JP2007087031A - Program, information storage medium and image creation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a program, an information storage medium and an image creation system, in which an image expressing wrinkles corresponding to a motion of an object can be created. <P>SOLUTION: A normal texture having a normal vector set to texels is prepared, a texture coordinate corresponding to each apex is determined based on a joint angle parameter of the object changing the angle of a joint by motion control and a joint effect parameter changed according to the distance between each apex constituting the object and the joint, and normal mapping of mapping the normal texture on the object is performed based on the determined texture coordinate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

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

In such an image generation system, in order to increase the player's virtual reality, it is desirable that a complex unevenness such as a wrinkle of clothes can be expressed realistically. However, with the conventional technology, it is difficult to express in real time wrinkles of clothes that should follow the movements of the joints of objects that perform various motions (motions).
JP-A-9-265548

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a program, an information storage medium, and an image generation system capable of generating an image in which wrinkles according to the motion of an object are expressed. It is in.

  (1) The present invention is an image generation system for generating an image, and a texture storage unit that stores a normal texture in which a normal vector is set in a texel, and a joint angle is changed by motion control. A texture coordinate calculation unit that obtains a texture coordinate corresponding to each vertex based on a joint angle parameter of the object and a joint influence parameter that changes according to the distance between each vertex constituting the object and the joint; And a normal mapping unit that performs normal mapping for mapping the normal texture to the object based on the texture coordinates. The present invention also relates to a program characterized by causing a computer to function as each of the above sections, or an information storage medium storing the program.

  The joint angle parameter may be the joint angle itself, or may be a parameter represented by a function that changes according to the joint angle. The joint influence degree parameter may be the distance between the joint and the vertex itself, or may be a parameter represented by a function that changes according to the distance between the joint and the vertex.

  In the present invention, the coordinates of the texel associated with the vertex of the object are obtained according to the joint angle and the distance to the joint which change according to the motion change of the object. In this texel, a normal vector necessary for lighting of the object is set, and unevenness on the surface of the object is expressed by shading according to the normal vector. Therefore, according to the present invention, it is possible to express wrinkles that follow a change in motion of an object in real time.

  (2) In the image generation system, the program, and the information storage medium of the present invention, the object is motion-controlled using a model in which a plurality of bones are connected by the joints, and the texture coordinate calculation unit is connected between the bones. The normal texture is a parameter that changes according to the angle formed by the joint angle parameter, and a parameter that includes a result of multiplying the weight value of each bone set for each vertex is the joint effect parameter. The texture coordinates may be obtained. In this way, it is possible to associate an appropriate normal vector according to the degree of bending or twisting of the object around the joint and the proximity to the joint with the constituent vertex of the object.

  In addition, the model here means a simulation model used for calculation for moving an object, and a model composed of at least two bones (bones) connected by joints (joints) is generally used. Called the skeleton system. In the skeleton system, there are vertices that constitute the surface (skin) of an object so as to contain bones connected by joints.

  (3) In the image generation system, the program, and the information storage medium of the present invention, the texture coordinate of the normal texture includes a first coordinate component and a second coordinate component, and the texture coordinate calculation unit includes the joint The first coordinate component of the texture coordinates may be obtained based on the joint angle parameter and the joint influence parameter that change according to the degree of bending.

  (4) In the image generation system, the program, and the information storage medium of the present invention, the normal texture has a high frequency in which the normal vector set in the texel on one end side of the texture space is directed in the same direction. The normal vector set in the texel on the other end side has a texel value pattern that is less frequently oriented in the same direction, and the texture coordinate calculation unit has a greater degree of bending of the joint or a vertex closer to the joint. The first coordinate component of the texture coordinate of the normal texture may be obtained so that the texel on the other end side of the texture space is associated. In this way, it is possible to realistically represent a state in which wrinkles increase as the degree of bending of the object around the joint increases, and a state in which wrinkles increase as the portion is closer to the joint.

  (5) In the image generation system, program and information storage medium of the present invention, the normal texture has a small color difference between adjacent texels on one end side of the texture space, and adjacent texels on the other end side of the texture space. The texture coordinate calculation unit associates the texel on the other end side of the texture space with a greater degree of bending of the joint or a vertex closer to the joint. The first coordinate component of the texture coordinate of the normal texture may be obtained. In this way, it is possible to realistically represent a state in which the wrinkle is deeper as the degree of bending of the object around the joint is larger, and a state in which the wrinkle is deeper as the portion is closer to the joint.

  (6) In the image generation system, the program, and the information storage medium of the present invention, the texture coordinates of the normal texture include a first coordinate component and a second coordinate component, and the texture coordinate calculation unit includes the joint The second coordinate component of the texture coordinate may be obtained based on the joint angle parameter and the joint influence parameter that change according to the degree of twist.

