JP6530453B2 - Game program and game system - Google Patents

Description

  The present invention relates to a game program and a game system for realizing a game for displaying an image of a virtual space on a head mounted display (hereinafter, HMD).

  BACKGROUND In recent years, games (hereinafter, VR compatible games) in which a user wearing an HMD can experience virtual reality (hereinafter, VR) have been realized. In the VR compatible game, the virtual space photographed by a pair of virtual cameras is displayed on the screen of the HMD as a pair of virtual two-dimensional images having parallax so that the user can stereoscopically view a three-dimensional virtual space.

  By the way, conventionally, in the game field, it is often used to display a graphical user interface (hereinafter, GUI) such as a menu or the like, character conversation, character status, etc. as information to be presented to the user on part of the game screen. To be done. Such user presentation information is often drawn in the foreground of the game screen in a game that displays a single virtual two-dimensional image. However, in the VR compatible game, there is a problem that it is difficult for the user to focus when the information presented to the user is drawn in the foreground. For this reason, in a VR compatible game, an object having a plane may be arranged in a virtual space, and user presentation information may be drawn on the plane.

  For example, in Patent Document 1, an object (for example, an object of a cup) to which a menu item is assigned is arranged in a virtual space, and a menu (for example, "enter", "drink") above the object in the virtual space. , "Move", is disclosed a game for arranging a display body displayed.

JP, 2017-58971, A

  Although the method of arranging the GUI above the object is shown in the above-mentioned Patent Document 1, the method of arranging the GUI is based on only the positional relationship with the virtual camera, for example, in front of the virtual camera A possible method is to arrange at a position separated by a predetermined distance. However, if the GUI arranged in the virtual space hides an object nearby, there is a possibility that the user may have difficulty grasping the state of the virtual space. Such a situation applies not only to the GUI but also to drawing text such as character conversations.

  Therefore, the present invention provides a game program and a game system capable of realizing a VR compatible game in which the user can easily grasp the state of the virtual space from an image obtained by drawing a drawing target element such as a GUI arranged in the virtual space. The purpose is

  In order to solve the above problem, a game program according to the present invention is a game program to be executed by a computer including an HMD that displays the virtual space photographed by a pair of virtual cameras as a pair of virtual two-dimensional images having parallax. A virtual space generation means for generating the virtual space in which objects are arranged; a camera arrangement means for arranging the pair of virtual cameras in the virtual space; and a pair of virtual cameras in the virtual space Planar arrangement means for arranging a planar element for drawing a drawing target element at a predetermined position opposite to each other, and calculating the distance to the object for each partial area when the planar element is divided into a plurality of partial areas Distance calculation means, for the partial region in which the distance is smaller than a set value, the portion Transparency determining means for determining the transparency of the partial element corresponding to the area to be higher as the distance is shorter, and drawing means for drawing the element to be drawn on the plane element based on the determined transparency, Act as

  According to the above-described game program, the user can easily grasp the situation of the object near the rendering target element because the transparency is increased as the portion closer to the object is closer to the object in the portion where the distance to the object in the rendering target element is smaller . Furthermore, even when the plane element is disposed at the position where the object intersects the object, it is possible to set the transparency so that the element to be drawn becomes transparent at the intersection with the object. Therefore, the visibility of the user is improved.

  The partial area is obtained by dividing the planar element in units of pixels of each image captured by the pair of virtual cameras, and the distance calculating unit is configured to calculate the partial area of the planar element from the virtual camera. By subtracting the second depth value of the partial area from the first depth value of the corresponding area of the object ahead of the line of sight when the partial area is viewed, from each of the partial areas to the corresponding area of the object The distance of may be calculated. Thereby, the distance between the partial area of the plane element divided in pixel units and the corresponding portion of the object is calculated using the depth value of each pixel acquired by the Z buffer method known as the hidden surface removal method. The processing load involved in the calculation can be reduced.

  The drawing target element is, for example, a GUI.

  Further, a game system according to the present invention includes a program storage unit storing the above-described game program, and a computer that executes a program stored in the program storage unit.

  According to the present invention, there is provided a game program and a game system capable of realizing a VR compatible game in which the user can easily grasp the state of the virtual space from an image obtained by drawing a drawing target element such as a GUI arranged in the virtual space. can do.

It is a block diagram showing the hardware constitutions of the game system concerning one embodiment. It is a block diagram which shows the functional structure of the game device shown in FIG. FIG. 2 is a plan view of a pair of virtual cameras arranged in a virtual space. It is a schematic diagram of the virtual two-dimensional image image | photographed with one virtual camera of a pair of virtual cameras shown in FIG. It is a top view of a pair of virtual cameras in a position different from the position shown in FIG. It is a schematic diagram of the virtual two-dimensional image image | photographed with one virtual camera of a pair of virtual cameras shown in FIG. It is a flowchart which shows the flow of GUI element drawing processing. It is an example of the graph which shows the relationship of the distance and transparency which were calculated by the distance calculation means.

  Hereinafter, a game program and a game system according to an embodiment of the present invention will be described with reference to the drawings.

[Hardware configuration]
FIG. 1 is a block diagram showing the hardware configuration of the game system 1. The game system 1 includes a game device 2 and a server device 3 which are computers. The game devices 2 can communicate with each other between the other game devices 2 and the server device 3 via a communication network NW such as the Internet or a LAN. The game apparatus 2 comprises a CPU 10 for controlling the operation thereof. The CPU 10 has a disk drive 12, a memory card slot 13, a storage unit (program storage unit) HDD 14 and ROM 15, and a RAM 16 via a bus 11. It is connected.

  The disk drive 12 can be loaded with a disk-type recording medium 30 such as a DVD-ROM. A game program 30a and game data 30b according to the present embodiment are recorded on the disc type recording medium 30. The game data 30 b includes various data necessary for the progress of the game, such as data necessary for forming a virtual space, and sound data reproduced in the game. In addition, a card type recording medium 31 can be loaded into the memory card slot 13, and save data indicating a play status such as progress of a game can be recorded according to an instruction from the CPU 10.

  The HDD 14 is a large-capacity recording medium built in the game apparatus 2 and records the game program 30a and the game data 30b read from the disk type recording medium 30, and further save data and the like. The ROM 15 is a semiconductor memory such as a mask ROM or a PROM, and stores an activation program for activating the game apparatus 2 and a program for controlling the operation when the disc type recording medium 30 is loaded. The RAM 16 is composed of a DRAM, an SRAM, etc., and reads a game program 30a to be executed by the CPU 10 and game data 30b required for the execution from the disk type recording medium 30 or the HDD 14 according to the play status of the game. Temporarily record at.

  The CPU 10 further includes an interface 17 for HMD, an interface 18 for light detection apparatus, a graphic processing unit 19, an audio synthesis unit 20, an audio interface 21, a wireless communication control unit 22, and a network interface 23 via the bus 11. It is connected. The HMD 40, the light detection device 46, and the headphones 47 are connected to the HMD interface 17, the light detection device interface 18, and the audio interface 21, respectively.

  The HMD 40 can be worn on the head of the user. The HMD 40 includes a pair of display units 41 (41a and 41b), an acceleration sensor 42, a gyro sensor 43, a light emitting unit 44, and a control unit 45. By mounting the HMD 40 on the head of the user, the display unit 41a for the left eye and the display unit 41b for the right eye are respectively disposed in front of the left eye and the right eye of the user.

  The acceleration sensor 42 and the gyro sensor 43 constitute a motion detection system that detects the motion of the user's head. The acceleration sensor 42 detects, for example, the orientation of the HMD 40 with respect to the direction of gravity, that is, the tilt of the head of the user. The gyro sensor 43 detects, for example, the angular velocity of the HMD 40, that is, the speed at which the user tilts or rotates the head. Motion information obtained from the acceleration sensor 42 and the gyro sensor 43 is sent to the graphic processing unit 19 and the audio synthesis unit 20 via the HMD interface 17.

  The light emitting unit 44 of the HMD 40, together with the light detection device 46, constitutes a position detection system that detects the position of the head of the user. In the present embodiment, the light emitting units 44 are, for example, a plurality of LED lights provided in the HMD 40 so as to be separated from each other. The light detection device 46 is fixedly disposed, for example, in front of the user, and detects the position of light emitted from the light emitting unit 44 of the HMD 40. The light detection device 46 detects the position of the light emitted from the light emitting unit 44 to acquire position information of the head of the user relative to the light detection device 46. The position information may be used to correct the motion information described above. The position information obtained from the light detection device 46 is sent to the graphic processing unit 19 and the audio synthesis unit 20 via the light detection device interface 18.

  In addition, the position detection system which detects the position of a user's head is not limited to this. For example, a light sensor may be provided on the HMD 40 side, and the position of the head of the user may be detected by detecting light emitted from a light emitting device disposed around the user with the light sensor.

  The control unit 45 controls various devices included in the HMD 40, such as transmission of data from the acceleration sensor 42 and the gyro sensor 43 to the game apparatus 2 and transmission of a signal to the light emitting unit 44.

  The graphic processing unit 19 draws a game image including a three-dimensional virtual game space and the like according to an instruction of the CPU 10. For example, the graphic processing unit 19 generates a pair of virtual two-dimensional images having a parallax so that the user can stereoscopically view a three-dimensional virtual space. That is, the graphic processing unit 19 generates a virtual two-dimensional image for the left eye and the right eye, which has parallax and is photographed by each of a pair of virtual cameras arranged in the virtual three-dimensional space. Then, the pair of virtual two-dimensional images is converted into a moving image format, sent to the HMD 40 through the HMD interface 17, and displayed on the pair of display units 41a and 41b. Also, the graphic processing unit 19 transmits to the HMD 40 in real time in accordance with the motion information and position information about the user sent from the HMD 40 and the light detection device 46 so as to give the user a sense of presence as if entering the virtual space. Change a pair of virtual two-dimensional images.

  The audio synthesizing unit 20 reproduces and synthesizes digital format sound data included in the game data 30 b according to an instruction of the CPU 10. The sound data reproduced and synthesized by the audio synthesizing unit 20 is decoded into an analog format, and then sent to and output from the headphone 47 via the audio interface 21. As a result, the user playing the game can listen to the reproduced sound. The headphones 47 may be configured integrally with the HMD 40. Also, the audio synthesis unit 20 is output from the headphone 47 in real time in accordance with the motion information and position information sent from the HMD 40 and the light detection device 46 so as to give the user a sense of presence as if entering the virtual space. Sound may be changed. A speaker may be connected to the audio interface 21 instead of the headphone 47.

  The wireless communication control unit 22 has a wireless communication module in the 2.4 GHz band, is wirelessly connected to the controller 48 attached to the game apparatus 2, and can transmit and receive data. The user can input a signal to the game apparatus 2 by operating an operation unit such as a button provided on the controller 48.

  The network interface 23 connects the game device 2 to a communication network NW such as the Internet or LAN, and can communicate with other game devices 2 and the server device 3. Then, by connecting the game apparatus 2 to another game apparatus 2 via the communication network NW and transmitting / receiving data to / from each other, it is possible to perform multiplay to progress the game synchronously in the same virtual space. .

[Functional configuration of game device]
FIG. 2 is a block diagram showing a functional configuration of the game device 2 provided in the game system 1. The game apparatus 2 functions as virtual space generation means 51, camera arrangement means 52, plane arrangement means 53, distance calculation means 54, transparency determination means 55, and drawing means 56 by executing the game program 30a of the present invention. . In addition, such functions are composed of the CPU 10, the HDD 14, the ROM 15, the RAM 16, the graphic processing unit 19, the audio synthesizing unit 20, the wireless communication control unit 22 and the like shown in FIG. 1 in terms of hardware.

  Among these, the virtual space generation unit 51 generates a three-dimensional virtual space having a predetermined spread. In this virtual space, various objects such as walls, buildings and characters are arranged. The camera placement unit 52 places a pair of virtual cameras for capturing the above-described virtual two-dimensional images for the left and right eyes in the virtual space. A projection plane is set at a predetermined position in front of the pair of virtual cameras CL and CR, and a virtual space S projected on the projection plane to each of the display unit 41 a for the left eye and the display unit 41 b for the right eye of the HMD 40 Is displayed.

  The plane placement unit 53, the distance calculation unit 54, the transparency determination unit 55, and the drawing unit 56 execute GUI element drawing processing for drawing a GUI element as a drawing target element in the virtual space. As described later, in the GUI element drawing process, the plane arrangement means 53 arranges a plane element at a predetermined position facing the virtual camera, and the drawing means 56 draws the GUI element on the plane element.

[Plane element and GUI element]
Before describing the details of the GUI element drawing process, first, the plane elements arranged in the virtual space by the plane arrangement unit 53 and the GUI elements drawn thereon will be described with reference to FIGS. 3 and 4.

  FIG. 3 is a plan view of a pair of virtual cameras CL and CR arranged in the virtual space S by the camera arranging means 52. As shown in FIG. These virtual cameras CL and CR are arranged by a cross method (a method in which mutual visual axes cross). In addition, you may use the parallel method (method which mutually makes a visual axis parallel) for arrangement | positioning of virtual camera CL and CR.

  In the present embodiment, in the virtual space S, there is a player character (not shown) whose user can directly control the operation by the operation of the controller 48. The camera placement unit 52 places the pair of virtual cameras CL and CR at the position of the head of the player character. In the present embodiment, the pair of virtual cameras CL and CR move in the virtual space S according to the movement of the player character, that is, according to the operation of the controller 48 by the user. The pair of virtual cameras CL and CR may move in the virtual space S in accordance with the movement of the head of the user on which the HMD 40 is attached.

  As shown in FIG. 3, the planar arrangement unit 53 arranges the planar element 61 at a predetermined position facing the pair of virtual cameras CL and CR in the virtual space S. The plane element 61 is for drawing the GUI element 62 (see FIG. 4) as a drawing target element. That is, the plane element 61 itself is an element that is invisible to the user and indicates the position where the drawing target element is drawn. The plane element 61 may be, for example, a transparent plane or, for example, a plane possessed by a transparent plate-like object.

  The planar element 61 is arranged to be included in each angle of view of the virtual cameras CL and CR. In addition, the planar element 61 is disposed away from the virtual cameras CL and CR by a predetermined distance or more so that the user can easily focus on the to-be-drawn element drawn thereon. For example, the distances from the virtual cameras CL and CR to the planar element 61 and the orientation of the planar element 61 with respect to the virtual cameras CL and CR are set according to the type and size of the drawing target element drawn on the planar element 61.

  Further, the planar element 61 is fixed at the arranged position in the virtual space S. That is, even when the virtual cameras CL and CR move in the virtual space S by the operation of the controller 48, the position of the planar element 61 is maintained. When the virtual cameras CL and CR move, the plane element 61 may move in the virtual space S so as to maintain the relative position with the virtual cameras CL and CR.

  FIG. 4 is a schematic view of a virtual two-dimensional image captured by one virtual camera (for example, the virtual camera CL) of the pair of virtual cameras CL and CR shown in FIG. As shown in FIG. 4, the GUI element 62 is drawn by the drawing means 56 on the plane element 61.

  The GUI element 62 is a menu element for selecting an item or equipment used by the character in the virtual space S or checking the status of the character in accordance with, for example, the user's operation on the controller 48. The GUI element 62 shown in FIG. 4 includes a plurality of selection items 63 and a pointer 64 for selecting one of the selection items 63. The pointer 64 moves on the plane element 61 in response to the operation of the controller 48. It should be noted that instead of the GUI element 62 including the pointer 64, one of the plurality of selection items 63 may be highlighted, and the selection item to be highlighted is changed according to the operation of the controller 48. It may be set.

[GUI element drawing process]
Next, GUI element drawing processing for drawing the GUI element 62 will be described with reference to FIGS. Similar GUI element drawing processing is executed for each of the images captured by the pair of virtual cameras CL and CR. Therefore, in the following description, the GUI element drawing process related to the virtual camera CL of the pair of virtual cameras CL and CR will be described, and the description of the GUI element drawing process related to the virtual camera CR will be omitted.

  FIG. 5 shows a plan view of the virtual camera CL at a position different from the position shown in FIG. 6 shows a schematic view of a virtual two-dimensional image taken by the virtual camera CL shown in FIG. As shown in FIGS. 5 and 6, a vertical wall object 65 extending from the near side to the far side to the left as viewed from the virtual camera CL is disposed in front of the virtual camera CL. The wall object 65 is located behind the plane element 61 as viewed from the virtual camera CL. In FIG. 6, the portion near the wall object 65 in the GUI element 62 has high transmittance.

  FIG. 7 is a flowchart showing the flow of GUI element drawing processing. The GUI element drawing process is started, for example, when there is a display request for the GUI element 62 by the user operation on the controller 48.

  When the GUI element drawing process is started, first, the plane arrangement unit 53 arranges the plane element 61 at a predetermined position facing the virtual camera CL in the virtual space S (step S1).

  Next, the distance calculation means 54 calculates the distance to the object arranged in the virtual space S for each partial area when dividing the plane element 61 into a plurality of partial areas (step S2). In the present embodiment, the unit for dividing the planar element 61 is set to the pixel of the image captured by the virtual camera CL. Then, the distance calculation means 54 calculates the distance between the partial area of the plane element 61 and the object, using the depth value of each pixel acquired by the Z buffer method known as the hidden surface removal method.

  The distance calculation method by the distance calculation means 54 will be described in more detail. In order to generate a hidden-surface-eliminated image, in the Z-buffer method, together with a frame buffer that stores color information of the pixels of the image, depth information from the virtual camera CL, which is a viewpoint, along its visual axis A Z buffer for storing a certain depth value is prepared in the RAM 16 or the like. That is, before the GUI element drawing processing is performed, the depth value (first depth value Z1) regarding the object viewed from the virtual camera CL is stored in the Z buffer for each pixel.

  The distance calculation means 54 uses the first depth value Z1 before drawing the GUI element 62. Specifically, for each partial region of the plane element 61 divided in pixel units, the distance calculation unit 54 calculates the first depth value Z1 of the corresponding portion of the object ahead of the line of sight when the partial region is viewed from the virtual camera CL. (In other words, the depth value stored in the Z buffer before execution of the GUI element rendering process) and the second depth value Z2 regarding the partial area ahead of the line of sight are acquired. Then, the distance calculation means 54 subtracts the second depth value Z2 from the first depth value Z1 for each partial region of the plane element 61 to obtain each partial region of the plane element 61 from the corresponding portion of the object. Calculate the distance.

  For example, FIG. 5 shows an intersection point X1 of a line of sight when looking at one partial region of the plane element 61 from the virtual camera CL and a corresponding portion of the wall object 65 and its depth value Z1. Further, FIG. 5 shows an intersection point X2 between the same line of sight and the partial area of the plane element 61 and its depth value Z2. The distance calculation means 54 subtracts the depth value Z2 of the point X2 from the depth value Z1 of the point X1 for this partial area of the plane element 61 to calculate the distance Z3 from the partial area to the wall object 65. Thus, the distance Z3 to the wall object 65 is calculated for all partial regions of the planar element 61.

  Next, for the partial area where the calculated distance Z3 is smaller than the set value Zs, the transparency determination means 55 determines the transparency α of the partial element corresponding to the partial area in the GUI element 62 to be higher as the distance Z3 becomes shorter. (Step S3).

  FIG. 8 is an example of a graph showing the relationship between the distance Z3 between the partial area of the plane element 61 and the object and the transparency α of the partial element of the GUI element 62 corresponding to the partial area. The transparency α of a subelement becomes completely transparent when the value is “1”, and completely opaque when the value is “0”. For example, the transparency α is a blend that blends the color of the corresponding portion of the object ahead of the line of sight when viewing the partial area from the virtual camera CL and the color of the partial element of the GUI element 62 drawn in the partial area ahead of the line of sight It is a rate.

  As shown in FIG. 8, a set value Zs is provided as a threshold of the distance Z3. For partial areas where the distance Z3 is smaller than the set value Zs, the transparency α of the corresponding partial element increases as the calculated distance Z3 decreases. For partial areas where the distance Z3 is larger than the set value Zs, the transparency α of the corresponding partial element is set to “0” which is a constant value.

  Thus, the transparency determining means 55 determines the transparency α for each subelement of the GUI element 62 which is a pixel unit of the image.

  Returning to FIG. 7, when the transparency α is determined for each partial element of the GUI element 62, the drawing unit 56 updates the color of each pixel according to the determined transparency α, and draws the GUI element 62. (Step S4).

  When the drawing of the GUI element 62 is completed, the GUI element drawing process is ended. While the GUI element 62 is within the angle of view of the virtual camera CL, steps S2 to S4 are repeated for each frame. Also, for example, when there is a non-display request of the GUI element 62 by the user operation to the controller 48, the plane element 61 is deleted from the virtual space S, and while the GUI element 62 is within the angle of view of the virtual camera CL. The repetition of the executed steps S2 to S4 also ends.

  As described above, in the game system 1 according to the present embodiment, the transparency α of the portion closer to the object is increased in the portion closer to the object in the portion where the distance Z3 to the object in the GUI element 62 is smaller than the set value Zs. Users can easily grasp the situation of nearby objects. Furthermore, even when the planar element 61 is disposed at a position intersecting the object, the GUI element 62 becomes transparent at the portion intersecting the object. Therefore, the visibility of the user is improved.

  Further, in the present embodiment, the distance calculation means 54 uses the depth value of each pixel obtained by the known Z buffer method as the hidden surface removal method, and corresponds the object to the partial area of the planar element divided in pixel units. Since the distance to the part is calculated, the processing load involved in the distance calculation can be reduced.

  The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the scope of the present invention.

  For example, the configuration of the hardware described in the above embodiment is only an example, and the configuration may be any configuration provided with the HMD 40 that displays a pair of virtual two-dimensional images having parallax. For example, the acceleration sensor 42, the gyro sensor 43, the light emitting unit 44, the light detection device 46, and the like, which the HMD 40 has, may be omitted.

  In the above embodiment, the planar element 61 is disposed by the user operation on the controller 48, but the planar element 61 may be disposed depending on, for example, the position of the virtual camera C on the virtual space S or the progress of the game. Good.

  In the above embodiment, the distance calculation unit 54 calculates the distance to the object for each partial area of the plane element 61 using the depth value of the Z buffer method, but the calculation method of the distance is not limited thereto. . For example, for each partial area of the plane element 61 divided in pixel units, the distance calculation means 54 measures the distance from the virtual camera to the object along the visual line direction when viewing a partial area from the virtual camera and The distance from the virtual camera along the line to the partial area may be subtracted. Alternatively, for example, for the partial area (for example, a rectangular area) obtained by dividing the plane element into units larger than the pixels, the distance calculating unit 54 sets the shortest distance from the center point of each partial area to the object, the partial area of the plane element It may be calculated as the distance to the object.

  Further, in the above embodiment, the transparency determining means 55 determines the transparency α of the partial element of the GUI element 62 based on the relationship shown in FIG. 8 from the distance Z3 calculated by the distance calculating means 54. The relationship is an example and does not limit the present invention. For example, for a partial area where the distance Z3 is larger than the set value Zs, the transparency α may be a fixed value other than “0” (for example, “0.3”), and the graph of FIG. The slope may not be constant. Also, the transparency determining means 55 may determine the opacity of the subelement of the GUI element 62 as an index indicating the transparency α of the subelement of the GUI element 62.

  Further, although the process of drawing a GUI element as a drawing target element has been described in the above embodiment, the present invention, for example, draws a text for explaining captions or objects that display serifs of characters on a plane element. It is applicable also to processing.

51: Virtual space generation means
52: Camera arrangement means
53: Flat arrangement means
54: Distance calculation means
55: Means of determining transparency
56: Drawing means
61: Plane element
62: GUI element
B: Wall object
C (CL, CR): virtual camera

Claims (4)

A game program to be executed by a computer including a head mounted display for displaying the virtual space photographed by a pair of virtual cameras as a pair of virtual two-dimensional images having parallax,
The computer,
Virtual space generation means for generating the virtual space in which objects are arranged;
Camera placement means for placing the pair of virtual cameras in the virtual space;
Planar arrangement means for arranging a planar element for drawing a drawing target element at a predetermined position facing the pair of virtual cameras in the virtual space;
Distance calculation means for calculating the distance to the object for each partial area when the plane element is divided into a plurality of partial areas;
A transparency determining unit configured to determine the transparency of the partial element corresponding to the partial area in the drawing target element to be higher as the distance is shorter, for the partial area whose distance is smaller than a set value;
A game program which functions as drawing means for drawing the drawing target element on the plane element based on the determined degree of transparency. The partial area is obtained by dividing the planar element in units of pixels of each image captured by the pair of virtual cameras,
The distance calculating means is configured to calculate, for each of the partial areas of the planar element, a second depth value of the partial area from a first depth value of a corresponding part of the object beyond the line of sight when the partial area is viewed from the virtual camera. The game program according to claim 1, wherein a distance from each of the partial areas to the corresponding portion of the object is calculated by subtracting a depth value.   The game program according to claim 1, wherein the drawing target element is a graphical user interface. A program storage unit storing the game program according to any one of claims 1 to 3.
A game system comprising: a computer that executes a program stored in the program storage unit.

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