JP2010055131A - Program, information storage medium, and image generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a program, an information storage medium and an image generation system, capable of generating a real shadow image of a model object. <P>SOLUTION: This image generation system includes the first drawing processing part for drawing-processing a plurality of objects including the model objects MOB1, MOB2, while executing shadowing processing, to generate an image displayed with images of the model objects MOB1, MOB2 and the shadow images SD1, SD2 thereof, and the second drawing processing part for drawing-processing shadow primitive faces corresponding to grounding parts LOB1, LOB2 of the model objects MOB1, MOB2, to generate an image composed with shadow images LSD1, LSD2 of the grounding parts LOB1, LOB2 in the shadow images SD1, SD2 of the model objects MOB1, MOB2. <P>COPYRIGHT: (C)2010,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 seen from a virtual camera (a given viewpoint) in an object space that is a virtual three-dimensional space is known. Popular. Taking an image generation system capable of enjoying a fighting game as an example, a player operates his / her character (model object) using a game controller (operation unit), and battles an opponent character or an enemy character operated by a computer. Enjoy the game.

  In such an image generation system, it is desired to generate a more realistic shadow of a model object such as a character. As such a shadow generation method, for example, a shadowing process such as a shadow volume (modifier volume) process disclosed in Patent Document 1 is known.

However, in such shadowing processing, although the shadow shape of the character falling on the game field can be expressed realistically, when aiming for a realistic shadow that matches the lighting on the spot, the shadow falling on the ground will become light There are many. Therefore, for example, a shadow of a so-called occlusion area under a grounding part such as a foot has a problem that it is difficult to express it realistically.
JP 2003-242523 A

  According to some aspects of the present invention, it is possible to provide a program, an information storage medium, and an image generation system that can generate a more realistic shadow image of a model object.

  The present invention is an image generation system for generating an image that is visible from a virtual camera in an object space, and performs a drawing process of a plurality of objects including a model object while performing a shadowing process, and an image of the model object A first rendering processing unit that generates an image on which a shadow image of the model object is displayed, and a shadow primitive surface corresponding to the grounding unit of the model object are rendered to the shadow image of the model object And an image generation system including a second drawing processing unit that generates an image in which the shadow image of the grounding unit is combined. The present invention also relates to a program that causes a computer to function as each of the above-described units, or a computer-readable information storage medium that stores the program.

  According to the present invention, an image in which an image of a model object and a shadow image of the model object are displayed is generated by performing drawing processing of a plurality of objects including the model object. In addition, the shadow primitive plane corresponding to the ground portion of the model object is drawn, thereby generating an image in which the shadow image of the ground portion is combined with the shadow image of the model object. In this way, it is possible to generate a more realistic shadow image by synthesizing the entire shadow image of the model object and the shadow image of the partial ground contact portion.

  In the present invention, the first drawing processing unit may generate the shadow image of the model object by shadow map processing.

  In this way, when a shadow image is generated by shadow map processing, the shadow falling on the ground becomes lighter when aiming for a realistic shadow that suits the situation. In this regard, according to the present invention, since the shadow image of the grounding portion is generated by a separate process called the shadow primitive plane drawing process, a more realistic shadow image can be generated with a small processing load.

  Also, in the present invention, the second rendering processing unit generates the shadow primitive generated by projecting a shadow generation primitive surface set for the ground unit onto a field in which the model object moves. A shadow image of the grounding unit may be generated by performing surface drawing processing.

  In this way, it is possible to generate a shadow image of the grounding part reflecting the movement of the grounding part and the projection direction of the shadow.

  In the present invention, the second drawing processing unit uses a projection direction different from a projection direction used by the first drawing processing unit to generate a shadow image of the model object, and uses the shadow image of the grounding unit. May be generated.

  In this way, since the shadow image of the grounding portion is generated in a projection direction different from the projection direction of the shadow image of the model object, it is possible to generate an image with a high effect effect.

  In the present invention, the second drawing processing unit may generate a shadow image of the grounding unit using a projection direction of the point light source when a point light source is present.

  In this way, it becomes possible to generate a shadow image of the grounding portion corresponding to the projection direction of the point light source.

  In the present invention, the second drawing processing unit Z-shifts the shadow primitive plane in the rearward direction when viewed from the virtual camera, and the Z value of each pixel of the shadow primitive plane is the Z buffer. The shadow primitive plane may be drawn with a Z comparison setting in which drawing is performed when the Z value is deeper than the Z value.

  In this way, it is possible to prevent a situation in which an unnatural image is generated when, for example, the ground portion of the model object is located near the end of the field.

  In the present invention, the first drawing processing unit writes a predetermined stencil value in an area of a stencil buffer corresponding to the drawing area of the model object when the drawing process of the model object is performed. The drawing processing unit may draw the shadow primitive surface in a region where the predetermined stencil value is not written in the stencil buffer and the stencil value is cleared.

  In this way, it is possible to prevent a situation in which an unnatural shadow image that causes a shadow to fall on the ground portion of the model object is generated.

  Further, in the present invention, the second drawing processing unit draws when the Z value of each pixel of the shadow primitive plane is drawn when the Z value is closer to the Z value than the Z buffer. In setting, the primitive surface corresponding to the shadow primitive surface may be drawn to clear the predetermined stencil value of the stencil buffer.

  In this way, it is possible to generate a shadow image free from unnaturalness even in a situation where, for example, the ground portion of the model object is embedded in the field.

  Further, in the present invention, the second drawing processing unit controls the darkness of the shadow image of the grounding unit according to an angle formed by the ground plane of the grounding unit and a field where the model object moves. Also good.

  In this way, for example, it is possible to prevent a situation in which an unnatural shadow image is generated when the angle formed between the ground plane of the grounding portion and the field becomes large.

  In the present invention, the first drawing processing unit may perform the drawing process of the background object after performing the drawing process of the model object.

  In this way, it is not necessary to draw the background object in the drawing area of the model object, and the load of the drawing process can be reduced.

  Hereinafter, this embodiment will be described. 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 block diagram of an image generation system (game system) of the present embodiment. Note that the image generation system of the present embodiment may have a configuration in which some of the components (each unit) in FIG. 1 are omitted.

  The operation unit 160 is for a player to input operation data, and the function can be realized by a direction key, operation buttons, analog stick, lever, steering, accelerator, brake, microphone, touch panel display, or the like.

  The storage unit 170 serves as a work area for the processing unit 100, the communication unit 196, and the like, and its function can be realized by a RAM (DRAM, VRAM) or the like. The storage unit 170 can be configured by a volatile memory that loses data when the power is turned off, but is a storage device that is faster than the auxiliary storage device 194. Then, the game program and game data necessary for executing the game program are held in the storage unit 170.

  An information storage medium 180 (a computer-readable medium) stores programs, data, and the like, and functions thereof by an optical disk (CD, DVD), HDD (hard disk drive), memory (ROM, etc.), and the like. realizable. The processing unit 100 performs various processes of the present embodiment based on a program (data) stored in the information storage medium 180. That is, in the information storage medium 180, a program for causing a computer (an apparatus including an operation unit, a processing unit, a storage unit, and an output unit) to function as each unit of the present embodiment (a program for causing the computer to execute processing of each unit). Is memorized.

  The display unit 190 outputs an image generated according to the present embodiment, and its function can be realized by a CRT, LCD, touch panel display, HMD (head mounted display), or the like. The sound output unit 192 outputs the sound generated by the present embodiment, and its function can be realized by a speaker, headphones, or the like.