  (7) In the image generation system, the program, and the information storage medium of the present invention, the normal texture has a high frequency in which the normal vector set in the texel is oriented in the same direction on one end side of the texture space. The normal vector set in the texel on the other end side has a texel value pattern that is less likely to face in the same direction, and the texture coordinate calculation unit has a greater degree of twist of the joint or a vertex closer to the joint. The second coordinate component of the texture coordinate of the normal texture may be obtained so that the texel on the other end side of the texture space is associated. In this way, it is possible to realistically represent a state in which wrinkles increase as the degree of twist of the object around the joint increases, and a state in which wrinkles increase as the portion is closer to the joint.

  (8) In the image generation system, program, and information storage medium of the present invention, the normal texture has a small color difference between adjacent texels on one end side of the texture space, and adjacent texels on the other end side of the texture space. The texture coordinate calculation unit associates the texel on the other end side of the texture space with a greater degree of twist of the joint or a vertex closer to the joint. The second coordinate component of the texture coordinate of the normal texture may be obtained. In this way, it is possible to realistically represent a state in which the wrinkle is deeper as the twisted state of the object around the joint is larger, and a state in which the wrinkle is deeper as the portion is closer to the joint.

  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 functional 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 of an object (for example, a player character). The operation unit 160 can be realized by, for example, a lever, a button, a steering, a touch panel display, or the like. Further, as an input interface of the player, for example, a sound detection unit such as a microphone (microphone) may be provided. 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 (VRAM) or the like.

  The information storage medium 180 (computer-readable medium) stores programs, data, and the like, and functions as an optical disk (CD, DVD), magneto-optical disk (MO), magnetic disk, hard disk, and magnetic tape. Alternatively, it can be realized by a memory (ROM). 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, the information storage medium 180 stores a program for causing a computer to function as each unit of the present embodiment (a program for causing a computer to execute processing of each unit).

  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 portable information storage device 194 stores player personal data, game save data, and the like. Examples of the portable information storage device 194 include a memory card and a portable game device. The communication unit 196 performs various controls for communicating with the outside (for example, a host device or other image generation system), and functions thereof are hardware such as various processors or communication ASICs, programs, and the like. It can be realized by.

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

  The processing unit 100 (processor) performs processing such as game processing, image generation processing, or sound generation processing based on operation data and programs from the operation unit 160. Here, as the game process, a process for starting a game when a game start condition is satisfied, a process for advancing the game, a process for placing an object such as a character or a map, a process for displaying an object, and a game result are calculated. There is a process or a process of ending a game when a game end condition is satisfied. The processing unit 100 performs various processes using the main storage unit 172 in 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, DSP, etc.), ASIC (gate array, etc.), and programs.

  The processing unit 100 includes a main processing unit 110, a drawing unit 120, and a sound generation unit 130. Note that some of these may be omitted.

  The main processing unit 110 includes an object space setting unit 112, a movement / motion processing unit 114, and a virtual camera control unit 116.

  The object space setting unit 112 is composed of various objects (polygons, free-form surfaces, subdivision surfaces, etc.) representing display objects such as characters, buildings, stadiums, cars, trees, pillars, walls, and maps (terrain). (Object) is set in the object space. 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). Arrange objects.

  The movement / motion processing unit 114 performs a movement / motion calculation (movement / motion simulation) of an object (such as a character, a car, or an airplane). That is, based on operation data input by the player through the operation unit 160, a program (movement / motion algorithm), various data (motion data), etc., the object is moved in the object space, or the object is moved (motion, animation). ) Is performed. Specifically, a simulation process for sequentially obtaining object movement information (position, rotation angle, speed, or acceleration) and motion information (part object position or rotation angle) every frame (1/60 second). Do. A frame is a unit of time for performing object movement / motion processing (simulation processing) and image generation processing. When performing movement / motion calculation, a model in which bones are connected by joints can be used. Such a simulation model is called a skeleton system, which simulates changes in the angle of the bone around the joint or changes in the position of the bone, and moves or moves the object according to the simulation result. Motion control can be performed.

  The virtual camera control unit 116 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, a process for controlling the position (X, Y, Z) or the rotation angle (rotation angle about the X, Y, Z axes) of the virtual camera (process for controlling the viewpoint position and the line-of-sight direction) is performed.

  For example, when an object (eg, character, ball, car) is photographed from behind using a virtual camera, the position or rotation angle of the virtual camera (the direction of the virtual camera is set so that the virtual camera follows changes in the position or rotation of the object. ) To control. In this case, the virtual camera can be controlled based on information such as the position, rotation angle, or speed of the object obtained by the movement / motion processing unit 112. 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. When there are a plurality of virtual cameras (viewpoints), the above control process is performed for each virtual camera.

