JP2007164582A - Program, information storage medium and image generation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate a high quality image expressing a state of change of cloud in real time. <P>SOLUTION: A pattern showing the density of cloud is searched based on a time pattern and the pattern of a perlin noise. A scaling parameter is prepared as a parameter for determining a pattern generation space to be cut, and a plurality of cross-sections whose width is different on a pattern generation space are acquired by using the scaling parameter, and the density patterns of cloud to be acquired from the respective cross-sections are combined, so that one composite pattern can be searched. The respective patterns are multiplied by different power parameters and combined as the intensity of composition in combining the plurality of density patterns of cloud. A threshold parameter is prepared, and the final shape of cloud is determined by carrying out filtering by clamping thin sections from among the density patterns of cloud based on the threshold parameter. <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. For example, an image generation system that generates a game image of an action game in which the player moves the object space by operating the character or causes the character to take some action. It is preferable that a natural environment such as a cloud can be expressed realistically.

In particular, what exists in the sky such as a cloud occupies a relatively large area in the field-of-view image of the virtual camera, and therefore its presence is easily noticeable in the image. For this reason, a technique capable of expressing in real time the state of the sky such as clouds has been desired. For example, conventionally, when a cloud is changed in real time, it has been dealt with by animating using a plurality of textures prepared in advance. However, in such a method, it is necessary to secure a memory area for storing a large amount of texture data, and there is a problem that a system with limited use of the memory cannot sufficiently utilize the characteristics.
JP 2002-298158 A

  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 that can generate a high-quality image that expresses how clouds change in real time. There is.

  (1) The present invention is an image generation system for generating an image viewed from a given viewpoint in an object space, an object space setting unit for setting a cloud object in the object space, and a pattern generation space A cloud information calculation unit that generates a given random pattern and calculates cloud information based on the generated random pattern, and a drawing unit that draws a cloud object reflecting the obtained cloud information, The cloud information calculation unit changes the pattern appearing on the cut surface of the pattern generation space by changing the position of the cut surface that cuts the pattern generation space along the first coordinate axis as time elapses. Both are related to an image generation system for obtaining the cloud information based on a pattern appearing on a cut surface of the pattern generation space. 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 such a program.

  In the present invention, a cloud object includes an aggregate of particles in addition to a plate-like polygon polygon. The cloud information includes texture information mapped to plate-like polygons, particle generation information (information related to generation, disappearance, and movement).

  According to the present invention, the pattern appearing on the cut surface of the pattern generation space in which a given random pattern is generated is used for calculating cloud information reflected in the cloud object. At this time, the position of the cut surface in the pattern generation space is changed by changing the Y coordinate component of the pattern generation space with the passage of time. Thus, by changing the position of the cut surface according to the passage of time, it is possible to express a cloud that changes in real time.

  (2) In the image generation system, the program, and the information storage medium of the present invention, the cloud information calculation unit appears on a plurality of cut surfaces having different sizes on the pattern generation space based on a given scaling parameter. While acquiring a pattern, you may make it obtain | require the said cloud information based on the synthetic | combination pattern which synthesize | combined the pattern which appears in the said some cut surface. In this way, it is possible to improve the randomness of the pattern that is the basis for obtaining cloud information by synthesizing patterns that appear on multiple cut planes, so that it can represent clouds that are closer to the actual natural environment. Can do.

  (3) In the image generation system, the program, and the information storage medium of the present invention, when the cloud information calculation unit synthesizes the patterns appearing on the plurality of cut surfaces, the patterns are multiplied by different synthesis rate parameters. You may make it synthesize | combine after that. In this way, it is possible to improve the randomness of the pattern and prevent a similar cloud by simply changing the composition ratio of the patterns appearing on the plurality of cut surfaces.

  (4) In the image generation system, the program, and the information storage medium of the present invention, the cloud information calculation unit applies the pattern appearing on the cut surface of the pattern generation space or the composite pattern based on a given threshold parameter. Alternatively, the cloud shape may be determined by performing filtering on the cloud. For example, if the threshold parameter is changed according to the weather condition, elapsed time, or occurrence event in the object space, a cloud suitable for the situation in the object space can be expressed. Become.

  (5) In the image generation system, the program, and the information storage medium of the present invention, the cloud information calculation unit sets the position of the cut surface of the pattern generation space to a second coordinate axis different from the first coordinate axis and the third coordinate axis. The pattern appearing on the cut surface of the pattern generation space may be changed by changing along at least one of the coordinate axes. In this way, for example, it is possible to express how the clouds move according to the weather conditions, the elapsed time, or the occurrence event in the object space. In this case, it becomes possible for the viewer to feel the wind direction and the like indirectly by the way the clouds move.

  (6) Further, in the image generation system, the program, and the information storage medium of the present invention, a color look-up table in which a correspondence relationship between at least one of cloud color and transparency and an index number is prepared is provided. Creating an index texture in which the index number obtained based on a given color range specifying parameter and the cloud information is set in a texel, and referring to the color lookup table for the cloud object You may make it map. For example, if the color range specification parameter is changed according to the weather conditions in the object space, the elapsed time, or the occurrence event, it becomes possible to express realistic clouds according to the situation. High nature.

  (7) The image generation system of the present invention further includes a light source information setting unit that sets light source information of a light source set in the object space, and the light source information setting unit includes weather conditions in the object space, Depending on at least one of the elapsed time and the occurrence event, at least one of the color and brightness of the light source that illuminates the cloud object may be changed in the light source information. In the program and information storage medium of the present invention, a computer may function as the light source information setting unit. In this way, a realistic cloud according to the situation can be expressed. For example, it is possible to express a cloud that is illuminated in red by sunrise or sunset.

  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 cloud information calculation unit 116, a weather condition setting unit 118, a light source information setting unit 119, a drawing unit 120, and a sound generation unit 130. including. 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. In particular, in the present embodiment, the object space setting unit 110 sets a cloud object in the object space. The cloud object may be a plate-like polygon polygon (for example, a rectangular polygon) or an aggregate of particles (particle-like objects).

  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.

  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 cloud information calculation unit 116 generates a given random pattern (noise pattern) in the pattern generation space and performs a process of calculating cloud information based on the generated random pattern. In this embodiment, Perlin noise is generated as a random pattern. The random pattern can be obtained by an arbitrary random function (noise function) without being limited to Perlin noise.

  The cloud information calculation unit 116 calculates cloud information based on a pattern that appears on a cut surface of a three-dimensional pattern generation space in which a random pattern (for example, Perlin noise) is generated. The cloud information here includes texture information (texel pattern) that is pasted on the cloud object, and, if the cloud object is an aggregate of particles, particle generation information (information about generation, disappearance, and movement), etc. Corresponds. Then, the cloud information calculation unit 116 changes the first coordinate axis component (Y-axis component) of the cut surface that cuts the pattern generation space over time, thereby changing the cut surface of the pattern generation space to the first coordinate axis ( Move along the Y axis).

  In addition, the cloud information calculation unit 116 acquires a pattern appearing on a plurality of cut surfaces having different sizes on the pattern generation space based on a given scaling parameter, and combines the patterns appearing on the plurality of cut surfaces. Do. In this case, cloud information is obtained based on the composite pattern. Further, when synthesizing patterns appearing on a plurality of cut surfaces, the synthesizing process may be performed after multiplying each pattern by a different synthesis rate parameter.

  In addition, the cloud information calculation unit 116 determines the shape of the cloud by filtering the pattern appearing on the cut surface of the pattern generation space based on a given threshold parameter. For example, by changing the threshold parameter according to the generation state of clouds, it is possible to express a state where clouds are formed or a state where clouds are dense.

  Further, the cloud information calculation unit 116 sets the cut surface of the pattern generation space in at least one of the second coordinate axis (X axis) and the third coordinate axis (Z axis) different from the first coordinate axis (Y axis). By moving, the process of changing the position of the cut surface of the pattern generation space is performed. For example, if the position of the cut surface is changed in accordance with weather conditions or the like, the wind direction over the object space can be indirectly recognized.

  The light source information setting unit 119 performs processing for setting light source information (light source position, orientation, color, brightness, etc.) of the light source set in the object space. In particular, in the present embodiment, the color and brightness of a light source (for example, ambient light: ambient) that illuminates a cloud object in the light source information according to at least one of weather conditions, elapsed time, and occurrence event in the object space. A process for changing at least one of the above is performed. In this way, various expressions such as realistic sunrise and sunset can be performed.

  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 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 vertex processing, geometry processing such as vertex movement processing, coordinate transformation (world coordinate transformation, camera coordinate transformation), clipping processing, perspective transformation, or light source processing is performed, and an object is configured based on the processing result. Change (update, adjust) the vertex data given for the vertex group. 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 (fragment processing) for drawing pixels constituting an image (fragments constituting a display screen) is performed. In pixel processing, various processes such as texture reading (texture mapping), color data setting / changing, translucent composition, anti-aliasing, etc. are performed to determine the final drawing color of the pixels that make up the image, and perspective transformation is performed. The drawing color of the object is output (drawn) to the drawing buffer 174 (buffer that can store 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) set 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 performed by the drawing unit 120 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). May be. Programmable shaders can be programmed with vertex-level processing and pixel-level processing, so that the degree of freedom of rendering processing is high, and the expressive power can be greatly improved compared to fixed rendering processing by hardware. .

  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.

  In particular, the image generation system of this embodiment supports text mapping using a color look-up table (CLUT) for index color / texture mapping stored in the color palette storage unit 179. In index color / texture mapping, an index texture in which an index number (index color) is set for a texel is associated with an index number and image information (R component, G component, B component, A component (α component)). This is a technique of texture mapping for a virtual object (for example, a polygon polygon such as a rectangular polygon) while referring to a color look-up table (CLUT).

  In the present embodiment, the drawing unit 120 uses the index color / texture mapping function described above to determine the basic color of the cloud (the color before considering the influence of the light source). Specifically, a color lookup table (CLUT) in which a correspondence relationship between at least one of cloud color and transparency and an index number is prepared in advance in the color palette storage unit 179. Then, an index texture in which the index information obtained based on the given color range designation parameter and the cloud information obtained by the cloud information calculation unit 116 is set in the texel is created and stored in the texture storage unit 178. Finally, the index texture stored in the texture storage unit 178 is mapped to the cloud object (for example, rectangular polygon) while referring to the color lookup table (CLUT) stored in the color palette storage unit 179. Process.

  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 a drawing pixel corresponding to the primitive (the minimum unit of the surface) of the object is 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 normal α blending, a process for obtaining a color obtained by combining two colors by performing linear interpolation with the α value as the strength of synthesis is performed.

  The α value is information that can be stored in association with each pixel (texel, dot), and is, for example, plus alpha information other than color information indicating the luminance of each RGB color component. The α value can be used as mask information, translucency (equivalent to transparency and opacity), bump information, and the like.

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

  Note that the image generation system of the present embodiment may be a system dedicated to the single player mode in which only one player can play, or may be a system having a multiplayer mode in which a plurality of players can play. Further, when a plurality of players play, game images and game sounds to be provided to the plurality of players may be generated using one terminal, or connected via a network (transmission line, communication line) or the like. Alternatively, it may be generated by distributed processing using a plurality of terminals (game machine, mobile phone).

2. 2. Method according to this embodiment In this embodiment, the following method is adopted to express how the clouds drifting in the sky as shown in FIG. 2 change in real time.

  First, in the present embodiment, as shown in FIG. 3A, a celestial sphere object that moves following the virtual camera is set in the object space, and a position corresponding to the sky (given in the celestial sphere object) 2 is generated by arranging a cloud object COB made of a rectangular polygon at the position (2) and drawing a scene that can be seen from a virtual camera.

  A plurality of cloud objects may be set in the celestial sphere object. For example, as shown in FIG. 3B, a cloud object COB0 expressing a high-rise cloud and a cloud object COB1 expressing a low-rise cloud are displayed on the ground surface. You may make it set changing the height from. In this way, it becomes possible to express a change in the sky according to the height of the clouds.

  Further, in the present embodiment, as shown in FIG. 4, Perlin noise is generated in a given pattern generation space, and the cloud thickness and shape are adjusted based on the noise density distribution state created in the pattern generation space. A corresponding cloud pattern (an example of cloud information) is obtained.

  Perlin noise is a method of generating irregular noise in the natural world developed by Ken Perlin. When generating Perlin noise, the noise density N is obtained by the sum of functions as shown below. Can do.

N = Σf (x) ≈Σ (amplitude * interpolate (random (x * frequency))
In the above equation, “x” is an arbitrary parameter, “amplitude” is the amplitude (difference between the maximum and minimum random numbers), “frequency” is the frequency (random number sampling period), and “interpolate” is between the random values Indicates that interpolation is performed. That is, Perlin noise is the sum of noise functions (fractal functions) having different amplitudes and frequencies (wavelengths). In this embodiment, such a Perlin noise generation algorithm is extended to a three-dimensional pattern generation space (X, Y, Z). For example, smoothing calculation is performed on the noise density N obtained for eight points having integer coordinate values (eight points forming a three-dimensional lattice) by linear interpolation, interpolation by a trigonometric function, Hermite interpolation, or the like. Thus, the noise density N at an arbitrary coordinate point (X, Y, Z) in the three-dimensional pattern generation space can be obtained.

  Next, a method for obtaining a cloud pattern (cloud information) that changes with time will be described with reference to FIGS.

  In this embodiment, in order to create a texture that procedurally expresses a cloud pattern as time elapses, an XZ coordinate plane (second coordinate axis component and third coordinate axis of the pattern generation space as shown in FIG. 5 is used. By changing the Y coordinate value (the value of the first coordinate axis component) of the cutting plane F formed along the plane defined by the component with time, the cutting plane F is changed to the Y axis (first axis). (Coordinate axis). As a result, the Perlin noise pattern P (noise pattern) appearing on the cut surface F changes with time. By replacing the distribution of the noise density N in the pattern P appearing on the cut surface F with the cloud density, a cloud pattern that changes in real time can be acquired.

  However, simply acquiring the pattern P that appears on the cut surface F and making it a cloud pattern as it is may result in lack of reality or pattern characteristics. Has been given.

  First, in the method of this embodiment, in order to express that the state of clouds changes according to weather conditions such as wind direction, the position of the cutting plane F in the pattern generation space is shifted as shown in FIG. The pattern appearing on the cut surface F ′ can be acquired. In this case, the X-axis direction (the direction of the vector Vx in FIG. 6B: the second coordinate axis direction) and the Z-axis direction (the direction of the vector Vz in FIG. 6B: the third coordinate axis direction) according to the passage of time. The position of the cutting plane F can be moved along at least one of the above. In this way, an illusion that an actual wind is blowing in the object space can be given to the observer of the image. When the cut surface F is moved in the X-axis direction or the Z-axis direction, the amount of movement (the magnitudes of the vectors Vx and Vz) in each axis direction may be changed according to weather conditions and the like. . For example, when the weather is good, the amount of movement can be reduced, and when the weather is bad, the amount of movement can be increased to perform appropriate expression according to the weather conditions.

  Further, in the method of this embodiment, in order to improve the randomness of the pattern, as shown in FIG. 7, a method of synthesizing the Perlin noise patterns P1 and P2 appearing on the plurality of cut surfaces F1 and F2 is adopted.

  Specifically, by scaling the width (area) of the cut surface in the pattern generation space using the scaling parameter, the noise patterns appearing on the cut surfaces F1 and F2 having a plurality of different widths are the same size field. Noise patterns P1 and P2 are obtained. Next, the noise pattern P1, P2 is added and synthesized, for example, to obtain a synthesized noise pattern SP. At this time, each noise pattern P1 and P2 is multiplied by a different synthesis rate parameter as the synthesis strength, thereby adjusting the degree of influence of each noise pattern in accordance with the cloud form to be expressed. For example, when it is desired to express a cloud with a relatively clear shape, in the example shown in FIG. 7, the synthesis rate parameter of the noise pattern P1 may be set to a high value. When it is desired to express a cloud, in the example shown in FIG. 7, the synthesis rate parameter of the noise pattern P2 may be set higher.

