JP4804122B2 - Program, texture data structure, information storage medium, and image generation system - Google Patents

Description

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

  2. Description of the Related Art Conventionally, an image generation system that generates an image that can be viewed from a virtual camera (a given viewpoint) in an object space that is a virtual three-dimensional space is known, and is popular as a device that can experience so-called virtual reality. Taking an image generation system that can enjoy a racing game as an example, a player operates a player object to run in an object space, and competes with an enemy object operated by another player or a computer to play a three-dimensional game. have fun.

In such an image generation system, it is an important technical problem to generate a more realistic image in order to improve the player's virtual reality. For this reason, it is desired that the shadow of an object reflected on the ground can be expressed more realistically.
Japanese Patent No. 3667393

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a program, a texture data structure, an information storage medium, and an image generation system that can realistically represent the shadow of an object.

  (1) The present invention is an image generation system for generating an image of an object space viewed from a given viewpoint, and includes a texture storage unit that stores shadow texture, a first object in the object space, Based on a distance calculation unit that obtains a distance parameter based on a positional relationship with the second object, the shadow parameter obtained based on the distance parameter, and the texel data of the shadow texture read from the texture storage unit And a shadow processing unit that performs a shadow process for generating a shadow of the first object on the second object. The present invention also relates to a program that causes a computer to function as each of the above-described units and an information storage medium that stores the program.

  According to the present invention, the distance parameter that changes according to the positional relationship between the first object and the second object and the texel data of the shadow texture correspond to the positional relationship between the first object and the second object. A shadow density parameter is determined. Therefore, according to the present invention, it is not necessary to prepare a shadow texture for each positional relationship between the first object and the second object, so that it is possible to expect a reduction in memory usage and a reduction in processing load.

  (2) In the image generation system, the program, and the information storage medium of the present invention, the shadow processing unit obtains the shadow density parameter so as to change in inverse proportion to the quadratic function of the distance parameter, You may make it perform the shadow process which produces | generates the shadow of a 1st object with respect to an object. In this way, it is possible to obtain a distribution pattern of shadow density parameters such that the cross section of the first object viewed from the second object becomes smaller and thinner according to a quadratic function of the distance between the objects.

  (3) In the image generation system, the program, and the information storage medium of the present invention, the texture storage unit includes a plurality of the shadow density parameters obtained according to the positional relationship between the first object and the second object. Based on the distribution pattern of (s), the luminance value (R, G, B) of each RGB color component of the texel and the texel so that the distance parameter (h) and the shadow density parameter satisfy the following relationship. The shadow texture in which the α value (A) is set may be stored.

  In this way, as the first object is closer to the second object, a shadow density parameter distribution pattern is obtained along the cross-sectional shape of the first object, and as the first object moves away from the second object. Thus, it is possible to obtain a shadow density parameter distribution pattern in which the shadow shape becomes ambiguous.

  (4) In the image generation system, the program, and the information storage medium of the present invention, the shadow texture texel includes the luminance values (R, G, B) of each of the RGB color components and the α value (A). Based on the shadow texture texel data (R, G, B, A) and the distance parameter (h), the shadow processing unit is set as texel data. The density parameter (s) may be obtained.

  In this way, the more the first object moves away from the second object according to the positional relationship between the first object and the second object, the more the shadow of the first object reflected in the second object becomes. Realistic expressions can be made thin.

  (5) In the image generation system, the program, and the information storage medium of the present invention, a player object and an enemy object are set as the first object in the object space, and a terrain object is set as the second object. Is set, and the shadow processing unit performs a first shadow process when the shadow of the player object is generated with respect to the terrain object, and generates a shadow of the enemy object with respect to the terrain object. Alternatively, a second shadow process having a different process content from the first shadow process may be performed. In this way, by changing the processing contents between the process of generating the shadow of the player object and the process of generating the shadow of the enemy object that are easily noticed by the player without making the contents of the shadow processing common to all objects, It is possible to reduce the processing load when a large number of enemy objects are drawn while maintaining the image quality.

