JP3609030B2 - Image generation method and program used therefor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for generating an image that realistically represents a rainfall state using computer graphics technology.
[0002]
[Prior art]
As a method to express how it is raining by computer graphics, each raindrop is drawn with a polygon model, and the position of each raindrop is calculated for each frame to represent the rain condition realistically. It has been.
[0003]
[Problems to be solved by the invention]
A conventional method for generating an image in a rain state has only moved a polygonal model of raindrops in a certain rain direction in consideration of the wind direction in a virtual three-dimensional space. However, in the real world, for example, in the case of a storm, raindrops jump not only from the top but also from the side. The generation of such images with computer graphics has not been fully studied.
[0004]
SUMMARY OF THE INVENTION An object of the present invention is to provide an image generation method capable of expressing a rainy state more realistically than before and a computer program used for realizing the method.
[0005]
[Means for Solving the Problems]
The present invention will be described below. In order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are appended in parentheses, but the present invention is not limited to the illustrated embodiment.
[0006]
The image generation method of the present invention is a method of creating a rain scene in a virtual three-dimensional space (1) by a computer and generating an image obtained by photographing the scene with a virtual camera (3). Arranges a predetermined polygon (4) to move in a direction different from the rain direction over a plurality of frames, and maps the translucent texture (5) representing a plurality of water drops (5a) to the polygon. To do.
[0007]
According to the image generation method of the present invention, a texture that represents a plurality of water droplets is mapped onto a polygon that moves in a direction different from the rain direction. I can express well how I am. Thereby, an image like a storm can be generated realistically.
[0008]
In the image generation method of the present invention, it is preferable to move the polygon in a direction different from the rain direction while enlarging the polygon. In this case, the interval between the water drops expressed by the texture gradually increases. Therefore, each water droplet appears to move separately, and the reality of the image is improved as compared with a case where the water droplets are moved while the size of the polygon is kept constant.
[0009]
In addition, it is preferable that a drop motion in consideration of the gravitational acceleration acting in the virtual three-dimensional space is given to each vertex of the polygon. In this case, it is possible to express the splashing while drawing a trajectory like a parabola, thereby improving the reality of the image.
[0010]
The polygon may be moved in a direction different from the rainfall direction while gradually changing the direction of the polygon in the virtual three-dimensional space. In this way, when the polygon is moved while changing its direction, the appearance of the texture attached to the polygon changes gradually. Therefore, the presence of the polygon becomes less noticeable and the reality of the image is improved.
[0011]
The polygon may be moved in a direction different from the rain direction while rotating around a predetermined rotation axis set along the surface thereof. Also in this case, the appearance of the texture attached to the polygon gradually changes as the polygon rotates. Therefore, the presence of the polygon becomes less noticeable and the reality of the image is improved.
[0012]
A plurality of the polygons may be moved together in a direction different from the rain direction. In this way, it is possible to express splashes more variably than when only one polygon is placed in the rain scene.
[0013]
The directions of the plurality of polygons may be different from each other. When only one polygon is placed, the texture attached to the polygon cannot be observed when the viewpoint is set to the side. However, when multiple polygons are placed in different directions, either polygon is placed. The texture of can be observed.
[0014]
The movement start positions of the plurality of polygons may be different from each other. In this case, splashes are observed at various positions in the image, and a powerful storm scene can be generated.
[0015]
In the rainy scene, the polygons may be arranged a plurality of times at different times, and at least one of the movement start position and the movement direction of the polygons with the time difference may be different from each other.
[0016]
Further, the program of the present invention is a program for creating a rain scene in a virtual three-dimensional space (1) using a computer and generating an image of a rain state, and a predetermined polygon ( 4) a process of arranging a plurality of frames so as to move in a direction different from the rain direction, and a process of mapping a translucent texture (5) representing a plurality of water drops (5a) on the polygon. The computer is configured to be executed.
[0017]
By reading and executing this program with a computer, the image generation method of the present invention can be implemented.
[0018]
In addition, the program of this invention can be provided with the preferable aspect of the production | generation method mentioned above as described below. That is, the program of the present invention may be configured to move the polygon in a direction different from the rainfall direction while enlarging the polygon. You may comprise so that the fall motion which considered the gravitational acceleration which acts in the said virtual three-dimensional space may be given to each vertex of the said polygon. The polygon may be configured to move in a direction different from the rainfall direction while gradually changing the direction of the polygon in the virtual three-dimensional space. The polygon may be configured to move in a direction different from the rainfall direction while rotating around a predetermined rotation axis set along the surface thereof. The plurality of polygons may be configured to move in a direction different from the raining direction as a group. The plurality of polygons may be configured to have different directions. The movement start positions of the plurality of polygons may be different from each other. In the rainy scene, the polygons may be arranged a plurality of times at different times, and at least one of the movement start position and the movement direction of the polygons with the time difference may be different from each other.
[0019]
Furthermore, the program of the present invention may be recorded on a storage medium and provided to the user, or may be provided to the user on a wired or wireless transmission medium.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of the present invention. FIG. 1A shows an example in which a rain scene is constructed in the virtual three-dimensional space 1. In the virtual three-dimensional space 1, a world coordinate system that is a three-axis orthogonal coordinate system of X, Y, and Z is set, and polygons 2... 2 representing raindrops and a virtual camera 3 are arranged there. The Y-axis direction corresponds to the vertical direction.
[0021]
The polygon 2 is a linear polygon having a predetermined length extending in the raining direction indicated by an arrow W in the drawing. The raining direction is determined in consideration of the wind direction set in the virtual three-dimensional space 1. In addition, various objects representing terrain, characters, and the like are arranged in the rain scene, but these are not shown. When the construction of the scene is completed, coordinate conversion is performed from the world coordinate system to the viewpoint coordinate system for the vertex coordinates of the polygon 2 and the like arranged in the virtual three-dimensional space 1, and a virtual screen (indeterminate) based on the viewpoint coordinate system. Projection onto the figure is performed, and the vertices of the polygon 2 and the like are converted into two-dimensional coordinates in the screen coordinate system. Thereafter, a rendering process such as texture mapping is performed to generate a three-dimensional image.
[0022]
Even though the polygon 2 described above can represent a state in which raindrops are falling in a certain direction, it is difficult to represent a state in which splashes are scattered in a direction different from the raining direction. Therefore, in the present embodiment, the rectangular polygon 4 is arranged in the virtual three-dimensional space 1 and moved in a direction different from the rain direction, and there are a plurality of water droplets 5a as shown in FIG. The translucent texture 5 expressing the above is mapped. The polygon 4 is moved as follows.
[0023]
First, an appropriate position in the virtual three-dimensional space 1 is determined as the movement start position Ps, and the polygon 4 is arranged there. This movement start position is determined so that the polygon 4 is not included in the field of view (shooting range) of the virtual camera 3 when the polygon 4 is arranged. That is, when the polygon 4 is arranged, the polygon 4 is made invisible on the screen. Further, the movement start position need not always be constant, and a different position may be determined as the movement start position every time the polygon 4 is arranged. That is, a plurality of polygons 4 can be arranged at different times in a rainy scene, and at least one of the movement start position and the movement direction of the polygons 4 to which the time differences are added may be different from each other.
[0024]
Next, the velocity vector V0 is given to the entire polygon 4, and velocity vectors V1 to V4 along the surface of the polygon 4 are also given to each vertex. The velocity vector V0 indicates the moving direction of the polygon 4 and is set in a direction different from the raining direction. The velocity vectors V1 to V4 at the respective vertices are given for gradually expanding the polygon 4 as it moves. For example, if there is a movement start position Ps in the lower left of the polygon 4 in FIG. 1A, for example, the velocity vector is increased as the vertex is longer from the movement start position Ps. As described above, when the polygon 4 is moved while being enlarged, the texture 5 is gradually extended, and the interval between the water droplets 5a is gradually enlarged. The polygon 4 is also given a velocity vector Vg considering the direction of gravity acting on the virtual three-dimensional space 1. Thereby, a mode that the water droplet 5a splashed sideways falls gradually is expressed.
[0025]
Further, the polygon 4 is also given a rotational motion about an appropriate rotational axis 6. As a result, the posture of the polygon 4 is changed so as to fall horizontally from the state of standing in the Y-axis direction as shown in the figure. From the above, the velocity vector of each vertex of the polygon 4 is a vector obtained by combining any of the velocity vectors V1 to V4, the velocity vectors V0 and Vg, and the velocity vector acting in the tangential direction of the rotational motion around the axis 6. Given.
[0026]
The above-described movement of the polygon 4 is performed over a plurality of frames (for example, 6 to 8 frames) photographed by the virtual camera 3. In a moving image configured as a set of those frames, the polygon 4 is expressed by a texture 5 mapped to the polygon 4 in order to move in the virtual three-dimensional space 1 so as to draw a parabola while being stretched. The interval between the water droplets 5a and the visible angle gradually change. That is, the water droplets 5a expressed by the texture 5 appear to be moving differently from each other. If the polygon 4 is moved in the same direction with the same size, all the water droplets 5a appear to move in the same direction, so that the splash is expressed more realistically than this. become.
[0027]
FIG. 2 shows an actual example of the texture 5 used in the above method, and FIG. 3 shows an actual example in which the polygon 4 is arranged in the rain scene of one frame. In FIG. 2, the gradation is inverted for easy observation. In FIG. 3, the polygon 4 is shown in a translucent white color for clarity. As is clear from FIG. 3, a plurality of polygons are arranged in a rainy scene as a group, and the motion described above is given to each polygon. In this case, the directions of the plurality of polygons are different from each other, and the movement start positions of the plurality of polygons are also different from each other. These polygons themselves are transparent, and if the color of each pixel of the texture is mapped to the polygon by associating the coordinates on each polygon with the U-V coordinates set in the texture of FIG. You can express how the is scattered. The splash expressed by these polygons and the rain expressed by the polygon 2 showing the raindrops in FIG. 1 can be well expressed in a stormy state.
[0028]
The image representation method described above can be used in three-dimensional image processing in various fields. As an example, an example in which the expression method of the present invention is implemented in a game machine using a computer will be described with reference to FIGS.
[0029]
FIG. 4 is a block diagram of a typical control system of a game machine using a computer. As is well known, the game machine 10 as a computer executes a predetermined game in accordance with a game program recorded on a storage medium (for example, a DVD-ROM) 25, and includes a CPU 11 mainly composed of a microprocessor, and the like. ROM 12 and RAM 13 as main storage devices for the CPU 11, image processing device 14 and sound processing device 16 that perform processing suitable for image processing and sound processing based on instructions from the CPU 11, and reading data from the storage medium And a storage medium reader 18. In the ROM 12, an operating system is written as a program necessary for overall operation control of the game machine 10. In the RAM 13, a game program or data read from a DVD-ROM 25 as a storage medium is written as necessary. The image processing device 14 receives the image data from the CPU 11 and develops the image data corresponding to the game screen on a built-in frame buffer (not shown), and converts the rendered image data into a predetermined video reproduction signal. The data is output to the monitor 19 at a predetermined timing. The sound processing device 16 reproduces data such as voice and musical sound read from the DVD-ROM 25, sound source data, and the like, and outputs them from the speaker 20. The reading device 18 reads a program or data recorded on the DVD-ROM 25 in accordance with an instruction from the CPU 11 and outputs a signal corresponding to the read content. The DVD-ROM 25 stores programs and data necessary for carrying out the image expression method according to the present invention. The monitor 19 generally uses a home-use television receiver, and the speaker 20 generally uses a built-in speaker of the television receiver. Further, an input device 22 and an external storage device 23 are connected to the CPU 11 via the bus 24. The external storage device 23 is a rewritable storage device such as a nonvolatile semiconductor memory, a hard disk, a magneto-optical disk, or the like. Such a configuration is merely an example, and the configuration of a computer to which the image generation method of the present invention is applied may be changed as appropriate.
[0030]
The program recorded in the DVD-ROM 25 as a storage medium includes a module describing a procedure necessary for constructing a rain scene and generating an image thereof by the method described above. The data recorded on the DVD-ROM 25 includes polygon model data and various texture data constituting various objects as data necessary for realizing the above-described method. The above-described polygons indicating raindrops, splashing polygons, and texture data are also included in these.
[0031]
The program module for generating a stormy state image is called and executed by the CPU 11 when it is necessary to express a stormy state according to the present invention in the process of generating image data of each frame. FIG. 5 is a flowchart showing an outline of processing executed in accordance with the program module. It should be noted that well-known techniques can be used as they are for processes other than those related to the polygons 4 and the textures 5 shown in FIG. 1, and descriptions thereof are omitted in this specification.
[0032]
In the process of FIG. 5, first, a starting point (movement start position) where the splashing polygon 4 is arranged is determined (step S1), and then a velocity vector at each vertex of the polygon 4 is set (step S2). The method of determining the velocity vector given here is as described above. Subsequently, the coordinates of each vertex of the polygon 4 in the next frame are calculated based on the given velocity vector (step S3). Thereafter, the texture 5 is mapped with reference to the calculated vertex coordinates (step S4), and an image based on the result is drawn in a predetermined buffer (step S5). When the process for the next frame is completed, it is determined whether or not the polygon 4 is drawn in the next frame according to a predetermined condition (step S6). For example, when the polygon 4 deviates from the field of view of the virtual camera 3, it is set not to draw the frame one after another, and the processing of FIG. Alternatively, the maximum number of frames is set for one polygon 4 and it is determined that the frames are not drawn one after another when drawing is repeated up to the maximum number of frames.
[0033]
When step S6 is affirmed, the process returns to step S2, and when negative, the process of FIG. 5 is finished. When a plurality of polygons 4 are arranged in the virtual three-dimensional space 1, the processing shown in FIG.
[0034]
The above embodiments are merely examples of the present invention, and the present invention may be implemented in various forms. For example, the content of the texture may be variously changed, and elements other than water drops may be included in the texture. For example, the speed for each vertex of the polygon 4 may be set as follows.
[0035]
Assuming that the vertices corresponding to the velocities V1, V2, V3, and V4 are P1, P2, P3, and P4, respectively, when generating these vertices, the direction of the line segment that connects the vertices P1 and P3 and the direction of the speed V0 So that the midpoint of the line segment connecting the vertices P2 and P4 is matched with the midpoint of the line segment connecting the vertices P1 and P3. Then, for each frame, the speed increase due to the gravitational acceleration is added to the speeds V1 to V4 of each vertex, and the change amount of the coordinates due to the speeds V1, V2, V3, and V4 is added to the vertex coordinates of the previous frame. When the coordinates and speed of each vertex are changed in this way, different speeds are made to correspond to each of the four vertices, and gravity acceleration is given to them, so that no special rotational motion is applied around the rotation axis 6. However, the polygon 4 naturally falls down in the horizontal direction. If the four vertices P1 to P4 and their velocities V1 to V4 are set so that the polygon 4 maintains flatness at the time of initialization, the premise that the four vertices are on the same plane is maintained.
[0036]
【The invention's effect】
As described above, according to the image generation method of the present invention, a texture that represents a plurality of water droplets is mapped onto a polygon that moves in a direction different from the direction of rainfall, so that fine splashes appear to be in the wind. You can express well how you are flying sideways. Thereby, an image like a storm can be generated realistically.
[Brief description of the drawings]
FIG. 1 is a diagram conceptually illustrating a method for generating an image expressing splashes according to the present invention.
FIG. 2 is a diagram illustrating an example of a texture used in the method of FIG. 1;
FIG. 3 is a diagram showing a plurality of polygons arranged in one frame of an actual image.
FIG. 4 is a block diagram of a game machine that executes the generation method of the present invention.
FIG. 5 is a flowchart showing a storm expression process executed by the CPU of the game machine of FIG. 4 to express a storm.
[Explanation of symbols]
1 Virtual 3D space 2 Polygon representing raindrop 3 Virtual camera 4 Polygon for splashing 5 Texture for splashing

Claims (18)

A method of constructing a rain scene in a virtual three-dimensional space by a computer and generating an image obtained by photographing the scene with a virtual camera, wherein a predetermined polygon is defined as a rain direction over a plurality of frames in the rain scene. A method for generating an image, characterized by being arranged to move in different directions, and mapping a translucent texture representing a plurality of water droplets to the polygon. The image generation method according to claim 1, wherein the polygon is moved in a direction different from the rainfall direction while enlarging the polygon. The image generation method according to claim 1, wherein a drop motion in consideration of gravitational acceleration acting in the virtual three-dimensional space is given to each vertex of the polygon. The image generating method according to any one of claims 1 to 3, wherein the polygon is moved in a direction different from the raining direction while gradually changing the direction of the polygon in the virtual three-dimensional space. . The polygon according to any one of claims 1 to 3, wherein the polygon is moved in a direction different from the rain direction while rotating around a predetermined rotation axis set along the surface thereof. Image generation method. The image generating method according to claim 1, wherein the plurality of polygons are moved as a group in a direction different from the raining direction. The image generating method according to claim 6, wherein directions of the plurality of polygons are made different from each other. The image generation method according to claim 6, wherein the movement start positions of the plurality of polygons are made different from each other. 9. The rain scene, wherein the polygons are arranged a plurality of times at different times, and at least one of the movement start position and the movement direction of the polygons with the time difference is made different from each other. The image generation method according to any one of the above. A method of constructing a rain scene in a virtual three-dimensional space by a computer and generating an image obtained by photographing the scene with a virtual camera, wherein a predetermined polygon is defined as a rain direction over a plurality of frames in the rain scene. A program that is arranged so as to move in different directions, and that maps a translucent texture representing a plurality of water droplets to the polygon. The program according to claim 10, wherein the program is configured to move in a direction different from the rainfall direction while enlarging the polygon. 12. The program according to claim 10, wherein the program is configured to give a falling motion in consideration of gravitational acceleration acting in the virtual three-dimensional space to each vertex of the polygon. The structure according to any one of claims 10 to 12, wherein the polygon is moved in a direction different from the rainfall direction while gradually changing the direction of the polygon in the virtual three-dimensional space. The program described. 13. The structure according to claim 10, wherein the polygon is configured to move in a direction different from the rain direction while rotating about a predetermined rotation axis set along the surface thereof. The program according to item 1. The program according to any one of claims 10 to 14, wherein the program is configured to move the plurality of polygons as a group in a direction different from the raining direction. The program according to claim 15, wherein each of the plurality of polygons is configured to have different directions. The program according to claim 15 or 16, wherein the movement start positions of the plurality of polygons are different from each other. In the rain scene, the polygon is arranged a plurality of times at different times, and at least one of the movement start position and the movement direction of the polygon with the time difference is configured to be different from each other. The program according to any one of claims 10 to 17.

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