JP2011095937A - 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, or the like, allowing fur shading processing by a pixel shader. <P>SOLUTION: The image generation system includes a texture storage portion; and an image generation portion for generating an image viewed from a virtual camera in an object space, by performing pixel shading processing using a texture. The texture storage portion stores a texture for fur shading. The image generation portion fetches a texel value of the texture for the fur shading while sequentially shifting texture coordinates in a texture space, in a direction specified by a normal vector of a drawing target pixel, and sets the composition value of a plurality of texel values, obtained by the fetch to a pixel value of the drawing target pixel to generate a fur shading image. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  Conventionally, there has been known 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 (virtual three-dimensional space) in which model objects such as characters are arranged and set. It is popular as a place to experience so-called virtual reality. Taking an image generation system capable of enjoying a fighting game as an example, a player operates a character (model object) using an operation unit (game controller), and another character (enemy character) operated by the opponent player or the computer. Enjoy the game by playing against.

  In such an image generation system, it is desirable to be able to realistically represent, for example, the hair that grows on the character and the fur clothes that the character wears. As a conventional technique related to fur shading that realizes such hair expression, there is a technique disclosed in Patent Document 1, for example.

  However, conventional fur shading has a problem such as a heavy processing load due to an increase in the number of polygons used. In addition, a method for realizing fur shading using a so-called pixel shader has not been proposed.

JP 2000-36058 A

  According to some aspects of the present invention, it is possible to provide a program, an information storage medium, an image generation system, and the like that can realize a fur shading process using a pixel shader.

  One aspect of the present invention includes a texture storage unit that stores a texture, and an image generation unit that generates an image seen from a virtual camera in the object space by performing pixel shader processing using the texture, and the texture storage unit Unit stores the texture for fur shading, and the image generation unit sequentially shifts texture coordinates in the texture space in the direction specified by the normal vector of the drawing target pixel, The present invention relates to an image generation system that generates a fur shading image by fetching a value and setting a composite value of a plurality of texel values obtained by the fetch to a pixel value of a drawing target pixel. 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 one aspect of the present invention, the texture for fur shading is stored in the texture storage unit. Then, the texel values of the texture for fur shading are fetched while the texture coordinates are sequentially shifted in the direction specified by the normal vector of the drawing target pixel. Then, the combined value of the plurality of fetched texel values is set to the pixel value of the drawing target pixel, and a fur shading image is generated. In this way, it is possible to realize the fur shading process with the pixel shader, and it is possible to generate a fur shading image with a smaller processing load and data amount than with the shell method or the like.

  In one aspect of the present invention, in the camera coordinate system of the virtual camera, when the coordinate axis along the viewing direction of the virtual camera is the Z axis, and the coordinate axis orthogonal to the Z axis is the X axis and the Y axis, The image generation unit sequentially shifts the texture coordinates (U, V) in the texture space in a direction specified by a direction opposite to the direction of the projection normal vector obtained by projecting the normal vector of the drawing target pixel onto the XY plane. However, the texel value of the fur shading texture may be fetched.

  In this way, it is possible to specify the shift direction of the texture coordinates (U, V) based on the direction of the projection normal vector, fetch the texel value of the texture for fur shading, and generate a fur shading image. Therefore, the texel value can be fetched by setting the shift direction of the texture coordinates by a simple process using the projection normal vector.

  In the aspect of the invention, the image generation unit fetches the texel value C1 = TEX (U1, V1) in the first fetch process, and the texel value C2 = TEX (U2, V2) in the second fetch process. ... In the Nth fetch process, the texel value CN = TEX (UN, VN) is fetched, and the combined value obtained by combining the fetched texel values C1 to CN is rendered. The pixel value of the target pixel is set, and the direction opposite to the direction of the projection normal vector is a direction from the texture coordinates (U1, V1) to the texture coordinates (UN, VN), and the length of the projection normal vector The longer the distance, the longer the distance from the texture coordinates (U1, V1) to the texture coordinates (UN, VN).

  In this way, the texture coordinate shift direction and shift amount can be obtained by simple processing.

  Also, in one aspect of the present invention, the image generation unit obtains a composite value by performing a composite process of K1 × C1 + K2 × C2 +... + KN × CN, and the weight value Ki + 1 is a weight value Ki (1 ≦ i < N) may be a smaller value.

  By providing such weight values, fur shading hair roots and hair ends can be expressed.

  In one aspect of the present invention, the image generation unit generates a fur shading image for the first part of the model object by a shell method using a plurality of stacked polygons to which textures are mapped, For the second part of the model object, a fur shading image may be generated by setting a composite value of a plurality of texel values obtained by fetching the fur shading texture to a pixel value of a drawing target pixel. .

  In this way, it is possible to achieve both realistic hair expression and reduction in processing load.

  In the aspect of the invention, the first part is an area set on the front side of the model object, and the second part is an area set on the back side of the model object. Also good.

  In the aspect of the invention, the image generation unit may variably set the number of texel values to be combined.

  In this way, it is possible to synthesize a plurality of texel values by variably setting the number of texel values to be combined (setting the number of fetches variably) according to the processing load and processing time, for example.

1 is a configuration example of an image generation system according to the present embodiment. FIG. 2A to FIG. 2C are explanatory diagrams of fur shading by the shell method. Explanatory drawing of fur shading by a shell method. 4A to 4E are explanatory diagrams of a fur shading method using a pixel shader. An example of fur shading texture. The flowchart explaining the fur shading method of this embodiment. 7A and 7B are explanatory diagrams of objects and normal vectors set for the objects. 8A and 8B are explanatory diagrams of the relationship between the virtual camera and the normal vector. FIG. 9A to FIG. 9C are explanatory diagrams of the fur shading method of the present embodiment. FIG. 10A to FIG. 10C are explanatory diagrams of the fur shading method of the present embodiment. FIG. 11A to FIG. 11C are explanatory diagrams of the fur shading method of the present embodiment. FIGS. 12A and 12B are explanatory diagrams of a method of applying a different fur shading method depending on each part of the model object. The flowchart of the whole process of this embodiment. 14A and 14B show examples of the hardware configuration of the image generation system.

  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 configuration of the image generation system of the present embodiment is not limited to that shown in FIG. 1, and various modifications may be made such as omitting some of the components (each unit) or adding other components. .

  The operation unit 160 is for a player to input operation data, and functions thereof are direction instruction keys, operation buttons, analog sticks, levers, various sensors (such as an angular velocity sensor and an acceleration sensor), a microphone, or a touch panel type. This can be realized with a display.

  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. 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 an LCD, an organic EL display, a CRT, a touch panel display, an 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 storage device used to supplement the capacity of the storage unit 170, and can be realized by a memory card such as an SD memory card or a multimedia card.

  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 movement processing unit 106, a motion processing unit 107, a virtual camera control unit 108, an image generation unit 120, and a sound generation unit 130. Various modifications may be made such as omitting some of these components or adding other components.

  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 objects (polygons) representing display objects such as moving objects (people, robots, cars, fighters, missiles, bullets, etc.), maps (terrain), buildings, courses (roads), trees, and walls. , An object configured with a primitive surface such as a free-form surface or a subdivision surface) is set in the object space. That is, the position and rotation angle (synonymous with direction and direction) of the object in the world coordinate system are determined, and the rotation angle (rotation angle around the X, Y, and Z axes) is determined at that position (X, Y, Z). Arrange objects. Specifically, the object data storage unit 172 of the storage unit 170 stores object data such as the position, rotation angle, moving speed, moving direction, etc. of the object (part object) in association with the object number. .

  The movement processing unit 106 performs a process of moving a moving object such as a model object. For example, the moving object is moved in the object space based on operation data input by the player through the operation unit 160, a program (movement algorithm), various data, and the like. Specifically, a simulation process for sequentially obtaining movement information (position, rotation angle, speed, or acceleration) of the moving object for each frame (1/60 second) is performed. Note that a frame is a unit of time for performing a movement process, a motion process, and an image generation process.

  The motion processing unit 107 performs motion processing (motion reproduction, motion generation) for causing a model object such as a character to perform motion (animation). This motion processing can be realized by reproducing the motion of the model object based on the motion data stored in the motion data storage unit 173.

  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 a model object (moving body) such as a character or a car is photographed from behind using a virtual camera, the virtual camera position or rotation angle (virtual angle) is set so that the virtual camera follows changes in the position or rotation of the model object. Control camera orientation). 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 movement processing 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 image generation unit 120 performs drawing processing based on the results of various processing (game processing and simulation processing) performed by the processing unit 100, thereby generating an image and outputting the image to the display unit 190. Specifically, geometric processing such as coordinate transformation (world coordinate transformation, camera coordinate transformation), clipping processing, perspective transformation, or light source processing is performed. Based on the processing result, drawing data (the position of the vertex of the primitive surface) Coordinates, texture coordinates, color data, normal vector, α value, etc.) are created. Then, based on the drawing data (primitive surface data), the perspective transformation (geometry processing) object (one or a plurality of primitive surfaces) is converted into image data in units of pixels such as a drawing buffer 176 (frame buffer, work buffer, etc.). Draw in a buffer that can be stored. Thereby, an image that can be seen from the virtual camera (given viewpoint) in the object space is generated.

  For example, the image generation unit 120 can include a vertex processing unit 122 and a pixel processing unit 124.

  The vertex processing unit 122 (vertex shader, geometry shader) performs vertex processing. Specifically, vertex processing (shading by a vertex shader) is performed based on vertex data of the object (vertex position coordinates, texture coordinates, color data, normal vector, α value, etc.). 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 the vertex processing, according to the vertex processing program (vertex shader program, first shader program), vertex movement processing, coordinate conversion (world coordinate conversion, camera coordinate conversion), clipping processing, perspective processing, and other geometric processing are performed. On the basis of the processing result, the vertex data given to the vertex group constituting the object is changed (updated or 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.

  The pixel processing unit 124 (pixel shader) performs pixel processing. More specifically, after 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, according to a pixel processing program (pixel shader program, second shader program), various processes such as texture reading from the texture storage unit 175 (texture mapping), color data setting / changing, translucent composition, anti-aliasing, etc. The final drawing color of the pixels constituting the image is determined, and the drawing color of the perspective-transformed object is output (drawn) to the drawing buffer 174. 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 the pixel processing can be realized by hardware that enables a polygon (primitive) drawing process to be programmed by a shader program described in a shading language, that is, a so-called programmable shader (vertex shader or pixel shader). 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 image generation unit 120 performs texture mapping processing and the like. The texture mapping process (texture fetch / texture sampling process) is a process for mapping the texture (texel value) stored in the texture storage unit 175 to the object. Specifically, the texture (surface properties such as color and α value) is read from the texture storage unit 175 using the texture coordinates or the like set (given) to the vertex or the like of the object (primitive surface). Then, a texture that is a two-dimensional image or pattern is mapped to the object.

  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.

  In the present embodiment, the texture storage unit 175 stores fur shading texture. Then, the image generation unit 120 generates an image that can be viewed from the virtual camera in the object space by performing pixel shader processing using a texture such as a fur shading texture.

  Specifically, the image generation unit 120 (pixel processing unit 124) is a direction specified by a normal vector of a drawing target pixel (pixel to be subjected to pixel shader processing) (for example, a direction opposite to the direction of the projection normal vector, Alternatively, the texture coordinates in the texture storage unit 175 are fetched (sampled) while the texture coordinates in the texture space are sequentially shifted in the opposite direction and the direction specified by a predetermined parameter or the like). . Then, a far shading image is generated by setting (drawing) a composite value (composite color value) of a plurality of texel values obtained by fetching to a pixel value of a drawing target pixel. The normal vector of the drawing target pixel can be acquired by interpolating the normal vector of the vertex of the object.

  Also, in the camera coordinate system (viewpoint coordinate system) of the virtual camera, the coordinate axis along the viewing direction of the virtual camera is the Z axis (third coordinate axis), the coordinate axis orthogonal to the Z axis is the X axis, and the Y axis (first and first axes). 2 coordinate axes). In this case, the image generation unit 120 projects the normal vector of the drawing target pixel onto the XY plane (the plane including the X axis and the Y axis. The plane including the first and second coordinate axes). While the texture coordinates (U, V) in the texture space are sequentially shifted (moved) in the direction specified by the reverse direction (the direction specified by the reverse direction of the direction of the projection normal vector and the predetermined parameter, etc.) Fetch texel value of shading texture. And the pixel value of a drawing object pixel is acquired by synthesize | combining several fetched texel values.

  More specifically, the image generation unit 120 fetches the texel value C1 = TEX (U1, V1) in the first fetch process, and fetches the texel value C2 = TEX (U2, V2) in the second fetch process. . Similarly, the texel value Ci = TEX (Ui, Vi) is fetched in the i-th fetch process (1 ≦ i <N), and finally the texel value CN = TEX (UN, VN) is fetched in the N-th fetch process. To do. Then, the combined value obtained by performing the combining process of these fetched texel values C1 to CN is written as a pixel value in the drawing target pixel.

  In this case, the reverse direction (direction corresponding to the reverse direction) of the projection normal vector obtained by projecting the normal vector of each drawing target pixel onto the XY plane of the camera coordinate system is changed from the texture coordinate (U1, V1) to the texture coordinate. The direction is (UN, VN). As the length of the projection normal vector increases, the distance from the texture coordinates (U1, V1) to the texture coordinates (UN, VN) increases. By doing in this way, the fur shading process by the pixel shader using a normal vector is realizable.

  Further, the image generation unit 120 performs a combination process of K1 × C1 + K2 × C2 +... + KN × CN to obtain a combined value. In this case, it is desirable that the weight value Ki + 1 is smaller than the weight value Ki (1 ≦ i <N). In this way, when viewed from the viewpoint of the virtual camera, it is possible to realize an image representation of hair that appears thicker from the hair root toward the hair tip.

  Further, the method of fur shading to be applied may be different for each part of the model object. Specifically, for the first part of the model object such as a character or clothes, the image generation unit 120 generates a fur shading image by a shell method using a plurality of stacked polygons to which textures are mapped. . That is, a plurality of polygons in which a texture representing a hair cross-sectional view is mapped to each polygon are stacked, and a fur shading image is generated by drawing these plurality of polygons. On the other hand, for the second part of the model object, a fur shading image is generated by a method of setting a composite value of a plurality of texel values obtained by fetching the fur shading texture as the pixel value of the drawing target pixel.

  Here, the first portion is an area where the virtual camera is likely to be watched or the frequency is high, for example, in a game or the like. Specifically, it is an area set on the front side of the model object, for example. More specifically, the region is close to the character's face. About this 1st part, a more realistic hair quality expression is implement | achieved by producing | generating an image by the fur shading method of a shell method. Note that another fur shading method such as a fin method may be applied to the first portion.

  On the other hand, the second part is an area where the possibility or frequency of the virtual camera in the game or the like is low. Specifically, the second part is an area set on the back side of the model object. Alternatively, even in the area on the front side of the model object, an area where the virtual camera is less likely to be watched or the frequency is low can be set as the second portion. About this 2nd part, a hair quality expression is implement | achieved by a small processing load by producing | generating an image with the fur shading method of this embodiment using a pixel shader. In this manner, when the processing load becomes too heavy when the fur shading method of the shell method is applied to all regions, the present embodiment using the pixel shader for the second portion wider than the first portion. By applying the fur shading method, it is possible to achieve both realistic hair expression and reduction of processing load.

  The image generation unit 120 may variably set the number of texel values to be combined (the number of texel value fetches). For example, when the processing load is heavy or the processing time is insufficient, the number of texel values to be combined is reduced. Thereby, processing load can be reduced and processing time can be saved. On the other hand, when there is a margin in processing load and processing time, the number of texel values to be combined is increased. As a result, the number of texel values to be combined can be increased to generate a fur shading image with higher quality.

  For example, the number of texel values to be combined (number of fetches) may be changed according to the processing capability of the processing unit (CPU). That is, when the processing capability is high, the number of texel values to be combined is increased, and when the processing capability is low, the number of texel values to be combined is decreased.

2. 2. Method of this Embodiment 2.1 Fur Shading First, the fur shading by the shell method will be described with reference to FIGS. 2 (A) to 2 (C). In this shell method, in order to express the hair as shown in FIG. 2A, a texture of a cross-sectional view of the hair is prepared, as shown in FIG. 2B. Then, as shown in FIG. 2C, for example, a plurality of polygons are arranged at regular intervals in the normal direction of the model object, and for each of these polygons, the polygon of FIG. Map the texture. Then, since the texture of the cross-sectional view overlaps with the direction of the hair, when viewed from the viewpoint of the virtual camera, the expression appears such that the hair appears on the surface of the object. Note that by setting an α value for translucent processing or the like for the texture of FIG.

  In the fur shading based on the shell method shown in FIGS. 2A to 2C, for example, 4 to 8 polygons need to be stacked and arranged in a portion where the hair of the model object is to be expressed. For example, when fur shading is applied to the areas indicated by E1 and E2 of the model object of the fur coat in FIG. 3, it is necessary to stack a plurality of polygons on these areas. For this reason, the number of polygons constituting the model object increases, and the processing load and data amount increase. In particular, if fur shading by the shell method is applied to all parts of the model object, the number of polygons constituting the model object may increase several times. In this case, a method of dynamically generating polygons to be stacked in real time using a so-called geometry shader can be considered, but this method also leads to an increase in processing load, and in an image generation system that does not have such a geometry shader. There is a problem that this method cannot be adopted.

  Therefore, in this embodiment, a fur shading method using a pixel shader is adopted. In other words, pseudo far shading is realized by performing multi-sampling of the texture with the inclination of the normal to the virtual camera (screen).

  For example, in FIGS. 4A to 4E, PIX is a pixel to be rendered (processed) by the pixel shader. FUR1 is a hair growing from the drawing target pixel PIX. The image of the hair FUR1 is an image that is thick at the hair root and narrows as it goes to the hair tip. When such an image of the hair FUR1 is generated, the pixel shader can draw only in units of pixels, and thus the image of the hair FUR1 cannot be generated by one drawing. Therefore, in the present embodiment, a method for generating such a hair image by texture multi-sampling is adopted.

  For example, FUR2 in FIG. 4B is a hair growing from a pixel adjacent to the right of the pixel PIX of the hair root of FUR1. In addition, FUR3 in FIG. 4C is a hair growing from a pixel right next to the hair root of FUR2, and FUR4 in FIG. 4D is a hair growing from a pixel right next to the hair root of FUR3. . Moreover, FUR5 of FIG.4 (E) is the hair which has grown from the pixel on the right side of the hair root of FUR4.

  As described above, the pixel shader can draw only in units of pixels. Therefore, in the present embodiment, in FIG. 4A, the image of the hair root of the hair FUR1 is drawn on the drawing target pixel PIX, and in FIG. 4B, for example, one pixel (texel) from the hair root of the adjacent hair FUR2. The image on the hair end side is drawn on the drawing target pixel PIX by the amount, and in FIG. 4C, the image on the hair tip side is drawn on the drawing target pixel PIX by, for example, 2 pixels from the hair root of the adjacent hair FUR3. To do. And in the last FIG.4 (E), the image of the hair | bristle tip (terminal) of hair FUR5 is drawn.

  4A to 4E, a pseudo fur shading process can be realized using a pixel shader. And in order to implement | achieve drawing of FIG. 4 (A)-FIG.4 (E), the multi-sampling of a texture and the normal vector information of each pixel are used.

  For example, FIG. 5 shows an example of the texture for fur shading of this embodiment. In the present embodiment, a multi-sampling method that samples the texel value of the texture for fur shading a plurality of times is adopted.

  FIG. 6 shows a flowchart of processing for realizing the fur shading method of this embodiment. First, the texel value C1 = TEX (U1, V1) sampled by the texture coordinates (U1, V1) is fetched (step S11). This texel value is a texel value (color data) that is fetched even in normal texture mapping that does not perform fur shading and is written to the drawing target pixel PIX. For example, the texel value corresponding to the image of the hair follicle (FIG. 4). (A) FUR1 hair root image).

  Next, the texture coordinates are shifted from (U1, V1) to (U2, V2), and the texel value C2 = TEX (U2, V2) sampled by the texture coordinates (U2, V2) is fetched (step S12). . This texel value is a texel value corresponding to an image on the hair end side by, for example, one pixel from the root of the adjacent hair (FUR2 in FIG. 4B).

  Next, the texture coordinates are shifted from (U2, V2) to (U3, V3), and the texel value C3 = TEX (U3, V3) sampled by the texture coordinates (U3, V3) is fetched (step S13). . This texel value is a texel value corresponding to an image on the hair end side, for example, by 2 pixels from the hair root of the adjacent hair (FUR3 in FIG. 4B).

  In steps S14, S15, and S16, as in steps S11, S12, and S13, the texture coordinates for the fur shading texture are fetched while sequentially shifting the texture coordinates.

  By performing texture multi-sampling while shifting texture coordinates in this way, a plurality of texel values C1 to C6 are fetched corresponding to the drawing target pixel PIX. Then, a synthesis process of these fetched texel values C1 to C6 is performed (step S17). Specifically, the composite value CSY = K1 * C1 + K2 * C2 + K3 * C3 + K4 * C4 + K5 * C5 + K6 * C6 is obtained, and the obtained composite value CSY is output as the pixel value (color value) of the drawing target pixel.

  In the weight values K1 to K6 (combination coefficient), the relationship that the weight value Ki + 1 is smaller than the weight value Ki (1 ≦ i <N) is established. In other words, the weight value is gradually reduced as it goes from K1 to K6. By doing so, as shown in FIGS. 4A to 4E, the weight value (K1) of the hair root image is the highest and the weight value (K6) of the hair tip image is the lowest. become.

  FIG. 6 shows a case where the number of fetches N of texel values N (the number of texel values to be combined) is 6, but the number of fetches N is arbitrary. For example, when the processing capacity of the CPU is high or there is a margin in processing, the number of fetches N may be increased. When the processing capacity of the CPU is low or when there is no margin in processing, the number of fetches N may be decreased.

  Next, details of the texture coordinate shift method will be described. FIG. 7A shows an example of an object OB that is a texture mapping target. Here, in order to simplify the description, the description will be made assuming that the object OB has a spherical shape.

  As shown in FIG. 7B, a normal vector (normal information) is set at each vertex of the object OB. When performing the pixel shader processing, the normal vector of the drawing target pixel PIX is obtained by interpolating the normal vector of the vertex.

  FIG. 8A shows the relationship between the normal vector N (Nx, Ny, Nz) set for the drawing target pixel PIX and the virtual camera VC. Here, in the camera coordinate system of the virtual camera VC, the coordinate axis along the visual line direction DV of the virtual camera VC is the Z axis (third coordinate axis), the coordinate axis orthogonal to the Z axis is the X axis, and the Y axis (first, Second coordinate axis). Then, the projection normal vector NP (Nx, Ny) obtained by projecting the normal vector N (Nx, Ny, Nz) of the drawing target pixel PIX onto the XY plane becomes a vector as shown in FIG. This projection normal vector NP corresponds to the normal vector N seen from the virtual camera VC. In this embodiment, the texture coordinates (U, V) of the texture to be fetched are obtained from the projection normal vector NP. Specifically, the texture coordinates (U, V) are obtained by a predetermined calculation formula (or calculation table) using the X coordinate Nx and the Y coordinate Ny of the projection normal vector NP.

  For example, in FIG. 9A, the drawing target pixel PIX of the pixel shader is set to the center point (the point where the line-of-sight direction DV and the spherical object OB intersect). The direction of the normal vector N of the drawing target pixel PIX is parallel to the visual line direction DV of the virtual camera VC. That is, the normal vector N is directed toward the virtual camera VC. Accordingly, the virtual camera VC looks as shown in FIG. 9B, and both the X coordinate Nx and the Y coordinate Ny of the projection normal vector NP are zero. In this way, in FIG. 9B, the projection normal vector NP appears as a point when viewed from the virtual camera VC. Therefore, in this case, as shown in FIG. 9C, the same point (point of the same texture coordinate) in the texture space is sampled and fetched six times.

  Specifically, in the first fetch process of step S11 in FIG. 6, the texel value C1 = TEX (U1, V1) is fetched from the texture coordinates (U1, V1) of the corresponding point FC1. Here, the texture coordinates (U1, V1) of the corresponding points are texture coordinates associated with the drawing target pixel PIX in normal texture mapping. Accordingly, in the first fetch process FC1 in step S11, the texel value C1 = TEX (U1, V1) associated with the drawing target pixel PIX is fetched.

  On the other hand, also in the second to sixth fetch processes in steps S12 to S16, the texture coordinate texel values of the same points FC2 to FC6 as the corresponding points FC1 are fetched. That is, the texture coordinates (U2, V2) in steps S12 to S16 are equal to the texture coordinates (U1, V1) in step S11, and the texel values C2 to C6 fetched in steps S12 to S16 are also fetched in step S11. It becomes equal to the value C1.

  Then, the same texel values (= C1) fetched in steps S11 to S16 are combined in step S17, and the combined value CSY = (K1 + K2 + K3 + K4 + K5 + K6) × C1 is drawn on the drawing target pixel PIX.

  In FIG. 10A, the drawing target pixel PIX is on the left side of the center point (the point where the line-of-sight direction DV and the sphere object OB intersect), and the direction of the normal vector N is leftward compared to FIG. 9A. ing. Accordingly, the virtual camera VC looks as shown in FIG. 10B, the X coordinate Nx of the projection normal vector NP becomes a negative value, and the Y coordinate Ny becomes zero. Thus, in FIG. 10B, the direction of the projection normal vector NP is the left direction when viewed from the virtual camera VC. Therefore, in this case, as shown in FIG. 10C, sampling is fetched six times in the right direction (opposite to the NP direction) from the corresponding point FC1.

  Specifically, in the first fetch process of step S11 in FIG. 6, the texel value C1 = TEX (U1, V1) is fetched from the texture coordinates (U1, V1) of the corresponding point FC1. In the second fetch process in the next step S12, the texel value C2 = TEX (U2, V2) is fetched from the texture coordinates (U2, V2) of the point FC2 in the right direction of FC1. In the third fetch process in the next step S13, the texel value C3 = TEX (U3, V3) is fetched from the texture coordinates (U3, V3) of the point FC3 in the right direction of FC2. The same applies to the fourth to sixth fetch processes in steps S14 to S16.

  Then, the texel values C1 to C6 fetched in steps S11 to S16 are combined in step S17, and the combined value CSY = K1 × C1 + K2 × C2 + K3 × C3 + K4 × C4 + K5 × C5 + K6 × C6 is drawn on the drawing target pixel PIX.

  That is, in FIG. 10C, the weight value K1 at the point FC1 is the largest, and the weight value K6 at the point FC6 is the smallest. K1 × C1 obtained from the texel value C1 fetched at the point FC1 corresponds to the image of the hair follicle of the hair FUR1 in FIG. 4A, and K6 × C6 obtained from the texel value C6 fetched at the point FC6. Corresponds to the image of the hair tip of the hair FUR5 in FIG. That is, fetching the texel values C1 to C6 as shown in FIG. 10C and drawing the combined value CSY = K1 × C1 + K2 × C2 + K3 × C3 + K4 × C4 + K5 × C5 + K6 × C6 on the drawing target pixel PIX is shown in FIG. This corresponds to drawing on the drawing target pixel PIX in (A) to (E) of FIG.

  In FIG. 11A, the drawing target pixel PIX is on the upper right side with respect to the center point, and the direction of the normal vector N is on the upper right side as compared with FIG. 9A. Accordingly, the virtual camera VC looks as shown in FIG. 11B, and both the X coordinate Nx and the Y coordinate Ny of the projection normal vector NP are positive values. Thus, in FIG. 11B, the direction of the projection normal vector NP is the upper right direction when viewed from the virtual camera VC. Therefore, in this case, as shown in FIG. 11C, sampling is fetched six times from the corresponding point FC1 in the lower left direction (opposite to the NP direction).

  Specifically, in the first fetch process of step S11 in FIG. 6, the texel value C1 = TEX (U1, V1) is fetched from the texture coordinates (U1, V1) of the corresponding point FC1. In the second fetch process in the next step S12, the texel value C2 = TEX (U2, V2) is fetched from the texture coordinates (U2, V2) of the point FC2 in the lower left direction of FC1. In the third fetch process of the next step S13, the texel value C3 = TEX (U3, V3) is fetched from the texture coordinates (U3, V3) of the point FC3 in the lower left direction of FC2. The same applies to the fourth to sixth fetch processes in steps S14 to S16.

  Then, the texel values C1 to C6 fetched in steps S11 to S16 are combined in step S17, and the combined value CSY = K1 × C1 + K2 × C2 + K3 × C3 + K4 × C4 + K5 × C5 + K6 × C6 is drawn on the drawing target pixel PIX.

  As described above, in this embodiment, the texel value of the texture for fur shading is fetched while sequentially shifting the texture coordinates (U, V) in the direction specified by the direction opposite to the direction of the projection normal vector NP.

  For example, in FIG. 10B, the direction of the projection normal vector NP is the left direction. Therefore, in this case, as shown by points FC1 to FC6 in FIG. 10C, the texel values are sequentially shifted while the texture coordinates (U, V) are sequentially shifted in the right direction opposite to the direction of the projection normal vector NP. Is fetched. In FIG. 11B, the direction of the projection normal vector NP is the upper right direction. Accordingly, in this case, as shown by points FC1 to FC6 in FIG. 11C, the texel values are sequentially shifted in the texture coordinates (U, V) in the lower left direction opposite to the direction of the projection normal vector NP. Is fetched.

  In the present embodiment, the reverse direction of the direction of the projection normal vector NP is changed from the texture coordinates (U1, V1) to the texture coordinates (U6, V1) as shown in FIGS. 6, 10C, and 11C. V6) (direction in a broad sense, texture coordinates (UN, VN)). As the length of the projection normal vector NP increases, the distance from the texture coordinates (U1, V1) to the texture coordinates (U6, V6) increases.

  For example, the length of the projection normal vector NP is longer in FIG. 11B than in FIG. 10B. Therefore, in FIG. 11C, the distance from the texture coordinates (U1, V1) to the texture coordinates (U6, V6), which is the distance from FC1 to FC6, is longer than in FIG. In this way, for example, fur shading can be realized in which the length of the hair is the shortest at the center point of the sphere object OB, and the hair looks longer as it approaches the boundary.

  As described above, in the present embodiment, for example, as shown in FIG. 6, the far shading process can be realized only by performing a plurality of texel value fetch processes by the pixel shader and the synthesis process of the obtained texel values. Therefore, it is possible to generate a fur shading image with a smaller processing load than the shell method or the like.

  Note that FIGS. 10A to 11C have been described by taking as an example the case where the direction in which the texture coordinates are shifted (the direction from FC1 to FC6) is opposite to the direction of the projection normal vector NP. The present embodiment is not limited to this. For example, the direction in which the texture coordinates are shifted may be changed from the direction opposite to the projection normal vector NP by adjusting parameters. For example, the direction in which the texture coordinates are shifted is changed by performing a process of rotating the projection normal vector NP using the direction adjustment parameter. By doing in this way, it becomes possible to adjust the so-called hair lying direction (direction of fur).

  Alternatively, the texture coordinate shift distance FC1 to FC6) may be adjusted by a parameter. For example, using the length adjustment parameter, the length of the projection normal vector NP is increased or decreased. In this way, the hair length in fur shading can be adjusted.

2.2 Different Use of Fur Shading Technique In this embodiment, the applied fur shading technique may be different for each part of the model object. For example, FIGS. 12A and 12B are examples of fur shading processing for a fur coat.

  As shown in FIG. 12A, in the fur coat, the collar portion and the shoulder portion are frequently captured by a virtual camera and are conspicuous portions. Also, it is desirable to express the three-dimensional feeling of fur in the collar and shoulder. Therefore, in such a collar portion and shoulder portion (first portion in the broad sense, front side), a fur shading image is obtained by the fur shading method based on the shell method described in FIGS. 2 (A) to 2 (C). Is generated. That is, a plurality of polygons to which textures are mapped are stacked in this portion, and a fur shading image is generated by a shell method using the plurality of polygons. In this way, fur shading processing by the shell method is performed on the front side of model objects such as fur coats and characters.

  On the other hand, as shown in FIG. 12B, the back side (rear side) of the fur is a region that is not so well captured by the virtual camera, and is an inconspicuous region. When such a wide back region is subjected to the fur shading process by the shell method, the number of polygons increases and the processing load increases. Therefore, on such a back side (second portion in a broad sense, the back side), as described in FIG. 6, a plurality of texel values are fetched, and a composite value of the fetched plurality of texel values is set as a pixel value. A fur shading image is generated by the fur shading method set to. In this way, when the shell method is applied to all regions, the processing load becomes too heavy, and the fur shading method of the present embodiment using the pixel shader for the back side (or the inconspicuous region on the front side). By applying, it becomes possible to achieve both realistic hair quality expression and reduction of processing load.

3. Processing Example Next, a processing example of this embodiment will be described with reference to the flowchart of FIG. FIG. 13 is a flowchart showing an example of the overall processing of the image generation system.

  First, an object space setting process for arranging and setting a plurality of objects such as model objects in the object space is performed (step S1). Then, movement processing for moving a moving object such as a model object in the object space, motion processing for expressing the movement of the model object, and the like are performed (steps S2 and S3). Specifically, a movement process for moving the model object based on operation data from the operation unit, or a motion process for moving each bone constituting the skeleton of the model object based on the motion data is performed.

  Next, the vertex shader process by the vertex shader program is performed (step S4). In this vertex shader processing (vertex processing), coordinate conversion processing in units of vertices (such as conversion from the local coordinate system to the world coordinate system), shading processing in units of vertices (shading processing), light source processing in units of vertices (lighting) Processing), texture coordinate calculation processing, and the like are performed. For example, the processing for obtaining the vertex position of the model object after the motion processing may be realized by this vertex shader processing. The vertex coordinates, line-of-sight vector, light source vector, normal vector, etc. obtained by this vertex shader processing are stored in the output register and passed to the pixel shader processing.

  Next, pixel shader processing by the pixel shader program is started (step S5). In this pixel shader process, various processes in units of pixels are performed after rasterization. Specifically, shading processing (shading processing), texture mapping processing, translucent processing, and the like are performed on a pixel basis. Thereby, a final image (game image) displayed on the display unit is generated.

  The fur shading process of the present embodiment described in FIG. 6 can be executed in step S5 of FIG. As a result, a fur shading image using a pixel shader is generated.

4). Hardware Configuration FIG. 14A shows a hardware configuration example that can realize the present 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 into 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. 14A, and may be, for example, a configuration as shown in FIG.

  In FIG. 14B, 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. 14B, 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 (front side, back side, etc.) that are described at least once together with different terms having a broader meaning or the same meaning (first portion, second portion, etc.) It can be replaced by the different terms at any point. Further, the normal vector direction acquisition processing, texture coordinate shift processing, texel value fetch processing, texel value synthesis processing, and the like are not limited to those described in this embodiment, and techniques equivalent to these are also included in the present invention. Included in the range. 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 game images, and a mobile phone. it can.

OB object, PIX drawing target pixel, N normal vector,
NP projection normal vector, VC virtual camera, DV gaze direction,
100 processing unit, 102 game calculation unit, 104 object space setting unit,
106 movement processing unit, 107 motion processing unit, 108 virtual camera control unit,
120 image generation units, 122 vertex processing units, 124 pixel processing units,
130 sound generation unit, 160 operation unit, 170 storage unit,
172 Object data storage unit, 173 Motion data storage unit,
174 Model data storage unit, 175 texture storage unit, 176 drawing buffer,
180 information storage medium, 190 display unit, 192 sound output unit, 194 auxiliary storage device,
196 Communication Department

Claims (9)

A texture storage unit for storing textures;
By performing pixel shader processing using the texture, an image generation unit that generates an image seen from a virtual camera in the object space,
Make the computer work,
The texture storage unit stores a texture for fur shading,
The image generation unit
The texture coordinates in the texture space are sequentially shifted in the direction specified by the normal vector of the drawing target pixel, the texel values of the texture for fur shading are fetched, and the composite value of a plurality of texel values obtained by the fetching A program for generating a fur shading image by setting to the pixel value of the drawing target pixel. In claim 1,
In the camera coordinate system of the virtual camera, when the coordinate axis along the viewing direction of the virtual camera is the Z axis, and the coordinate axis orthogonal to the Z axis is the X axis and the Y axis,
The image generation unit
While the texture coordinates (U, V) in the texture space are sequentially shifted in the direction specified by the direction opposite to the direction of the projection normal vector obtained by projecting the normal vector of the drawing target pixel onto the XY plane, A program that fetches a texel value of a texture for shading. In claim 2,
The image generation unit
The texel value C1 = TEX (U1, V1) is fetched in the first fetch process, and the texel value C2 = TEX (U2, V2) is fetched in the second fetch process .... the texel in the Nth fetch process The value CN = TEX (UN, VN) is fetched, and the synthesized value obtained by synthesizing the fetched texel values C1 to CN is set as the pixel value of the drawing target pixel.
The direction opposite to the direction of the projection normal vector is a direction from the texture coordinates (U1, V1) to the texture coordinates (UN, VN). The longer the length of the projection normal vector, the more the texture coordinates (U1 , V1) to the texture coordinates (UN, VN) is long. In claim 3,
The image generation unit
K1 × C1 + K2 × C2 +... + KN × CN is combined to obtain a combined value,
The program is characterized in that the weight value Ki + 1 is smaller than the weight value Ki (1 ≦ i <N). In any one of Claims 1 thru | or 4,
The image generation unit
For the first part of the model object, a fur shading image is generated by a shell method using a plurality of stacked polygons to which textures are mapped,
For the second part of the model object, a fur shading image is generated by setting a composite value of a plurality of texel values obtained by fetching the fur shading texture to a pixel value of a drawing target pixel. A featured program. In claim 5,
The program according to claim 1, wherein the first part is an area set on the front side of the model object, and the second part is an area set on the back side of the model object. In any one of Claims 1 thru | or 6.
The image generation unit
A program characterized by variably setting the number of texel values to be synthesized.   A computer-readable information storage medium, wherein the program according to any one of claims 1 to 7 is stored. A texture storage unit for storing textures;
An image generation unit that generates an image seen from a virtual camera in the object space by performing pixel shading processing using the texture;
The texture storage unit stores a texture for fur shading,
The image generation unit
The texture coordinates in the texture space are sequentially shifted in the direction specified by the normal vector of the drawing target pixel, the texel values of the texture for fur shading are fetched, and the composite value of a plurality of texel values obtained by the fetching A fur-shaded image is generated by setting to the pixel value of the drawing target pixel.