  (6) In the image generation system, the program, and the information storage medium of the present invention, the distance calculation unit obtains the distance parameter based on the position of the reference point set in the player object, and the shadow processing unit Projecting the shadow texture onto the terrain object with a reference point as the projection center, associating the vertex of the terrain object with the texel of the shadow texture, texel data of the texel associated with the vertex, and each vertex The process of darkening the color of the terrain object according to the shadow density parameter obtained based on the distance parameter obtained in the above may be performed as the first shadow process. In this way, high-definition expression can be performed for the shadow of the player object that is likely to be noticed by the player.

  (7) In the image generation system, the program, and the information storage medium of the present invention, the distance calculation unit obtains the distance parameter based on the position of the reference point set for the enemy object, and the shadow processing unit obtains the distance parameter. The shadow density parameter obtained based on the distance parameter and the texel data of the texel of the shadow texture previously associated with the vertex of the shadow polygon, the shadow density parameter obtained by associating the shadow color with the vertex in advance. As the translucency, a process of rendering the shadow polygon translucently in a given area of the terrain object determined according to the position of the enemy object may be performed as the second shadow process. In this way, for example, when the number of appearances of enemy objects is larger than that of the player object, the processing load can be reduced by expressing the shadows in a simplified manner.

  (8) According to the present invention, the computer obtains a distance parameter that changes according to the positional relationship between the first object and the second object set in the object space, and is generated for the second object. A texture data structure used for shadow processing for changing a shadow of a first object according to a shadow density parameter calculated based on a distance parameter, and comprising texel data composed of a luminance value and an α value of each color component of RGB Is associated with the texture coordinates, and is related to the texture data structure in which the texel data is set so that the shadow density parameter changes in inverse proportion to the quadratic function of the distance parameter. The present invention also relates to an information storage medium for storing the texture data structure.

  According to the present invention, it is possible to obtain a distribution pattern of shadow density parameters such that the cross section of the first object viewed from the second object becomes smaller and thinner according to a quadratic function of the distance between the objects.

  (9) In the present invention, the computer obtains a distance parameter (h) that changes according to the positional relationship between the first object and the second object set in the object space, A texture data structure used for shadow processing that changes a shadow of a generated first object according to a shadow density parameter (s) calculated based on a distance parameter (h), and the luminance of each RGB color component The texel data consisting of the values (R, G, B) and the α value (A) are associated with the texture coordinates (U, V), and the distance parameter (h), the shadow density parameter (s), Is related to the texture data structure in which the texel data (R, G, B, A) is set so that the following relationship is satisfied. The present invention also relates to an information storage medium for storing the texture data structure.

  According to the present invention, as the first object is closer to the second object, a distribution pattern of shadow density parameters along the cross-sectional shape of the first object is obtained, and as the first object moves away from the second object. Thus, it is possible to obtain a shadow density parameter distribution pattern in which the shadow shape becomes ambiguous.

  (10) In the present invention, the computer obtains a distance parameter (h) that changes according to the positional relationship between the first object and the second object set in the object space, A texture data structure used for shadow processing that changes a shadow of a generated first object according to a shadow density parameter (s) calculated based on a distance parameter (h), and the luminance of each RGB color component The texel data consisting of the values (R, G, B) and the α value (A) are associated with the texture coordinates (U, V), and the distance parameter (h), the texel data (R, G, B, A) and the shadow density parameter (s) are related to the texture data structure having the following relationship. The present invention also relates to an information storage medium for storing the texture data structure.

  According to the present invention, since it is not necessary to prepare a shadow texture for each positional relationship between the first object and the second object, it is possible to save memory usage and reduce processing load. According to the present invention, the shadow of the first object reflected in the second object increases as the first object moves away from the second object according to the positional relationship between the first object and the second object. Realistic expressions can be made so that is thin.

  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.

  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 a player object (an example of a moving object, a player character operated by the player), and functions thereof are a lever, a button, a steering, a microphone, and a touch panel display. Alternatively, it can be realized by a housing or the like. The storage unit 170 serves as a work area for the processing unit 100, the communication unit 196, and the like, and its function can be realized by a RAM (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.

  Note that a program (data) for causing a computer to function as each unit of this embodiment is distributed from the information storage medium of the host device (server) to the information storage medium 180 (storage unit 170) via the network and communication unit 196. 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 an object space setting unit 110, a movement / motion processing unit 112, a virtual camera control unit 114, a distance calculation unit 116, a drawing unit 120, and a sound generation unit 130. Note that some of these may be omitted.

  The object space setting unit 110 is an object 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). ) 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 object data including the vertex coordinates of the object is stored in the object data storage unit 176 of the storage unit 170.

  The movement / motion processing unit 112 performs a movement / motion calculation (movement / motion simulation) of an object (character, car, train, airplane, etc.). That is, based on operation data input by the player through the operation unit 160, a program (movement / motion algorithm), various data (motion data), or the like, the object is moved in the object space, or the object is moved (motion, animation). ) Process. Specifically, object movement information (position, rotation angle, speed, or acceleration) and motion information (position or rotation angle of each part that constitutes the object) are sequentially transmitted every frame (1/60 seconds). Perform the required simulation process. A frame is a unit of time for performing object movement / motion processing (simulation processing) and image generation processing. In particular, in the present embodiment, processing for moving the illumination source object (moving object) in the object space is performed based on operation data input by the player through the operation unit 160.

  The virtual camera control unit 114 performs a virtual camera (viewpoint) control process for generating an image viewed 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 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 distance calculation unit 116 performs a process for obtaining a distance parameter based on the positional relationship between the first object and the second object in the object space. The distance parameter can be obtained based on the position (height) of the reference point (representative point) of the first object. The distance parameter may be obtained for each vertex of the shadow processing target area in the second object, or only one distance parameter is obtained for the shadow processing target area in the second object. It may be.

  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 generating a so-called three-dimensional game image, first, object data (model data) including vertex data (vertex position coordinates, texture coordinates, color data, normal vector, α value, etc.) of each vertex of the object (model) ) Is input, and vertex processing (shading by a vertex shader) is performed based on the vertex data included in the input object data. 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. Subsequent to rasterization, pixel processing (shading or fragment processing by a pixel shader) for drawing pixels (fragments forming a display screen) constituting an image is performed. In pixel processing, according to a pixel processing program (pixel shader program, second shader program), various processes such as texture reading (texture mapping), color data setting / change, translucent composition, anti-aliasing, etc. are performed, and an image is processed. The final drawing color of the constituent pixels is determined, and the drawing color of the perspective-transformed object is output (drawn) to the drawing buffer 174 (a buffer capable of storing image information in units of pixels; VRAM, rendering target). 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. Note that when there are a plurality of virtual cameras (viewpoints), an image can be generated so that an image seen from each virtual camera can be displayed as a divided image on one screen.

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

  The drawing 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 178 of the storage unit 170 to an object. Specifically, the texture (surface properties such as color (RGB) and α value) is read from the texture storage unit 178 of the storage unit 170 using the texture coordinates set (given) at 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 with texels, bilinear interpolation or the like is performed as texel interpolation.

  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).

  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.

  Further, in the present embodiment, the drawing unit 120 includes a shadow processing unit 122.

  The shadow processing unit 122 applies the shadow of the first object to the second object based on the shadow density parameter obtained based on the distance parameter and the texel data of the shadow texture read from the texture storage unit 178. Performs shadow processing to be generated. As the shadow processing, the shadow texture is projected and mapped onto the second object with the reference point set on the first object as the projection center, and the color of the second object is changed based on the shadow density parameter that changes according to the distance parameter. Shadow (decrease brightness) (first shadow processing), shadow polygons with shadow color and shadow texture texture coordinates set in advance are prepared, and the shadow is converted according to the distance parameter. With the density parameter as semi-transparency, a process (second shadow process) for rendering a semi-transparent image by overlaying a shadow polygon on a second object according to the position of the first object can be performed. These shadow processes may be switched according to the type of the first object.

  The shadow processing unit 122 includes a shadow density calculation unit 124.

  The shadow density calculation unit 124 is obtained by the distance calculation unit 116 using texel data including luminance values (R, G, B) and α values (A) of RGB color components set for each texel of the shadow texture. Based on the distance parameter (h) corresponding to the positional relationship between the first object and the second object, a process for obtaining the shadow density parameter s using a predetermined conversion formula is performed.

  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. In this embodiment, as shown in FIG. 2, in order to realistically express the shadow of the vehicle object OB1 (first object) reflected in the terrain object OB2 (second object), the following method is used. The method is adopted.

  First, the present embodiment employs a technique in which a shadow texture is prepared in advance, which can determine a distribution pattern of shadow density parameters according to the height of the vehicle object relative to the terrain object (distance between the terrain object and the vehicle object). ing.

  FIG. 3 shows an example of the shadow texture TEX. In this shadow texture TEX, the texture coordinates (U, V), the luminance values (R, G, B) of each RGB color component, and the α value (A) are associated with each texel, and a predetermined conversion equation is obtained. As shown in FIG. 4, the shadow density parameter distribution pattern in which the shadow density decreases according to the height of the vehicle with respect to the terrain can be obtained by calculating the shadow density parameter. It has become.

  The shadow density parameter (s), distance parameter (h: height parameter), and texel data (R, G, B, A) have a relationship based on the following conversion formula.

  Here, the texel data (R, G, B, A) of the shadow texture TEX includes, as shown in FIG. 5, a shadow density parameter (s0) that represents the shadow density when the vehicle object OB1 is on the ground surface, Based on the shadow density parameter (s1) representing the darkness of the shadow when the vehicle object OB1 is at a position higher than the ground surface and the distance parameter (h1) representing the height of the position higher than the ground surface, The shadow density parameter s is set to change in inverse proportion to the quadratic function.

  At this time, as shown in FIG. 6, texel data (R, G, B, A) is generated using a surface light source LS that illuminates an object (object) with light of uniform intensity from the entire celestial sphere. That is, the distribution of the darkness of the shadows (main shadow (hard shadow) and penumbra (soft shadow)) reflected on the projection surface when the irradiation light from the surface light source LS is shielded by the vehicle object OB1 from the ground surface of the vehicle object OB1. Is obtained as a shadow density parameter distribution pattern according to the height of the vehicle (the distance between the vehicle object OB1 and the ground surface), and the parameters (β, γ, δ, ε) are fitted so as to have the relationship of A shadow texture TEX can be obtained by setting data (R, G, B, A).

  In this way, the cross section of the vehicle object OB1 viewed from the projection plane becomes smaller and thinner according to the square of the distance from the vehicle object OB1 to the projection plane (in a broad sense, a quadratic function with the distance as a variable). Various distribution patterns of shadow density parameters can be obtained. That is, by preparing a shadow texture TEX that integrates a plurality of shadow density parameter distribution patterns in advance, the closer the vehicle object OB1 is to the topographic object OB2, the more the shadow density parameter distribution pattern along the cross-sectional shape of the vehicle object OB1 is. As a result, it is possible to obtain a shadow density parameter distribution pattern in which the shadow shape becomes ambiguous as the vehicle object OB1 moves away from the terrain object OB2.

  In the present embodiment, as a vehicle object (first object), a player vehicle object operated by a player and an enemy vehicle object that is a competitor of the player vehicle object appear in the object space to perform a racing game. In addition, the shadow of the player vehicle object reflected on the terrain object (second object) and the shadow of the enemy vehicle object reflected on the terrain object are generated by different methods.

  First, a shadow generation method (first shadow processing method) for the player vehicle object will be described. For the player vehicle object, the shadow texture is projected and mapped onto the terrain object, and the shadow of the player vehicle object is generated by darkening the color of the terrain object according to the distribution pattern of the shadow density parameter obtained from the shadow texture.

  Specifically, as shown in FIG. 7, a reference point C is set for the vehicle object OB1, and a virtual camera VC for projection mapping with the reference point C as the projection center is set toward the terrain object OB2.

  Then, the region R1 intersecting with the projection space from the virtual camera VC is set as a target region for the projection mapping of the shadow texture TEX, and the vertex V (X, Y, Z included in the region R1 when the shadow texture TEX is placed in the region R1. ) And the texel T (U, V) of the shadow texture TEX.

  Specifically, the vertex coordinates of the terrain object OB2 and the texels of the shadow texture TEX are associated by converting the vertex coordinates in the region R1 of the terrain object OB2 into the texture coordinates of the shadow texture TEX using a given conversion matrix. It is done. For example, a world matrix W that converts the coordinate value of the vertex of the terrain object OB2 from the coordinate value of the local coordinate system (model coordinate system) to the coordinate value of the world coordinate system, and the view coordinate system that has the projection center of the virtual camera VC as the origin View matrix V for conversion to (viewpoint coordinate system), shadow spread according to size (H, W) of vehicle object OB1 (expansion rate of shadow texture TEX according to distance from projection center) and projection The projection matrix P representing the deviation of the generation position of the shadow with respect to the center and the center (origin) of the coordinate system of the texture coordinate obtained by each matrix W, V, P are shifted and the range is normalized (-1 to 1) And a correction matrix including matrix elements for normalization to 0 to 1, and based on each of these matrices, the course object OB2 Can be obtained conversion matrix m to convert the point coordinates to the texture coordinates.

  When the shadow texture TEX is projected and mapped onto the terrain object OB2, the distance parameter (h) is obtained based on the position of the reference point C set for the vehicle object OB1 and the position of the terrain object OB2. The distance parameter (h) is preferably obtained for each vertex in the region R1 of the terrain object OB2. In this way, it is possible to generate a shadow that reflects the inclination and unevenness of the surface of the topographic object OB2.

  Then, based on the texel data (R, G, B, A) of the texel associated with the vertex in the region R1 of the topographic object OB2, and the distance parameter (h), the shadow density parameter s is calculated using the above conversion formula. As shown in FIG. 8, for the region R1 of the terrain object OB2, the color RGB (m) obtained based on the object data of the terrain object OB2 as RGB (o) = RGB (m) × (1-s) ) In accordance with the shadow density parameter s, the color RGB (o) darkened (lower brightness) is set as the drawing color, so that the shadow of the vehicle object OB1 can be generated in the region R1 of the topographic object OB2. On the other hand, for the region R2 other than the region R1 of the terrain object OB2, the color RGB (m) obtained based on the object data of the terrain object OB2 is set as the drawing color as it is. Note that the color RGB (m) may be the vertex color of the object, the texel color of the decal texture (pattern texture) mapped to the object, or the vertex color and the texel of the decal texture. It may be a multiplication result with a color.

  Next, a shadow generation method (second shadow processing method) for the enemy vehicle object will be described. For enemy vehicle objects, a shadow polygon, which is a single-color quadrilateral polygon set with black (shadow color) as the vertex color, is drawn semi-transparently overlaid on the terrain object using the shadow density parameter obtained from the shadow texture as the translucency. Thus, the shadow of the enemy vehicle object is generated by darkening the color of the terrain object according to the distribution pattern of the shadow density parameter.

  Specifically, as shown in FIG. 9A, based on the position of the reference point C set on the vehicle object OB1, the region R1 on the terrain object OB2 is determined as the drawing position of the shadow polygon. At this time, the region R1 may be a position (directly below) where the vehicle object OB1 is parallel-projected on the terrain object OB2, but in the present embodiment, the drawing position of the shadow polygon is set to a position shifted from the center of the vehicle object OB1. ing. In this way, it is possible to make the viewer of the image aware of the direction of the light source in a pseudo manner. The shadow polygon may be placed at a position slightly lifted from the terrain object OB2. In this way, it is possible to prevent a situation in which a part of the shadow polygon is sunk under the terrain object OB2 due to the inclination or unevenness of the surface of the terrain object OB2.

  As shown in FIG. 9B, the shadow polygon SP has texture coordinates for the shadow texture TEX set in advance at the vertices, and the four texels T1 to T4 of the shadow texture TEX with respect to the vertices V1 to V4. Are associated.

  When the shadow polygon SP is drawn over the region R1 of the terrain object OB2, as shown in FIG. 10, the texel data (R, G, B, A) of the shadow texture TEX and the reference point of the vehicle object OB1 Based on the distance parameter (h) obtained based on the position (height) of C and the position (height) of the topographic object OB2, the distribution pattern of the shadow density parameter (s) is obtained by the above conversion formula, The distribution pattern of the shadow density parameter (s) is rendered translucent as the α plane of the shadow polygon SP. In this way, the drawing color RGB (o) of the topographic object OB2 in the region R1 is obtained by RGB (o) = RGB (m) × (1−s) + RGB (s) × s. Note that RGB (m) is a color obtained based on the object data of the terrain object OB2, and RGB (s) is a color (shadow color) set to the vertices V1 to V4 of the shadow polygon SP. In this embodiment, since the shadow color set in the shadow polygon SP is black (R = 0, G = 0, B = 0), the actual drawing color RGB (o) of the topographic object OB2 is RGB ( o) = RGB (m) × (1−s), and the shadow is drawn in the region R1 with the color of the terrain object OB2 darkened according to the shadow density parameter (s).

  As described above, according to the method of the present embodiment, the texel data (R of the shadow texture TEX) such that the density of the shadow decreases as the vehicle object OB1 (player vehicle object or enemy vehicle object) moves away from the terrain object OB2. , G, B, A) are set, and the shadow density parameter (s) that changes in inverse proportion to the quadratic function of the distance parameter (h) is obtained by using the above conversion formula. Can do. Then, by darkening the color of the terrain object OB2 according to the distribution pattern of the shadow density parameter (s) obtained from one shadow texture TEX (lowering the brightness value), the memory consumption can be saved while saving the memory consumption. A realistic vehicle shadow according to the height of the vehicle can be generated.

3. Processing of this embodiment Next, a detailed processing example of this embodiment will be described with reference to the flowcharts of FIGS. 11 and 12.

  First, an example of shadow processing when the vehicle object is a player vehicle object will be described with reference to FIG.

  First, the position and orientation of the vehicle object OB1 are obtained (step S10), and a conversion matrix m is calculated according to the position of the vehicle object OB1, the orientation of the vehicle object OB1, and the size (shape) of the vehicle object OB1 ( Step S11).

  Next, the position coordinates of the vertices of the terrain object OB2 are converted into texture coordinates using the conversion matrix m, and the distance parameter (h) corresponding to the position of the vertices of the terrain object OB2 is obtained. Then, the shadow texture TEX is sampled based on the obtained texture coordinates, and the shadow density parameter s is obtained based on the texel data (R, G, B, A) of the shadow texture TEX and the distance parameter h.

  Then, the terrain object OB2 is drawn while multiplying the color (R, G, B) obtained based on the object data of the terrain object OB2 by 1-s, the vehicle object OB1 is drawn, and the vehicle object OB1 is drawn on the terrain object OB2. An image in which a shadow corresponding to the height of the image is generated is obtained (steps S14 and S15).

  Next, an example of shadow processing when the vehicle object is an enemy vehicle object will be described with reference to FIG.

  First, the position and orientation of the vehicle object OB1 are obtained (step S20), and the position and orientation of the shadow polygon SP are calculated based on the position and orientation of the vehicle object OB1 (step S21). Further, a distance parameter h is obtained based on the position of the vehicle object OB1 (step S22).

  Next, the shadow texture TEX is read (step S23), and the shadow density parameter s is obtained based on the texel data (R, G, B, A) of the shadow texture TEX and the distance parameter h (step S24). Then, the terrain object OB2 is drawn, and the shadow density parameter s is set to the α value of the shadow polygon SP, and the shadow polygon SP is superimposed on the terrain object OB2 to be rendered translucent (step S25). Then, by drawing the vehicle object OB1, an image in which a shadow corresponding to the height of the vehicle object OB1 is generated on the terrain object OB2 is obtained (step S26).

4). Hardware Configuration FIG. 13 shows an example of a hardware configuration that can realize 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 cited as broad or synonymous terms in the description in the specification or drawings can be replaced with broad or synonymous terms in other descriptions in the specification or 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 the above-described embodiment, a method of generating a shadow for a terrain object by texture projection or drawing of a shadow polygon is employed, but a method other than the above may be employed.

  The present invention can be applied to various games (racing game, fighting game, shooting game, robot battle game, sports game, competition game, role playing game, music playing game, dance game, etc.). Further, the present invention is applied to various image generation systems such as a business game system, a home game system, a large attraction system in which a large number of players participate, a simulator, a multimedia terminal, a system board for generating a game image, and a mobile phone. it can.

The functional block diagram of the image generation system of this embodiment. The image drawn using the method of this embodiment. The example of the shadow texture used with the method of this embodiment. Explanatory drawing of the shadow texture used with the method of this embodiment. Explanatory drawing of the production | generation process of the shadow texture used with the method of this embodiment. Explanatory drawing of the production | generation process of the shadow texture used with the method of this embodiment. The figure for demonstrating the method of this embodiment. The figure for demonstrating the method of this embodiment. The figure for demonstrating the method of this embodiment. The figure for demonstrating the method of this embodiment. The flowchart which shows the example of the process of this embodiment. The flowchart which shows the example of the process of this embodiment. An example of a hardware configuration.

Explanation of symbols

OB1 vehicle object (first object),
OB2 Terrain object (second object),
TEX shadow texture, SP shadow polygon, C reference point,
100 processing unit, 110 object space setting unit, 112 movement / motion processing unit,
114 virtual camera control unit, 116 distance calculation unit, 120 drawing unit, 122 shadow processing unit,
124 shadow density calculation unit, 160 operation unit, 170 storage unit, 172 main storage unit,
174 Drawing buffer, 176 Object data storage unit,
178 texture storage unit, 180 information storage medium, 190 display unit,
192 sound output unit, 194 portable information storage device, 196 communication unit,

Claims (7)

A program for generating an image of an object space viewed from a given viewpoint,
A texture storage unit for storing shadow texture;
A distance calculation unit for obtaining a distance parameter based on a positional relationship between the first object and the second object in the object space;
Shadow processing for generating a shadow of the first object for the second object based on the shadow density parameter obtained based on the distance parameter and the texel data of the shadow texture read from the texture storage unit As a shadow processing unit to perform
Make the computer work ,
In the shadow texture texel, luminance values (R, G, B) of each color component of RGB and an α value (A) are set as the texel data,
The shadow processing unit
A program for obtaining the shadow density parameter (s) corresponding to each texel based on the texel data (R, G, B, A) of the shadow texture and the distance parameter (h) . In claim 1,
The shadow processing unit obtains the shadow density parameter (s) corresponding to each texel by the following equation .
In claim 1 or 2,
  In the object space, a player object and an enemy object are set as the first object, and a terrain object is set as the second object.
  The shadow processing unit
  When the shadow of the player object is generated for the terrain object, a first shadow process is performed. When the shadow of the enemy object is generated for the terrain object, the first shadow process is a process. A program that performs second shadow processing with different contents.   In claim 3,
  The distance calculation unit is
  Obtaining the distance parameter based on the position of the reference point set in the player object;
  The shadow processing unit
  Projecting the shadow texture onto the terrain object with the reference point as the projection center to associate the vertex of the terrain object with the texel of the shadow texture, texel data of the texel associated with the vertex, and A program for performing a process of darkening the color of the terrain object as a first shadow process according to a shadow density parameter obtained based on a distance parameter.   In claim 3,
  The distance calculation unit is
  Obtaining the distance parameter based on the position of the reference point set in the enemy object;
  The shadow processing unit
  The shadow color is previously associated with the vertex using the shadow density parameter obtained based on the obtained distance parameter and the texel data of the texel of the shadow texture previously associated with the vertex of the shadow polygon. A program which sets transparency of a shadow polygon and draws the shadow polygon in a given area of the terrain object determined according to the position of the enemy object as a second shadow process. An information storage medium readable by a computer, wherein the program according to any one of claims 1 to 5 is stored.   An image generation system for generating an image of an object space viewed from a given viewpoint,
  A texture storage unit for storing shadow texture;
  A distance calculation unit for obtaining a distance parameter based on a positional relationship between the first object and the second object in the object space;
  Shadow processing for generating a shadow of the first object for the second object based on the shadow density parameter obtained based on the distance parameter and the texel data of the shadow texture read from the texture storage unit A shadow processing unit to perform;
  Including
  In the shadow texture texel, luminance values (R, G, B) of each color component of RGB and an α value (A) are set as the texel data,
  The shadow processing unit
  An image generation system, wherein the shadow density parameter (s) corresponding to each texel is obtained based on texel data (R, G, B, A) of the shadow texture and a distance parameter (h).