JP3390167B2 - Program used to generate images - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of generating an image that realistically expresses water drops and the like by utilizing computer graphics technology.

[0002]

2. Description of the Related Art Conventionally, a polygon model or a texture animation has been used to generate a three-dimensional image that realistically represents wind and rain using computer graphics technology.

[0003]

However, it is not possible to sufficiently express a realistic image simply by expressing raindrops using polygons. For example, it is necessary to describe how raindrops adhere to the camera and how raindrops hit the floor and create ripples.

Therefore, the present invention is a method of generating an image capable of realistically expressing an image containing water drops generated by rainfall or the like.
It is intended to provide a computer program used for realizing the law .

[0005]

The present invention will be described below. In addition, in order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are added in parentheses, but the present invention is not limited to the illustrated forms.

The program of the present invention causes a computer to perform image processing for constructing a predetermined scene in a virtual three-dimensional space (1) and generating an image obtained by shooting the scene at a predetermined angle of view.
A program to be executed, on a predetermined specific image representing the scene, and processing for mapping while performing addition semitransparent processing a first texture representing the water droplets (6,7) (8A) , A process of mapping the second texture (8B) expressing the water droplet on the specific image while performing a subtractive semi-transparent process on a computer.
Is performed, wherein the time of texture mapping, is also <br/> was configured to water droplet portion of each texture (8a) adjusts the mapping position of each texture so as to overlap partially.

Read the program of this invention on a computer
According to the image generation process that is realized by only performing the subtraction, the region where only the first texture that has been subjected to the additive semitransparency process is mapped and the subtraction process are performed on the specific image. An area in which only the second texture subjected to the semi-transparent process is mapped and an area in which both textures are mapped occur. The water drops become brighter in the part where only the addition semi-transparency process is applied, while the water drops become darker in the part where only the subtraction semi-transparency process is applied, and the addition semi-transparency process and the subtraction semi-transparency process in the part where the water drops of both textures overlap. Are canceled out and the brightness does not change unless the pixel is saturated by the addition or subtraction process. By overlapping the textures in this way, it is possible to change the facial expression of the water droplets and improve the reality of the image.

In the program of the present invention, the relative positional relationship of each texture may be changed among a plurality of frames. In this case, the movement of the water droplet can be expressed, and the reality of the image is further improved.

The deviation direction of the water drop portion of each texture may be set in consideration of the direction of the light source arranged in the virtual three-dimensional space. This makes it possible to express how the light from the light source enters the water drop and be refracted, or to correctly express the shadow in the direction of the light from the light source to express the ripples generated in the water drop. It is possible to express images with consideration.

In a preferred form of the program of the present invention, the relative positional relationship of each texture may be periodically changed between a plurality of frames. In this case, it can be well expressed that the water droplets are shaking due to wind and vibration.

The water drop portion represented by one of the first texture and the second texture reciprocates within a predetermined angle range around the water droplet portion represented by the other texture. The relative positional relationship of each texture may be changed between a plurality of frames. In this case, it is possible to express well how the water drops shake.

Each texture may be mapped such that the water drop portion of the first texture is displaced from the water drop portion of the second texture in the direction of gravity in the virtual three-dimensional space. In this case, it can be expressed that the water droplets attached to the glass surface or the like receive the weight and swell downward, and light is incident on the swollen portion to shine white.

Each texture may be mapped such that the water drop portion of the second texture is displaced from the water drop portion of the first texture toward the light source (4) arranged in the virtual three-dimensional space. In this case, it is possible to represent a state in which the image of the light source is inverted and projected to the side distant from the actual light source due to the lens effect of water drops attached to the glass surface or the like.

In the virtual three-dimensional space, a plurality of light sources (4,
4 ′) is arranged, each water drop portion of the second texture is shifted toward the light source (4) side closest to the water drop portion of the first texture in the virtual three-dimensional space. May be mapped.