  The auxiliary storage device 194 (auxiliary memory, secondary memory) is a large-capacity storage device that is used to supplement the capacity of the storage unit 170, and may be a memory card such as an SD memory card or a multimedia card, an HDD, or the like. realizable. The auxiliary storage device 194 is detachable, but may be built-in. The auxiliary storage device 194 is used to save save data such as the game midway results, personal image data and music data of the player (user), and the like.

  The communication unit 196 communicates with the outside (for example, another image generation system, a server, or a host device) via a wired or wireless network, and functions as a communication ASIC, a communication processor, or the like. It can be realized by hardware and communication firmware.

  Note that a program (data) for causing a computer to function as each unit of the present embodiment is obtained from an information storage medium of a server (host device) via an information storage medium 180 (or storage unit 170, auxiliary storage) via a network and communication unit 196. May be distributed to the device 194). Use of an information storage medium by such a server (host device) can also be included in the scope of the present invention.

  The processing unit 100 (processor) performs game processing, image generation processing, sound generation processing, and the like based on operation data from the operation unit 160, a program, and the like. The processing unit 100 performs various processes using the storage unit 170 as a work area. The functions of the processing unit 100 can be realized by hardware such as various processors (CPU, GPU, etc.), ASIC (gate array, etc.), and programs.

  The processing unit 100 includes a game calculation unit 102, an object space setting unit 104, a moving body calculation unit 106, a virtual camera control unit 108, a drawing processing unit 120, and a sound generation unit 130. Note that some of these may be omitted.

  The game calculation unit 102 performs game calculation processing. Here, as a game calculation, a process for starting a game when a game start condition is satisfied, a process for advancing the game, a process for calculating a game result, or a process for ending a game when a game end condition is satisfied and so on.

  The object space setting unit 104 displays various display objects such as model objects (moving objects such as people, robots, cars, fighters, missiles, bullets, etc.), maps (terrain), buildings, courses (roads), trees, and walls. Processing for setting an object (an object composed of a primitive surface such as a polygon, a free-form surface, or a subdivision surface) in the object space is performed. In other words, the position and rotation angle of the object in the world coordinate system (synonymous with direction and direction) are determined, and the rotation angle (rotation angle around the X, Y, and Z axes) is determined at that position (X, Y, Z). Place the object. Specifically, the object data storage unit 172 of the storage unit 170 stores object data such as object position, rotation angle, moving speed, moving direction and the like in association with the object number. Then, the object data is sequentially updated by a moving object calculation process or the like of the moving object calculation unit 106.

  A moving object calculation unit (moving object control unit) 106 performs an operation for moving a model object or the like that is a moving object. It also performs calculations for operating the model object. That is, a model object (moving object) is moved in the object space based on operation data input by the player through the operation unit 160, a program (movement / motion algorithm), various data (motion data), etc. Performs processing to make the object move (motion, animation). Specifically, a simulation process for sequentially obtaining model object movement information (position, rotation angle, speed, or acceleration) and motion information (part object position or rotation angle) for each frame (1/60 second). I do. A frame is a unit of time for performing movement / motion processing (simulation processing) and image generation processing.

  More specifically, the mobile object calculation unit 106 performs processing for reproducing the motion of the model object based on the motion data stored in the motion data storage unit 173. That is, motion data including the position or rotation angle (direction) of each part object (bone constituting the skeleton) constituting the model object (skeleton) is read from the motion data storage unit 173. Then, by moving each part object (bone) of the model object (by deforming the skeleton shape), the motion of the model object is reproduced.

  The virtual camera control unit 108 performs a virtual camera (viewpoint) control process for generating an image that can be seen from a given (arbitrary) viewpoint in the object space. Specifically, processing for controlling the position (X, Y, Z) or rotation angle (rotation angle about the X, Y, Z axis) of the virtual camera (processing for controlling the viewpoint position, the line-of-sight direction or the angle of view) I do.

  For example, when shooting a model object such as a character, a car, or a fighter from behind using a virtual camera, the position or rotation angle of the virtual camera (virtual camera is set so that the virtual camera follows changes in the position or rotation of the model object. The direction). In this case, the virtual camera can be controlled based on information such as the position, rotation angle, or speed of the model object obtained by the moving object computing unit 106. Alternatively, the virtual camera may be controlled to rotate at a predetermined rotation angle or to move along a predetermined movement path. In this case, the virtual camera is controlled based on the virtual camera data for specifying the position (movement path) or rotation angle of the virtual camera.

  The drawing processing unit 120 (image generation unit) performs drawing processing of a plurality of objects including model objects. For example, a drawing process is performed based on the results of various processes (game process, simulation process) performed by the processing unit 100, thereby generating an image and outputting it to the display unit 190. When generating a so-called three-dimensional game image, first, vertex data (vertex position coordinates, texture coordinates, color data, normal vector, α value, etc.) of each vertex of the model object is generated, and based on these data Thus, vertex processing (shading by a vertex shader) is performed. When performing the vertex processing, vertex generation processing (tessellation, curved surface division, polygon division) for re-dividing the polygon may be performed as necessary.

  In vertex processing (vertex shader processing), vertex movement processing, coordinate transformation (world coordinate transformation, camera coordinate transformation), clipping processing, perspective transformation, etc. according to a vertex processing program (vertex shader program, first shader program) Geometry processing is performed, and based on the processing result, the vertex data given to the vertex group constituting the object is changed (updated, adjusted). Then, rasterization (scan conversion) is performed based on the vertex data after the vertex processing, and the surface of the polygon (primitive) is associated with the pixel. Subsequent to rasterization, pixel processing (shading or fragment processing by a pixel shader) for drawing pixels (fragments forming a display screen) constituting an image is performed.

  In pixel processing (pixel shader processing), according to a pixel processing program (pixel shader program, second shader program), reading of texture (texture mapping) stored in the texture storage unit 174, setting / changing of color data, and translucency Various processes such as synthesis and anti-aliasing are performed to determine the final drawing color of the pixels constituting the image, and the drawing color of the perspective transformed model is drawn buffer 176 (a buffer that can store image information in pixel units. VRAM). (Rendering target, frame buffer). That is, in pixel processing, per-pixel processing for setting or changing image information (color, normal, luminance, α value, etc.) in units of pixels is performed. Thereby, an image that can be seen from the virtual camera (given viewpoint) in the object space is generated.

  The vertex processing and pixel processing are realized by hardware that enables polygon (primitive) drawing processing to be programmed by a shader program written in a shading language, so-called programmable shaders (vertex shaders and pixel shaders). Programmable shaders can be programmed with vertex-level processing and pixel-level processing, so that the degree of freedom of drawing processing is high, and expressive power is greatly improved compared to conventional hardware-based fixed drawing processing. Can do.

  The drawing processing unit 120 performs lighting processing (shading processing) based on an illumination model or the like. Specifically, this lighting processing includes light source information (light source vector, light source color, brightness, light source type, etc.), line-of-sight vector of virtual camera (viewpoint), normal vector of object (translucent object), object material ( Color, material) and the like. Illumination models include Lambert's diffuse lighting model that considers only ambient light and diffused light, Phong lighting model that considers specular light in addition to ambient light and diffused light, and Brin Phong lighting model. is there.

  The drawing processing unit 120 can perform processing for mapping a texture to an object (polygon). Here, the texture mapping process is a process of mapping a texture (texel value) stored in the texture storage unit 174 to an object. Specifically, the texture (surface properties such as color and α value) is read from the texture storage unit 174 using the texture coordinates set (given) to the vertices and pixels of the object (primitive surface). Then, a texture that is a two-dimensional image or pattern is mapped to the object. In this case, processing for associating pixels with texels, bilinear interpolation (texel interpolation in a broad sense), and the like are performed.

  The drawing processing unit 120 can perform hidden surface removal processing. For example, a hidden surface removal process is performed by a Z buffer method (depth comparison method, Z test) using a Z buffer 177 (depth buffer) in which a Z value (depth information) of each pixel is stored. That is, when drawing each pixel of the primitive surface of the object, the Z value stored in the Z buffer 177 is referred to. Then, the Z value of the referenced Z buffer 177 is compared with the Z value of the drawing target pixel. If the Z value at the drawing target pixel is the Z value that is on the near side when viewed from the virtual camera, Pixel drawing processing is performed and the Z value of the Z buffer 177 is updated to a new Z value.

  The drawing processing unit 120 performs a shadowing process for generating a shadow image. Specifically, in the present embodiment, the drawing processing unit 120 includes a first drawing processing unit 121 and a second drawing processing unit 122.

  Then, the first drawing processing unit 121 performs drawing processing of a plurality of objects including model objects, and generates an image in which an image of the model object and a shadow image of the model object are displayed. Specifically, a model object drawing process is performed to generate an image of the model object. Next, the background object is drawn while performing the shadowing process, and an image in which the shadow of the model object is displayed on the background such as the field to which the model object moves is generated.

  As described above, the first drawing processing unit 121 performs the drawing process of the background object after performing the drawing process of the model object. As a result, it is not necessary to draw a background object in the area where the model object is drawn, and the drawing processing load can be reduced.

  The first drawing processing unit 121 generates a shadow image of the model object by, for example, shadow map processing. Specifically, the shadow map texture is generated by rendering the Z value of the object in the shadow projection direction. Then, a shadow image is generated by performing an object drawing process using the shadow map texture and the texture of the object.

  Further, the first drawing processing unit 121 may generate a shadow image by distributed shadow map processing. In this case, the shadow map texture may be generated by rendering the Z value of the object in the shadow projection direction and rendering the Z value squared. In addition to the distributed shadow map, various processes such as a conventional shadow map process, a light space shadow map process, and an opacity shadow map process can be employed as the shadow map process. Alternatively, in addition to the shadow map process, a shadowing process such as a volume shadow (stencil shadow) process or a projected texture shadow process may be employed.

  On the other hand, the second drawing processing unit 122 performs a shadow primitive surface drawing process corresponding to the grounding part of the model object, and generates a shadow image of the grounding part. As a result, an image in which the shadow image of the grounding portion is combined with the shadow image of the model object is generated.

  Here, the grounding unit is a part of the model object, for example, a foot or a hand, and is a part scheduled to be grounded to a field where the model object moves. When the model object falls to the field (ground), the back or the like where the model object touches the field when it falls may be set as the grounding unit. In the present embodiment, in order to express the shadow of the so-called occlusion area of such a grounding portion, a rendering process of a shadow primitive surface (shadow polygon such as a foot shadow polygon in a narrow sense) corresponding to the grounding portion is performed.

  Specifically, the second drawing processing unit 122 projects the shadow generation primitive surface set for the grounding unit onto the field (game field, ground) on which the model object moves, thereby projecting the shadow primitive surface. Is generated. Then, by performing the shadow primitive plane drawing process, a shadow image of the grounding portion is generated.

  In this case, the second drawing processing unit 122 generates a shadow image of the grounding unit based on a projection direction different from the projection direction used by the first drawing processing unit 121 to generate the shadow image of the model object. Also good. For example, it is assumed that the first drawing processing unit 121 performs shadowing processing such as shadow map processing using the projection direction of the main light source. If a point light source is present at this time, the second drawing processing unit 122 generates a shadow image of the grounding unit using the projection direction (projection vector, light source vector) of the point light source. Specifically, for example, when the brightness (brightness) of the point light source is equal to or greater than a predetermined threshold, a shadow image of the grounding unit is generated based on the projection direction of the point light source. on the other hand. When the brightness of the point light source is smaller than a predetermined threshold value, a shadow image of the grounding unit is generated based on the projection direction (projection vector, light source vector) of the main light source.

  The second drawing processing unit 122 Z-shifts the shadow primitive surface in the back direction as viewed from the virtual camera. Then, the Z value of each pixel of the shadow primitive surface is drawn when the Z value is the back Z value as viewed from the virtual camera rather than the Z value of the Z buffer 177. With this setting, the drawing process of the shadow primitive surface may be performed. This makes it possible to generate an appropriate shadow image of the grounding portion even when the grounding portion of the model object is located near the end of the field.

  More specifically, the first drawing processing unit 121 writes a predetermined stencil value in an area (pixel) of the stencil buffer 178 corresponding to the drawing area of the model object when the drawing process of the model object is performed. That is, the predetermined stencil value is also written to the stencil buffer 178 when drawing the model object.

  Then, the second drawing processing unit 122 draws a shadow primitive surface in a region (pixel) in which a predetermined stencil value is not written in the stencil buffer 178 and the stencil value is cleared to, for example, zero. In this way, it is possible to prevent a situation where a shadow image is generated with respect to the ground portion of the model object.

  In this case, the second drawing processing unit 122 is drawn when the Z value of each pixel of the shadow primitive surface is the Z value closer to the virtual camera than the Z value of the Z buffer 177. The shadow primitive plane may be drawn with the normal Z comparison setting to clear the predetermined stencil value in the stencil buffer 178. This makes it possible to generate an appropriate shadow image of the grounding portion even in a situation where the grounding portion of the model object is embedded in the field.

  The stencil buffer 178 can be formed in the upper bit area of the Z buffer 177. For example, when the number of bits of each pixel in the Z buffer 177 is 24 bits, the upper 8 bits may be set in the stencil buffer 178 so that the stencil value can be written.

  Further, the second drawing processing unit 122 may control the darkness of the shadow image according to the angle formed by the ground plane of the ground unit and the field where the model object moves. For example, as the angle between the ground plane and the field increases, the darkness of the shadow image is reduced. In this way, for example, when a model object that is a character falls, an unnatural shadow image of a foot that is a ground contact portion can be prevented from being generated.

  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 may be a system having a multiplayer mode in which a plurality of players can play. 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 by distributed processing using a plurality of terminals (game machine, mobile phone).

2. 2. Technique of this embodiment 2.1 Shadow density control according to distance In this embodiment, in order to express a more realistic shadow of a model object such as a character, for example, shadowing processing such as shadow map processing described later is performed. Thus, a shadow image is generated.

  However, when a shadow image is generated by shadow map processing or the like, the shadow shape can be expressed realistically, but the shadow of an occlusion area such as a foot is difficult to express realistically.

  Therefore, in the present embodiment, a method of generating a shadow image of the model object (entire shadow image) by shadowing processing and combining the shadow image of the grounding portion such as the foot of the model object with the shadow image is adopted. is doing. Specifically, a foot shadow polygon (a shadow primitive surface in a broad sense) corresponding to a foot portion (a ground contact portion in a broad sense) is drawn, and a foot shadow image ( In a broad sense, an image in which a shadow image of the grounding portion is combined is generated.

  For example, FIG. 2 shows an example of a game image generated by this embodiment. FIG. 2 is an example of a game image in which the model objects MOB1 and MOB2 that are characters face each other.

  In FIG. 2, the entire shadow image SD1 of the model object MOB1 is generated by shadowing processing such as shadow map processing. The shadow image SD1 is a more realistic shadow that faithfully reflects the shape of the model object MOB1. However, the shadow image SD1 is generally darker due to the brightness of the light source. It has become. The same applies to the shadow image SD2 of the model object MOB2.

  And it is difficult to generate a real shadow like the real world for the shadow image of the foot part of the model object only by such shadowing processing. That is, a so-called occlusion area, such as under the foot part, is an area where light from the outside does not reach, and thus a very dark shadow is generated in the real world. However, since the light of the main light source used in the shadowing process often becomes light, the shadow image generated thereby increases in number of light shadows. Therefore, it is difficult to express a dark shadow under the foot portion by shadowing processing. If such a realistic expression of the shadow of the foot portion cannot be realized, the model object that is the character will appear to float from the ground, and the expression of the so-called ground contact feeling of the character will be insufficient.

  In this case, for example, a technique for expressing the shadow of such an occlusion area by performing strict physical calculation is conceivable. However, this technique has a problem that the processing load becomes very heavy.

  In this regard, as shown in FIG. 2, in the present embodiment, the foot shadow image LSD1, which is a shadow of the foot portion LOB1, is generated by a foot shadow polygon drawing process, and is realized by a so-called round shadow. Then, the shadow of the model object MOB1 is expressed by synthesizing the shadow image SD1 generated by shadowing processing such as shadow map processing and the foot shadow image LSD1 obtained by drawing the foot shadow polygon. Similarly, the shadow of the model object MOB2 is expressed by combining the shadow image SD2 of the model object MOB2 and the foot shadow image LSD2.

  In this way, the shadow shape and the like of the entire shadow of the model object MOB1 can be realistically represented by the shadow image SD1 obtained by the shadowing process.

  On the other hand, regarding the partial shadow of the occlusion area of the foot portion LOB1, the darkness of the shadow can be realistically expressed by the foot shadow image LSD1 drawn by the foot shadow polygon. As a result, it is possible to prevent the model object MOB1 from appearing floating from the ground, and to express a feeling of grounding appropriately.

  As described above, in this embodiment, the shadow image SD1 and the foot shadow image LSD1 are generated independently from each other by different methods, and the overall shadow image SD1 and the partial foot shadow image LSD1 are synthesized, thereby reducing the processing load. It has succeeded in generating more realistic shadows.

2.2 Shadow Map Processing A shadow image of a model object such as a character can be generated by, for example, shadow map processing. Next, details of the shadow map processing will be described with reference to FIG.

  In the shadow map processing, first, a shadow map texture SDTEX is generated by rendering Z values (depth values and depth values) of objects such as the model object MOB and the background object BOB as viewed from the light source LS for generating shadows. . That is, the virtual camera VC is set at the position of the light source LS, and the Z value of the object is rendered. For example, in FIG. 3, the Z value Z1 of the point P1 'of the model object MOB, the Z value Z2 of the point P2 of the background object BOB, and the like are rendered to generate the shadow map texture SDTEX.

  For example, FIG. 4 shows an example of a shadow map texture SDTEX. This shadow map texture SDTEX corresponds to the game image of FIG. 2, and is an example of a texture generated when the light source for shadow generation is set in the upper right of FIG. In FIG. 4, the Z value closer to the virtual camera is drawn in black, and the Z value farther from the virtual camera is drawn in white.

  Next, the virtual camera VC is set at the viewpoint position for generating the visual field image displayed on the screen SC, and rendering of objects such as the model object MOB and the background object BOB is performed. At this time, the object is rendered while comparing the Z value of each pixel of the object with the Z value of each corresponding texel of the shadow map texture SDTEX.

  For example, in FIG. 3, the Z value (distance) of the point P1 viewed from the virtual camera VC is larger than the Z value of the corresponding point P1 'of the shadow map texture SDTEX. Accordingly, it is determined that the point P1 is a portion that is shadowed by the point P1 ', and a shadow color (for example, black) is drawn on the pixel corresponding to the point P1.

  On the other hand, for the point P2, the Z value viewed from the virtual camera VC is equal to the Z value in the shadow map texture SDTEX, for example. Therefore, it is determined that the point P2 is not a shadow portion, and the shadow color is not drawn.

  By doing so, it is possible to generate a shadow of the model object MOB falling on the background, a self-shadow of the model object MOB, and the like.

  Now, in the conventional shadow map process, the process of determining whether or not it is a shadow part is performed by binary determination of 0 or 1. For this reason, jaggy or the like is conspicuous in the shadow outline (the boundary between the shadow portion and the portion other than the shadow), and there is a problem that the quality of the generated shadow image cannot be improved.

  In order to solve such a problem, it is desirable to adopt a technique called a distributed shadow map. In this distributed shadow map, the probability of light hitting (maximum probability) is calculated using the idea of Chebyshev's inequality, which is probability theory. That is, in the distributed shadow map processing, the result of the determination as to whether or not it is a shadow is represented by a probability (maximum probability) that is a real number in the range of 0 to 1. Therefore, this probability value is directly used as the shadow density (shadow shadow). Color). Therefore, compared with the conventional shadow map process in which the shadow determination process is performed with binary values of 0 (shadow part) or 1 (lighted part), the shadow image jaggies and the like may be made inconspicuous. And can express a smooth shadow outline.

  For example, Chebyshev's inequality, which is a basic theorem of probability theory, is expressed as the following equation (1).

Here, x is a random variable in the probability distribution, μ is an average, σ is a variance, and t is an arbitrary real number that satisfies t> 0. For example, when t = 2, it is derived that a value that is 2σ or more away from the average μ in the probability distribution does not exceed 1/4 of the whole. That is, it is derived that the probability that x> μ + 2σ and x <μ−2σ does not exceed ¼.

  The distributed shadow map process utilizes the Chebyshev inequality idea, and the moments M1 and M2 of the following expressions (2) and (3) are obtained.

From these formulas (2) and (3), the average μ and the variance σ ² expressed as the following formulas (4) and (5) are obtained.

Based on the Chebyshev inequality, the following equation (6) is established under the condition of t> μ.

Here, t corresponds to the Z value of the pixel, and x corresponds to the Z value of the shadow map texture subjected to the blurring process. The darkness (color) of the shadow is determined from this probability pmax (x).

  In this embodiment, the following expression (7) obtained by modifying the above expression (6) is used.

Here, Σ is a value obtained by clamping σ ² + ε within a range of 0 to 1.0, and is an adjusted dispersion value.

The ε is the variance adjustment parameter is a parameter for adding a bias value to the variance sigma ^2. By increasing the value of the dispersion adjustment parameter ε, the degree of dispersion in the dispersion shadow map can be forcibly increased. If the dispersion adjustment parameter is set to ε = 0, noise pixels are generated in a region that is not originally shaded. However, by setting ε> 0, the noise pixels can be reduced.

  For example, in the conventional shadow map process, only the Z value is rendered. In the distributed shadow map process, the Z value is rendered, and the square of the Z value is rendered to generate a shadow map texture in a two-channel buffer. The shadow map texture is then subjected to filter processing such as blur (Gaussian filter, etc.).

Next, the moments M1 and M2 of the above equations (2) and (3) are obtained from the shadow map texture, and the average (expected value) μ and the variance σ ² of the above equations (4) and (5) are obtained. Further, based on the dispersion σ ² and the dispersion adjustment parameter ε, Σ which is an adjusted dispersion value is obtained.

  If t, which is the Z value (depth) of a pixel (fragment), is t <μ, it is determined that the portion is not a shadow. On the other hand, when t ≧ μ, the light attenuation rate is obtained from the probability pmax (t) of the above equation (7), and the shadow density (color) is determined. Instead of the probability pmax (t) itself, a power (for example, the fourth power) of pmax (t) may be used.

  By performing the shadow map process as described above during the drawing process of the model object and the background object, the shadow images SD1 and SD2 of the model objects MOB1 and MOB2 shown in FIG. 2 can be generated.

2.3 Foot Shadow Image Generation Method Next, a specific generation method of the foot shadow images LSD1 and LSD2 in FIG. 2 will be described.

  First, as shown in FIG. 5A, a foot shadow generation polygon GPL (a shadow generation primitive surface in a broad sense) corresponding to a foot portion LOB (a ground contact portion in a broad sense) of the model object is generated. Specifically, based on the position BP1 of the ankle bone BN1 (the coordinate conversion matrix of BN1) and the position BP2 of the toe bone BN2 (the coordinate conversion matrix of BN2), the vertex V1 constituting the foot shadow generation polygon GPL ~ V6 is generated.

  More specifically, a size table as shown in FIG. 5B and a vertex data table as shown in FIG. 5C are prepared.

  Here, in the size table of FIG. 5B, standard foot shadow sizes are stored corresponding to the types of model objects, male, female, and monster. For example, foot shadow sizes SZA, SZB, SZC, SZD, SZE, and SZF for a small man, a large man, a small woman, a large woman, a small monster, and a large monster are stored. The vertex data table in FIG. 5C stores vertex data (vertex coordinates) corresponding to each type.

  Then, the distance LB between the position (joint) BP1 of the bone BN1 and the position (joint) BP2 of the bone BN2 in FIG. Next, when the type of the model object is, for example, male, the minimum distance LBA corresponding to the small male and the maximum distance LBB corresponding to the large male are read from the size table of FIG. Then, an interpolation rate is obtained based on the distances LBA and LBB. Then, using the obtained interpolation rate, the foot shadow size of the model object is obtained by performing an interpolation process between the small male foot shadow size SZA and the large male foot shadow size SZB. Then, based on the obtained foot shadow size (interpolation rate), interpolation processing of the corresponding types of vertex data in the vertex data table of FIG. 5B is performed, thereby generating the foot shadow of FIG. 5A. Vertex data (vertex coordinates) of the vertices V1 to V6 of the polygon GPL is obtained.

  Next, as shown in FIG. 6, vertices V1 to V6 of the foot shadow generation polygon GPL are set in the game field FLD (field in a broad sense) in the projection direction PD of the light source LS (main light source, point light source) for shadow generation. To generate a foot shadow polygon SPL constituted by the projected vertices VP1 to VP6.

  Also, the height distances LH1 to LH6 of the vertices V1 to V6 of the foot shadow generating polygon GPL from the game field FLD (ground) are obtained. The maximum darkness of the foot shadow obtained from the brightness of the light source LS is attenuated by the distance according to the height distances LH1 to LH6, whereby the darkness of the shadow set at the vertices VP1 to VP6 of the footshadow polygon SPL. I ask for it. Specifically, the shadows of the vertices VP1 to VP6 of the foot shadow polygon SPL are calculated using an arithmetic expression set so that the shadow becomes transparent at a predetermined distance and the attenuation amount increases as the height distances LH1 to LH6 increase. Find the density of. Then, by drawing the foot shadow polygon SPL with this shadow density, foot shadow images LSD1 and LSD2 as shown in FIG. 2 are generated. In this manner, an image in which the overall shadow images SD1 and SD2 of the model objects MOB1 and MOB2 and the foot shadow images LSD1 and LSD2 are combined is generated.

  In the present embodiment, the foot shadow images LSD1 and LSD can be generated using projection vectors different from the projection vectors used for generating the overall shadow images SD1 and SD2 of the model objects MOB1 and MOB2.

  For example, in FIG. 7, a point light source is generated by an event in which the sword of the model object MOB1 and the sword of the model object MOB2 hit. When such a point light source is generated, for example, foot shadow images LSD1 and LSD2 of the model objects MOB1 and MOB2 are generated using the projection direction (projection vector, light source vector) of the point light source. In this case, the foot shadow images LSD1 and LSD2 are generated using a projection direction PD of a point light source different from the light source (for example, main light source) of the shadow images SD1 and SD2 of the model objects MOB1 and MOOB2. Accordingly, the foot shadow images LSD1 and LSD2 fall in a direction different from the direction in which the overall shadow images SD1 and SD2 fall. As a result, it becomes possible to visually appeal to the user the generation of a point light source as shown in FIG. 7, and the virtual reality of the user can be improved.

  Note that the switching of the light source that generates the foot shadow image may be performed based on the brightness of the light source. For example, when a point light source representing torches or the like is set in advance on the game field, the brightness of the point light source at the position of the model object is obtained according to the distance between the model object and the point light source. If the brightness is smaller than a predetermined threshold value, a foot shadow image is generated using the projection direction of the main light source. On the other hand, when the brightness of the point light source is equal to or greater than a predetermined threshold, the main light source is switched to the point light source, and a foot shadow image is generated in the projection direction of the point light source. In this way, the presence of a point light source such as a torch can be visually appealed to the player, and the virtual reality of the player can be further improved.

  8 to 11 show examples of game images generated according to this embodiment.

  For example, in FIG. 8, since the main light source is arranged on the left front side of the screen, the entire shadow image SD1 of the model object MOB1 is displayed on the game field FLD along the direction from the left front side to the right back side of the screen. drop down. On the other hand, in FIG. 8, since the very bright point light source is arranged on the right back side of the screen, the foot shadow image LSD1 of the model object MOB1 is opposite to the overall shadow image SD1, and on the right back side of the screen. It falls to the game field FLD along the direction from the side toward the left front side.

  In FIG. 9, when the weapon of the model object MOB2 hits the model object MOB1, a point light source for virtual effects is generated near the chest of the model object MOB1. Thereby, the foot shadow image LSD1 of the model object MOB1 falls on the game field FLD along the projection direction of the point light source.

  In FIG. 10, the foot portion of the model object MOB1 is floating upward. Then, as the foot portion floats in this way, the darkness of the foot shadow image LSD1 becomes lighter. In FIG. 11, since the height distance of the foot portion exceeds the predetermined value, the darkness of the foot shadow image LSD1 becomes almost transparent and is not displayed. By doing so, the state in which the foot of the model object MOB1 gradually rises is expressed by the foot shadow image LSD1, and the real feeling and virtual reality of the generated image can be improved.

2.4 Generation of Foot Shadow Image near End of Game Field Now, when a foot shadow image is generated by the method described in FIG. 5A to FIG. It has been found that a defect occurs in the generated image when placed near the edge of the. In order to eliminate such a problem, the present embodiment employs a method described below.

  First, as shown in FIG. 12A, the Z-shift of the foot shadow polygon SPL (shadow primitive plane) generated by the method of FIGS. 5A and 6 is performed. Specifically, the foot shadow polygon SPL is Z-shifted in the back direction when viewed from the virtual camera so that the foot shadow polygon SPL is on the back side when viewed from the virtual camera rather than the surface of the game field FLD. For example, in a coordinate system in which the Z value increases as the distance from the virtual camera increases, the Z shift value is added to the Z value of the foot shadow polygon SPL. In a coordinate system in which the Z value decreases as the distance from the virtual camera increases, the Z shift value is determined. Subtract.

  The Z value of each pixel of the shadow polygon SLP is set to Z comparison so that drawing is performed when the Z value of the corresponding pixel in the Z buffer 177 is a Z value on the back side as viewed from the virtual camera. The shadow polygon SPL is drawn. That is, in the normal Z comparison, the front side polygon is set to be drawn, but on the contrary, the back side polygon is set to be drawn, and the shadow polygon SPL is drawn.

  In this way, in the portion indicated by A1 in FIG. 12A, the shadow polygon SPL is behind the game field FLD, so that the SPL is drawn, and in the portion indicated by A2, the SPL is not drawn. become. Therefore, a foot shadow image is appropriately generated below the foot portion LOB.

  That is, when the shadow polygon SPL is drawn without setting Z shift and Z comparison as described above, when the foot portion LOB is near the end of the game field FLD, not only the portion shown in A1 but also A2 shows. The shadow polygon SPL is drawn also in the portion, and there is a possibility that an unnatural image in which a shadow appears in space is generated.

  In this regard, according to the method of FIG. 12A, the shadow polygon SPL is drawn only in the portion indicated by A1 by performing the Z shift and Z comparison as described above, and the shadow polygon is indicated in the portion indicated by A2. Since the SPL is not drawn, an appropriate foot image can be generated.

  Further, in the method of FIG. 12A, since the Z comparison setting is performed in which the shadow polygon SPL is drawn not only for the game field FLD but also for the foot portion LOB, the shadow appears to be dropped on the foot portion LOB. An image may be generated.

  That is, such a situation can be prevented by drawing the model object in the order of drawing the game field FLD and the shadow polygon SPL. However, in this embodiment, in order to reduce the load of the drawing process, a method of drawing a model object first and then drawing a background object such as a game field FLD is adopted. In this way, it is not necessary to draw the background object in the area where the model object has already been drawn. Therefore, when the area occupied by the model object is large on the game screen, useless drawing processing can be omitted, and the drawing processing load can be greatly reduced.

  However, if the drawing processing is performed in such an order, in FIG. 12A, since the foot portion LOB is set to be hidden by the shadow polygon SPL in the Z comparison, the foot portion LOB is set to the foot portion LOB. An image with shadows will be generated.

  Therefore, in FIG. 12B, when the drawing process of the model object is performed, a predetermined stencil value is written in the area of the stencil buffer 178 corresponding to the drawing area of the model object. Then, the shadow polygon SPL is drawn in the area where the predetermined stencil value is not written in the stencil buffer 178 and the stencil value is cleared.

  In this way, since the shadow polygon SPL is not drawn in the area of the foot portion LOB indicated by A3 in FIG. 12B, it is unnatural that the foot shadow has fallen on the foot portion LOB. It is possible to prevent a situation where an image is generated.

  Further, for example, when the motion of the model object is reproduced based on the motion data, as shown in FIG. 12C, the foot portion LOB of the model object may be embedded in the game field FLD. In other words, when performing motion reproduction based on motion data, such a dip in the foot can be eliminated to some extent by performing motion correction or the like, but there is a limit to this. For example, when the foot of the character is striking, the foot portion LOB will sink below the game field FLD.

  When such indentation occurs, a predetermined stencil value is also written in the area indicated by A4 in FIG. 12C by the process in FIG. Therefore, the shadow polygon SPL is not drawn in the area A4, and an unnatural image in which only the area A4 has a shadow is generated.

  Therefore, in FIG. 12C, processing for clearing a predetermined stencil value is performed in the stencil buffer 178 for the area corresponding to A4. Specifically, a normal Z comparison setting is drawn in which the Z value of each pixel of the shadow polygon SPL is drawn when the Z value is closer to the virtual camera than the Z value of the Z buffer 177. To. Then, by drawing the polygon (primitive surface) corresponding to the shadow polygon SPL in the stencil buffer 178 with such a normal Z comparison setting, the stencil buffer 178 for the area corresponding to A4 in FIG. Clear the predetermined stencil value of and set it to zero.

  In this way, since the shadow polygon SPL is drawn also in the area A4, it is possible to prevent a situation in which an unnatural image in which only the shadow of the area A4 is lost is generated.

  Next, a specific drawing process according to the present embodiment will be described with reference to images in FIGS.

  In FIG. 13, first, model objects MOB1 and MOB2 are drawn. When the model objects MOB1 and MOB2 are drawn in this way, as shown in FIG. 14, the area of the stencil buffer 178 corresponding to the drawing area of MOB1 and MOB2 is described with reference to FIG. A predetermined stencil value (a stencil value other than 0) is written in. For example, in FIG. 14, a predetermined stencil value is written in a white area, and the stencil value is cleared to zero in a black area.

  Next, a background object is drawn as shown in FIG. Thus, by drawing the background object after drawing the model objects MOB1 and MOB2, it is not necessary to draw the background in a useless area, and the load of the drawing process can be greatly reduced. When the background object drawing process is performed, the shadow map process described with reference to FIGS. 3 and 4 is performed, so that the entire shadow image SD1 of the model object MOB1 is generated.

  After drawing the background object in this way, the drawing process of the foot shadow polygon SPL described with reference to FIGS. 5A to 6 and FIGS. 12A to 12C is performed. For example, in FIG. 16, a foot shadow generation polygon GPL corresponding to the foot portion LOB1 of the model object MOB1 is generated. A shadow polygon SPL is generated by projecting the foot shadow generating polygon GPL onto the game field in the shadow projection direction, and a foot shadow image is generated by drawing the shadow polygon SPL.

  Specifically, as described with reference to FIG. 12C, by writing the polygon corresponding to the shadow polygon SPL to the stencil buffer 178 with the normal Z comparison setting, the area indicated by A4 in FIG. The predetermined stencil value is cleared to zero.

  FIG. 17 shows the state of the stencil buffer 178 after such drawing processing has been performed. As is apparent from a comparison between FIG. 14 and FIG. 17, in FIG. 17, the stencil value in the region indicated by C1 is cleared to zero. Therefore, a foot shadow image is also generated in the area indicated by C1.

That is, in FIG. 15, the toe of the foot portion LOB1 of the model object MOB1 is recessed into the game field. In this case, if a foot shadow image is not generated in the area indicated by C1 in FIG. 17, an unnatural image in which only the area indicated by C1 is shadowed is generated. In this regard, as shown in FIG. If the stencil value in the area shown in (2) is cleared to zero, a shadow image is also generated in this area, and it is possible to prevent a situation where an unnatural image in which only the shadow is lost is generated. .

  For example, FIG. 18 shows an example of an image generated when the foot part LOB1 of the model object MOB1 is near the end of the game field FLD. The upper image in FIG. 18 is an actually displayed image. On the other hand, in the lower image in FIG. 18, the foot shadow generation polygon GPL and the foot shadow polygon SPL are also shown for ease of explanation.

  As shown in the upper image of FIG. 18, by adopting the method of the present embodiment, not only the entire shadow image SD1 of the model object MOB1, but also the foot shadow image LSD1 of the foot portion LOB1 of the MOB1 is appropriately generated. Has been. In other words, even when the foot portion LOB1 is placed near the end of the game field FLD, the proper foot shadow image LSD1 has been successfully generated.

  For example, in FIG. 18, the point light source for the foot shadow is disposed at a position as low as the height of the game field FLD. Accordingly, as indicated by D1 in the lower image of FIG. 18, the foot shadow polygon SPL extends long toward the outside of the game field FLD. In such a case, if the method described with reference to FIG. 12A is not adopted, a foot shadow is also displayed on the portion indicated by D1, and an unnatural image may be generated. By adopting the form technique, such a situation can be prevented. In addition, by employing the method shown in FIGS. 12B and 12C, an unnatural image is generated when a shadow falls on the foot portion LOB or the foot portion LOB sinks into the game field FLD. It will be possible to prevent the situation.

2.5 Detailed Processing Example Next, a detailed processing example of this embodiment will be described with reference to the flowcharts of FIGS. FIG. 19 is a flowchart for explaining the overall drawing process flow.

  First, as described in FIG. 3, by rendering the Z value of each object in the shadow projection direction (illumination direction of the light source for shadow generation), a shadow map texture as shown in FIG. 4 is generated ( Step S1). In the case of the distributed shadow map process, a shadow map texture may be generated by performing rendering for the Z value and rendering for the square of the Z value.

  Next, the drawing buffer, Z buffer, stencil buffer, etc. are cleared (step S2). Then, using the texture of the model object (original picture texture) and the shadow map texture generated in step S1, the model object is rendered by, for example, a pixel shader (step S3). At this time, as described with reference to FIGS. 12B and 14, a predetermined stencil value is written into the area of the stencil buffer 178 corresponding to the drawing area of the model object.

  Next, using the background object texture (original picture texture) and the shadow map texture, a background object drawing process is performed by, for example, a pixel shader (step S4). As described above, if the drawing process of the model object is first performed (step S3) and then the drawing process of the background object (step S4) is performed, the background object is not drawn in the drawing area of the model object. You can do it. Therefore, since it is possible to prevent unnecessary drawing processing, it is possible to prevent a situation in which drawing processing within one frame is not in time. In particular, when the area occupied by the model object is large in the entire screen, it is effective to perform the drawing processing in the order shown in steps S3 and S4.

  Next, the foot shadow polygon is drawn by the method described in FIGS. 5A to 6 and FIGS. 12A to 12C, and the foot shadow image is synthesized with the shadow image of the model object. Generated images are generated (step S5).

  20 and 21 are flowcharts for explaining the details of the foot shadow polygon drawing process.

  First, it is determined whether or not the viewpoint setting of the virtual camera looking up from a position lower than the game field (ground) is set (step S11). In such a viewpoint setting, the foot shadow polygon SPL is drawn. The process is terminated without performing. This is because if the foot shadow polygon SPL is drawn with such a viewpoint setting, an unnatural foot shadow image may be generated.

  Next, it is determined whether the brightness of the point light source described with reference to FIG. 7 is equal to or higher than a predetermined threshold (step S12). If it is equal to or greater than the predetermined threshold value, the illumination direction of the point light source is set to the foot shadow projection direction (step S13). In this way, a foot shadow image can be generated using a projection direction different from the projection direction used for generating a shadow image of the model object. When setting the illumination direction, a process for slightly adjusting the projection direction is performed if necessary. That is, when a point light source is generated at a position as shown in FIG. 7, the foot shadow is often displayed directly below the foot at the position of this point light source. Therefore, the projection direction is adjusted, for example, slightly toward the horizontal direction.

  On the other hand, when the brightness of the point light source is smaller than a predetermined threshold value, the illumination direction of the main light source (LS in FIG. 3) used for the shadow map process is set as the foot shadow projection direction (step S14). . In this case, the projection direction used for generating the shadow image of the model object is the same as the projection direction for generating the foot shadow image.

  Next, as described with reference to FIGS. 5A to 5C, a size table and a vertex data table corresponding to the type of model object (character) are selected (step S15). Then, a distance LB between the position BP1 of the ankle bone BN1 and the position BP2 of the toe bone BN2 is obtained, and interpolation processing is performed based on the distance set in the size table to obtain the size of the foot shadow (step S16). ).

  Next, the maximum darkness of the foot shadow is obtained based on the brightness of the light source employed in step S13 or S14 (step S17). Specifically, the maximum darkness of the foot shadow is increased as the light source is brighter. For example, when the point light source is selected as in step S13, the maximum darkness of the foot shadow becomes deeper as the distance from the point light source becomes closer and brighter. Thereby, the virtual reality of a player can be improved.

  Next, the maximum darkness of the foot shadow obtained in step S17 is adjusted so that the Y-axis component of the ankle bone BN1 (the component of the axis in the height direction in the absolute coordinate system) becomes smaller (step S17). S18). In this way, it is possible to control the darkness of the foot shadow image according to the angle formed by the ground plane of the foot portion (ground portion) and the game field where the model object moves. As a result, for example, when the model object is down and falls, an unnatural foot shadow image can be prevented from being generated.

  Next, a foot shadow generation polygon GPL is generated based on the size of the foot shadow obtained in step S16 and the vertex data table described in FIG. 15C (step S19). Then, as described with reference to FIG. 6, the foot shadow polygon SPL is generated by projecting each vertex of the foot shadow generation polygon GPL in the projection direction of the foot shadow set in step S13 or S14 (step S20). ). At this time, based on the height distance with respect to the game field of each vertex of the foot shadow generation polygon GPL, the maximum darkness of the foot shadow is attenuated to set the shadow density of each vertex of the foot shadow polygon SPL.

  Next, it is determined whether the sum of the darkness of the shadows of all the vertices of the foot shadow polygon SPL is equal to or smaller than a predetermined threshold value (step S21). The processing ends without drawing SPL. By doing so, as shown in FIG. 10, it is possible to realize an image expression in which the foot shadow disappears as the foot rises.

  Next, all the vertices of the foot shadow polygon SPL are converted into the screen coordinate system, and it is determined whether or not these vertices are outside the screen (step S22). If it is outside the screen, the process ends without drawing the foot shadow polygon SPL.

  Next, the foot shadow polygon SPL is Z-shifted to the near side when viewed from the virtual camera (step S23). Then, as described with reference to FIG. 12C, the normal Z comparison setting is such that drawing is performed when the Z value of the foot shadow polygon SPL is closer to the Z value of the Z buffer 177. Then, the drawing process is performed, and the predetermined stencil value of the corresponding area of the stencil buffer 178 is cleared to zero (step S24). That is, the stencil value in the area indicated by A4 in FIG.

  Next, as described with reference to FIG. 12A, the foot shadow polygon SPL is Z-shifted rearward as viewed from the virtual camera (step S25). A predetermined stencil value is stored in the stencil buffer 178 with a Z comparison setting different from normal, in which drawing is performed when the Z value of the foot shadow polygon SPL is a Z value on the back side of the Z value of the Z buffer 177. A drawing process of the foot shadow polygon SPL is performed on an area (pixel) that has not been written and is cleared to zero (step S26). Thereby, as shown in FIG. 18, an appropriate foot shadow image LSD1 corresponding to the foot shadow polygon SPL is generated. Then, the Z comparison setting is returned to the original normal setting, and the stencil function is disabled (step S27).

3. Hardware Configuration FIG. 22A shows a hardware configuration example that can realize this embodiment.

  The CPU 900 (main processor) is a multi-core processor including a plurality of CPU cores 1, CPU cores 2, and CPU cores 3. The CPU 900 includes a cache memory (not shown). Each of the CPU cores 1, 2, and 3 is provided with a vector calculator and the like. Each of the CPU cores 1, 2, and 3 can execute, for example, two H / W thread processes in parallel without performing a context switch, and a multi-thread function is supported by hardware. A total of three CPU cores 1, 2, and 3 can execute six H / W thread processes in parallel.

  The GPU 910 (drawing processor) performs vertex processing and pixel processing to realize drawing (rendering) processing. Specifically, according to the shader program, the vertex data is created / changed and the drawing color of the pixel (fragment) is determined. When an image for one frame is written in the VRAM 920 (frame buffer), the image is displayed on a display such as a TV via a video output. The main memory 930 functions as a work memory for the CPU 900 and the GPU 910. Further, in the GPU 910, a plurality of vertex threads and a plurality of pixel threads are executed in parallel, and a multi-thread function of drawing processing is supported by hardware. The GPU 910 is also provided with a hardware tessellator. The GPU 910 is a unified shader type in which the vertex shader and the pixel shader are not distinguished in terms of hardware.

  The bridge circuit 940 (south bridge) is a circuit that controls the flow of information inside the system, and incorporates a controller such as a USB controller (serial interface), a network communication controller, an IDE controller, or a DMA controller. The bridge circuit 940 implements an interface function among the game controller 942, the memory card 944, the HDD 946, and the DVD drive 948.

  Note that the hardware configuration capable of realizing this embodiment is not limited to FIG. 22A, and may be, for example, a configuration as shown in FIG.

  In FIG. 22B, the CPU 902 includes a processor element PP and eight processor elements PE1 to PE8. The processor element PP is a general-purpose processor core, and the processor elements PE1 to PE8 are processor cores having a relatively simple configuration. The architectures of the processor element PP and the processor elements PE1 to PE8 are different, and the processor elements PE1 to PE8 are SIMD type processor cores that can simultaneously perform the same processing on a plurality of data with one instruction. Thereby, multimedia processing such as streaming processing can be executed efficiently. The processor element PP can execute two H / W thread processes in parallel, and each of the processor elements PE1 to PE8 can execute one H / W thread process. Therefore, the CPU 902 can execute a total of 10 H / W thread processes in parallel.

  In FIG. 22B, the GPU 912 and the CPU 902 are closely linked, and the GPU 912 can directly perform the rendering process on the main memory 930 on the CPU 902 side. Further, for example, the CPU 902 can perform geometry processing to transfer vertex data, or easily return data from the GPU 912 to the CPU 902. It is also easy for the CPU 902 to perform rendering pre-processing and post-processing, and the CPU 902 can execute tessellation (plane division) and dot fill. For example, the CPU 902 can perform a process with a high level of abstraction, and the GPU 912 can perform a detailed process with a low level of abstraction.

  When the processing of each unit of the present embodiment is realized by hardware and a program, a program for causing the hardware (computer) to function as each unit of the present embodiment is stored in the information storage medium. More specifically, the program instructs a processor (CPU, GPU), which is hardware, to pass data if necessary. And a processor implement | achieves the process of each part of this invention based on the instruction | indication and the passed data.

  Although the present embodiment has been described in detail as described above, it will be easily understood by those skilled in the art that many modifications can be made without departing from the novel matters and effects of the present invention. Accordingly, all such modifications are intended to be included in the scope of the present invention. For example, in the specification or the drawings, terms (foot) that are described at least once together with different terms having broader or the same meaning (grounding portion, shadow primitive surface, foot shadow generation primitive surface, foot shadow image, field, model object, etc.) (Parts, foot shadow polygons, foot shadow generating polygons, ground shadow images, game fields, characters, etc.) can be replaced with their different terms anywhere in the specification or drawings.

  In addition, shadow image processing such as model object shadow image generation processing, ground image shadow image generation processing, model object drawing processing, shadow map processing, and distributed shadow map processing are also described in this embodiment. Without being limited thereto, techniques equivalent to these are also included in the scope of the present invention. The present invention can be applied to various games. Further, the present invention is applied to various image generation 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, a system board for generating a game image, and a mobile phone. it can.

The example of the block diagram of the image generation system of this embodiment. The example of the game image produced | generated from this embodiment. Explanatory drawing of a shadow map process. An example of a shadow map texture. FIG. 5A to FIG. 5C are explanatory diagrams of a method for generating a foot shadow image. Explanatory drawing of the production method of a foot shadow image. Explanatory drawing of the production method of the foot shadow image by a point light source. The example of the game image produced | generated from this embodiment. The example of the game image produced | generated from this embodiment. The example of the game image produced | generated from this embodiment. The example of the game image produced | generated from this embodiment. 12 (A) to 12 (C) are explanatory diagrams of a method for generating a foot shadow image. The figure for demonstrating the concrete drawing process of this embodiment. The figure for demonstrating the concrete drawing process of this embodiment. The figure for demonstrating the concrete drawing process of this embodiment. The figure for demonstrating the concrete drawing process of this embodiment. The figure for demonstrating the concrete drawing process of this embodiment. The figure for demonstrating the concrete drawing process of this embodiment. The flowchart explaining the detailed process of this embodiment. The flowchart explaining the detailed process of this embodiment. The flowchart explaining the detailed process of this embodiment. 22A and 22B show examples of hardware configurations.

Explanation of symbols

100 processing unit, 102 game calculation unit, 104 object space setting unit,
106 moving object calculation unit, 108 virtual camera control unit, 120 drawing processing unit,
121 a first drawing processing unit, 122 a second drawing processing unit, 130 a sound generation unit,
160 operation unit, 170 storage unit, 172 object data storage unit,
173 motion data storage unit, 174 texture storage unit, 176 drawing buffer,
177 Z buffer, 178 stencil buffer, 180 information storage medium,
190 Display unit, 192 Sound output unit, 194 Auxiliary storage device, 196 Communication unit

Claims (12)

A program for generating an image visible from a virtual camera in an object space,
A first drawing processing unit that performs drawing processing of a plurality of objects including a model object while performing shadowing processing, and generates an image in which an image of the model object and a shadow image of the model object are displayed;
As a second drawing processing unit that performs a drawing process of a shadow primitive surface corresponding to the grounding unit of the model object, and generates an image in which the shadow image of the grounding unit is combined with the shadow image of the model object ,
A program characterized by causing a computer to function. In claim 1,
The first drawing processing unit includes:
A program for generating the shadow image of the model object by shadow map processing. In claim 1 or 2,
The second drawing processing unit
The shadow primitive surface generated by projecting the shadow generating primitive surface set for the grounding portion onto the field in which the model object moves is drawn, so that the shadow of the grounding portion is processed. A program characterized by generating an image. In any one of Claims 1 thru | or 3,
The second drawing processing unit
A program characterized in that the first drawing processing unit generates a shadow image of the grounding unit using a projection direction different from a projection direction used for generating a shadow image of the model object. In claim 4,
The second drawing processing unit
A program that generates a shadow image of the grounding unit using a projection direction of the point light source when a point light source exists. In any one of Claims 1 thru | or 5,
The second drawing processing unit
When the shadow primitive plane is Z-shifted in the rearward direction when viewed from the virtual camera, and the Z value of each pixel of the shadow primitive plane is the rear Z value of the Z buffer. A program that performs drawing processing of the shadow primitive surface with a Z comparison setting of drawing. In claim 6,
The first drawing processing unit includes:
When performing the drawing process of the model object, a predetermined stencil value is written to the area of the stencil buffer corresponding to the drawing area of the model object,
The second drawing processing unit
A program for drawing the shadow primitive surface in an area where the predetermined stencil value is not written in the stencil buffer and the stencil value is cleared. In claim 7,
The second drawing processing unit
Drawing a primitive surface corresponding to the shadow primitive surface by setting Z comparison in which the Z value of each pixel of the shadow primitive surface is drawn when the Z value is closer to the Z value in the Z buffer. A program that performs processing to clear the predetermined stencil value of the stencil buffer. In any one of Claims 1 thru | or 8.
The second drawing processing unit
A program for controlling a darkness of a shadow image of the grounding portion according to an angle formed by a grounding surface of the grounding portion and a field where the model object moves. In any one of Claims 1 thru | or 9,
The first drawing processing unit includes:
A program for performing a drawing process for a background object after performing a drawing process for the model object.   A computer-readable information storage medium, wherein the program according to any one of claims 1 to 10 is stored. An image generation system for generating an image visible from a virtual camera in an object space,
A first drawing processing unit that performs drawing processing of a plurality of objects including a model object while performing shadowing processing, and generates an image in which an image of the model object and a shadow image of the model object are displayed;
A second rendering processing unit that performs a rendering process of a shadow primitive surface corresponding to the grounding unit of the model object, and generates an image in which the shadow image of the grounding unit is combined with the shadow image of the model object; ,
An image generation system comprising: