incident direction L relative to the card 20 may be determined using this as a reference direction. In this case, the camera 60 functions as an example of a sensor for detecting the reference direction. If the direction of ambient light in the real world is detected as the reference direction, changes in this direction can be reflected in changes in the incident direction L relative to the card 20. This makes it possible to change the appearance of the background image 18 in accordance with changes in the direction of ambient light around the game machine 2.

Detection of the real incident direction Lr is not limited to the camera 60, and any device that can obtain a signal correlated with the incident direction Lr will do. For example, if a brightness sensor detects the brightness of the real world around the game console 2, the incident direction Lr in the real world can be determined using changes in brightness as a clue. Multiple brightness sensors may be provided on the game console 2 so that they generate output differences according to the incident direction Lr, and the incident direction Lr can be detected based on the outputs of these brightness sensors. For example, if multiple brightness sensors are arranged so that they are each sensitive to a different direction, the incident direction Lr can be determined using the difference in brightness detected by each sensor as a clue. Note that the light source 61 is shown in Figure 12 for convenience's sake. The light source 61 does not necessarily need to be included in the shooting range PA of the camera 60.

Regarding the gaze direction E, as shown in FIG. 13, the position of the user's real eyes 62 may be determined from the image captured by the camera 60, and the user's real gaze direction Er may be detected from the determination result. This may then be used as the reference direction to determine the gaze direction E relative to the card 20. In this case, the camera 60 also functions as an example of a sensor used to detect the reference direction. The method of determining the gaze direction E relative to the card 20 based on the real gaze direction Er is applicable when the gaze direction E relative to the card 20 is changed relative to the card 20, as shown in FIG. 6. In this case, the real gaze direction Er can be reflected in the gaze direction E relative to the card 20. Furthermore, the real incident direction Lr captured by the camera 60 may also be detected as the reference direction, and the incident direction L and gaze direction E relative to the card 20 may be changed in relation to changes in the real incident direction Lr and gaze direction Er. This method is suitable for use when both the incident direction L and gaze direction E are changed in response to changes in the attitude of the game console 2, as in the example of FIG. 7. The incident direction L and gaze direction E can be reflected in the real-world incident direction Lr and gaze direction Er. The position of the user's actual eyes 62 can be determined using known methods.

While the above embodiment assumes that the card 20 is a flat object, the card 20 may be bent or deformed in response to the orientation of the controller 5. For example, in the game console 2 of FIG. 1, if the controllers 5A and 5B are detachable from the main body 4, the controllers 5A and 5B may assume different orientations. Therefore, for example, if the left first controller 5A is tilted leftward and the right second controller 5B is tilted rightward, this may be considered a bending operation of the card 20, and the left and right sides of the card 20 may be bent or deformed as shown in FIG. 14. In this case, by changing the normal vector N specified in the bump map 30 according to the degree of bending of the card 20, the incident direction L and the line of sight direction E can be relatively changed according to the bending of the card 20, and the appearance of the background image 18 can be changed accordingly. Note that while FIG. 14 illustrates an example in which the left and right ends of the card 20 are bent or deformed downward, the left and right ends of the card 20 may also be displaced upward if the controllers 5A and 5B are tilted in the opposite direction. Furthermore, when the controllers 5A and 5B are tilted forward or backward, respectively, it is possible to bend and deform the top and bottom ends of the card 20.

In the above embodiment, the representation of the background image 18 of the card image 14 is changed to a hologram sheet-like representation, but the target area to which the hologram sheet-like representation is applied according to the present invention is not limited to the background image 18. Any appropriate area of a card-like object may be set as the target area. Card-like objects are not limited to cards used in games. The present invention is applicable to applications in which at least a portion of various card-like objects is used as the target area and the representation thereof is changed to a hologram sheet-like representation.

The user device in the present invention is not limited to a game console, but may be any device operated by a user, such as a smartphone, tablet, or mobile PC. The present invention may also involve having a computer different from the user device execute processing and displaying an image corresponding to the processing results on the user device. For example, the user device may function as a remote input/output terminal device for another computer, such as a server or a remotely accessed computer, and the other computer may execute processing for drawing a card-shaped object and display the processing results on the user device.

Various aspects of the present invention derived from the above-described embodiments and variations are described below. In the following description, corresponding components shown in the accompanying drawings are noted in parentheses to facilitate understanding of each aspect of the present invention, but this does not mean that the present invention is limited to the illustrated forms.

A computer program according to one aspect of the present invention is a computer program (Pg) for causing a predetermined computer (50) to execute a process for displaying an image (14) of a card-like object (20) on a user device (2). The computer program is configured to cause the computer to execute the following steps: a step (S11) of detecting a reference direction (e.g., a direction indicating the orientation of the game console 2) required for determining color information of a target area included in the object based on output from a sensor (8; 60) of the user device; and steps (S21-S23) of determining the color information of the target area in association with the reference direction so that the representation of the target area changes in the form of a hologram sheet as the detected reference direction changes. In the step of determining the color information, the color information is determined by referring to the incident direction (L) of light incident on the target area and the line of sight direction (E) of the user of the user device relative to the target area, while changing at least one of the incident direction and the line of sight direction in association with the reference direction.

According to the above aspect, by referring to the incident direction and viewing direction when determining the color information of the target area, the direction from which light strikes the object and the direction from which the object is being observed can be reflected in the representation of the target area. Furthermore, by changing at least one of the incident direction and viewing direction in association with changes in the reference direction detected based on the output of the sensor in the user device, the representation of the target area can be varied in a variety of ways depending on the direction from which light strikes and the direction from which it is observed, just like a real hologram sheet.

In the above aspect, in the step of determining the color information, the incident direction may be changed according to the reference direction while the line of sight direction is kept constant to determine the color information (see FIG. 5 for an example). Alternatively, in the step of determining the color information, the line of sight direction may be changed according to the reference direction while the incident direction is kept constant to determine the color information (see FIG. 6 for an example). Furthermore, in the step of determining the color information, the color information may be determined while changing each of the line of sight direction and the incident direction according to the reference direction (see FIG. 7 for an example). In either case, it is possible to change the representation of the target area in the form of a hologram sheet by changing either the incident direction or the line of sight direction of light with respect to the target area of the object, or both, in association with changes in the reference direction detected using a sensor in the user device.

In the above aspect, the step of determining the color information may involve determining the normal direction of each pixel based on information in a bump map (30) that describes the normal direction (N) of each pixel when the target area is defined as a collection of multiple pixels, and determining the color information for each pixel by changing the color information depending on the relationship between the determined normal direction and the incident direction and the line of sight. In this way, by varying the normal direction of each pixel using the bump map information, it is possible to impart pseudo-unevenness to the target area and appropriately change the color information depending on the relationship between the normal direction and the light incident direction and line of sight.

A computer program according to another aspect of the present invention is a computer program (Pg) that causes a predetermined computer (50) to execute a process for displaying an image (14) of a card-like object (20) on a user device (2). The computer program is configured to cause the computer to execute the following steps: a step (S11) of detecting a reference direction (e.g., a direction indicating the attitude of the game console 2) required for determining color information of a target area included in the object based on the output of a sensor (8; 60) of the user device; and steps (S21-S23) of determining the color information of the target area in association with the reference direction so that the representation of the target area changes in the form of a hologram sheet as the detected reference direction changes. In the step of determining the color information, the incident direction (L) of light incident on the target area is changed in association with the reference direction, and the color information is determined by referring to the incident direction.

According to the above aspect, by referring to the incident direction when determining the color information of the target area, the direction from which light is hitting the object can be reflected in the representation of the target area. Furthermore, by changing the incident direction in association with changes in the reference direction detected based on the output of the sensor in the user device, the representation of the target area can be varied in a variety of ways depending on the direction from which light hits, just like a real hologram sheet.

In each of the above aspects, the object may be a card to be displayed in a game played on the user device. In this case, the target area may be at least a part of the background of the card. By changing the representation of at least a part of the card used in the game, and even at least a part of the card's background, to a hologram sheet, the decorativeness and presentation of the card can be enhanced, increasing the user's desire to own or acquire it, and ultimately increasing the enjoyment of the game.

In each of the above aspects, the sensor may output a signal corresponding to the posture of the user device. This makes it possible to change the representation of the target area of the object in the form of a hologram sheet in response to changes in the posture of the user device.

Note that a computer program according to one aspect of the present invention may be provided in a state stored on a storage medium. By using this storage medium, for example, the computer program according to the present invention can be installed on a computer and executed, thereby enabling the system of the present invention to be realized using the computer. The storage medium storing the computer program may be a non-transitory storage medium such as a CD-ROM.

The present invention may be configured as an image display method that causes a predetermined computer (50) to execute a process to display an image (14) of a card-like object (20) on a user device (2), and may be configured as an image display method that causes the computer to execute a step (S11) of detecting the reference direction based on the output of a sensor (8) of the user device and steps (S21-S23) of determining color information of the target area in accordance with the computer program (Pg) of the above-mentioned aspect. The present invention may also be configured as an image display system (1) that causes a predetermined computer (50) to execute a process to display an image (14) of a card-like object (20) on a user device (2), and may be configured as an image display system that causes the computer to execute a step (S11) of detecting the reference direction based on the output of a sensor (8) of the user device and steps (S21-S23) of determining color information of the target area in accordance with the computer program (Pg) of the above-mentioned aspect. These image display methods and systems make it possible to change the representation of at least a partial area of a card-like object to a hologram sheet in accordance with the computer program of the above aspect.

1. Game system (image display system)
2. Game console (user device)
8 Gyro sensor 14 Card image 18 Background image (target area)
20 Cards (Objects)
30 Bump map 50 Control unit 60 Camera E View direction L Incident direction N Normal vector (normal direction)

Claims (11)

A computer program for causing a predetermined computer to execute a process of displaying an image of a card-like object on a user device,
detecting a reference direction necessary for determining color information of a target region included in the object based on an output of a sensor of the user device;
determining color information of the target area in relation to the reference direction such that the representation of the target area changes on the hologram sheet as the detected reference direction changes;
In the step of determining the color information, a computer program is provided which determines the color information by referring to an incident direction and a line-of-sight direction , while changing at least one of the incident direction, which is virtually set as the direction of light incident on the target area, and the line-of-sight direction, which is virtually set as the direction in which a user of the user device observes the target area, in relation to the reference direction. The computer program of claim 1, wherein in the step of determining the color information, the incident direction is changed according to the reference direction while the line of sight direction is kept constant to determine the color information. The computer program of claim 1, wherein in the step of determining the color information, the line of sight direction is changed according to the reference direction while the incident direction is kept constant to determine the color information. The computer program of claim 1, wherein in the step of determining the color information, the color information is determined while changing each of the incident direction and the line of sight direction according to the reference direction. A computer program according to any one of claims 1 to 4, wherein the step of determining the color information involves determining the normal direction of each pixel based on bump map information describing the normal direction of each pixel when the target area is defined as a collection of multiple pixels, and determining the color information of each pixel so that the color information changes depending on the relationship between the determined normal direction and the incident direction and the line of sight direction. A computer program that causes a predetermined computer to execute a process of displaying an image of a card-like object on a user device,
detecting a reference direction necessary for determining color information of a target region included in the object based on an output of a sensor of the user device;
determining color information of the target area in relation to the reference direction such that the representation of the target area changes on the hologram sheet as the detected reference direction changes;
A computer program, in which in the step of determining the color information, an incident direction that is virtually set as the direction of light incident on the target area is changed in relation to the reference direction, and the color information is determined by referring to the incident direction. The computer program described in any one of claims 1 to 6, wherein the object is a card to be displayed in a game played on the user device. The computer program of claim 7, wherein the target area is at least a portion of the background of the card. The computer program described in any one of claims 1 to 8, wherein the sensor outputs a signal corresponding to the posture of the user device. An image display method for causing a predetermined computer to execute a process for displaying an image of a card-like object on a user device, comprising:
An image display method that causes a computer to execute the steps of: detecting the reference direction based on the output of a sensor of the user device; and determining color information of the target area in accordance with the computer program of any one of claims 1 to 9. An image display system that causes a predetermined computer to execute a process of displaying an image of a card-like object on a user device,
An image display system that causes a computer to execute the steps of detecting the reference direction based on the output of a sensor of the user device and determining color information of the target area in accordance with the computer program of any one of claims 1 to 9.