It is determined whether or not the light source (4) is included in a predetermined range with respect to the photographing direction of the virtual three-dimensional space, and when the light source is included in the predetermined range, the second texture is included. The respective textures are mapped so that the water drop portion of the first texture shifts toward the light source side arranged in the virtual three-dimensional space from the water drop portion of the first texture, and when the light source is not included in the predetermined range, Each texture may be mapped such that the water droplet portion of the first texture is displaced from the water droplet portion of the second texture in the gravity direction of the virtual three-dimensional space.

In this case, when there is no particularly noticeable light source in the photographing range, the lower side of the water drop becomes bright, and the light source enters the photographing range or when the light source approaches the photographing range. Considering the incidence of light from the light source, the bright part of the water droplet moves to the side away from the light source so as to represent the image of the light source. Thereby, it is possible to express the difference in the appearance of the water droplet according to the change in the relationship between the shooting direction and the direction of the light source.

In another preferred form of the program of the present invention, the first texture and the second texture are gradually expanded over a plurality of frames while the shift amount (δ) of the textures is gradually increased. Good. In this case, virtual 3
It can be seen that water droplets attached to some surface arranged in the dimensional space gradually spread. In this case,
The amount of texture deviation is gradually increased when the textures are expanded while the deviation amount remains constant, the overlapping parts of the water drop parts of both textures expand relative to the other parts, and the textures are arranged in a staggered manner. This is because the effect of doing is impaired.

Further, a ripple pattern may be given to each of the water droplets expressed by the first and second textures (see FIG. 11). By doing this, it is possible to express how the water droplets spread while drawing ripples. Since the texture expands while the ripple patterns overlap or shift, the ripples will appear appropriately due to the relationship between the addition semi-transparency processing and the subtraction semi-transparency processing. become. This further improves the reality of the image.

In the image generating method of the present invention, the first and second textures represent water droplets attached to a transparent or semi-transparent surface arranged in the virtual three-dimensional space . However, the present invention is not limited to these aspects, and can express changes in water droplets in various portions.

In the case of expressing a water droplet attached to a transparent or semitransparent surface arranged in the virtual three-dimensional space, the shooting direction of the virtual three-dimensional space and the wind direction set in the virtual three-dimensional space are further defined. The appearance rate of the water droplets may be set based on the relationship, and the numbers of the first and second textures to be mapped on the specific image may be changed according to the appearance rate. In this case, when the wind hits the surface to which the water drops adhere from the front, many water drops appear, and it can be expressed that the water drops decrease as the direction of the wind shifts sideways.

[0021]

[0022]

[0023]

Further, the program of the present invention may be recorded in a storage medium and provided to the user, or may be provided on the wired or wireless transmission medium to the user.

[0025] Note that in the program of the present invention, the specific image may be equivalent to the two-dimensional image formed by projecting the scene on the virtual screen disposed in a virtual three-dimensional space (5) Good. When mapping the textures, for example, polygon models corresponding to the textures are arranged at the positions of the water droplets to be expressed by the first and second textures, the polygon models are projected on a virtual screen, and the projected images are projected. U-for polygon model
The procedure may be performed by performing V conversion and mapping each texture.

In the present invention, the texture is classified into two types by the first and second words. These words are subjected to the additive semi-transparency process for the specific image and are mapped, or the subtractive semi-transparency. It was only used to distinguish the processed and mapped differences. The present invention does not exclude sharing of data of a single texture as the first texture and the second texture, respectively.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention. FIG. 1 shows an example in which a rainfall scene is constructed in a virtual three-dimensional space 1. X, Y, Z in the virtual three-dimensional space 1
A world coordinate system which is a three-axis orthogonal coordinate system is set, and polygons 2 ... 2, which represent raindrops, a virtual camera 3, a light source 4, a virtual screen 5, and the like are arranged therein. The Y-axis direction corresponds to the vertical direction.

The polygon 2 is a linear polygon having a predetermined length and extending in the rainfall direction. The rainfall direction is determined in consideration of the wind direction set in the virtual three-dimensional space 1. Besides,
Various objects representing terrain, characters, etc. are arranged in the rain scene, but they are not shown. Once the scene is constructed, the virtual 3D space 1
The coordinates of the vertices of the polygons 2 and the like placed in the coordinate system are converted from the world coordinate system to the viewpoint coordinate system, and the polygon 2 and the like are projected on the virtual screen (not shown) based on the viewpoint coordinate system. 2 is the screen coordinate system
Converted to dimensional coordinates. After that, rendering processing such as texture mapping is performed to generate a three-dimensional image.

In the polygon 2 described above, even if it is possible to express the state that raindrops are falling in a certain direction, the virtual screen 5
It is difficult to represent the water droplets 6 attached to the water droplets 7 and the water droplets 7 formed by the raindrops falling on the floor surface or the like. Therefore, in this embodiment, the water drops 6 and 7 are represented by the method described below.

First, a method of expressing the water droplets 6 attached to the virtual screen 5 will be described with reference to FIGS. In this embodiment, in order to express one water drop 6, FIG.
Two textures 8 as shown in are used. The texture 8 is a rectangle as a whole, and a pattern expressing a water drop is drawn therein. In order to express a state in which the water droplet 6 is blurred, it is desirable to appropriately blur around the water droplet portion 8a of the texture 8. The water drop portion 8a has a substantially circular shape, and the other portions are defined as transparent portions.

As shown in FIG. 2B, these textures 8 are referred to as a first texture 8A and a second texture 8B in a state where the centers of the respective water drop portions are displaced by a predetermined displacement amount δ. Mapping is performed on the two-dimensional image projected on the virtual screen 5 so as to overlap. Moreover, at the time of mapping, the addition semi-transparency processing is performed on one texture 8A and the subtraction semi-transparency processing is performed on the other texture 8B. In this way, the water drop portion is divided into an area A1 in which only the translucent processing is performed, an area A3 in which only the translucent processing is performed, and an area A2 in which both of the translucent processing are performed. The brightness of each of the areas A1 to A3 is the brightest in the area A1 and the next brightest in the area A2, as shown in FIG.
The area A3 becomes the darkest. However, FIG. 2B is a schematic diagram on the assumption that the water drop portions of the texture 8 and the areas on the destination two-dimensional image to which these are mapped have uniform colors. Yes, in reality, the color of each pixel on the finally observed water droplet changes depending on the texture 8 and the color of the mapped region.

3 and 4 show examples of textures for expressing the water droplets 6. In the texture of FIG. 3, water drops are expressed as a circular pattern in which the gradation gradually decreases from the center to the periphery. The texture of FIG. 4 also has a gradation change substantially similar to that of FIG. 3 while placing the region with the highest gradation (that is, the brightly visible portion) at a position eccentric from the center. The two types of textures shown in FIGS. 3 and 4 may be used as the first texture and the second texture, respectively, or only one of the textures is shared as the first texture and the second texture. You may.

FIG. 5 shows an image of a water droplet obtained by mapping two textures of FIG. 4 as shown in FIG. 2B. As is clear from this example, according to the present embodiment, it is possible to realistically represent the state in which the water droplets attached to the lens surface of the camera are blurred by simple processing.

The direction of shifting the texture 8 may be set appropriately, but preferably, the water drop portion of the first texture 8A is lower than the water drop portion of the second texture 8B, as shown in FIG. 6 (a). That is, it is set so as to shift in the direction of gravity in the virtual three-dimensional space 1. By doing so, it is possible to express how water drops swell downward due to gravity and light is incident on the swollen portion to shine. On the other hand, when the light source 4 is imprinted on the virtual screen 5, the water drop portion of the second texture 8B is the first texture 8 as shown in FIG. 6B.
You may set so that it may shift to the light source 4 side rather than the water droplet part of A. By doing so, it is possible to represent a state in which the image of the light source is inverted and projected by the lens effect of the water droplets. When a plurality of light sources 4 and 4'is shown on the virtual screen 5, the displacement direction of the texture 8 may be set as described above with reference to the light source 4 in the direction close to the virtual camera 3.

The method of setting the displacement direction in consideration of the light source 4 is not limited to the method of determining only whether or not the light source 4 is included in the image projected on the virtual screen 5. For example, the texture is based on the relationship between the shooting direction of the virtual camera 3 (shown by the alternate long and short dashed line 9A in FIG. 1) and the direction of viewing the light source 4 from the viewpoint of the virtual camera 3 (shown by the alternate long and short dashed line 9B in FIG. 1). You may set the shift direction of. That is, when the deviation angle of the direction of the light source with respect to the shooting direction is within a predetermined range, the light source is taken into consideration and the result shown in FIG.
As shown in FIG. 6, when the displacement direction of the texture is set, and the displacement angle exceeds a predetermined range, gravity is taken into consideration.
The texture shift direction may be set as shown in (a).

The texture deviation direction and the texture deviation amount may be changed between a plurality of frames. For example, in FIG.
As shown in (a), the first texture 8A is periodically reciprocated around the second texture 8B within a predetermined angle range, and if the state is photographed over a plurality of frames, the water droplets 6 will not move. It is possible to express a state of trembling due to vibration. As shown in FIG. 7B, each texture 8A,
The shift amount of 8B may be changed. In any case, by changing the relative positional relationship of each texture,
It is possible to dynamically change the state of the water droplets 6 and provide an image with a realistic feeling.

The number of water droplets attached to the virtual screen 5 can be set in consideration of the wind direction (indicated by the arrow W in FIG. 1) set in the virtual three-dimensional space 1. For example, when the wind hits the virtual screen 5 from the front, FIG.
As shown in FIG. 8A, when many water droplets 6 are attached and the wind is blowing along the virtual screen 5, a change may be given so that the water droplets 6 are not attached much as shown in FIG. 8B. . That is, the difference between the shooting direction and the wind direction is 180 °
(That is, the wind is blowing from the front of the virtual camera 3)
It is preferable to set the appearance rate of the water droplets 6 to be larger as it gets closer to.

The appearance position of the water droplet 6 on the virtual screen 5 may be randomly determined. Further, as shown in FIG. 9, a state in which the water droplets flow by wind may be expressed by gradually changing the positions of some of the water droplets 6A in a specific direction between a plurality of frames. In this case, the flow direction of the water droplets may take into consideration the wind direction and the wind force. For example, the greater the wind power, the greater the frequency with which water drops flow.
When the wind hits the virtual screen 5 upward, the frequency of water droplets may be set low.

Next, a method of expressing the water droplet 7 in FIG. 1 will be described. When expressing the water droplet 7, basically, FIG.
Two textures 8 as shown in are used. As shown in FIG. 10A, the texture 8 is set as a first texture 8A and a second texture 8B so that the centers of the water droplet portions are overlapped with each other with a predetermined shift amount δ. Mapping is performed on the two-dimensional image projected on the screen 5. Moreover, at the time of mapping, the addition semi-transparency processing is performed on one texture 8A and the subtraction semi-transparency processing is performed on the other texture 8B.
This point is similar to the case of the water droplet 6.

In order to show how the water droplet 7 expands with time, the textures 8A and 8B expressing the water droplet 7 are gradually expanded with time, as shown in FIG. 10 (b). Further, the shift amount δ of the textures 8A and 8B is increased so as to be linked with the expansion of the texture. This allows
Even if each texture is enlarged, the area where the water droplets do not overlap is secured. Further, in order to express the ripples generated on the surface of the water drop 7, the water drop portion 8a of the texture 8 is given a ripple pattern as shown in an example in FIG. Note that FIG.
Inverts the gradation.

An example of the image thus obtained is shown in FIG. As is clear from this figure, according to the present embodiment,
It is possible to realistically express, by simple processing, how water drops that have fallen on the floor spread while creating ripples. The light source may or may not be considered in the texture shift direction. When considering the light source, it is preferable to shift the texture in the direction in which the light from the light source enters. The first textures 8A and 8B may be the same or different. However, when a single texture is shared as the first texture 8A and the second texture 8B, overlapping of ripples represented by the texture and addition semitransparent processing and subtractive semitransparent processing of those textures are performed. The effect overlaps with each other to create a shadow on the ripples, and the appearance of the shadow gradually changes as the texture expands. This makes it possible to emphasize the stereoscopic effect.

The image representation method described above can be used in three-dimensional image processing in various fields. As an example thereof, an example of implementing the expression method of the present invention on a game machine using a computer will be described with reference to FIGS.

FIG. 13 is a block diagram of a typical control system of a game machine using a computer. As we all know,
The game machine 10 as a computer executes a predetermined game in accordance with a game program recorded in a storage medium (for example, a DVD-ROM) 25, a CPU 11 mainly composed of a microprocessor, and a main CPU for the CPU 11. A ROM 12 and a RAM 13 as storage devices, and an image processing apparatus 1 that performs processing suitable for image processing and audio processing based on an instruction from the CPU 11.
4 and a sound processing device 16, and a storage medium reading device 18 for reading data and the like from the storage medium. An operating system as a program necessary for controlling the overall operation of the game machine 10 is written in the ROM 12. DVD as a storage medium in the RAM 13
-The program and data for the game read from the ROM 25 are written as necessary. The image processing device 14 receives the image data from the CPU 11, develops the image data corresponding to the game screen on a built-in frame buffer (not shown), and converts the drawn image data into a predetermined video reproduction signal. It is output to the monitor 19 at a predetermined timing. The sound processing device 16 is a DVD
-Reproduce the data such as voice and tone read from the ROM 25, the sound source data, etc., and output them from the speaker 20.
The reading device 18 is a DVD according to an instruction from the CPU 11.
Read the program or data recorded on the ROM 25 and output a signal corresponding to the read content.
The DVD-ROM 25 stores programs and data necessary for implementing the image expression method according to the present invention.
The monitor 19 is a television receiver for home use, and the speaker 20 is
In general, the built-in speaker of the television receiver is used. Further, an input device 22 and an external storage device 23 are connected to the CPU 11 via a bus 24. The external storage device 23 is a rewritable storage device such as a non-volatile semiconductor memory, a hard disk, or a magneto-optical disk. Such a configuration is merely an example, and the configuration of the computer to which the image generation method of the present invention is applied may be appropriately changed.

The program recorded in the DVD-ROM 25 as a storage medium includes a module which describes the procedure necessary for constructing a rain scene and generating an image thereof by the method described above. In addition, DVD-ROM2
The data recorded in 5 includes, as data necessary for implementing the above-described method, data of polygon models forming various objects and data of various textures. The texture data for expressing the above-mentioned water droplets are also included in these.

The program module for generating an image containing water droplets is called and executed by the CPU 11 when it is necessary to represent water droplets according to the present invention in the process of generating image data of each frame. Note that known techniques can be used as they are for the processing other than the portion related to the water droplets 6 and 7, and the description thereof will be omitted in this specification.

FIG. 14 is a flow chart showing an outline of the processing executed according to the program module for expressing the water droplets 6 attached to the virtual screen 5.

In the processing of FIG. 14, the number of water droplets 6 is determined according to the appearance rate set in consideration of the relationship between the wind direction and the photographing direction as described above (step S1), and the wind force or the like is taken into consideration. The water droplets 6 displayed on the virtual screen 5 are classified into those vibrating at a fixed position and those moving on the screen 5 according to the set frequency of water droplets set (step S2). Next, the shift direction of the texture 8 is determined from the relationship between the shooting direction and the direction of the light source (step S3).
Then, according to the amplitude and phase of the vibration of the water droplets, the position of the water droplets that are distinguished as being vibrated on the screen 5 and the shift state (the direction and amount of the shift) of the texture forming the water droplets are determined (step S4). The amplitude of the vibration may be determined based on the wind force, for example. The vibration here is shown in Fig. 7.
It means a periodical change in the relative positional relationship of the texture as shown in (3), and the larger the wind force, the larger the amplitude or the shorter the period.

Then, the position in the next frame of the water droplet discriminated as moving is calculated according to the velocity and direction of the water droplet (step S5). After determining the position of the water droplet as described above, texture mapping is performed on the water droplet for the next frame based on the obtained data, and an image of the water droplet is drawn in a predetermined frame buffer (step S6).

After the drawing is completed, the relationship between the shooting direction and the wind direction of the frames and the wind force are acquired one after another (step S7), and it is determined whether or not the appearance rate of the water droplet 6 is changed based on these values (step S8). ), If there is a need to change the appearance rate, it is changed (step S9), and then it is determined whether or not it is necessary to change the frequency of water droplets in consideration of the relationship between the shooting direction and the wind direction and the wind force. (Step S10), the frequency is changed if necessary (step S11). After performing these processes, it returns to step S1 and starts the drawing process regarding the water droplet of another frame.

FIG. 15 is a flow chart showing the outline of the processing executed according to the program module for expressing the water droplet 7 that drops and spreads on the floor surface or the like of the virtual three-dimensional space 1.

In the processing of FIG. 15, it is first determined whether or not there is a raindrop newly falling on the floor surface within the photographing range of the virtual camera 3 (step S21), and if this is affirmative, a new drop position is set. A water droplet 7 is generated at step S22. When denied, step S22 is skipped. Then, the size of the texture corresponding to all the water droplets 7 to be displayed in the next frame and the shift state (shift direction and amount) between the textures are updated (step S23). In this case, for each water drop, the number of display frames that have elapsed from the time of occurrence is counted, the texture of each water drop is gradually expanded according to the number of frames, and the amount of deviation of the textures that make up each water drop is also framed. Expand according to the number.

Subsequently, the water drops that have reached the predetermined display period are erased from the display object (step S24). For example, the water droplets displayed for a predetermined number of frames from the time of occurrence are extinguished. After that, 1 is added to the number of display frames for each water drop, and then the process returns to step S21. By such a process, it is possible to express how water drops that have fallen on the floor surface spread while drawing ripples.

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 changed variously, and elements other than water drops may be included in the texture. The present invention is not limited to the expression of water droplets associated with rainfall, and can be used to express various water droplets such as water splashes and water splashes from fountains, showers, pools, and the like. The present invention is not limited to the example of using two textures, and three or more textures may be superimposed and mapped.

[0054]

As described above, the program of the present invention is
According to Lam , it is possible to change the facial expression of a water drop by performing mapping of at least two textures by adding semitransparent processing and subtractive semitransparent processing, respectively.
The reality of the image can be improved. Moreover,
By changing the relative positional relationship of the water drop portion expressed by the texture between a plurality of frames, various changes can be given to the water drop to further enhance the reality of the image.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a scene constructed in a virtual three-dimensional space in an embodiment of the present invention.

FIG. 2 is a diagram showing an outline of textures for expressing water droplets and an example of how to superimpose them.

FIG. 3 is a diagram showing an example of a texture for expressing a water drop.

FIG. 4 is a diagram showing another example of a texture for expressing a water drop.

FIG. 5 is a diagram showing an example of an image in which water drops are expressed by using the texture of FIG.

FIG. 6 is a diagram showing an example of how to shift a texture.

FIG. 7 is a diagram showing an example in which a relative positional relationship of textures is changed.

FIG. 8 is a diagram showing changes in the number of water droplets attached to a virtual screen.

FIG. 9 is a diagram showing how water droplets attached to a virtual screen move.

FIG. 10 is a diagram showing how to superimpose textures when a water drop that has fallen on a floor or the like spreads with ripples.

FIG. 11 is a diagram showing an example of a texture used when expressing how a water drop that has fallen on a floor spreads with ripples.

FIG. 12 is a diagram showing an actual example of an image in which water drops are expressed using the texture of FIG.

FIG. 13 is a block diagram of a game machine to which the generation method of the present invention is applied.

FIG. 14 is a flowchart showing a procedure of processing executed by the CPU of the game machine shown in FIG. 13 to express water droplets attached to a virtual screen.

FIG. 15 is a flowchart showing a procedure of processing executed by the CPU of the game machine shown in FIG. 13 to express a water droplet that drops and expands on a floor or the like.

[Explanation of symbols]

1 virtual three-dimensional space 2 Polygons that represent raindrops 3 virtual camera 4,4 'light source 5 virtual screen 6 Water drops attached to the virtual screen 7 Water drops that drop on the floor and expand 8 Texture for expressing water drops 8A First texture 8B second texture 8a Water drop part

Continuation of the front page (56) References JP-A-10-198819 (JP, A) JP-A-10-295934 (JP, A) JP-A-11-175746 (JP, A) JP-A-7-92959 (JP , A) JP-A-7-37083 (JP, A) JP-A-8-161528 (JP, A) JP-A-9-146447 (JP, A) JP-A-2001-283250 (JP, A) (58) Survey Areas (Int.Cl. ⁷ , DB name) G06T 15/00 300 G06T 15/70

Claims (14)

(57) [Claims] 1. A program for causing a computer to execute image processing for constructing a predetermined scene in a virtual three-dimensional space and generating an image obtained by shooting the scene at a predetermined angle of view. and on a specific image, and the procedure for mapping while performing addition semitransparent processing a first texture representing the water droplets, the particular image while the second texture representing said water droplets subjected to subtraction translucent process A program for causing a computer to execute the above mapping procedure, and adjusting the mapping position of each texture so that the water drop portions of each texture partially overlap when the texture is mapped. 2. The program according to claim 1 , wherein the relative positional relationship of each texture is changed between a plurality of frames. 3. A process according to claim 1, characterized in that it is configured to set the displacement direction of the water droplet portion of each texture by considering the direction of the light source arranged in the virtual three-dimensional space or
The program described in 2 . 4. The program according to claim 1 , wherein the relative positional relationship of each texture is periodically changed between a plurality of frames. 5. A plurality of relative positional relationships among the textures are arranged so that the water droplet portion represented by the first texture reciprocates around the water droplet portion represented by the second texture within a predetermined angle range. The program according to claim 1 , wherein the program is configured to be changed between frames. 6. The water drop portion of the first texture is the second
The program according to claim 1 , wherein each texture is mapped so as to be shifted in a gravity direction of the virtual three-dimensional space from a water drop portion of the texture. 7. The water drop portion of the second texture is first
Claim than water droplet portion of the texture, characterized in that it is configured to map the each texture as deviated light source disposed side in the virtual three-dimensional space 1
The program described in. 8. When a plurality of light sources are arranged in the virtual three-dimensional space, the water drop portion of the second texture is closest to the light source side in the virtual three-dimensional space than the water drop portion of the first texture. The program according to claim 1 , wherein the textures are configured to be mapped such that the textures are offset from each other. 9. It is determined whether or not a light source is included in a predetermined range with respect to the imaging direction of the virtual three-dimensional space, and when the light source is included in the predetermined range, the second texture Each texture is mapped such that the water drop portion is shifted to the light source side arranged in the virtual three-dimensional space from the water drop portion of the first texture, and when the light source is not included in the predetermined range, the first texture is described. claim waterdrop portions texture is characterized in that it is configured to map the each texture as shifted in the direction of gravity of the virtual three-dimensional space than the water droplet portion of the second texture 1
The program described in. The method according to claim 10, wherein the first and second texture, claim 1, characterized in that it is configured to represent the water droplets attached to the virtual three-dimensional space is disposed a transparent or translucent surface 10. The program according to any one of items 9 to 10 . 11. The appearance rate of the water droplets is set based on the relationship between the shooting direction of the virtual three-dimensional space and the wind direction set in the virtual three-dimensional space, and mapping is performed on the specific image according to the appearance rate. The program according to claim 10 , wherein the program is configured to change the number of first and second textures to be executed. 12. The program according to claim 1 , wherein the first and second textures are configured to be gradually expanded over a plurality of frames, and the shift amount between the textures is gradually increased. . 13. The program according to claim 12 , wherein textures in which a ripple pattern is given to each water drop are used as the first and second textures, respectively. 14. The method of claim 13, wherein the specific image, claim 1, characterized in that corresponding to 2-dimensional image formed by projecting the scene on the virtual screen disposed in a virtual three-dimensional space
The program according to any one of items 1 to 13 .