  In this embodiment, a threshold parameter is prepared as a parameter for finally determining the cloud shape, and a method of filtering the synthesized noise pattern SP using the threshold parameter is adopted. ing. Specifically, as shown in FIG. 8, a cloud pattern is obtained by clamping an area equal to or less than the threshold parameter Nth from the noise density N of the synthesized noise pattern SP to a given value (for example, 0). CP is determined to determine the cloud shape. Since the distribution of the noise density N in each pattern changes randomly according to the noise function (random function), it has a cloud shape according to the situation such as weather conditions by changing the threshold parameter. A cloud pattern CP can be obtained. For example, if the threshold parameter Nth is lowered, a cloud pattern CP that expresses how the sky is covered over a wide range can be obtained, and if the threshold parameter Nth is increased, the clouds are scattered. It is possible to obtain a cloud pattern CP that expresses how to do. Further, if the threshold parameter Nth is also changed according to the passage of time or the like, it is possible to simulate the state of clouds above the natural environment. The filtering using the threshold parameter Nth may be performed not only on the synthesized noise pattern SP but also individually on the noise pattern P appearing on the cut surface of the pattern generation space.

  Next, a cloud color determination method performed by the method of the present embodiment will be described with reference to FIGS.

First, in the present embodiment, as shown in FIG. 9A, a color lookup table in which a correspondence relationship between cloud color (R, G, B) and cloud transparency (A: α value) is set ( CLUT) is prepared. In the color look-up table, 256-tone color data ((R ₀ , G ₀ , B ₀ ) to (R ₂₅₅ , G ₂₅₅ , B ₂₅₅ )) and transparency data (A _{0 to} A ₂₅₅ ) are stored. Corresponding to 256-level index numbers (0 to 255).

  In this embodiment, in order to be able to determine the range of cloud color and transparency according to the situation, processing for changing the range of index numbers used in the texture is performed.

  Specifically, the noise in the cloud pattern CP obtained by the processes of FIGS. 5 to 8 using the dynamic range parameter (first color range specifying parameter) and the offset parameter (second color range specifying parameter). The process of converting the density N of the image into an index number is performed. The dynamic range parameter and the offset parameter can be changed based on various factors such as an elapsed time in the object space, a weather condition, and an occurrence event. In this way, since the color and transparency of the cloud can be flexibly changed according to the situation, a realistic cloud can be expressed, which is highly convenient.

  Specifically, as shown in FIG. 9B, the noise density N in the cloud pattern CP is normalized to a given range (for example, a range of 0 to 1) and then multiplied by the dynamic range parameter. Then, a color band (dynamic range) that determines how much the color and transparency of the cloud are changed is determined. For example, when the normalized range of 0 to 1 is multiplied by 128 as the dynamic range parameter, an index number of 129 levels of 0 to 128 can be associated with the noise density N. Thereby, a temporary index number can be determined.

  Next, the initial value of the index number is offset with the offset parameter. For example, when the offset parameter is 20, the temporary index numbers 0 to 128 are offset to 20 to 148. An index texture TEX (cloud pattern texture) can be obtained by setting the offset index number obtained in this way as a texel value. When obtaining an index number, the index number after the offset has a minimum value of 0 so as not to exceed the range of the 256-level index number associated with the color look-up table (CLUT) by the offset. Is clamped at 0, and if the maximum is above 255, it is clamped at 255.

  Then, as shown in FIG. 10, the index texture TEX obtained from the cloud pattern CP is subjected to texture mapping on the cloud object COB (rectangular polygon composed of vertices V1 to V4) while referring to the color look-up table (CLUT). It is possible to express the state of clouds changing in real time.

  In the present embodiment, the color or brightness of the light source LS that illuminates the cloud object COB is changed according to the situation. For example, the time of the light source LS in the object space (morning, noon, night, etc.), weather conditions (sunny, cloudy, rain, etc.), the height of the light source LS (sun height), etc. By shading the cloud object COB by changing the color and brightness, it becomes possible to express a cloud dyed red due to sunrise or sunset. In addition, the color of the light source LS may be changed in order to enhance the effect according to an event (for example, an appearance scene of a special character) that occurs in the object space. Furthermore, when the amount of clouds and cloud thickness are prepared as parameters and the noise pattern generated in the pattern generation space is changed accordingly, parameters corresponding to the cloud amount and cloud thickness are set. The color or brightness of the light source LS may be changed according to the above. When the weather is fine and the amount of clouds is low, the ambient light is set brighter, and when the weather is cloudy or rainy and the amount of clouds is high, the ambient light is set darker to adjust the brightness in the object space according to the weather conditions. Can be expressed.

  The cloud expression method of the present embodiment described above can express a cloud that changes in real time by having the following characteristics.

  First, a pattern indicating cloud density is obtained based on a time parameter and a pattern of Perlin noise generated in a given pattern generation space. Specifically, a pattern appearing in a cross section along the XZ plane of the pattern generation space is obtained. By changing the Y coordinate of the cross section according to the time parameter, the pattern appearing on the cross section changes with time.

  Next, a scaling parameter is prepared as a parameter for deciding where to cut out the pattern generation space. By using the scaling parameter, multiple cross sections with different sizes on the pattern generation space are obtained, and The resultant cloud density pattern is synthesized to obtain one synthesized pattern.

  Next, as a combination strength (combination ratio) when combining a plurality of cloud density patterns, the patterns are combined after being multiplied by different power parameters.

  Next, threshold parameters are prepared, and the final shape of the cloud is determined by performing filtering by clamping a thin portion from the cloud density pattern based on the threshold parameter.

  Next, dynamic range parameters and offset parameters that determine the change range of cloud color and transparency are prepared, and based on the dynamic range parameters and offset parameters, the cloud density pattern (which may be a composite pattern) is converted into an index texture ( Cloud pattern texture). Thereby, the change range of the basic color of the cloud can be changed according to the situation. Then, an index color texture mapping is performed on the rectangular cloud polygon while referring to a color look-up table (CLUT) prepared in advance, thereby expressing cloud colors according to various situations.

  When shading a cloud polygon, the color and brightness of ambient light (ambient) are changed according to an event, time, and the like. By doing so, it is possible to express a cloud dyed in red or orange by, for example, sunset or sunrise.

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

  First, the pattern generation space (X, Y, Z) in which Perlin noise is generated is set, and the Y coordinate is determined according to the time T, so that 2 based on the cut surface (XZ plane) at the determined Y coordinate. Kinds of noise patterns P1 and P2 are obtained (step S10). As shown in FIG. 7, the noise patterns P1 and P2 are obtained by scaling (enlarging or reducing) a pattern appearing on a cut surface having a different area on the pattern generation space to the same field.

  Next, the noise pattern P1 is multiplied by the synthesis rate A1, the noise pattern P2 is multiplied by the synthesis rate A2, and then the noise patterns P1 and P2 are synthesized as shown in FIG. 7 (step S11).

  Next, as shown in FIG. 8, the synthesized pattern SP obtained by synthesizing the noise patterns P1 and P2 is filtered with the threshold value Nth to obtain the cloud pattern CP, and the cloud shape is determined (step). S12).

  Next, as shown in FIG. 9B, based on the dynamic range parameter and the offset parameter, an index texture TEX is generated by converting the final noise density N in the cloud pattern CP into an index number (step). S13).

  Next, a rectangular cloud polygon (cloud object COB) is set at a predetermined position in the celestial sphere object moving in the object space together with the virtual camera, and the influence of ambient light (ambient) on the cloud polygon is calculated (step S14). .

  Finally, with reference to a color look-up table (CLUT) in which cloud colors (R, G, B) and transparency (A) are set for cloud polygons, index texture TEX (cloud pattern texture) is texture-mapped. Then, by drawing a cloud polygon (step S15), a cloud image can be obtained.

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 the 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.

  The cloud information calculation method and the method for reflecting the cloud information to the object are not limited to those described in the above embodiment, and a method equivalent to the above method may be used.

  In the above embodiment, the case where the cloud pattern texture to be pasted on the cloud object is generated using the pattern appearing on the cut surface of the pattern generation space, but the pattern appearing on the cut surface of the pattern generation space is used. The present invention can also be applied to a case where cloud particles are generated and a cloud object is configured by an aggregate of cloud particles.

  Moreover, although the case where the texture produced | generated based on the cloud pattern was mapped with respect to the cloud object was demonstrated to the example in the said embodiment, you may make it map the texture with respect to a celestial sphere object.

  In the above-described embodiment, a method for expressing a cloud has been described. However, the method described in this embodiment may be applied to fog processing. For example, a pattern appearing on the cut surface of the pattern generation space can be used as information for expressing fog unevenness (non-uniformity).

  The present invention can be applied to various games (action game, racing game, fighting game, shooting game, robot battle game, sports game, competition game, role playing game, simulation game, music playing game, dance game, 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 example of the image produced | generated by applying 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 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 figure for demonstrating the method of this embodiment. The flowchart which shows the example of the specific process of this embodiment. An example of a hardware configuration.

Explanation of symbols

COB cloud object,
CLUT color lookup table,
TEX texture (index texture),
100 processing unit,
110 Object space setting unit, 112 Movement / motion processing unit,
114 virtual camera control unit, 116 cloud information calculation unit, 118 light source information setting unit,
120 drawing units, 130 sound generation units,
160 operation unit, 170 storage unit,
172 Main storage unit, 174 drawing buffer, 176 object data storage unit,
178 texture storage unit, 179 color palette storage unit,
180 information storage medium, 190 display unit, 192 sound output unit,
194 Portable information storage device, 196 communication unit

Claims (10)

A program for generating an image viewed from a given viewpoint in an object space,
An object space setting unit for setting a cloud object with respect to the object space;
A cloud information calculation unit that generates a given random pattern in the pattern generation space and calculates cloud information based on the generated random pattern;
As a drawing unit that draws cloud objects reflecting the obtained cloud information,
Make the computer work,
The cloud information calculation unit,
While changing the position of the cut surface that cuts the pattern generation space along the first coordinate axis over time, the pattern appearing on the cut surface of the pattern generation space is changed,
A program for obtaining the cloud information based on a pattern appearing on a cut surface of the pattern generation space. In claim 1,
The cloud information calculation unit,
While obtaining a pattern appearing in a plurality of cut surfaces having different widths on the pattern generation space based on a given scaling parameter,
A program for obtaining the cloud information based on a composite pattern obtained by combining patterns appearing on the plurality of cut surfaces. In claim 2,
The cloud information calculation unit,
When synthesizing patterns appearing on the plurality of cut surfaces, the program is synthesized after multiplying each pattern by a different synthesis rate parameter. In claim 1,
The cloud information calculation unit,
A program for determining a cloud shape by filtering a pattern appearing on a cut surface of the pattern generation space based on a given threshold parameter. In claim 2 or 3,
The cloud information calculation unit,
A program for determining a cloud shape by performing filtering on the synthesized pattern based on a given threshold parameter. In any one of Claims 1-5,
The cloud information calculation unit,
By changing the position of the cut surface of the pattern generation space along at least one of the second coordinate axis and the third coordinate axis different from the first coordinate axis, the pattern appearing on the cut surface of the pattern generation space is changed. A program characterized by letting In any one of Claims 1-6,
There is a color lookup table that sets the correspondence between at least one of cloud color and transparency and index number.
The drawing unit
Create an index texture with the texel set as the index number obtained based on the given color range specification parameter and the cloud information,
The index texture is mapped to the cloud object while referring to the color lookup table. In any one of Claims 1-7,
Causing a computer to function as a light source information setting unit for setting light source information of a light source set in the object space;
The light source information setting unit is
Changing at least one of the color and brightness of the light source that illuminates the cloud object in the light source information according to at least one of weather conditions, elapsed time, and occurrence event in the object space. A featured program.   An information storage medium readable by a computer, wherein the program according to any one of claims 1 to 8 is stored. An image generation system for generating an image viewed from a given viewpoint in an object space,
An object space setting unit for setting a cloud object with respect to the object space;
A cloud information calculation unit that generates a given random pattern in the pattern generation space and calculates cloud information based on the generated random pattern;
A drawing section for drawing a cloud object reflecting the obtained cloud information;
Including
The cloud information calculation unit,
While changing the position of the cut surface that cuts the pattern generation space along the first coordinate axis over time, the pattern appearing on the cut surface of the pattern generation space is changed,
An image generation system, wherein the cloud information is obtained based on a pattern appearing on a cut surface of the pattern generation space.