JP2006318389A - Program, information storage medium, and image generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a program, information storage medium, and image generation system capable of expressing various fog effects according to various situations. <P>SOLUTION: The program is used for generating an image of an object space seen from a virtual camera. The program makes a computer function as an original image generating section 122 for generating an original image by drawing an object while shading, a fog information setting section 124 for setting the fog color and α value according to the depth value based on the depth value of the original image, and an α blending section 126 for blending the color of the original image and the fog color according to the depth value based on the α value according to the depth value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a program, an information storage medium, and an image generation system.

  Conventionally, an image generation system (game system) that generates an image that can be viewed from a virtual camera (a given viewpoint) in an object space (virtual three-dimensional space) in which an object such as a character is set is known. It is popular as a place to experience so-called virtual reality.

In such an image generation system, a scene with fog such as fog, haze, smoke, and dust may be displayed. In this case, in order to improve the player's virtual reality, it is desirable to change the fog density according to the distance from the virtual camera (viewpoint) to express the real world fog characteristics. As a technique for controlling the fog density, there is a conventional technique disclosed in Japanese Patent Laid-Open No. 2003-323630.
JP 2003-323630 A

  However, in the conventional image generation system, the change in fog is only controlled by the α value (fog riding condition), and there is a limit to the image expression by the fog effect.

  The present invention has been made in view of the problems as described above, and an object thereof is a program, an information storage medium, and an image generation system capable of expressing various fog effects according to various situations. Is to provide.

  (1) The present invention is an image generation system that generates an image of an object space viewed from a virtual camera, and is a program for generating an image of the object space viewed from a virtual camera while performing hidden surface removal. An original image generation unit that generates an original image by drawing an object, a fog information setting unit that sets a fog color and an α value according to the depth value based on the depth value of the original image, and the original image And an α blending unit for blending the color of the color and the fog color corresponding to the depth value based on the α value corresponding to the depth value.

  The present invention also relates to a program that causes a computer to function as each of the above-described units. The present invention also relates to a computer-readable information storage medium that stores (records) a program that causes a computer to function as each unit.

  In the present invention, the depth value can be the Z value of the original image stored in the Z buffer, or distance information obtained by converting the Z value.

  According to the present invention, the α value that is a parameter for controlling the fog density and the fog color (for example, R, G, and B components) that is a parameter for controlling the fog color are set according to the depth value of the original image. Change. Then, the color of the original image and the fog color corresponding to the depth value of the original image are blended based on the α value corresponding to the depth value of the original image. Thereby, it is possible to generate an image with a fog effect in which the fog density and the fog color change according to the depth value of the original image.

(2) In the image generation system, program, and information storage medium according to the present invention,
In the invention of (1), the fog information setting section changes the first fog color for the depth value on the near side from the first fog color for the depth value on the near side to the second fog color for the depth value on the far side. The fog color may be set so that the gradation changes according to the depth value.

  According to the present invention, as the virtual camera is viewed from the near side to the far side, an image expressing a fog effect in which the fog color changes in gradation from the first fog color to the second fog color is generated. Can do.

  Here, the fog color corresponding to the depth value between the depth value on the near side and the depth value on the back side is obtained by interpolating the first fog color and the second fog color according to the depth value, The fog color can be changed in gradation according to the depth value. For example, when the first fog color is blue and the second fog color is red, purple is set as the intermediate color, and the color changes from blue to purple and red as it goes from the near side to the far side as viewed from the virtual camera. It is possible to generate an image in which a fog effect with gradation changes is expressed.

  As a result, for example, when generating an image that looks at the sunset from the virtual camera, a red fog that is strongly affected by the sunset is generated on the back, and a blue fog that is not significantly affected by the sunset on the front is generated. Fog can be generated and a light scattering spectrum can be expressed in a pseudo manner. Note that various methods such as linear interpolation can be applied to the interpolation method of the first fog color and the second fog color.

(3) In the image generation system, the program, and the information storage medium according to the present invention,
In the invention of (2), the fog information setting unit sets the α value so that the α value changes according to the depth value of the original image between the fog change start depth and the fog change end depth. At the same time, the fog color may be set so that the fog color changes in gradation according to the depth value of the original image between the fog change start depth and the fog change end depth.

  In the present invention, the fog change start depth refers to a depth value at which the fog effect change starts, and the fog change end depth refers to a depth value at which the fog effect change started from the fog change start depth ends.

  According to the present invention, the fog color can be gradation-changed from the first fog color to the second fog color between the fog change start depth and the fog change end depth for changing the α value. Various fog effects according to the situation can be expressed.

(4) In the image generation system, the program, and the information storage medium according to the present invention,
In the invention of (1), the fog information setting unit sets an α value such that the α value changes according to a depth value of the original image between a fog change start depth and a fog change end depth. You may do it.

  According to the present invention, the fog density can be changed according to the depth value between the fog change start depth and the fog change end depth, for example, a realistic fog effect reflecting actual fog characteristics is expressed. be able to.

(5) In the image generation system, the program, and the information storage medium according to the present invention,
In any one of the inventions of (3) and (4), the fog information setting unit clamps and sets an α value corresponding to a depth value closer to the fog change start depth to a first α value, and the fog information The α value corresponding to the depth value on the back side from the change end depth may be clamped to the second α value.

(6) In the image generation system, the program, and the information storage medium according to the present invention,
In any one of the inventions of (1) to (5),
The fog information setting unit may set the α value so that the fog density is minimized at a depth value closer to the depth value corresponding to the farthest view of the original image.

  In the present invention, the farthest view refers to a portion of the object space to be drawn that is farthest from the virtual camera. Also, the depth value for setting the α value so that the fog density is minimized can be a depth value in a predetermined range on the near side of the depth value corresponding to the farthest view of the original image.

  According to the present invention, it is possible to prevent the farthest view from being fogged. For example, even when a background sprite or the like is set for the farthest view to express the sky, the background sprite is fogged. This can be prevented.

(7) In the image generation system, the program, and the information storage medium according to the present invention,
In any one of the inventions (1) to (6), the image processing apparatus further includes a storage unit that stores a lookup table for index color / texture mapping that associates an index number with a fog color and an α value, and the fog information setting unit includes: , Treating the depth value of the original image as an index number of the lookup table, performing index color / texture mapping on the virtual object using the lookup table, and the fog color and α value corresponding to the depth value And may be set.

  According to the present invention, since it is not necessary to store actual color information (for example, 24-bit color information) in the texture storage unit, the use storage capacity of the texture storage unit can be greatly saved, and the fog corresponding to the depth value can be saved. Color and alpha value can be set.

  (8) In the image generation system, the program, and the information storage medium according to the present invention, an original image generation unit that generates an original image by drawing an object while performing hidden surface removal, an index number, a fog color, and an α value A storage unit for storing a lookup table for index color / texture mapping to be associated, a depth value of the original image as an index number of the lookup table, and an index color for a virtual object using the lookup table A texture mapping unit that performs texture mapping and sets a fog color and an α value according to the depth value; and α blending based on the α value according to the depth value between the color of the original image and the fog color And an α blending portion to be included.

  Hereinafter, the present embodiment will be described with reference to the drawings.

  In addition, this embodiment demonstrated below does not unduly limit the content of this invention described in the claim. In addition, all the configurations described in the present embodiment are not necessarily essential configuration requirements of the present invention.

1. Configuration FIG. 1 shows an example of a functional block diagram of an image generation system (game system) of the present embodiment. In this figure, the present embodiment only needs to include at least the sound generation unit 130 in the processing unit 100 (or include the processing unit 100 and the storage unit 170), and the other units (functional blocks) are optional. It can be made into the component of.

  The operation unit 160 is for a player to input operation data, and the function can be realized by hardware such as a lever, a button, a steering, a shift lever, an accelerator pedal, a brake pedal, a microphone, a sensor, or a housing. .

  The storage unit 170 serves as a work area such as the processing unit 100 or the communication unit 196, and its function can be realized by hardware such as a RAM.

  The information storage medium 180 (computer-readable medium) stores programs, data, and the like, and functions as an optical disk (CD, DVD), magneto-optical disk (MO), magnetic disk, hard disk, and magnetic tape. Alternatively, it can be realized by hardware such as a memory (ROM). The processing unit 100 performs various processes of this embodiment based on a program (data) stored in the information storage medium 180. That is, the information storage medium 180 stores (records and stores) a program for causing the computer to function as each unit (each unit) of the present embodiment (a program for causing the computer to implement each unit).

  The display unit 190 outputs an image generated according to the present embodiment, and the function thereof can be realized by hardware such as a CRT, LCD, or HMD (head mounted display).

  The sound output unit 192 outputs the sound generated by the present embodiment, and its function can be realized by hardware such as a speaker or headphones.

  The portable information storage device 194 stores player personal data, game save data, and the like. As the portable information storage device 194, a memory card, a portable game device, and the like can be considered.

  The communication unit 196 performs various controls for communicating with the outside (for example, a host device or other image generation system), and functions thereof are hardware such as various processors or a communication ASIC, It can be realized by a program.

  Note that a program (data) for causing a computer to function as each unit of this embodiment is distributed from the information storage medium of the host device (server) to the information storage medium 180 (storage unit 170) via the network and communication unit 196. You may do it. Use of such an information storage medium of the host device (server) is also included in the scope of the present invention.

  The processing unit 100 (processor) performs various processes such as a game process, an image generation process, and a sound generation process based on operation data from the operation unit 160, a program, and the like. In this case, the processing unit 100 performs various processes using the main storage unit 172 in the storage unit 170 as a work area. The function of the processing unit 100 can be realized by hardware such as various processors (CPU, DSP, etc.) or ASIC (gate array, etc.) and a program (game program).

  The processing unit 100 includes a movement / motion processing unit 110, an object space setting unit 112, a virtual camera control unit 114, an image generation unit 120, and a sound generation unit 130. Note that the processing unit 100 does not need to include all these units (functional blocks), and some of them may be omitted.

  The movement / motion processing unit 110 performs processing for obtaining movement information (position, rotation angle) and motion information (position, rotation angle of each part of the object) of the object (moving body). That is, based on operation data input by the player through the operation unit 160, a game program, or the like, processing for moving an object or moving (motion, animation) is performed.

  The object space setting unit 112 includes various objects (polygons, free-form surfaces, subdivision surfaces, etc.) such as moving objects (characters, cars, tanks, robots), columns, walls, buildings, maps (terrain), and the like. A process for arranging and setting (object) in the object space is performed. More specifically, the position and rotation angle (direction) of the object in the world coordinate system are determined, and the rotation angle (rotation around the X, Y, and Z axes) is determined at that position (X, Y, Z). Arrange objects.

  The virtual camera control unit 114 performs processing for controlling a virtual camera set in the object space. That is, virtual camera information such as the position (X, Y, Z) or rotation (rotation around the X, Y, Z axes) of the virtual camera is obtained, and the virtual camera is controlled (controls the viewpoint position and line-of-sight direction). .

  For example, when a moving object is photographed from behind with a virtual camera, the position or rotation (direction of the virtual camera) of the virtual camera may be controlled so that the virtual camera follows changes in the position or rotation of the moving object. desirable. In this case, the virtual camera is controlled based on information such as the position, direction, or speed of the moving object obtained by the movement / motion processing unit 110. Alternatively, the virtual camera may be rotated at a predetermined angle while being moved along a predetermined movement route. In this case, camera path information for specifying the position (movement path) and rotation angle of the virtual camera is prepared in advance, and the virtual camera is controlled based on the camera path information.

  The image generation unit 120 performs drawing processing based on the results of various processes performed by the processing unit 100, thereby generating an image and outputting the image to the display unit 190. In particular, in the present embodiment, an image in which an object space in which an object is fogged is viewed from a virtual camera is generated.

  For example, when generating a so-called three-dimensional game image, the original image generation unit 122 included in the image generation unit 120 first performs geometric processing such as coordinate conversion, clipping processing, perspective conversion, or light source processing. Based on the result, drawing data (position coordinates, texture coordinates, color (luminance) data, normal vector or 癇 l, etc.) given to the vertex (component point) of the primitive surface is created. Based on the drawing data (primitive surface data), an image of the object (one or a plurality of primitive surfaces) after the geometry processing is stored in a drawing buffer 174 (frame buffer, work buffer, or other image information in units of pixels). ) To draw.

  Further, the original image generation unit 122 performs processing for mapping the texture stored in the texture storage unit 178 to the object (primitive surface).

  In addition, the original image generation unit 122 uses the Z buffer 176 (depth buffer) in which the Z value (depth value) is stored, and performs the hidden surface removal by the Z buffer method (depth comparison method) while the object is stored in the drawing buffer 174. Render to generate the original image. The Z value of the original image is stored (generated) on the Z buffer 176 by the Z buffer method (depth comparison method) performed at the time of the drawing process.

  The Z value of the present embodiment may be the Z value of the Z buffer 176 (Z value of the Z coordinate axis of the camera coordinate system) itself, or may be a parameter mathematically equivalent to this Z value. . For example, it may be a parameter corresponding to a reciprocal of the Z value of the Z buffer 176 or a parameter obtained by applying a given conversion process to the Z value of the Z buffer 176.

  The fog information setting unit 124 included in the image generation unit 120 responds to the depth value based on the Z value of each pixel of the original image stored in the Z buffer 176 and the depth value including the distance information obtained by converting the Z value. Set the fog color and alpha value. For example, by causing the fog information setting unit 124 to function as the texture mapping unit 124 and performing texture mapping using an index color / texture mapping LUT (lookup table) stored in the LUT storage unit 179, A fog color and an α value corresponding to the depth value of each pixel can be set.

  In this case, the LUT storage unit 179 stores an index color / texture mapping lookup table that associates the index number with the fog color and the α value, and the texture mapping unit (fog information setting unit) 124 stores the depth of the original image. The value is treated as an index number of the lookup table, and index color / texture mapping is performed on a virtual object (for example, display screen size sprite, polygon) using the lookup table, and the depth value of each pixel of the original image Set the fog color and α value according to.

  When the lookup table for index color / texture mapping is set as 256 colors, the fog information setting unit 124 sets the Z value of the original image in the Z buffer to a 256-step distance from 0 to 255. It may be converted into information and handled as an index number.

  The fog information setting unit 124 may change the correspondence relationship of information stored in the lookup table LUT stored in the LUT storage unit 179 based on the input information. As a result, fog colors and α values that change in various manners according to the depth value can be set, and fog effects according to various situations can be expressed.

  The α blending unit 126 included in the image generation unit 120 performs processing for blending the color of the original image and the fog color corresponding to the depth value of the original image based on the α value corresponding to the depth value of the original image (α blending processing). In a broad sense, image generation processing based on an α value corresponding to the depth value of the original image is performed. The α blending process in this case includes normal α blending, addition α blending, subtraction α blending, and the like. For example, in the case of normal α blending, the following processing is performed.

R _Q = (1−α) × R ₁ + α × R ₂
G _Q = (1−α) × G ₁ + α × G ₂
B _Q = (1−α) × B ₁ + α × B ₂
On the other hand, in the case of addition α blending, the following processing is performed.

R _Q = R ₁ + α × R ₂
G _Q = G ₁ + α × G ₂
B _Q = B ₁ + α × B ₂
In the case of subtractive α blending, the following processing is performed.

R _Q = R ₁ −α × R ₂
G _Q = G ₁ −α × G ₂
B _Q = B ₁ −α × B ₂
Here, R ₁ , G ₁ , B ₁ are RGB components of an image (original image) already drawn in the drawing buffer 174 (frame buffer), and R ₂ , G ₂ , B ₂ are drawing buffers 174. Are RGB components of the image to be drawn. R _Q , G _Q , and B _Q are RGB components of an image obtained by α blending. The α value is information that can be stored in association with each pixel (texel, dot), for example, plus alpha information other than color information. The α value can be used as translucency (equivalent to transparency and opacity) information, mask information, or bump information. In the present embodiment, by R _{2, G 2,} B ₂ in fog color of R, by setting G, B components performing α blending processing such as described above, fog (mist original image, clouds, steam , Haze, dust, dust, smoke, tornado or dew).

  The sound generation unit 130 performs sound processing based on the results of various processes performed by the processing unit 100, generates game sounds such as BGM, sound effects, or sounds, and outputs the game sounds to the sound output unit 192.

  Note that the image generation system of the present embodiment may be a system dedicated to the single player mode in which only one player can play, or not only the single player mode but also a multiplayer mode in which a plurality of players can play. The system may also be provided.

  Further, when a plurality of players play, game images and game sounds to be provided to the plurality of players may be generated using one terminal, or connected via a network (transmission line, communication line) or the like. Alternatively, it may be generated using a plurality of terminals (game machine, mobile phone).

2. Next, the method of this embodiment will be described with reference to the drawings. In the following, the case where the method of the present embodiment is applied to fog expression will be mainly described as an example, but the method of the present embodiment can also be applied to image representation other than fog.

2.1 Change in fog density and fog color according to distance When generating an image that can be seen from a virtual camera in object space, in order to express a more realistic fog effect, depending on the distance from the virtual camera (viewpoint) It is desirable to change the fog density. That is, the fog density increases as the distance from the virtual camera increases. In addition, if the fog color is changed according to the distance from the virtual camera (viewpoint), various fog effects corresponding to various situations such as weather and time zone can be expressed.

  In order to change the fog density and the fog color in this way, an α value that is a parameter for controlling the fog density and a fog color component that is a parameter for controlling the fog color, for example, R, G, It is desirable to change the B component according to the distance from the virtual camera. That is, the α value is controlled so that the fog density increases as the distance from the virtual camera increases, and the R, G, and B components are controlled so that the fog color changes.

  Therefore, in the present embodiment, a method of converting the α value and the R, G, and B components of the fog color based on the Z value (Z value of the Z buffer) that is a distance parameter from the virtual camera is employed. Specifically, as shown by A1 in FIG. 2, first, the Z value ZP of the original image (image drawn on the drawing buffer) is converted into the depth distance information D (distance information from the virtual camera, the Z value of the original image). To the second Z value obtained by doing so. In the present embodiment, the Z value ZP of the original image is converted into 256-step depth distance information D from 0 corresponding to the near side when viewed from the virtual camera to 255 corresponding to the back side. Then, as shown in A2, the depth distance information D is converted into an α value αP and a fog color FCP.

  Then, as shown by A3 in FIG. 2, the original image color ICP (RGB, YUV, etc.) and the fog color (white, blue, red, etc.) FCP are α-blended based on αP. As a result, it is possible to generate a post-fogging image (completed image) with a fog effect in which the fog density and the fog color change according to the distance from the virtual camera.

  When the Z value of the Z buffer is converted into the depth distance information D, the minimum value and the maximum value of the depth distance information D between the Z value corresponding to the virtual screen position and the Z value corresponding to the farthest view. Can be set arbitrarily.

2.2 Generation of fog image by index color / texture mapping In this embodiment, the process of converting depth distance information D into α value αP and fog color FCP shown in A2 of FIG. Realized by effective use.

  In normal index color / texture mapping, in order to save the storage capacity of the texture storage unit, an index number, not actual color information (RGB), is associated with each texel of the texture as shown in B1 of FIG. Is memorized. Also, as indicated by B2 in FIG. 3, the color information specified by the index number is stored in the index color / texture mapping LUT (color palette). When texture mapping is performed on an object, the LUT is referred to based on the index number of each texture texel, the corresponding color information is read from the LUT, and the read color information is read from the drawing buffer (frame buffer). Etc.).

  In such texture mapping in the index color mode, the number of colors that can be used is smaller (for example, 256 colors) than in texture mapping in the normal mode that does not use the LUT. However, since there is no need to store actual color information (for example, 24-bit color information) in the texture storage unit, the used storage capacity of the texture storage unit can be greatly saved.

  Therefore, in the present embodiment, such index color / texture mapping is used in a form different from normal, and the depth distance information D is converted into an α value and a fog color component.

  For this reason, in this embodiment, as shown by B3 in FIG. 4, the 256-step depth distance information D is handled as the index number of the lookup table LUT (the depth distance information D is regarded as the index number). The look-up table LUT stores the R, G, B components and the α value of the fog color designated by the index number.

  Then, as shown in B4, index color / texture mapping is performed on a virtual object (for example, a sprite having a display screen size, a polygon) using the LUT by treating the depth distance information D as an index number. Thereby, the α value corresponding to the depth value of each pixel of the original image and the R, G, and B components of the fog color can be obtained. Then, as shown in B5, the color of the original image and the fog color corresponding to the depth value are blended based on the α value corresponding to the depth value to generate an image after fog processing.

  In particular, in the present embodiment, as shown in FIG. 5, the look-up table LUT includes a first fog color for the depth value on the near side as viewed from the virtual camera and a second fog value for the depth value on the back side. The fog color R, G, and B components are stored such that the fog color changes in gradation according to the depth value of the original image. In the example of the look-up table LUT in FIG. 5, the index number 0 corresponding to the near side depth distance information D has blue (R = 0, G = 0, B = 255) as the fog color for the near side depth value. ) And the index number 255 corresponding to the depth distance information D on the back side is associated with red (R = 255, G = 0, B = 0) as the fog color for the depth value on the back side. ing. The values of the R, G, and B components of the fog color are stored so that the fog color gradually changes from blue to red according to the depth value from the near side to the far side.

  Then, the fog information setting unit 124 (texture mapping unit 124) uses the look-up table LUT, and based on the depth value of the original image, the blue for the depth value on the near side to the red for the depth value on the back side. Next, the fog color is set so that the fog color changes in gradation according to the depth value of the original image. Therefore, as shown in FIG. 6, as the virtual camera is viewed from the near side to the far side, it is possible to generate an image that expresses a fog effect in which the fog color changes from blue to purple to red. As a result, for example, when generating an image that looks at the sunset from the virtual camera, a red fog that is strongly affected by the sunset is generated on the back, and a blue fog that is not significantly affected by the sunset on the front is generated. Fog can be generated and a light scattering spectrum can be expressed in a pseudo manner.

  In the example of FIG. 5, only the R component and the B component of the fog color are changed. However, the present embodiment is not limited to this, and the G component is also changed to change the first depth value for the near side. And a second fog color for the depth value on the back side can be set. For example, the index number 0 corresponding to the depth depth information D on the near side is associated with white (R = 255, G = 255, B = 255) as the fog color for the depth value on the near side, and the depth on the far side The index number 255 corresponding to the distance information D may be associated with blue (R = 0, G = 0, B = 255) as the fog color for the depth value on the back side. Then, the values of the R, G, and B components of the fog color are set so that the fog color gradually changes from white to blue according to the depth value from the near side to the far side. In this case, for example, when generating an image in which the horizon is viewed from the back side from the virtual camera, blue fog that is strongly influenced by the blue sky is generated on the back side and the influence of dust in the air is generated on the front side. It is possible to generate white fog.

  Thus, according to the present embodiment, the first fog color for the depth value on the near side and the second fog color for the depth value on the far side are arbitrarily set, and the depth value on the near side is set. By setting the fog color so that the fog color changes in gradation according to the depth value of the original image from the first fog color for the second to the second fog color for the depth value on the back side, the weather and time Various fog effects according to various situations such as bands can be expressed.

  In FIG. 4, texture mapping is performed on a virtual object having a display screen size. However, texture mapping may be performed on a virtual object having a size obtained by dividing the display screen.

2.3 Relationship between Z Value, α Value, and R, G, and B Components of Fog Color FIG. 7A is a graph showing the relationship between depth distance information D (index number of lookup table LUT) and α value. It is a thing. In the graph of FIG. 7A, the horizontal axis represents depth distance information D (index number), with 0 corresponding to the near side and 255 corresponding to the back side. In addition, the vertical axis represents the α value, and 256 levels are represented by 0.0 to 1.0.

  As shown in FIG. 7A, in the lookup table LUT according to the present embodiment, the α value is changed when the depth distance information D is between D1 and D2. That is, when the fog change is viewed from the near side, D1 is set as the fog change start depth, D2 is set as the fog change end depth, and the fog information setting unit 124 determines that the fog change start depth and the fog change end depth are between The α value is set so that the α value changes according to the depth distance information D. Thereby, between the fog change start depth and the fog change end depth, for example, the α value can be increased as the depth distance information D becomes deeper, and the fog density can be increased, reflecting the actual fog characteristics. The realistic fog effect can be expressed.

  In the example of FIG. 7A, the α value corresponding to the depth distance information D on the near side from the fog change start depth is clamped to 0.0, and the depth distance information D on the far side from the fog change end depth is supported. The α value to be clamped to 1.0. Here, the value for clamping the α value can be arbitrarily set. That is, the fog information setting unit 124 clamps and sets the α value corresponding to the depth distance information D on the near side from the fog change start depth to the first α value, and sets the depth value information D on the back side from the fog change end depth. The corresponding α value is clamped to the second α value. Thereby, a real fog effect reflecting the actual fog characteristic can be expressed between the fog change start depth and the fog change end depth.

  In the example of FIG. 7A, the α value is minimum at D3 which is depth distance information D on the near side of the depth distance information Dmax (Dmax = 255) corresponding to the farthest view of the original image. That is, the fog information setting unit 124 sets the α value so that the fog density is minimized in the depth distance information D3 on the near side of the depth distance information Dmax corresponding to the farthest view of the original image. This prevents fog from being applied to the farthest view.For example, even when a background sprite or the like is set for the farthest view to express the sky, fog is prevented from reaching the background sprite. can do.

  FIG. 7B is a graph showing the relationship between the depth distance information D (index number of the lookup table LUT) and the R, G, B components of the fog color. In the graph of FIG. 7B, the horizontal axis represents the depth distance information D (index number) of the original image, with 0 corresponding to the near side and 255 corresponding to the back side. The vertical axis represents the values of the R, G, and B components of the fog color, the graph R represents the change in the R component according to the depth distance information D, and the graph G represents the change in the G component according to the depth distance information D ( In the example of this figure, the graph B represents a change in the B component according to the depth distance information D.

  As shown in FIG. 7B, in the lookup table LUT according to the present embodiment, when the depth distance information D is between D1 and D2, the fog color R increases as the depth distance information D becomes the back side. On the other hand, the value of the R component and the value of the B component are changed so that the component gradually increases while the B component gradually decreases. That is, the fog information setting unit 124 sets the α value so that the α value changes according to the depth distance information D between the fog change start depth and the fog change end depth, and the fog change start depth and the fog change depth. The fog color changes from the front fog color (B component) to the rear second fog color (R component) according to the depth distance information D between the change end depth and the depth distance information D. Set the fog color. Thereby, the fog color is changed in gradation between the fog color for the near side and the fog color for the far side as the depth distance information D becomes the far side between the fog change start depth and the fog change end depth. It is possible to express various fog effects according to various situations such as weather and time zone.

2.4 Change of Look-up Table LUT Information In the present embodiment, the fog information setting unit 124 changes the correspondence relationship of information stored in the look-up table LUT based on input information and a given program. Let That is, fog parameter setting information is received as input information, and the fog effect is changed. For example, the depth distance information D used as the fog change start depth and the depth distance information D used as the fog change end depth are changed. Thereby, the range in which fog changes can be changed. For example, a fog effect in which the fog changes locally can be expressed by narrowing the range in which the fog changes.

  Also, the R, G, and B component values and α values of the fog color corresponding to the depth distance information D on the near side from the fog change start depth, and the fog color corresponding to the depth distance information D on the far side from the fog change end depth. The values of R, G, and B components and the α value are changed. Accordingly, the fog color change characteristic and the fog density change characteristic according to the depth distance information D can be changed.

  Further, the range of the depth distance information D having an α value of 0.0 and the depth distance information D handled as an index number is changed. Thereby, the range which eliminates a fog effect can be changed.

3. Processing of this Embodiment Next, the processing of this embodiment will be described with reference to the flowchart of FIG.

  First, in step S1, the depth information D used as the fog change start depth, the depth distance information D used as the fog change end depth, and the fog colors R, G corresponding to the depth distance information D before the fog change start depth, Depth distance information D with the B component value, α value, and fog color R, G, B component values, α value, and α value corresponding to depth distance information D behind the fog change end depth being 0.0 From the fog parameter setting information received as input information, such as the range of the depth distance information D treated as the index number, the index number (depth distance information D), the values of the R, G, and B components of the fog color, and the α value are obtained. A lookup table LUT to be associated is created.

  In step S2, the original image (the object after perspective transformation) is drawn in the frame buffer. At this time, the Z value of each pixel is written in the Z buffer. Then, in step S3, the Z value of the Z buffer is converted into 256 steps of depth distance information D and stored in the work buffer. In step S4, the depth distance information D of the work buffer is set as an index texture of 256 colors, A lookup table LUT created from fog parameters is set as a lookup table LUT for index texture color / texture mapping.

  In step S5, a polygon is drawn at the position on the screen corresponding to the converted Z buffer. That is, based on the α value determined by the lookup table LUT, the fog color determined by the lookup table LUT and the color of the original image are linearly synthesized and written to the frame buffer. At this time, α blending processing according to the following equation is performed.

R _Q = (1−α) × R ₁ + α × R ₂
G _Q = (1−α) × G ₁ + α × G ₂
B _Q = (1−α) × B ₁ + α × B ₂
Here, R ₁ , G ₁ , and B ₁ are R, G, and B components of the color (luminance) of the original image, and R ₂ , G ₂ , and B ₂ are R, G, and B components of the fog color. is there. In this way, a fog-processed image is generated by blending the fog color corresponding to the depth value of the original image with the α value corresponding to the depth value of the original image.

4). Hardware Configuration Next, an example of a hardware configuration capable of realizing the present embodiment will be described with reference to FIG.

  The main processor 900 operates based on a program stored in the CD 982 (information storage medium), a program transferred via the communication interface 990, or a program stored in the ROM 950 (one of information storage media). Various processes such as processing, image processing, and sound processing are executed.

  The coprocessor 902 assists the processing of the main processor 900, has a product-sum calculator and a divider capable of high-speed parallel calculation, and executes matrix calculation (vector calculation) at high speed. For example, if a physical simulation for moving or moving an object requires processing such as matrix operation, a program operating on the main processor 900 instructs (requests) the processing to the coprocessor 902. )

  The geometry processor 904 performs geometry processing such as coordinate transformation, perspective transformation, light source calculation, and curved surface generation, has a product-sum calculator and a divider capable of high-speed parallel computation, and performs matrix computation (vector computation). Run fast. For example, when processing such as coordinate transformation, perspective transformation, and light source calculation is performed, a program operating on the main processor 900 instructs the geometry processor 904 to perform the processing.

  The data decompression processor 906 performs a decoding process for decompressing the compressed image data and sound data, and a process for accelerating the decoding process of the main processor 900. As a result, a moving image compressed by the MPEG method or the like can be displayed on the opening screen, the intermission screen, the ending screen, or the game screen. Note that the image data and sound data to be decoded are stored in the ROM 950 and the CD 982 or transferred from the outside via the communication interface 990.

  The drawing processor 910 performs drawing (rendering) processing of an object composed of primitives (primitive surfaces) such as polygons and curved surfaces at high speed. When drawing an object, the main processor 900 uses the function of the DMA controller 970 to pass the object data to the drawing processor 910 and transfer the texture to the texture storage unit 924 if necessary. Then, the rendering processor 910 renders the object in the frame buffer 922 at high speed while performing hidden surface removal using a Z buffer or the like based on the object data and texture. The drawing processor 910 can also perform numbness lending (translucent processing), depth cueing, mip mapping, fog processing, bilinear filtering, trilinear filtering, anti-aliasing, shading processing, and the like. When an image for one frame is written in the frame buffer 922, the image is displayed on the display 912.

  The sound processor 930 includes a multi-channel ADPCM sound source and the like, and generates high-quality game sounds such as BGM, sound effects, and sounds. The generated game sound is output from the speaker 932.

  Operation data from the game controller 942 (lever, button, chassis, pad type controller, gun type controller, etc.), save data from the memory card 944, and personal data are transferred via the serial interface 940.

  The ROM 950 stores system programs and the like. In the case of an arcade game system, the ROM 950 functions as an information storage medium, and various programs are stored in the ROM 950. A hard disk may be used instead of the ROM 950.

  The RAM 960 is used as a work area for various processors.

  The DMA controller 970 controls DMA transfer between the processor and memory (RAM, VRAM, ROM, etc.).

  The CD drive 980 drives a CD 982 (information storage medium) in which programs, image data, sound data, and the like are stored, and enables access to these programs and data.

  The communication interface 990 is an interface for transferring data to and from the outside via a network. In this case, as a network connected to the communication interface 990, a communication line (analog telephone line, ISDN), a high-speed serial bus, or the like can be considered. By using a communication line, data transfer via the Internet becomes possible. Further, by using the high-speed serial bus, data transfer with other image generation systems becomes possible.

  Note that all the units (units) of the present embodiment may be realized only by hardware, or only by a program stored in an information storage medium or a program distributed via a communication interface. May be. Alternatively, it may be realized by both hardware and a program.

  And when each part of this embodiment is implement | achieved by both hardware and a program, the program for functioning hardware (computer) as each part of this embodiment is stored in an information storage medium. Become. More specifically, the program instructs each processor 902, 904, 906, 910, 930, etc., which is hardware, and passes data if necessary. Each of the processors 902, 904, 906, 910, 930 and the like implements each unit of the present invention based on the instruction and the passed data.

5. Modifications The present invention is not limited to that described in the above embodiment, and various modifications can be made. For example, terms (sprites, polygons, etc.) cited as broad terms (virtual objects) in the description in the specification can be replaced with broad terms in other descriptions in the specification.

  Also, the blending method of the α value is not limited to the method described in detail in the present embodiment, and various modifications can be made. Further, the blending process of the α value and the color may be performed in units of planes or in units of pixels. Alternatively, a fog image in which an α value and a fog color are set according to the depth value of the original image may be generated, and the original image and the fog image may be blended based on the α value of the fog image.

  In the invention according to the dependent claims of the present invention, a part of the constituent features of the dependent claims can be omitted. Moreover, the principal part of the invention according to one independent claim of the present invention can be made dependent on another independent claim.

  The present invention can also be applied to various games (such as fighting games, competitive games, shooting games, robot battle games, sports games, role-playing games, etc.). The present invention is also applicable to various image generation systems (game systems) such as a business game system, a home game system, a large attraction system in which a large number of players participate, a simulator, a multimedia terminal, and a system board for generating game images. Can be applied.

It is an example of a functional block diagram of the image generation system of this embodiment. It is a figure for demonstrating the method of converting the Z value of an original image into fog information, and blending the color of an original image, and the color of fog with the obtained (alpha) value. It is a figure for demonstrating index color and texture mapping. It is a figure for demonstrating the method of converting Z value into fog information using an index color texture mapping. It is an example of the lookup table of this embodiment. It is a figure which shows the example of the image after fog processing. FIGS. 7A and 7B are diagrams for explaining an example of conversion characteristics of the lookup table. It is a flowchart which shows an example of the process of this embodiment. It is a figure which shows an example of the structure of the hardware which can implement | achieve this embodiment.

Explanation of symbols

ICP Original image color ZP Original image Z value FCP Fog color αP Fog α value LUT Look-up table D Depth distance information 100 Processing unit 120 Image generation unit 122 Original image generation unit 124 Fog information setting unit (texture mapping unit)
126 α blending unit 130 sound generation unit 170 storage unit 172 main storage unit 174 drawing buffer 176 Z buffer 178 texture storage unit 179 LUT storage unit 190 display unit

Claims (10)

A program for generating an image of an object space viewed from a virtual camera,
An original image generation unit that generates an original image by drawing an object while performing hidden surface removal;
A fog information setting unit that sets a fog color and an α value according to the depth value based on the depth value of the original image;
As an α blending unit for blending the color of the original image and the fog color corresponding to the depth value based on the α value corresponding to the depth value,
A program characterized by causing a computer to function. In claim 1,
The fog information setting unit
The fog color is changed from the first fog color for the depth value on the near side to the second fog color for the depth value on the back side so that the fog color changes in gradation according to the depth value of the original image. A program characterized by setting. In claim 2,
The fog information setting unit
The α value is set so that the α value changes according to the depth value of the original image between the fog change start depth and the fog change end depth, and the fog change start depth and the fog change end depth are The fog color is set such that the fog color changes in gradation according to the depth value of the original image. In claim 1,
The fog information setting unit
A program that sets an α value such that the α value changes according to a depth value of the original image between a fog change start depth and a fog change end depth. In any one of Claims 3 and 4,
The fog information setting unit
The α value corresponding to the depth value closer to the fog change start depth is clamped to the first α value, and the α value corresponding to the depth value deeper than the fog change end depth is set to the second α value. A program characterized by clamp setting. In any one of Claims 1-5,
The fog information setting unit
A program for setting an α value so that a fog density is minimized at a depth value closer to the depth value corresponding to the farthest view of the original image. In any one of Claims 1-6,
Further causing the computer to function as a storage unit for storing a lookup table for index color / texture mapping that associates the index number with the fog color and α value,
The fog information setting unit
The depth value of the original image is treated as an index number of the lookup table, index color / texture mapping is performed on the virtual object using the lookup table, and the fog color and α value corresponding to the depth value are A program characterized by setting. A program for generating an image of an object space viewed from a virtual camera,
An original image generation unit that generates an original image by drawing an object while performing hidden surface removal;
A storage unit for storing a lookup table for index color / texture mapping that associates an index number with a fog color and an α value;
The depth value of the original image is treated as an index number of the lookup table, index color / texture mapping is performed on the virtual object using the lookup table, and the fog color and α value corresponding to the depth value are A texture mapping unit for setting
As an α blending unit that α blends the color of the original image and the fog color based on an α value corresponding to the depth value,
A program characterized by causing a computer to function.   A computer-readable information storage medium, wherein the program according to any one of claims 1 to 8 is stored. An image generation system for generating an image of an object space viewed from a virtual camera,
An original image generation unit that generates an original image by drawing an object while performing hidden surface removal;
A fog information setting unit that sets a fog color and an α value according to the depth value based on the depth value of the original image;
An α blending unit for blending the color of the original image and the fog color corresponding to the depth value based on the α value corresponding to the depth value;
An image generation system comprising:

Images