  The drawing unit 120 performs drawing processing based on the results of various processing (game processing) performed by the processing unit 100, thereby generating an image and outputting the image to the display unit 190. When a so-called three-dimensional game image is generated, a vertex list including vertex data (vertex position coordinates, texture coordinates, color data, normal vector, α value, etc.) of each vertex of the object is first input and input. Based on the vertex data included in the vertex list, vertex shading (vertex processing in a broad sense) by a vertex shader is performed. When performing vertex shading, vertex generation processing (tessellation, curved surface division, polygon division) for subdividing a polygon can be performed as necessary. In vertex shading, according to the vertex shader program (first shader program in a broad sense), vertex movement processing, coordinate transformation (world coordinate transformation, camera coordinate transformation), clipping processing, or geometric processing such as perspective transformation is 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 shading, and pixel shading (pixel processing, fragment in a broad sense) that draws pixels (fragment that configures the display screen) that constitute an image by the pixel shader. Process). In pixel shading, according to the pixel shader program (second shader program), various processes such as texture reading (texture mapping), color data setting / change, translucent composition, antialiasing, etc. A specific drawing color is determined, and the drawing color of the perspective-transformed object is output (drawn) to a drawing buffer 174 (a buffer capable of storing image information in units of pixels; VRAM). That is, in pixel shading, per-pixel processing for setting or changing image information (color, normal, luminance, α value, etc.) of a frame image in units of pixels is performed. As a result, an image (frame image) that can be seen from the virtual camera (given viewpoint) in the object space is generated. In addition, when there are a plurality of virtual cameras (viewpoints), a frame image can be generated so that an image seen from each virtual camera can be displayed on one screen as a divided image.

  Here, the vertex shader and the pixel shader described above are a kind of so-called programmable shader that can program polygon (primitive) drawing processing by a shader program written in a shading language. Programmable shaders can be programmed with vertex-based processing and pixel-by-pixel processing, so the degree of freedom of polygon rendering processing is high, and the expressive power is greatly improved compared to fixed image generation processing using conventional hardware. Can be improved.

  The drawing unit 120 performs geometry processing, texture mapping, hidden surface removal processing, α blending, and the like when drawing an object.

  In the geometry processing, processing such as coordinate conversion, clipping processing, perspective projection conversion, or light source calculation is performed on the object. Then, object data (positional coordinates of object vertices, texture coordinates, color data (luminance data), normal vector, α value, etc.) after geometry processing (after perspective projection conversion) is stored in the main storage unit 172. The

  Texture mapping is a process for mapping a texture (texel value) stored in the texture storage unit of the storage unit 170 to an object. Specifically, the texture (surface properties such as color and α value) is read from the texture storage unit 176 of the storage unit 170 using the texture coordinates set (given) to the vertex of the object. Then, a texture that is a two-dimensional image is mapped to an object. In this case, processing for associating pixels and texels, bilinear interpolation (texel interpolation), and the like are performed. The texture mapping here includes normal mapping (bump mapping in a broad sense) that treats color information set in texels as normal vector information. In normal mapping, a texture mapped to an object is called a normal texture (bump texture in a broad sense). The normal texture and the like are also stored in the texture storage unit 176 of the storage unit 170.

  As the hidden surface removal processing, hidden surface removal processing can be performed by a Z buffer method (depth comparison method, Z test) using a Z buffer (depth buffer) in which Z values (depth information) of drawing pixels are stored. . That is, when drawing pixels corresponding to the primitive of the object are drawn, the Z value stored in the Z buffer is referred to. Then, the Z value of the referenced Z buffer is compared with the Z value at the drawing pixel of the primitive, and the Z value at the drawing pixel is a Z value (for example, a small Z value) on the near side when viewed from the virtual camera. In some cases, the drawing process of the drawing pixel is performed and the Z value of the Z buffer is updated to a new Z value.

  α blending (α synthesis) is a translucent synthesis process (usually α blending, addition α blending, subtraction α blending, or the like) based on an α value (A value). For example, in the case of normal α blending, the following formulas (1) to (3) are performed.

R _Q = (1−α) × R ₁ + α × R ₂ (1)
G _Q = (1−α) × G ₁ + α × G ₂ (2)
B _Q = (1−α) × B ₁ + α × B ₂ (3)
In addition, in the case of addition α blending, the following processes (4) to (6) are performed.

R _Q = R ₁ + α × R ₂ (4)
G _Q = G ₁ + α × G ₂ (5)
B _Q = B ₁ + α × B ₂ (6)
Further, in the case of subtraction α blending, the following formulas (7) to (9) are performed.

R _Q = R ₁ −α × R ₂ (7)
G _Q = G ₁ −α × G ₂ (8)
B _Q = B ₁ −α × B ₂ (9)
Here, R ₁ , G ₁ , B ₁ are RGB components of an image (original image) already drawn in the drawing buffer 174, and R ₂ , G ₂ , B ₂ should be drawn in the drawing buffer 174. This is the RGB component of the image. R _Q , G _Q , and B _Q are RGB components of an image obtained by α blending. The α value is information that can be stored in association with each pixel (texel, dot), for example, plus alpha information other than color information. The α value can be used as mask information, translucency (equivalent to transparency and opacity), bump information, and the like.

  Furthermore, the drawing unit 120 includes a texture coordinate calculation unit 122 and a normal mapping unit 124. Alternatively, texture coordinate calculation may be performed on the main processing unit 110 side, and normal mapping may be performed on the drawing unit 120 side using the result.

  The texture coordinate calculation unit 122 is based on the joint angle parameter of the object whose joint angle is changed by motion control and the joint influence parameter that changes according to the distance between each vertex constituting the object and the joint. Processing for obtaining texture coordinates corresponding to the vertex is performed.

  As processing for obtaining texture coordinates, for example, a given coordinate component of texture coordinates changes depending on how the object bends or twists at a joint (connecting point) that connects a plurality of bones constituting the simulation model of the object. The calculation for associating the texel with the vertex is performed. In this case, a first coordinate component (for example, a U coordinate component of the UV coordinate system) is obtained based on a parameter (an example of a joint angle parameter) that changes according to the degree of bending of the joint of the object, and the like. The second coordinate component (for example, the V coordinate component of the UV coordinate system) can be obtained based on a parameter (another example of the joint angle parameter) that changes according to the degree of twist. Also, by considering the proximity of each vertex from the joint as the degree of influence, it is possible to provide normal vector information such that the concavo-convex changes dramatically as the vertex is closer to the joint. In other words, normal information can be given so that the vertex closer to the joint has more wrinkles and deeper wrinkles. As the influence degree determined according to the proximity from the joint, a parameter (an example of a joint influence degree parameter) including a multiplication result of bone weight values given to each vertex can be used. In this way, it is possible to dynamically control the degree of wrinkle according to the motion state of the object. In addition, one of the first coordinate component and the second coordinate component of the texture coordinate can be determined in advance for each vertex. For example, by assigning a weight according to the vertex position in the model coordinate system, by obtaining one of the coordinate components, texture coordinates that are uniquely associated with each vertex are obtained. Also good. For example, the vertices inside the joint and the vertices outside the joint may be weighted differently.

  At this time, it is necessary to devise how to create a normal texture stored in the texture storage unit 176 of the storage unit 170. For example, the normal vector set in the texel on one end side of the first coordinate component (or the second coordinate component) is frequently directed in the same direction, and the method set in the texel on the other end side of the coordinate component. A normal vector can be set for each texel in the texture space so that the frequency with which the line vector points in the same direction is low. In addition, when the direction of a certain reference surface (flat surface) is set as the reference direction, the normal vector that faces the reference direction is frequently set on one end side of the texture space (for example, the minimum value side of the coordinate component), and the other end. On the side (for example, the maximum value side of the coordinate component), the setting frequency of the normal vector that faces the reference direction can be lowered. For example, it is possible to prepare a normal texture of a texel value pattern in which the normal vector frequently changes as the U coordinate component increases. Note that a normal texture of a texel value pattern in which the normal vector frequently changes as the V coordinate component increases may be prepared. In this way, it is possible to express the surface of the object with less wrinkles in the region where the normal vector facing the reference direction is high, and in the region where the frequency of the normal vector facing the reference direction is low, the surface of the object Can express wrinkles.

  Also, for example, the normal texture has a small color difference between adjacent texels on one end side of the texture space (for example, the minimum value side of the coordinate component), and adjacent texels on the other end side (for example, the maximum value side of the coordinate component) It can be built in such a way that the color difference between is large. In this way, it is possible to express the appearance of shallow wrinkles on the surface of the object in a region where the color difference between adjacent texels is small, and deep wrinkles on the surface of the object in a region where the color difference between adjacent texels is large. A certain state can be expressed.

  The normal mapping unit 124 performs normal mapping that maps a normal texture to an object based on the texture coordinates obtained by the texture coordinate calculation unit 122. Normal mapping is a type of texture mapping that sets the normal vector for each drawing pixel by calculating the direction of the normal vector given to the drawing pixel from the correspondence between vertices and texels. In this embodiment, by performing shading (shading) of an object based on the normal vector information associated with each vertex in the normal mapping 124, it is possible to realistically express the wrinkle unevenness of clothes and the like. it can.

  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. Method of this embodiment In this embodiment, based on a parameter that changes according to the angle between bones of a model in which a plurality of bones are connected by joints, and a parameter that changes according to the proximity from the joint, A technique for obtaining texture coordinates for a normal texture associated with a vertex is adopted. That is, in the method described below, the UV coordinate component of normal mapping can be dynamically adjusted according to the motion state of the object.

  First, the normal texture (normal map texture) for wrinkle expression will be described. In the following, a case will be described as an example where the values (luminance values) of the R, G, and B color components of the texture are used as the X-axis component, Y-axis component, and Z-axis component of the normal vector. Note that the present invention is not limited to the examples described below.

  As a texture for normal mapping (normal texture), an image is prepared in which one side (one end side) has almost no color difference as shown in FIG. 2 and the color changes drastically toward the other side (the other end side). When normal mapping (normal mapping) is performed, the unevenness becomes deeper as the amount of color change increases, and the unevenness becomes finer as the changing distance becomes shorter, so in FIG. 2, the U axis is 0 (the minimum value of the U coordinate component). As the value approaches 1.0 (the maximum value of the U coordinate component), a deeper and finer “wrinkle” can be expressed. That is, in the texture shown in FIG. 2, it can be said that the larger the U coordinate component, the deeper the wrinkle density and the deeper the wrinkle can be expressed.

  Next, the normal mapping target object will be briefly described, and how to obtain the texture coordinates of the normal texture for each vertex will be described.

  First, the target object of normal mapping is assumed as shown in FIG. This object includes two bones B1 and B2 connected by a joint K, and vertices V1 to V6 on the model surface including the bones. Although there are many vertices other than those shown in FIG. 3 as vertices constituting the object, they are omitted for convenience of explanation. A weight value indicating the degree of influence of the bones B1 and B2 is set for each vertex V1 to V6. W11, W12, W13, W14, W15, and W16 are weight values indicating the degree of influence of the bone B1 on the vertices V1 to V6, and W21, W22, W23, W24, W25, and W26 are for the vertices V1 to V6. This is a weight value indicating the degree of influence of bone B2.

In such an object, the cosine of the angle θ formed by the bones B1 and B2 is obtained by the inner product of vectors parallel to the bones B1 and B2.
cos θ = (VB1 · VB2) / (| VB1 | · | VB2 |) (1A)
(However, the possible range of θ is 0 to π). In other words, the closer the angle θ is to 0, the deeper the curve. In the normal texture shown in FIG. 2, the parameter U (θ) (joint angle parameter) of the U coordinate component with respect to the angle θ can be obtained as follows.

U (θ) = (π−θ) / π (2A)
From the equation (2A), it can be said that the closer the angle θ is to 0, the greater the degree of bending of the object having the joint K as the bending point, and the easier the formation of deep wrinkles. Further, the parameter U (θ) equivalent to the expression (2A) can be obtained as follows.

U (θ) = (1 + cos θ) / 2 = cos 2 (θ / 2) (2A ′)
Even when the angle θ is set as shown in FIG. 4, the cosine of the angle θ can be obtained by the above equation (1A). However, when the angle θ is set in this way, the parameter U (θ) can be obtained as follows.

U (θ) = θ / π (2B)
Alternatively, U (θ) = sin (θ / 2) (2B ′)
Next, the degree of influence of the ease of wrinkling according to the positions of the vertices V1 to V6 will be considered. In the present embodiment, the degree of follow-up to the bone is set at each vertex as a weight value, and the degree of influence on the motion of the bone connected by the joint is obtained based on the weight value. Note that this method of determining the degree of influence is merely an example of an embodiment of the present invention, and a similar degree of influence can be obtained by appropriately setting a parameter that changes according to the distance from the joint.

  First, when expressing wrinkles, the vertices closer to the joint K tend to have more wrinkles and become deeper. For this reason, in order to appropriately paste the normal texture shown in FIG. 2 according to the degree of wrinkles, the U-coordinate component needs to be closer to 1.0 as the vertex is closer to the joint K (connection point). In other words, it is necessary that the U coordinate component approaches 0 as the vertex is farther from the joint K.

  When the range of possible weight values of the bones B1 and B2 set at each vertex is 0 to 100, the maximum value when the weight values of the two bones B1 and B2 are multiplied is 2500 (50 × 50). ) Therefore, when the weight values of the bones B1 and B2 with respect to a certain vertex V are W1 and W2, the influence degree L (joint influence degree parameter) due to the distance from the joint K can be obtained as follows.

L = (W1 × W2) / 2500 (3A)
From the expression 3A, for example, it becomes easier to specify texture coordinates of a wrinkled region assuming that the weight values of the bones B1 and B2 set for a certain vertex are 50/50. For example, the weight value is 90/10. This makes it easier to specify texture coordinates for areas with less wrinkles compared to 50/50. Also, the success or failure of wrinkles is determined by whether the vertices that make up the object are inside or outside the joints. It is preferable to keep it. Specifically, the closer to the inside of the joint, the easier the wrinkle can be made, and the closer to the outside of the joint, the less the wrinkle. That is, when the direction in which the object bends (bending direction) is limited as in the case of a part such as an elbow or knee, a weight (internal / external influence degree) can be prepared for each vertex in advance. For example, in the case of mapping the normal texture shown in FIG. 2, texture coordinates having a large U-coordinate component value are obtained so that vertices closer to the inner side of the joint are more prone to wrinkles, and on the outer side of the joint. It is possible to obtain a texture coordinate having a smaller value of the U coordinate component so that the closer vertex is not wrinkled. If the inside / outside influence is A1, the U coordinate component of the texture coordinates can be obtained as follows.

U = U (θ) × L × A1 (4A)
Here, as the inside / outside influence degree A1, it is preferable that a value closer to the vertex closer to the inside of the joint is set to be larger than the vertex closer to the outside of the joint.

  By the way, if there is a high degree of rotational freedom of the joint, such as the hip joint (joint at the base of the thigh) or the shoulder joint, and the object may bend in any direction, how much is bent in which direction? Must be considered according to the motion state of the object. That is, since any vertex may be inside or outside the joint, weighting (internal / external influence degree) cannot be set in advance for each vertex. In this case, the U coordinate component of the texture coordinates can be obtained as follows.

  First, it is determined to which bone each vertex is located.

  For example, as shown in FIGS. 5 (A) and 5 (B), a plane CP is obtained, and it becomes a reference for obtaining the degree of internal / external influence depending on which side of the plane CP a vertex is present. Define the bone.

  Specifically, VB12, which is a combined vector of vector VB1 and vector VB2, and normalized vectors nVB1 and nVB2 of vector VB1 and vector VB2 are obtained. Next, a vector nVB connecting points moved in the respective directions of the vectors nVB1 and nVB2 from the intersection (joint K) of the bones B1 and B2 is obtained. Next, VCnB, which is an orthogonal vector for the combined vector VB12 and the vector nVB, is obtained. Then, based on the combined vector VB12 and the orthogonal vector VCnB, a plane CP formed by these vectors can be obtained. In this way, since the bone B1 and the bone B2 are divided by the plane CP, the reference bone can be determined depending on which side each vertex is present with respect to the plane CP. it can. If the vertex is on the plane CP, either bone B1 or B2 may be used as a reference.

  In the example shown in FIG. 5, it is determined that the vertex V is present on the bone B1 side with respect to the plane CP. Hereinafter, a method for obtaining the degree of internal / external influence related to the vertex V on the basis of the bone B1 will be described.

  Specifically, as shown in FIGS. 6A and 6B, the plane orthogonal to the bone B1 is projected on P1, the intersection of the bone B1 and the plane P1 is projected on BP1, and the vertex V is projected on the plane P1. VP1 and the point formed by projecting a point on the plane P1 that is not in contact with the bone B1 on the bone B2 is α and the angle formed by BB1 and VP1-BP1-BB1 is α. Asking.

A2 = cos (α / 2) (5A)
From the above, the U coordinate component of the normal texture associated with the vertex V is
U = Umax × L × A2 (6A)
Is required.

  In the above, the U coordinate component of the texel associated with the vertex may be obtained, and the V coordinate component can be determined for each vertex in advance. For example, a value of 0 to 1.0 of the V coordinate component can be assigned along the direction of rotation around the bone as shown in FIG.

  Also, the amount and depth of wrinkles may be changed in the V coordinate component of the normal texture. In this case, for example, wrinkles due to the twisted state of the arm can be expressed. That is, the V coordinate component of the texture coordinate may be obtained using the twist angle ω between the bones as shown in FIG. 8 and the multiplication result of the weight values (for example, W11 and W21) representing the proximity from the joint as parameters. Good. At this time, the texel value pattern from one end side (for example, 0: minimum value of V coordinate component) to the other end side (for example, 1.0: maximum value of V coordinate component) of the texture space is as follows. It is preferable to prepare a changed normal texture.

  The frequency that the normal vector points in the same direction on one end side is high, and the frequency that the normal vector points in the same direction on the other end side is low.

  The frequency of normal vectors facing the reference direction (direction indicating the plane) on one end side is high, and the frequency of normal vectors facing the reference direction on the other end side is low.

  -The color difference between adjacent texels is small on one end side, and the color difference between adjacent texels is large on the other end side.

  As described above, according to the method of the present embodiment, texture coordinates for normal mapping are assigned according to the joint angle and the weight value given to the vertex, and the normal vector mapped based on the texture coordinates is mapped. The effect can express wrinkled unevenness. That is, according to the method of the present embodiment, by performing normal mapping, it is possible to generate a high-quality image that follows the amount and depth of wrinkles in accordance with changes in model motion.

3. Processing of this embodiment Next, a detailed processing example of this embodiment will be described with reference to the flowcharts of FIGS. 9 and 10.

  As shown in FIG. 9, the main processing unit first determines whether or not it is a frame update (1/60 second) timing (step S10). If it is time to update the frame (YES in step S10), object motion processing is performed (step S11). That is, a simulation calculation is performed to obtain a matrix for each bone. The angle between bones can also be obtained by this calculation. Next, the shader program for the vertex shader and the pixel shader is transferred, and various parameters necessary for performing the rendering process by executing the shader program are set (steps S12, S13, S14). In step S14, the parameters sent from the main processing unit to the drawing unit include an angle between bones obtained as a result of the simulation calculation. Then, the vertex list of the model is transferred to the vertex shader (step S15), and the vertex shader program transferred in step S12 and the pixel shader program transferred in step S13 are sequentially executed by the drawing unit (steps S17 and S18).

  The vertex shader performs vertex shading according to S20 to S22 of the flowchart shown in FIG. Specifically, after determining whether the vertex to be processed exists inside or outside the joint and obtaining the degree of internal / external influence (step S20), the angle θ and the vertex formed by the bones B1 and B2 are set. Texture coordinates are obtained based on the weight values of the bones B1 and B2 and the degree of influence inside and outside (step S21). That is, the UV coordinate of the normal texture corresponding to the vertex to be processed is designated. Next, the vertex data including the UV coordinate data is transferred to the pixel shader side (step S22).

  Then, the rasterizer performs processing (rasterization) for determining the drawing pixel of the object according to the vertex data transferred from the vertex shader (step S23), and the pixel shader performs pixel shading according to S24 and subsequent steps in the flowchart shown in FIG. Specifically, normal mapping is performed on the object based on the normal vector set in the texel read from the texture coordinates of the vertex (step S24). That is, a process for obtaining a normal vector for each drawing pixel of the object is performed. Then, the object subjected to shading (shading) is drawn based on the normal vector given to the drawing pixel (step S25). That is, a process of writing pixel color information into the drawing buffer is performed. In this way, it is possible to express how the wrinkles of clothes and the like dynamically change according to the motion state of the object.

4). Hardware Configuration FIG. 11 shows an example of a hardware configuration capable of realizing this embodiment. The main processor 900 operates based on a program stored in a DVD 982 (information storage medium, which may be a CD), a program downloaded via the communication interface 990, a program stored in the ROM 950, or the like. Perform processing, sound processing, etc. The coprocessor 902 assists the processing of the main processor 900, and executes matrix operation (vector operation) at high speed. For example, when a matrix calculation process is required for a physical simulation for moving or moving an object, a program operating on the main processor 900 instructs (requests) the process to the coprocessor 902.

  The geometry processor 904 performs geometry processing such as coordinate conversion, perspective conversion, light source calculation, and curved surface generation based on an instruction from a program operating on the main processor 900, and executes matrix calculation at high speed. The data decompression processor 906 performs decoding processing of compressed image data and sound data, and accelerates the decoding processing of the main processor 900. Thereby, a moving image compressed by the MPEG method or the like can be displayed on the opening screen or the game screen.

  The drawing processor 910 executes drawing (rendering) processing of an object composed of primitive surfaces such as polygons and curved surfaces. When drawing an object, the main processor 900 uses the DMA controller 970 to pass the drawing data to the drawing processor 910 and, if necessary, transfers the texture to the texture storage unit 924. Then, the drawing processor 910 draws the object in the frame buffer 922 while performing hidden surface removal using a Z buffer or the like based on the drawing data and texture. The drawing processor 910 also performs α blending (translucent processing), depth cueing, mip mapping, fog processing, bilinear filtering, trilinear filtering, anti-aliasing, shading processing, and the like. When a programmable shader such as a vertex shader or a pixel shader is installed, the vertex data is created / changed (updated) and the drawing color of a pixel (or fragment) is determined according to the shader program. When an image for one frame is written in the frame buffer 922, the image is displayed on the display 912.

  The sound processor 930 includes a multi-channel ADPCM sound source and the like, generates game sounds such as BGM, sound effects, and sounds, and outputs them through the speaker 932. Data from the game controller 942 and the memory card 944 is input via the serial interface 940.

  The ROM 950 stores system programs and the like. In the case of an arcade game system, the ROM 950 functions as an information storage medium, and various programs are stored in the ROM 950. A hard disk may be used instead of the ROM 950. The RAM 960 is a work area for various processors. The DMA controller 970 controls DMA transfer between the processor and the memory. The DVD drive 980 (may be a CD drive) accesses a DVD 982 (may be a CD) in which programs, image data, sound data, and the like are stored. The communication interface 990 performs data transfer with the outside via a network (communication line, high-speed serial bus).

  The processing of each unit (each unit) in this embodiment may be realized entirely by hardware, or may be realized by a program stored in an information storage medium or a program distributed via a communication interface. Also good. Alternatively, it may be realized by both hardware and a program.

  When the processing of each part of this embodiment is realized by both hardware and a program, a program for causing the hardware (computer) to function as each part of this embodiment is stored in the information storage medium. More specifically, the program instructs the processors 902, 904, 906, 910, and 930, which are hardware, and passes data if necessary. Each processor 902, 904, 906, 910, 930 realizes the processing of each unit of the present invention based on the instruction and the passed data.

  The present invention is not limited to that described in the above embodiment, and various modifications can be made. For example, terms (link points, normal map texture, normal mapping, plane direction) cited as broad or synonymous terms (joint, normal texture, normal mapping, reference direction, etc.) in the description or drawings And the like can be replaced with terms having a broad meaning or the same meaning in other descriptions in the specification or the drawings. Further, the method of expressing the contact trace is not limited to that described in the present embodiment, and a method equivalent to these is also included in the scope of the present invention.

  In this embodiment, the first coordinate component of the texture coordinate is associated with the U coordinate component of the UV coordinate system, and the second coordinate component of the texture coordinate is associated with the V coordinate component of the UV coordinate system. However, the first coordinate component may be set as the V coordinate component, and the second coordinate component may be set as the U coordinate component.

  Further, in the present embodiment, one end side of the texture space is described as the minimum value side of the coordinate component, and the other end side of the texture space is described as the maximum value side of the coordinate component. The other end side may be the minimum value side of the coordinate component. In this case, calculation may be performed so that the designation of the texture coordinates is opposite to the method of the present embodiment.

  The present invention can also be applied to various games (such as fighting games, shooting games, robot fighting games, sports games, competitive games, role playing games, music playing games, dance games, etc.). The present invention is also applicable 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.

The functional block diagram of the image generation system of this embodiment. The figure which shows an example of a normal texture. Explanatory drawing of the method of this embodiment. Explanatory drawing of the other method of this embodiment. 5A and 5B are explanatory diagrams of the method of the present embodiment. 6A and 6B are explanatory diagrams of the method of the present embodiment. Explanatory drawing of the method of this embodiment. Explanatory drawing of the other method of this embodiment. The flowchart which shows the specific process example of this embodiment. The flowchart which shows the specific process example of this embodiment. Hardware configuration example.

Explanation of symbols

100 processing unit,
110 Main processing unit,
112 object space setting unit, 114 movement / motion processing unit,
114 virtual camera control unit,
120 drawing part,
122 texture coordinate calculation unit, 124 normal mapping unit,
130 sound generator,
160 operation unit, 170 storage unit,
172 Main storage unit, 174 drawing buffer, 176 texture storage unit,
180 information storage medium, 190 display unit, 192 sound output unit,
194 Portable information storage device, 196 communication unit

Claims (11)

A program for generating an image,
A texture storage unit for storing a normal texture in which a normal vector is set in the texel;
The texture corresponding to each vertex based on the joint angle parameter of the object whose joint angle is changed by the motion control and the joint influence parameter that changes according to the distance between each vertex constituting the object and the joint. A texture coordinate calculation unit for obtaining coordinates;
As a normal mapping unit that performs normal mapping for mapping the normal texture to the object based on the obtained texture coordinates,
A program characterized by causing a computer to function. In claim 1,
The object is motion-controlled using a model in which a plurality of bones are connected by the joints,
The texture coordinate calculation unit is
A parameter that changes according to an angle formed between the bones is the joint angle parameter, and a parameter including a multiplication result of the weight value of each bone set for each vertex is the joint influence parameter. A program for obtaining texture coordinates of the normal texture. In claim 1 or 2,
The texture coordinates of the normal texture include a first coordinate component and a second coordinate component,
The texture coordinate calculation unit is
A program for obtaining a first coordinate component of the texture coordinate based on the joint angle parameter and the joint influence parameter that change according to the degree of bending of the joint. In claim 3,
In the normal texture, the normal vector set to the texel on one end side of the texture space is frequently directed in the same direction, and the normal vector set to the texel on the other end side of the texture space is directed to the same direction. Having a texel value pattern that is less frequent,
The texture coordinate calculation unit is
Obtaining the first coordinate component of the texture coordinate of the normal texture so that the texel on the other end side of the texture space is associated with the greater the degree of bending of the joint or the vertex closer to the joint. A featured program. In claim 3 or 4,
The normal texture has a texel value pattern in which the color difference between adjacent texels is small on one end side of the texture space, and the color difference between adjacent texels is large on the other end side of the texture space;
The texture coordinate calculation unit is
Obtaining the first coordinate component of the texture coordinate of the normal texture so that the texel on the other end side of the texture space is associated with the greater the degree of bending of the joint or the vertex closer to the joint. A featured program. In any one of Claims 1-5,
The texture coordinates of the normal texture include a first coordinate component and a second coordinate component,
The texture coordinate calculation unit is
A program for obtaining a second coordinate component of the texture coordinate based on the joint angle parameter and the joint influence parameter that change in accordance with the degree of twist of the joint. In claim 6,
In the normal texture, the normal vector set to the texel on one end side of the texture space is frequently directed in the same direction, and the normal vector set to the texel on the other end side of the texture space is directed to the same direction. Having a texel value pattern that is less frequent,
The texture coordinate calculation unit is
Obtaining the second coordinate component of the texture coordinate of the normal texture so that the texel on the other end side of the texture space is associated with the greater the degree of twist of the joint or the vertex closer to the joint. A featured program. In claim 6 or 7,
The normal texture has a texel value pattern in which the color difference between adjacent texels is small on one end side of the texture space, and the color difference between adjacent texels is large on the other end side of the texture space;
The texture coordinate calculation unit is
Obtaining the second coordinate component of the texture coordinate of the normal texture so that the texel on the other end side of the texture space is associated with the greater the degree of twist of the joint or the vertex closer to the joint. A featured program. In any one of Claims 1-8,
The program, wherein the normal texture is a texture for expressing wrinkle irregularities.   An information storage medium readable by a computer, wherein the program according to any one of claims 1 to 9 is stored. An image generation system for generating an image,
A texture storage unit for storing a normal texture in which a normal vector is set in the texel;
The texture corresponding to each vertex based on the joint angle parameter of the object whose joint angle is changed by the motion control and the joint influence parameter that changes according to the distance between each vertex constituting the object and the joint. A texture coordinate calculation unit for obtaining coordinates;
A normal mapping unit that performs normal mapping for mapping the normal texture to the object based on the obtained texture coordinates;
An image generation system comprising: